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Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: ttomas on August 26, 2007, 08:22:58 AM
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most of us were not born in a bus. therefore, without instruction it would be difficult to know the proper techniques of driving a 30,000 lb rig.
What is the proper technique to descend a major grade?
In my last rig, I would shift to low 2nd, let it pull up to max rpm, and brake back down. It worked, but I never could find out if this was the best way for my brakes etc. thanks Tomas
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Yes to shift to lower gears but you need to have the lowest that will let you use the least brakeing. the brakes need time to cool between applications depending on how much braking was needed to slow to controled speed Jerry
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This is the best argument for the use of a Jake Brake.
A little history of the Jake brake. Clessie Cummins-the founder of Cummins engine company, invented the Jake brake-when he almost lost it a couple of times coming down steep grades. Cummins did not have the capacity to make his new braking device in bulk so he awarded the Jacobs chuck company the rights to make and market the new compression brake-hence the Jake brake. Cummins engine company still makes their own version called the Interbrake.
For those that don't know how the Jake brake works, here's the short version. Most of the truck engines have an additional camshaft lobe and rocker arm that operates the unit injectors (whether it be mechanical or electronic). The Jake unit sits over the rocker arms and when the system is activated, the unit is charged with oil pressure from the engine. The pressure servo is then extended down to touch the cam side of the injector rocker arm. When the rocker arm is pushed up from the camshaft, the pressure servo is also pushed up that creates pressure inside the Jake unit that causes a hydraulic cylinder over the exhaust valve to push the exhaust valves open on that cylinder. So what you get is the exhaust valve opening when the injector is activated. This happens at the highest point of compression, so all that built up energy is released into the exhaust pipe (hence the noise), and with the expulsion of that energy, causes the engine to act like an air compressor that makes the braking force. For other engines that don't have unit injectors-like some Caterpillars, they will use other exhaust rockers from other cylinders for the exhaust Jake activation across the engine to another cylinder.
I drove for 21 years always with a Jake brake (I don't sell any big trucks without Jake brakes). I have a very well adjusted (by Don Fairchild) Jake brake on my 8V-71 and can tell you it works extremely well!! Coming down the north bound side of the I-5 Grapevine which is a 5 mile 6% grade. The Jake is so effective I have to switch between one head and both head activation to keep from slowing to much, and not touch the brakes at all.
To those that don't have a Jake brake and have intentions on travelling west of interstate 25, going to Canada or Alaska, PLEASE have one installed. It isn't a frivolous toy-it can and will save your brakes from smoking and possibly failing. Good Luck, TomC
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I agree with Tom about Jakes being absolutely worth the cost! I drove big trucks for yrs, some with Jakes and some with out! I'd never drive one with out Jakes again (unless it was just across town!) I don't have them on my buses but my Setra's come with transmission retarders that work very well, and the MCI my dad drives doesn't have them and he doesn't see it worth the $ to put them on it! Well as I said he drives it, and he does a very good job of it! Jakes are nice, and as TomC said if driving out in the Rockies or on the west coast I'd have them installed immediately (even on dad's bus wether he wanted them or not!), but out here in the mid west they are not an absolute necessity that we can't live with out!
Now back to the original question! As a general rule it is best to go down the hill in the same gear you came up it ! And also using the brakes off---on-off---on-off----on-off---- to allow them time to cool.
Now the one thing that has always stuck in my mind is what an old timer told me once when I was nervous about dropping off one of the passes out west (I don't remember which one) he told me "Son just remember you can go down many mountains, many times too slow, but you'll only go down one, one time too fast!"
;D BK ;D
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Great quote! I'll have to remember that! haha
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I know it's controversial and I'll probably get flamed but here goes. Once in the correct gear so the engine is doing most of the braking. The service brakes should be applied continuously and just enough to maintain the desired speed. This will result in the lowest temperature rise of the brakes. Letting speed build up then braking to a lower speed and repeating will result in hotter brakes. In other words riding the brakes, contrary to popular belief is the best technique.
Regards
Jerry 4107 1120
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Jerry, I have heard the same thing many times and have seen a few instances where a control was installed that allowed you to actually adjust the amount of air pressure that was applied to the braking system continuously. In other words, for example you could set it for 15 pounds of continuous air pressure. This was adjustable so you could set the correct amount to maintain the desired speed.
Two different thoughts obviously of proper braking techniques.
Richard
I know it's controversial and I'll probably get flamed but here goes. Once in the correct gear so the engine is doing most of the braking. The service brakes should be applied continuously and just enough to maintain the desired speed. This will result in the lowest temperature rise of the brakes. Letting speed build up then braking to a lower speed and repeating will result in hotter brakes. In other words riding the brakes, contrary to popular belief is the best technique.
Regards
Jerry 4107 1120
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Jerry and Richard are right. The on-off-on is not correct but I used to think it was and did it until I studied for my CDL and found out it was not correct.
The reason it is not is explained very well by Jerry.
I used the steady pressure along with the Jake on the 18 wheeler I drove and use it on my 4104 (No Jake). I've made three trips across the Rockies and Cascades and have not once overheated the brakes.
I don't shift down my 4 sp but I do make sure I start down a grade very slowly and don't ever let the speed build up over 55-60 until I'm sure I can see the bottom.
One little town in UT has a 35 mph speed limit right at the bottom of a very long, steep grade. That one got them a bit warm but still didn't overheat.
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My wife is a Certified CDL Examiner in Denver. She is also a driver/trainer for cars, busses, and semi's. She has 25+ years experience of city bus driving. According to the CDL manual in Colorado the ON-OFF-ON braking is the proper method. Section 2.16 of the Colorado cdl manual.. The truck driving school that she works for teaches the ON-OFF-ON technique as part of their state certified course.
Constant steady braking, no matter how light the pressure, is a receipe for disaster on a mountain grade.
Don & Sheila
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I have used the on off method because I thought that constant applied pressure would result in heating the shoes and drums, no matter how light. Now I wonder which is the correct way for our Eagle, 20 tons of flying metal and rust.
Paul
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I think just point it down the hill and pray is a good way. :)
I think I have seen truck drivers doing that on Monteagle plenty of times!
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Don, Shelia & anyone in Colorado.
I said it was controversial!
Apparently Colorado has it's own laws of physics and/or some very STUPID bureaucrats. The correct method is riding the brakes and has been proven over and over in experiments. Colorado and it's bureaucrats are NOT above the laws of physics, I'm sure glad I don't live there. You should take on the challenge of removing this dangerous urban legend from your state.
Regards
Jerry 4107 1120
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Lots of versions around. My impression was that the on off system is not recommended because many drivers tend to use a too-rapid and too-heavy on-off brake application and it can run your air down low enough that the parking/maxi brake can apply.
Light constant braking for a long time was said to glaze the linings over and result in loss of brakes.
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Does anyone have a link to post on this subject? In other words a tested experiment that proves the proper method beyond a shadow of a doubt. Not biased by state laws, but by proven methods in the trucking industry.
Paul
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As I have already said, I don't have much experience here so I have to go by what others say.
I will say that after some research, the 'experts' say that SNUB braking is the correct method and that is what CDL testing now calls for. Snub braking is off-on-off.
