BCM Community
Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: Jcparmley on October 18, 2020, 01:47:03 PM
-
I just bought a 20kw PowerTech Gen Used. I have been reading on the best way to install it in my MCI 102DL3 coach. Of course I want to build a quiet box. My plan is to remote mount the radiator in the old AC bay. I plan to also pipe the exhaust to the roof. My question is how to bring air through the quiet box over the gen and vent it outside without defeating the "soundproofness". I found pics of a gentleman making his Gen compartment on another site. I was planing on mimicking his build. Check out the pics and tell me what you think will work and not work. Thanks
-
More pics.
-
More pics
-
Some final pics
-
Openings have to go around corners to suppress sound.
Creating a series of switchback cavities, with enough cross section to satisfy the particular air flow needs of the equipment is the challenge.
Sound deadening material lining the switchback takes all the bounce out, and silence will be lovely.
Switchback cavities consume space, but the silence of operation will make you forget soon enough...
Happy coaching!
Buswarrior
-
Put a shroud on the squirrel cage that matches up to the radiator so you get the maximum air flow through the radiator. I used sheetmetal on the fan and a rubber edge against the radiator so as not to damage it from vibration. I see that you have it perpendicular to the center line of the bus. I had to rotate mine because when we were parked it worked fine BUT when we hit highway speeds the fan (by the way my fan draws approx 7.5 amps) could not keep the generator cool. I'm guessing the fan could not push the air out but I don't know. I just turned the radiator and fan 90 degrees (it blows towards the back of the bus now and really has only a small area to vent out of) and all was well.
HTH
Melbo
-
If that's in the bay where the a/c used to be, aren't you pushing air in the opposite direction the factory did? Not saying it won't work, but perhaps there was a reason the factory did it the way they did which has something to do with cooling efficiency, low pressure zones, etc.
My thought is that you might find there was a reason the factory sucked air in the side and blew it out the floor. If so, it wouldn't be that difficult to turn the squirrel fan around and follow the same air flow direction the factory did.
Otherwise, that's a great looking install and I'm jealous at how clean it looks.
-
Are you using those little airbags for mounts on your generator?
-
Are you using those little airbags for mounts on your generator?
I would like to use the air bag mounts but PowerTech wants over two hundred dollars a piece. Anyone know if you can get them cheaper somewhere?
-
http://forum.prevostownersgroup.com/archive/index.php/t-6209.html
I know this is putting the cart before the horse, but may come in handy soon.
-
Interesting thread. I wonder if the air bags are the best type of isolation.
http://forum.prevostownersgroup.com/archive/index.php/t-6209.html
I know this is putting the cart before the horse, but may come in handy soon.
-
Quite common on Prevost Marathons. My nephews 92 has them. He mentuoned he started the generator and there was quite a bit of vibration till they inflated. 17 kw Martin. Other Owners mention them on Prevost forums.
-
My generator "doghouse" was a little more ghetto (no fancy welding involved or slideouts), but it does a good job of soundproofing. My biggest mistake was to make the air cavities too small in order to make everything fit (I put the radiator in the same bay). It's hard to make things bigger, later, that's for sure.
Using any sort of shock absorber (such as rubber feet) for the generator and using sound deadening plywood (it's dense plywood with an internal lead liner) combined with reflecting insulation worked out well. I wish I had made more room and more plumbing for a better muffler, that's the biggest source of noise at this point, so that's a future project.
Pics:
http://bus.getdave.com/Album/Electrical/Generator/
-
Hi Dave
Does your setup kill most of the noise? What do you mean when you suggest you would do something different with the exhaust? You also mention the intake. Is it too small? Not enough air flow? Does your gender overheat?
My generator "doghouse" was a little more ghetto (no fancy welding involved or slideouts), but it does a good job of soundproofing. My biggest mistake was to make the air cavities too small in order to make everything fit (I put the radiator in the same bay). It's hard to make things bigger, later, that's for sure.
Using any sort of shock absorber (such as rubber feet) for the generator and using sound deadening plywood (it's dense plywood with an internal lead liner) combined with reflecting insulation worked out well. I wish I had made more room and more plumbing for a better muffler, that's the biggest source of noise at this point, so that's a future project.
Pics:
http://bus.getdave.com/Album/Electrical/Generator/
-
Hi Dave
Is it too small? Not enough? Does your gender overheat?
LOL! Sorry! ;D ;D ;)
-
That is hilarious! I can't believe I wrote that and didn't catch it. Must have been too much wine.
LOL! Sorry! ;D ;D ;)
-
;D ;D ;)
-
heres the part number for the airbags Nephew says he can get them around 80 bucks each.
-
https://www.ebay.com/itm/FIRESTONE-W01-358-7001-W013587001-BRAND-NEW-/392717297261?redirect=mobile
A little checking with that number may find a better price. Was also available on Amazon, but not presently. Watch air pressure. Use regulator. Go to Firestone info for pressure. Don't inflate unloaded.
-
Do those have lateral stability?
Do they hold air even when the bus is not aired up? Would hate to have to run the bus just to be able to air up the generator air bags.
Interesting idea though, if they add enough isolation to make worth the effort.
-
Call marathon. 😙 they should stay up fine if they don't have any leaks, just like airbags.
-
Call marathon. 😙 they should stay up fine if they don't have any leaks, just like airbags.
They do those 2 ways,tied into the bus air system with a check valve or manually inflate each one they hold air for months you can find those at truck wrecking yards some trucks use those for cab mounts and seats lol I forgot what truck now
-
Do those have lateral stability?
Do they hold air even when the bus is not aired up? Would hate to have to run the bus just to be able to air up the generator air bags.
Interesting idea though, if they add enough isolation to make worth the effort.
Absolutely worth the effort, no more mechanical vibration and related noise transmitted to the chassis.
A good piece of braided flex pipe is part of the install for the exhaust
The little bags have a rating, stay under it, no one has ever indicated a lateral stability problem in all the years i've been playing this game.
Air integrity is the same as a tire. It will only leak when something gets old...
Happy coaching!
Buswarrior
-
A little more on air cushion settings on Prevost group.
http://forum.prevostownersgroup.com/archive/