This article is most telling. It was written by a forensics expert who studied the reason for truck crashes and it appeared in Trucker's World magazine. I will quote the first paragraph here and interested parties can follow the link to read the entire article.
When the Commercial Drivers License (CDL) manual was first published, it recommended that a driver use a light and steady application of the brakes when descending steep grades. This recommendation was based on an old theory that heavy brake applications would generate more heat than light applications. This method (controlled braking) was commonly taught to drivers and, even after changes were made to the CDL manual because this theory was proven wrong, the method is still taught and practiced today.
http://www.johncglennon.com/papers.cfm?PaperID=36 - John C. Glennon Jr - CrashForensics.com
Every other state CDL site I looked at recommended snub braking without exception.
I still like the 'point n' pray' way! :)
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From
http://www.johncglennon.com/papers.cfm?PaperID=36
Downhill Braking
John C. Glennon, Jr., BSAT
[ Reprinted from the Trucker's World Magazine, Volume 5, Issue 6, June 2001]
When the Commercial Drivers License (CDL) manual was first published, it recommended that a driver use a light and steady application of the brakes when descending steep grades. This recommendation was based on an old theory that heavy brake applications would generate more heat than light applications. This method (controlled braking) was commonly taught to drivers and, even after changes were made to the CDL manual because this theory was proven wrong, the method is still taught and practiced today.
Snub braking is now the recommended method of downhill braking. This method works by: first, choosing the correct gear for the hill; second, allowing the truck to speed up to the maximum safe speed as it descends the hill; third, applying the brakes hard to slow the truck down 5 mph; and then repeating this process to the bottom of the hill. To understand why this method is recommended takes some understanding of the basics about how brakes work. Slowing a truck with it.s brakes, creates friction between the brake shoes and brake drum to convert the kinetic (forward movement) energy of the truck into heat energy dissipated by the brakes. The amount of heat energy produced is dependent upon the weight of the truck and the amount of slowing desired. Assuming these two factors remain constant, the manner in which the brakes are applied, hard for a short time or lightly for a long time, will not change the amount of heat energy and heat produced by the brakes. This heat energy will be distributed among all the brakes that are working. Again, assuming all other factors constant, the more brakes the system has working the cooler each brake will be.
This explains why the old theory of light and steady braking is incorrect. However, to understand why snub braking is the recommended practice, you must also understand the basics of pneumatic balance. Trucks have relay valves to control the application and release of the air brakes. A standard truck-trailer usually has one relay valve for the tractor drive axles and one for the trailer axles. The relay valves are controlled by air pressure from the foot valve (brake pedal). This control pressure opens the relay valve allowing the desired amount of air pressure from the air tanks to pass through the valve and supply pressure to the brakes. Pneumatic balance is created by having equal air pressure at all wheel ends. Pneumatic imbalance is a result of these valves that open at different pressures. For example, a tractor may be setup with a relay valve that opens at 15psi (15psi crack pressure relay valve) and the trailer being towed may have a relay valve with a 3psi crack pressure. A vehicle setup this way would only apply the trailer brakes during controlled brake application, which typically has an application pressure of less than 10psi. However, a .snub. brake application of 20 to 30psi will open all valves and apply all brakes. This type of imbalance can also be a result of contaminants and alcohol in the air system that can cause these valves to hang-up and have higher than normal crack pressures.
Snub braking became the recommended method of downhill braking as a result of testing done by University of Michigan Transportation Research Institute. This research found that trucks with properly balanced brake systems had basically the same average brake temperature when using either the controlled or snub braking method. However, trucks with poor brake balance were found to have more uniform brake temperatures when the snub method was used. Unless pneumatic testing is performed on a truck to ensure that proper brake balance is maintained, there is no way to know if a truck has good brake balance. This type of testing is difficult to perform in most trucking operations since a tractor is usually hooked to several trailers over relatively short time periods. Therefore, for the purposes of deciding which braking method to use, it would be virtually impossible to determine if a truck has good brake balance. This is why snub braking is the recommended method.
Although snub braking does compensate for imbalances in the pneumatic system of the brakes, there is a misconception that snub braking also compensates for brakes that are not evenly adjusted. Brakes that are not evenly adjusted have a torque imbalance. Torque balance is created by having matched mechanical components that are working properly and adjusted correctly. Snub braking has limited ability to compensate for torque imbalance. A good example of this would be a truck with a six-inch slack adjuster on one side of the axle and a five-inch slack adjuster on the other side. This truck will always have an imbalance at any pressure because the brake with the six- inch slack adjuster has more leverage. The same imbalance can happen with uneven brake adjustment because the force output of a brake chamber is directly related to the brake adjustment (push rod stroke).
Since the snub braking method cannot compensate for torque imbalance, trucks should always be inspected and repaired with the following in mind. A truck.s brake system should have matched mechanical components such as the same size brake chambers and same length slack adjusters on both sides of an axle and, most of the time, on all brakes in a group of axles (i.e. tractor drive axles). When inspecting the condition of the brakes, any isolated premature wear found is an indication of a balance problem. If one brake wears faster than the rest, there is a torque balance problem and that brake is doing more work than the rest. If one brake wears much slower than the rest then that brake is not working as hard as the rest. When brakes are repaired, it is important that the cause of an identified torque imbalance be found before repairs are made. Repairs made without correcting the torque imbalance could amplify the problem causing the overworked brake to work even harder. It is equally important to ensure that the same repairs are done on both sides of an axle. If the brake hardware is replaced on the right side of an axle it should also be replaced on the left side. If the s-cam bushings are replaced on the right side they should be replaced on the left.
Snub braking is the method that every truck driver should be using. Although snubbing is a very good precautionary measure, it is still no substitute for a properly balanced brake system. Brake imbalances not only cause brakes to overheat when driving in the mountains, but also can cause instability both on slick driving surfaces and during hard brake applications. These stability problems (to be discussed in a future article) are the primary cause of jackknifes and trailer swingouts. Therefore, I recommend not only that trucks be tested, repaired, and maintained to ensure that they have good brake balance, but also that the snub braking method be used to compensate for any variances that result from interchanging tractors and trailers.
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Tonylee,
Constantly applied braking also loses FAR less air because the only time air is expelled from air brakes is when they are released. The lining glazing argument is similarly bogus. Glazing of linings is a function of temperature and the peak temperature is lower with the constant application. This can be proven mathematically and has been verified in many carefully set up experiments.
Regards
Jerry 4107 1120
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Another...
Proper Braking Technique
Remember: The use of brakes on a long and/or steep downgrade is only a supplement to the braking effect of the engine. Once the vehicle is in the proper low gear, the following is a proper braking technique.
1. Apply the brakes just hard enough to feel a definite slowdown.
2. When your speed has been reduced to approximately 5 m.p.h. below your “safe” speed, release the brakes. (This brake application should last for about three (3) seconds.)
3. When your speed has increased to your “safe” speed, repeat steps 1 and 2. For example, if your “safe” speed is 40 m.p.h., you would not apply the brakes until your speed reaches 40 m.p.h. You now apply the brakes hard enough to gradually reduce your speed to 35 m.p.h. and then release the brakes. Repeat this as often as necessary until you have reached the end of the downgrade.
From drivingrules.net CDL Study Guide - http://www.drivingrules.net/cdl/cdlsecb/b11mountian.htm
I think everyone should go ahead and use whatever method they feel comfortable with. As for me, as a new guy, I am going to trust the trained expert who studies truck crashes for a living. There is a reason the CDL manuals have all been changed and that is good enough for me. The Bachelor of Science in Automotive Technology degree he has tells me that he knows more about heating brakes than I will ever know.
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CA has snub braking in thier cdl
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The reason 'snub' braking is being advocated is light pressure often concentrates all the heat in one brake while heavier braking forces all the brakes to share the heating. So the argument is with poorly adjusted brakes over heating of one wheel's brake may occur so it's better to spread a little more heat among 4 or more brakes than concentrate all the heat in one brake. Take your choice.
Regards
Jerry 4107 1120
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Jerry L.
I see lots of stuff supporting snub braking but nothing supporting your claims. Do you really expect me to believe that virtually state in the nation, that supports snub braking as the safest method, is wrong? I'll stick with the experts on this one.
Don & Sheila
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Skihor,
Tonylee's post above quotes a Truckers World article that acknowledges that with a properly balanced braking system the temperature rise is 'virtually the same' The problem of poorly balanced brakes forcing all the heat into a few of the brakes is the reason snub braking is now advocated as it results in more even heating of the brakes even though more total heat is generated. Hopefully a bus has a well balanced braking system unlike a tractor trailer big rig.
Regards
Jerry 4107 1120
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My last post was not meant to be mean. Quite the opposite. The issue here is how to decend a grade safely. I'm willing to bet you could test every one of our busses to see if ALL of the brakes function equally and not one would pass. Thus, if for no other reason, snub braking is the safest way. Not many of us, myself included, have big rig driving experience. I feel this is a very important issue in the operation of these 30,000+LB monsters.
Don & Shela
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Hopefully a bus has a well balanced braking system unlike a tractor trailer big rig.
That is an awfully big word to post your life on. All things being equal, I would prefer the method that makes it best if something is wrong. You never know when something could go wrong in a braking system that you don't know about.
And that is the point... In a brake system where everything is fine, both systems would equally well. So no big deal. But if everything is not fine, which is probably the case in a lot of scenarios, snub braking gives you a better chance of keeping your brakes cool and functional.
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The no longer recommended technique of rideing the brakes is still safer if the braking system is properly balanced which is the case if it is on a single vehicle that has been properly maintained. But if it is on a composite vehicle, like a tractor trailer, or has maintenance issues then the now recommended technique of 'snub' braking is safer. So next time you come to a long downgrade try rideing the brakes down it, then stop at the bottom and run around the bus with your infrared thermometer and read the temperature of all the hubs. if they are'nt within say 10 degrees you should be using the snub technique.
Regards
Jerry 4107 1120
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In order to do the constant brake pressure technique, you should really have a brake air pressure gauge that reads the pressure you're putting into the system when you press on the brake. From many years of experience, no more than 10psi of pressure should be pressed, unless you want to smoke the brakes. Course the normal way a good truck driver comes down a grade is to come down at the speed that will allow only light usage of only the trailer brakes keeping the tractor brakes cool for emergency stops. You can use the off-on-off method, but have to learn a very light foot to keep the brakes from overheating. Stabbing the brakes relatively hard is a sure way to over heat them. The best way to tell you came down the hill right is that you did NOT smoke your brakes. Good Luck, TomC
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Going fast then going slow by using the brakes just makes them hotter. The drums get hotter simply because the vehicle is going faster. True, it takes the same amount of energy no matter which method is used but the rate of heat buildup is faster and takes longer to dissipate.
Constant braking allows the heat to constantly flow from the brake shoes. When the brakes aren't applied the the shoes don't have nearly as good a heat path as they do through the drums when applied.
Which is better, hot and not so hot back and forth or constant medium hot?
Lining glazing is only a problem when first breaking in new linings. Some types of new linings are purposely gotten hot so the resins flow and level the lining face.
Brakes are used gently all the time in normal driving so that obviously is not a problem.
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I live in a mountainous region of North Jersey. While our mountains are not as big as those out west, the hills are very steep. I have been driving dump trucks and equipment haulers up and down these hills for thirty years, and I genrally use the higher gear constant pressure method. I find it gives me much more brake left at the bottom of the hill. That said, I am familiar with all the grades I go down and know what to expect and just how to approch them. For the less experianced, I think I would recomend a lower gear and the on-off -on method.Keep in mind that both methods will get you in trouble if used too hard.If you are unfamiliar with the terrain, it is best to take it slow and get it stopped at the first sign of overheating of the brakes while you still can.I can attest to the fact that it is no fun at all screeming down a hill with the brakes on fire praying that no one pulls out in front of you and the light at the bottom doesn't turn red. Donn
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I can attest to the fact that it is no fun at all screeming down a hill with the brakes on fire praying that no one pulls out in front of you and the light at the bottom doesn't turn red
Hi Don,
This sounded like me back in April... ;D There is always a traffic light at the bottom of a steep mountain...
Tis why I installed Jakes..
Nick-
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Just a thought here:
I have little experience with the pros and cons of this subject, but would additional cooling help the brakes??
I was just thinking back to my other thread about putting an air dam on the front of the bus and running air ducts back to the brakes. I will do this when I try my air dam experiment :) but could some sort of air deflectors or diverters help at all? It seems that you have quite a bit of air flowing by, why not try to direct it towards the brakes?
I duuno, just thinkin,
Chaz
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It looks like the debate on this could be very involved and seems to depend a lot on a persons own comfort level of what the different experts opinions and studies would show, for every expert in one area, you can counter with another expert that shares a different opinion. To me, the best solution would be to have a back up system that would allow for variables that would be more easily controlled, my comfort level would tell me that if a jake helped as a back up system, it would be worth the added expence, that is the direction I'm leaning here. I have no doubt that each area of study here has merit but the variables a person would encounter would make each one inconsistant based on the individual equipment and the condition of it, wow, I never knew I could use those big words all in a row, I have to thank Slow Rider for that lol.
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All -
Folk are overlooking an important point from all these various sources regarding controlled constant braking vs snub braking techniques:
Being in the RIGHT GEAR when you start down the grade!
Too high a gear puts additional stress on the service brakes to keep speeds under control.
Engine braking, regardless of whether equipped with a Jake or not, is an essential part of keeping the service brake temps manageable on long downgrades. Vehicles equipped with a Jake can usually descend using a higher gear than those who are not blessed with this additional safety device.
The old adage "Come down in the same gear you go up" still has merit, especially if you are unfamiliar with the terrain and do not have a Jake.
The extra time needed to descend a grade in a lower gear is well worth it compared to the potential for disaster by being in a hurry.
FWIW & HTH. . .
;)
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Hi all,
We just got back from a 5500 mile round trip to CA from MN. We went through some of the toughest ranges in this country, and while I have very little experience in the long term sense , this is my take on it.
I used both the off-on-off and the constant pressure methods.
I think that as I got a little more used to the grades I used the constant pressure technique more.
I am fortunate to have a four-spd with which to control my descent, lending to the constant pressure method.
But, there was a range in Wyo. (Bighorn Mountains, Hwy. 14A) which dropped 3600' in 10 miles (10% grade).
I think I used every bit of my three years driving exp. in the bus to get to the bottom of that hill. It just wouldn't quit. >:(
I did get to the bottom safely, and there was no real smoking of the brakes. It did take more than an hour though. ;D
Lessons learned:
Check your brakes before every trip, and often during.
The go down in same gear as you went up is a good rule.
I will be installing a jake system.
Driving techniques are not something you can learn from reading, unfortunately.(so get out there and practice!!!)
My $.02 worth
Devin
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Thank you Russ - you have reinforced the point I was about to make which is that kinetic energy rises as a function of the square of the velocity. What that means in english is that, if you are going twice as fast you have 4 times the energy. In other words, if you descend a grade at 60 MPH instead of 30 MPH you have to dissipate 4 times the heat through your brakes in order to slow to a stop. The only safe way down a hill is slowly. Jakes help but they don't work miracles. You can argue all week about stab braking vs. steady applications and it won't change the underlying physics which is not about dissipation of heat in the brake drums but rather about speed and its relation to energy. Go slow and it won't matter how you brake.
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Many loggers (the heaviest, steepest, hardest trucking) use windshield washers at each tandem position. They plumb the hose to dump on top of the drum (not in it) to cool the brakes coming down big, steep grades.
The brakes on our buses (especially the transits and those with tags) are bigger than on trucks. Also, most of us are not near the maximum gvw rating of the bus since we are not hauling people (I'm 5,000lbs from my gvw). With properly adjusted brakes (tighten down, then back off 1/4 turn) and a little common sense coming down grades, there shouldn't be a problem. The vast majority of buses still use drum brakes-just like what we all have now (maybe a very few with air discs).
I still advocate having Jake Brakes! In my opinion being able to descend a 6% grade without brakes at 60mph with the Jakes slowing the bus down, is almost miraculous. Good Luck, TomC
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Not trying to flame anyone, as I for one have no clue what I'm talking about! I only have 20+ yrs of commercial driving experience in which I have driven tow trucks (cleaning up wrecks), dump trucks, equipment haulers, Reefer Units (chicken hauler), and Buses. I have been coast to coast top to bottom many times and have crossed many if not all of the worst passes this great country has to offer! And I did it safely to be around to tell about it today! I always used the same gear down as I went up, with the occasional on-off----on----off method. The trick is to let the engine do the work while occasionally touching the brakes to help maintain that low speed desired! I agree with TomC 100% Jakes do make it a lot easier to come down in the proper gear with out touching the brakes at all in a bus! An 80,000+ lb tractor trailer still requires a little assistance from the brakes.
But as I said before the advice given to me by an "Old timer" has always stuck in my mind any time I'm driving in the mountains!
"You can go down many mountains, many times too slow, but you'll only go down one, one time too fast!"
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Ok, maybe a dumb question but........... should I pull the automatic trany down a gear when going down hill??
No on has made the distinction of a manual over an auto, so i just want to be sure. It just kept sounding like you guys were talking about manuals.
Chaz
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the same gear down as up is a bit dated........as with 450HP and higher engines some units can climb grades at much higher speeds while brake technology has not advanced at the same rate.
I have only found one grade where I would have liked a Jake.....the trans retarder didn't cut the mustard and it is a road most of you would have never been on.......I was being paid to drive there and was the victim of poor pre trip planning by my client
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Ok, maybe a dumb question but........... should I pull the automatic trany down a gear when going down hill??
No on has made the distinction of a manual over an auto, so i just want to be sure. It just kept sounding like you guys were talking about manuals.
Chaz
First off Chaz the only truely dumb question is the one not asked, until it's too late!
Second off when I say come down the hill in the same gear you went up in, it means just that! Auto, manual it doesn't matter if your automatic trans had to go down to 1st or 2nd to pull the hill then that is what you should use to descend the hill! FWIW
;D BK ;D
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Thanks Chas for asking the question about the auto trans.. This is my first automatic transmission. Tomas
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Keep in mind while I am slow typing this...many more good posts came. So here goes my 2 cents worth.
Snub braking and riding braking is two kinds of braking.
Snub braking is applying brake until speed is reducing about 5 mph and repeat after it gains 5 mph.
Brake riding is a steadily applied pedal pressure to maintain safe speed without “cooling” and “building up of compound” relief.
The reason “snub brake” is safer is 3 reasons:
1) Drum expands due to heat, about 0.010 inches per 100 F. At 600 F, a drum could grow by 0.060 inches. Multiply that by the mechanical advantage (leverage) between the slack adjuster and the cam, and you could need an extra half inch of brake stroke. The hotter the drum, the more extra stroke you’ll need. Also, if temperatures get too hot, the bond holding the friction material in the brake shoes starts to weaken, and the shoes become less effective. So by brake snubbing, it cool down drum some in-between braking.
2) Lining material is only good as long it below fading temperature. Shoe’s heat is being reduce while released to allow cooler ambient air enter gap & shoes.
3) Whenever apply brake produce wearing compound from shoe’s lining & drum. So by having off & on shoe contact to drum will release its compound to roll off before next braking. Otherwise it will build up hard spot on lining to cause lesser fiction and brake squealing later.
I would NEVER, NEVER ride with a so call truck driver that rides their brake going down hill. I learn these in early years of driving on truck farming. Had many close calls and it is avoidable by driving smart. It never fails after tried two difference type of braking. Snub braking keeps me in control every time.
Link about temperature of fading:
http://www.e-z.net/~ts/ts/Brakfade.htm
Caution to anyone who have purchase a used bus or vehicle. Please inspect drum’s surface for deep groove…my bus had about 1” wide groove with a new set of lining already on. I didn’t do the inspection thinking the seller (charter Bus Company) said it ok to drive 5000 miles trip. Yes I should know by the way of stopping power but only happen when I was in emergency. That when I learn that it was not good. It was after the trip home that I learned about deep grooves in both front drums. Then I learn why not happy the way it stop. Also make sure you have matching air cylinder assembly for left & right of each axle. Otherwise uneven braking. Mine was unmatched from charter company.
Bottom-line is Not to follow any vehicle that can stop quicker than yours. In other word stay off that truck’s lane or stay way, way back behind them. Or you may be victim of serious injury or death.
Another bottom-line is Never to gamble on yours brake stopping power whenever you are near border line of fading braking temperature. You can only tell when it starts smoking while drum is expanding larger and it usually already too late. So never mind what others are passing you…either they have ADS (disc brake) or they are gambling. Take your time going down hill even if it 5 mph while you’re ahead in the long run.
Link to CDL controlling speed: http://drivingrules.net/cdl/cdlsecb/b6speed.htm
About transmission…if youre driving on level hwy then have to go down hill always slow vehicle and shift to next lower range….then if it very steep like 7%...then shift to lower still and be careful not over rev your engine by snub braking till safer. BK quotes is ok if you are climbing same grade as if you go down. I know he mean well.
FWIW
Sojourn for Christ, Jerry
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Sojouner,
None of your reasons for 'snub' braking are valid. The facts simply are that, for the same time to descend a given hill, more heat is generated by 'snub' braking. The only reason for 'snub' braking is that it is more likely to distribute the heat to all brakes rather than concentrating it on the one(s) that are applied first. On the other hand all of your reasons are reasons for going slow enough. Simply slower is safer.
Regards
Jerry 4107 1120
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I love all you guys... I really do... But I am still going with the guy with the degree in Automotive Technology whose job it is to study truck crashes and figure out what caused them. We can say his reasons are invalid all day long, but he has teams and labs running tests to prove what he says. I need more than 'that is invalid' typed on a forum to make me see why I should ignore him and trust some typed words on the internet.
If all these things were invalid, why does the expert say otherwise, and why did every state change their CDL requirements? I'm not being a smartass. I just find it hard to believe that every expert is posting things as tested and proven fact that are 'invalid'. Please show me some tests that back it up. The guy started his article by saying 'This is the method that everyone always believed was right but now we have proven scientifically that it is wrong."
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Chaz,
We downshift our MC-8 with 8V71/740 automatic. I have found that if I downshift to 3rd and the hill we are going down is steep enough for the speed to build, the transmission will still shift into 4th to prevent over revving the engine. So, the technique we use is to downshift and use enough brake to keep engine RPM low enough to prevent shifting. Jack
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Read the article in this forum very carfully.
If I understand it correctly snub braking is preferred to constant braking because on a tractor trailer setup there is a good chance that the braking pressure between the tractor and trailer may not be balanced.
A bus is different because it is not swapping trailers. Does this mean that the brake system on a bus is more likely to be balanced? (maybe)
Testing and numbers don't lie, but the DOT may be following a wide average based more on tractor trailer rigs then looking at buses as a different animal. (was there a braking test done on buses?)
I am confused,,,, but will defer to the "low gear brake as necessary method."
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You see, that is the thing for me, zimtok. As a relatively new driver of buses, I am here to learn. Obviously there is more than one way to do anything.. Probably even more than one way to do it correctly. But never more than one way to do it best.
And I really am not trying to be an @$# here... But on the one hand, I have a degreed expert saying one thing, and then on the other, a guy is saying that all the testing is invalid and it has been proven scientifically. Now I know the expert has scientific testing, but I honestly want to see the other side scientific testing. This is a real search for knowledge. Not a prove someone right or wrong.
Also, there are two sides here saying the each way bleeds off heat better. They both can't be true.
Honestly, my gut tells me that fleet rigs probably have brakes tested more than a person's bus would... So again, even by what Jerry said, go with the one that works best in less than optimal conditions.
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Lets see some articles, test results etc for the Steady pressure.
I always try to have backup documentation when I pipe up in here and often post links to the same ( search tire ballancing)
I had loads of backup doc and the gentleman who said tire ballancing was poppy cock....could not come up with any
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Lets see some articles, test results etc for the Steady pressure.
I always try to have backup documentation when I pipe up in here and often post links to the same ( search tire ballancing)
I had loads of backup doc and the gentleman who said tire ballancing was poppy cock....could not come up with any
Yes Doug I have to agree you usually do have the documentation to back up what you say, and also usually provide links to it! I have to agree that it sure makes it easier to follow your train of thought (even though I don't always agree 100%), I have to give credit where due! I on the other hand usually don't take time to research/provide links to documentation on what I say/post as I usually speak from the School Of Hard Knocks (experience) which I have graduated from! I may not know much, but I have survived 20+ yrs of over the road driving experiences and have been just about everywhere in the US that you can drive too! (with Alaska being the one exception)
That being said I'll politely back out of a subject which I am truly under qualified to comment on!
;D BK ;D
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BK, you're on the same side with that edukated feller this time.
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I go away for a couple days and you guys.....
two parts to my post, some pi$$ing and a training example:
Pi$$ing:
One other poster mentioned the key factor:
What SPEED are we talking about?
No matter which Blessed House of the Mountain Descent you happen to be a member of...
The big issue when teaching either method is to keep the SPEED well under control, for many/most descents in the bus or a truck, meaning below the posted speed limits
Both Blessed Houses can agree to choose a lower gear which helps to maintain a certain lower SPEED
SPEED makes exponential heat, so the slower one goes, the less heat to be made in the brakes when controlling it. The faster one goes, great whallops of heat must be dealt with.
In litigious America.... if some government body advocated a certain driving technique which was flawed... and its use caused a death, or two.... You don't suppose that a court would have put a stop to this "snub braking" long ago, and awarded the plaintiff a huge sum?
As for balanced braking, unless you hook your brake lines up to gauges to check for plumbing functionality, and put the wheels on a brake dynometer to ensure mechanical functionaility, you have no way of knowing which end of your coach, or which side, or which ONE, is doing all your stopping.
I would bet that out of the membership of this board, there will be a couple of buses that do most of their stopping with the front brakes, the relay valve in the back having failed to apply the called for pressure to the brake chambers, or the foot valve failed to call. Yes the linkage moves, but how hard is it squeezing?
And then a whole bunch more of us have brake linings that were destroyed by the abuses of the previous owner, or ourselves, and they don't produce the proper friction when they are squeezed against the drums.
Way too much science and measurable facts are available, personal experience lacks control or measurement of the variables. And few, if any of us, are able to confirm that our ride is in tip top shape, gripping the road according to spec under all tires.
eh?
Training example:
MC8, 8V71 with HT740 auto tranny, 3.7 diff gear, NO Jake.
Downhill off Fancy Gap in Virginia, I77. some what? 5 miles of 5-6 % ?
Snub braking target is 45 mph.
3rd gear in auto tranny
used the brakes three times over that 5 miles to snub the speed down to 40 mph
At a higher target speed, or in a higher gear, the coach accelerates downhill faster after the brake application, requiring more frequent use of the brakes.
The trick is to keep lowering your target speed to a point, and a gear, where the coach only accelerates downhill lazily and requires little use of the brakes.
Best advice on here has been stated twice before, and paraphrased here:
You'll only go down too fast once.... take your time!
happy coaching!
buswarrior
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Buswarrior,
VERY WELL SAID. However we all should try to keep our equipment in the best shape possible. Even with 'snub' braking those brake issues you've mentioned will cause a, possibly great, difference in temperature of different wheels. Brake failures happen with 'snub' braking too. It's still a good idea to every now and then descend a long grade using the 'ride the brakes' technique then stop at the bottom and check the relative temperatures with that handy infrared thermometer. If only the front brakes are hot you'd best get that relay valve, or whatever the cause is, fixed. Likewise if the left is much hotter than the right on one axle you'd best find out why and fix it. To be safest we all need to go slow enough, have properly maintained TESTED equipment and use the 'snub technique'.
Regards
Jerry 4107 1120
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I have been reading this thread with much interest. No matter how good of a PM or current maintenance ones
has things can go south very quickly. BT more than once so I don't think I have anymore grace in this matter.
So along the same vain IS there anytime dynamiting the brakes is a proper choice?
Personally I have always looked for a soft bank.....not always available though!
A runaway is probably the scariest thing I have ever been through, something I hope nobody here
has to go through.......
Skip
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Just because some guy with the degree in Automotive Technology says it is so doesn't make it so. One can study books and accident reports all day and know nothing about braking heavy vehicles. My ole Grandpappy always told me to watch out for any guy who calls himself an expert.
Where is the documentation that shows a direct comparison of the two types was made under actual condition-lab results don't prove a thing?
Constant braking has worked for me both with an 80,000 lb 18 wheeler and my 4104, never have I even had my brakes get so hot they smoked or smelled, so there has to be pretty strong proof to get me to change.
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Chaz- I also have the V730 in my bus and use the shifter all the time. First to down shift as soon as I can, makes for smoother down shifts than to wait for the transmission.
I also downshift going down steep grades. I've been in 1st going 20-30mph on twisty mountain roads (Kern River to Bakersfield). You can use the lower 2 gears also, as long as you have a shift selector that says R-N-3-2-1. If you just have a F-N-R, you won't be able to down shift. A properly adjusted Allison will not allow the transmission to down shift until you're at the proper rpm-so you don't have to worry about over speeding the engine. Good Luck, TomC
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Hey Jerry or anyone else that wants to prove their position,
How about a little test? Make a run down a hill using constant pressure braking at say 40mph. Then make the same run using snub braking at 45 down to 35mph for an average speed of 40. Take some temp readings after each one. You might have to adjust the speeds to fit the hill and your bus but you get the picture. So come on, lets have a real world test or two!
Without an application pressure gauge it is hard to tell what is happening. Old bus has one. 4107 does not yet. ???
Don't put to much weight on government info/tests. They are written for the lowest common denominator, and I do mean LOW. :o Example, the CDL handbooks and test suggest that a fully loaded truck will stop faster than an empty one. Please don't start a debate on this. I don't have 2 million miles with an 18 wheeler, but I do have enough to know that when it weighs 80k that it takes more room to stop than when it is 30K. And yes I understand the control issues of brakes locking easier when empty. If I have to bomb the brakes and there is a big rig in my mirrors, I'm hoping he is empty and has half a brain.
Meaningless side note. It always amazes me when people that would say government in general is inept at most things site them as the authority to support an argument. ;D
Want to muddy the waters even more? How does each braking style affect buses with trailers/toads with various braking systems? Are your auxiliary vehicles brakes balanced with the bus brakes? Is one carrying more of the braking load? Should you change your braking style with toad?
If you start down the hill at a reasonable speed with good brakes and use what ever braking style you like there should be no drama. If there is, the only solution is going slower.
Don 4107
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Don
The tests you propose are good. I don't know when or where but I'll probably try them. They are what the U of M allegedly did. The reccomended snub braking technique only uses a 5 MPh variation, you've proposed 10, I believe that is enough to clearly show that snub braking actually produces HOTTER brakes if the vehicle has well balanced brakes. It doesn't change the fact that if your brakes get too hot you were going too fast.
Regards
Jerry 41`07 1120
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OK, this sounds like a good idea for an episode of "Mythbusters".
Two similar bus/trucks go down a hill, using each braking method, and have drum temps measured once at the bottom.
Anyone have an in to "Mythbusters"?
Jay
87 SaftLiner
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Thanx Jack and Tom!!! I have yet to do the "mountains", so I really appreciate the insight for my automatic.
Just curious......... If I'm out and about, and not really knowing the terrain, what % or sign or ?? do I watch for, so as to know when I have to be implimenting all this new found knowledge?? Here in Indiana, there are a few decent sized hills, but not too many. But I do plan to go to Bristol for the spring race! (I-75 south, 25E, etc.) ;D
Thanx guys,
chaz
p.s. good thought Jay!!
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Chaz -
The easiest is to simply pay attention to the signs posted for truckers. Usually they're yellow, but sometimes orange or white, all with black lettering. Keep w/in those guidelines and you'll be a happy (and safe!) camper.
FWIW & HTH. . .
;)
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In my opinion-and this from 1.3 million miles of driving over 21 years of owner/operator (my own truck). When going down ANY kind of long grade, you should be in full control. That translates into the fact that you should only have to use a very light brake pedal pressure to keep the truck at speed-this involves being in the right gear going the right speed-whether or not you have a Jake brake. If you smoke the brakes-you're going to fast! I can go down the Grapevine without touching the brakes at 60mph with just the Jakes. If I didn't have Jakes, I'd be going down the hill in a lower gear with the trucks at 35mph-but still under control and not smoking the brakes. If you have to constantly have to drag your brakes going down the hill, you're going to fast.
If you're going down the hill at the correct speed in the right gear, you should be just barely accelerating so that you go a minute or two without brakes, then a very light application of brakes for about 20 seconds will bring you back down to speed. With this technique, you can go down a 100 mile hill and not overheat the brakes (I'd like to see that grade!). And this from a trucker that got 350,000 miles on a set of brakes. My truck has 1.2 million miles on it. I did a brake job at 355,000 miles, then at 775,000 miles then at 1,050,000 miles. Now at 1.2 million miles they still have about 20% brakes left. With the size of the brakes on the buses and our relatively light loads, if you smoke the brakes or can smell them, you need to rethink you're braking techniques. Good Luck, TomC
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Chaz,
You're right that Ohio and Indiana don't have real problem hills, at least that I've found. But Kentucky, Tennessee and especially North Carolina have some pretty bad ones From my experiences in Wash Oregon California, Utah,Idaho, Colorado the nasty hills are very well marked with all kinds of warning signs, much more so than in the eastern states. Any time you have a 5% or more grade lasting 1/2 mile or more or sharp curves with climbs and descents, it's time to slow down, gear down and be extra cautious.
Regards
Jerry 4107 1120
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Thanx guys.
I'm hip to the signs, Russ. Just wasn't sure if there was anything else. Thanx.
Tom, Do you find that they are ALWAYS marked well enough to give plenty of notice?
Jerry, thanx for the more specifics. I was kinda looking for a "rule of thumb" like that.
'preciate it,
Chaz
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Do you find that they are ALWAYS marked well enough to give plenty of notice?
Hi Chaz,
No they are not always marked, especially on secondary highways. However, the interstates are usually marked pretty good.
-Brian
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I propose that; all other things being equal (properly adjusted brakes,distance,weight,etc.), the amount of 'total' heat produced by the brakes is the same with continuous brake pressure or brake stabbing (i.e.- your stopping the same weight over a certain distance). The biggest difference would be your speed - the higher your speed the more air cooling is provided to the brakes,hubs,etc., slowing the bus down too slow will decrease the air cooling - So whether you're stabbing or applying continuous light pressure you're creating the same heat, though at different rates - how you're going to deal with the heat is most important question - Jakes allow you to remove most of the brake heat from the equation by transfering that heat to the mill, and that's how I choose to deal with the heat.
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Niles,
You are on absolutely sound ground with you proposal. If the speed is the same at the top and bottom and the vehicle's mass is the same the energy that must be lost, as heat, is the difference in potential energy at the top and bottom of the hill. It simply doesn't matter how, when or where the heat was dissipated. This is because of a very fundamental law of physics called the conservation of energy. Going slower down the hill allows more time to dissipate the energy. Dissipating most of it through he engine means less for the brakes to deal with. 'Snub' braking gives some assurance that the brakes share the energy more equally, that's it's only virtue. Continuous light braking means that the brakes are dissipating the energy all the time rather than in bursts which will average to the same total amount of energy but must have a higher peak rate of energy flow to make up for the time when no energy flow is occurring. The only way to get a higher energy flow through the brakes is by them being hotter.
Regards
Jerry 4107 1120
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I think I'll just stay in Florida. As long as I avoid Mount Dora, should be OK.
Len
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This is an excellent thread!!
It's good to be able to benefit from all the experience and knowledge represented here.
One thing that has not been mentioned is the relationship between speed and resistance. The faster a vehicle goes the more resistance it encounters, both from air and rolling (frictional) resistance. This translates into some amount of braking going downhill or less fuel mileage on flats. If you are on a road that would allow unlimited speed, you could safely not use any brakes, ASSUMING YOU WOULD NOT BE REQUIRED TO STOP. At some point, the resistance would overcome the forces of gravity on the incline and speed would level off. This is why an empty truck or bus can safely descend faster than a loaded one. Not only does it have more braking power per pound, but it also has less gravitational pull down the incline.
This is just another reason to do any tests using the same grade, and the same equipment in order to get reliable results.
Just another variable in the mix ...... ;D ;D
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okieman,
What you say may be true about a bus but it is not about a big truck.
Big truck springs and brakes are designed for max braking when loaded. An empty 18 wheeler will skip the tires with full brake application unless it has some kind of automatic brake system. Just notice all the black skip marks on the highway, this is the cause of them.
Strange as it may seem, a loaded truck will brake better than an empty one.
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Wow....looks like, "What we have here is a failure to communicate!!!" (that's supposed to be a joke from Cool Hand Luke) :) :) What I used to do is select the proper road gear and the appropriate very low road speed, then turn on the Jake and...if everyting else was correct, never had to touch the brakes at all..all the way down. BROOOMMMMMMMMM......sounded soosss b.t.."in! :) :)
Automatic transmission retarders have their place, but sometimes (nearly always?) may not survive coming down our endless Western Interstate grades. Seems the tranny cooling system is overwhelmed by the heat generated by making it work as a service brake system. The result may be a severely cooked (ruined!) automatic transmission. $Ouch$ :) :)
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Nice to know HB. When time comes, that would be or could have been an option.
Chaz
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The trick with an automatic transmission and keeping its retarder from cooking the internals is to also select a lower gear that gives high engine RPM.
High RPM lets the cooling system deal more effectively with the massive heat the tranny is trying to dump into it.
On the unlimited downhill run, years ago, training films from the Colarado State Troopers suggested that a run-away 18 wheeler could easily attain 110 to 120 miles an hour on some of the interstate descents.
I assume run-away means the brakes are gone, and the novice driver attempted a downshift, thus losing all engine braking, when he couldn't get it back into any gear.
As noted, great ride, as long as there isn't a bend at the bottom....!!
happy coaching!
buswarrior
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BW - Colorado has plenty of Runaway ramps, and to quote a popular comedian, THEY USE 'EM.
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Gus
The thrust of my post was frictional resistance; however, I did make this statement:
"This is why an empty truck or bus can safely descend faster than a loaded one."
Are you saying a loaded truck can safely descend a grade at the same speed as an empty one?
Also, the "black skip marks" are left when a driver applies the brakes excessively while stopping. The trailer wheels will lock up because that set of axles have less traction empty then the tandem or steering axles. This situation can usually be overcome with proper driving techniques. There were very few "skip marks" left on the highway 40 years ago when we had a better educated (in driving) and more conscientious driver pool.
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We shouldn't lose sight of the fact that whatever technique is used as far as the brake application goes, the CORRECT technique requires us to be in a low enough gear that almost no braking is required anyway. Those who get to the bottom with smoking brakes maybe forgot that.
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Thanks tonylee for the idea jostle, try this on for size:
Remember, the point is to be descending slowly enough that the engine, in a lower gear, is able to, for the most part, prevent the coach from accelerating down the hill, with only a small amount of infrequent brake application.
The goal is little use of the brakes. Choose a speed and gear to accomplish this.
Remember folks with experience, we gotta get it all in there in a way that the first timer gets the point without having to find out missing bits the hard way!
happy coaching!
buswarrior
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Tom,
You probably mistyped your third sentence but I think I know what you mean.
Speed makes no difference whether loaded or empty if it is safe
Stopping is the problem. I was talking about braking.
There is more friction in a loaded truck than an empty one.
Air resistance is the same for both.
There were probably more skips on older trucks because most didn't have front wheel brakes at all. I remember being instructed by an old timer to always apply trailer brakes first. A sure way to get passed by your trailer!
Skip marks are caused by all kinds of things, not just trailers. Driving without a trailer or with an unbalanced load can cause skips on any axle. The tractor rear will skip if the trailer is empty.
It usually isn't the front axle that skips because the load shifts to the front upon braking.
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Gus,
I did mistype the third sentence. Thanks! I fixed it.
"There were probably more skips on older trucks because most didn't have front wheel brakes at all."
I would disagree with that but I am not going to argue about it.
"Skip marks are caused by all kinds of things, not just trailers. Driving without a trailer or with an unbalanced load can cause skips on any axle. The tractor rear will skip if the trailer is empty."
I agree. They can also be caused by braking or accelerating over railroad tracks, bridge joints, or other uneven pavement. That bad habit was a surefire way to get fired when I was driving. But, that was a long time ago in a far away land. My kids say I am living in the past and they are probably right. It is, however, a nice place to visit.. ;D
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My Conclusion,
I think we all learned quite a bit about braking in this thread.
What I came away with from all your posts is to have all this info under my belt and use what is most comfortable
for me. And, most important, judge your speed for the grade your descending on.
This wealth of knowledge alone will better prepair me for my next decent.
Thanks All...
Nick-
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Another point to remember with a stick is to START OUT IN THE LOWER GEAR. If you get going a little too fast down hill, and are near max rpm, it can be difficult if not impossible to down shift. If you miss a shift and cannot get it completely stopped with the brakes, it's going to be a bad day.
Len
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No matter what method you use to come down a hill (you could also use an anchor or Fred Flintstone's way) the bottom line is that you stay under control, at or under the speed limit, and reach the bottom of the hill relaxed without having to pry your hands off the steering wheel or go change your shorts. Good Luck, TomC
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I hate getting old and demented! What I MEANT to say is "What we have here is a failure to communabrake"! He...he...he...! :) :) :) Broommmmmmmm.....!!
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I heard on the radio last nite that a truck coming down from shaver lake with the driver riding the brakes got them to hot and at the bottom of the hill the right rear brake came apart and started a 160 acre froest fire. Don't have any other news. don't know if he was loaded or empty. Maybe R.J has some other info on it.
Don
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I know this one thing for sure, don't go any faster up a hill than you can go down. I have no problem taking it easy and letting the engine do the work. If I'm slow, so what. If other big rigs pass me, I don't care. I am in for the journey not how fast I can get there. I don't care about hot rodding the motor to make it fly, cause you gotta have the bakes to stop it. Don't get me wrong I like drag racing, but they have a parachute, I don't.
It all boils down to one thing, drive safe at any speed. Only go as fast as you feel comfortable with when having to stop suddenly, for that idot in front of you when he slams on the brakes after he cruised by at lightening speed because he thinks you can stop just as fast. I don't know about you but it involves my life and the dear person sitting next to me, let alone others on the road.
It just means common sense, and not all have that! :'(
Paul
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Shaver lake hill is a nasty one with a big curve at the bottom. About an 8% grade. Good Luck, TomC
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Someone mentioned people waving at them with 1 finger. Gee, I thought they were telling me I was number 1! You would rather spend more time getting to the bottom. The other people that get upset are not the ones that pay for the repairs to your bus from wearing out parts. Jack
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On the note on being told you're number one- I have two sayings that keep me from getting balistic from driving Los Angeles freeways everyday. First- if someone cuts me off, I just say to myself "is this going to make any difference at the end of the day?" Then if I get the number one middle finger, I just figure I won. Keeps the blood pressure down. Good Luck, TomC
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I just give 'em the peace sign or an OK sign and a big smile. I think it pisses 'em off even more.
Don & Sheila
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I just blow them a kiss and mouth "I Love You". Drives them crazy :D
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Someone mentioned people waving at them with 1 finger. Gee, I thought they were telling me I was number 1! You would rather spend more time getting to the bottom. The other people that get upset are not the ones that pay for the repairs to your bus from wearing out parts. Jack
Jack back when I was a dumb ol' hick from the hills drivin' a big ol' purty large car with all kinds of chrome, stainless, chicken lights, and 10" straight stacks, I figured out that it wasn't a # 1 sign but rather a NEW JERSEY SALUTE, because everywhere I went and everything I did there they were giving saluting me with that one finger! Well I started paying attention and noticed they just didn't do it to me, but almost everybody! So that's how I figured out it was a salute because everybody can't be # 1 !
But anyways I found that if ya start bouncin' up and down and wav'n back at them (using all4 fingers & yer thumb), while just smile'n from ear to ear! It just drives the crazy that they didn't make ya mad, and that they think yer ignorant as they are, to be act'n a fool instead of gett'n all fired up and rasing yer blood pressure fer nut'n! JMHO FWIW ;D BK ;D
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I have a co-worker who does something to really tick off those who give others "the finger", or when a driver does something really dumb (like cut him off).
He makes eye-contact and makes sure they see that he gives them a "tumbs down" all while shaking his head side to side and mouthing the word "no". I've been in a car with him when he did this to a lady driving a Mercedes, and she just crouched in her seat and made like "a hole in the asphalt" after that.
I'm sure that others might not respond very well to a dissapproving vote on their driving, but it's better than swerving to run them off the road... :o
My two cents on the braking topic is similar to that of my performance driving knowledge - forced-air cooling the brakes (as I believe Chaz had suggested) is a good idea, so long as the incoming air doesn't have a lot of debris/contaminents. Engine braking is easiest for speed control (i.e. get in the right gear for the hill and your rig's weight and let the centrifugal/pumping losses of the engine drag down the speed of the rig). When "stock" engine braking is not enough, a supplemental engine braking system like a Jake will increase the pumping losses enough to not need to touch the service brakes (YMMV) - heat here isn't an issue (and I think that most will agree that on a 2-stroke, the engine will cool down quite a bit while the Jakes are running due to the lack of combustion on the cylinders).
Where Jakes aren't allowed or don't fit (due to regional restrictions [I'm in Ohio now and I see a lot of "No Engine Brake" signs around] or engine height clearance issues, since Jakes need taller valve covers) and there's extra drive-train length space available, a transmission retarder might be the right ticket (or you might have one on your tranny already) - caution should be used to ensure that the tranny fluid doesn't boil (transmission retarders work by restricting the flow of fluid which puts the fluid under imense pressure - creating a lot of heat), the heat in the tranny fluid needs to be rejected to the atmosphere to avoid build-up, so on heavy rigs or those with small fluid-to-air exchangers (and I think there are even some which exchange heat with the engine) - this may only be good for a short while, so "careful" use should still be the name of the game. A temperature gauge on the tranny fluid inlet should help manage the heat within the tranny.
For those who are using transmissions where retarders are not feasable, Jakes are hard to find, or concern for shaft breakage is a design consideration - a Telma is probably the ticket. A "Focal" model retarder can be mounted right to the differential's pinion input, and only requires electrical power to run. Again, caution should be used in the design of a Telma installation (this is why Telmas are supposed to be installed by authorized installers/dealers) because the electrical system must be able to sustain the draw of a full-load Telma (up to 400Amps in some installations), and the heat which is rejected by the Telma must go somewhere "safely" (i.e. it must be kept clear of wires, air lines, fuel lines, etc.).
After that, one can consider retro-rockets and parachutes to slow you down - but if you need to resort to this extreme, just give me a call before you hit the road so I can get off it ;D.
As an asside, with automatic transmissions and engine/jake braking one must ensure that the tranny's torque converter is in "lockup" or the engine resistance will be lost without the direct mechanical connection to the engine (a torque converter uses fluid resistance to rotate the transmission relative to the engine when the engine "turbine" is rotating faster than the transmission "turbine", when the inverse is the case, the converter resistance is lower so the trany turbine can spin much faster than the engine turbine - letting the rig go down hill faster without much of the rotational energy getting to the engine. A lockup clutch connects the engine turbine to the tranny turbine and the rotational energy can go both ways (engine to transmission or transmission to engine). I believe there was an article by Brian Diehl on how to force this for an Allison HT754 transmission on this board, and he may still have the web page on this topic up on his website. On my first trip, I found that downshifting out of "drive" into one of the numbered gears, kept the tranny in lockup all the way down to 15MPH (YMMV). If you can hear your prime mover while driving, a transmission in lockup should maintain roughly the RPMs when you reduce your pressure on the accelerator - while a transmission out of lockup should have the engine RPMs drop off sharply with less throttle (causing a coast).
I won't comment on the braking method that anyone should use, I personally use the pumping but this is due to my track time in cars (where a constant pressure may end up with locked up wheels, whereas a "pulse" or "cadence" braking would allow wheels which had locked up a chance to re-gain traction and help keep the vehicle track correct). With ABS, this isn't much of a concern - but since most of our old rigs don't have ABS, it's a point to bring up (if you're used to cadence braking you're more likely to use it correctly in an emergency).
Cheers!
-Tim
P.S. My ideal system would include both a Telma and Jakes, with the option to pick which or both should be used in a specific region (4-position switch Off-Jake-Telma-Both for selection), with both a separate pedal for retarder control and an air/retarder brake pedal to control the level of retarding power (with modern PWM tecniques, we can get more than a 2-to-4-step level control on electrically controlled retarders, now we can get more than 32 steps for better control). -T
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Skid marks deserve a few words. Skid marks are warning signs to a professional driver. If you see skid marks someone else has had a problem here. Take a good look around, you may need to slow down. If you see alot of skid marks you are in a danger zone.
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I noticed on our bus hunting trip last year that when close to any town on I5 in SoCal it was hard to go more than 100 yards without seeing skid marks . Also could not help but notice that many of them were dual wheel marks.........
Don 4107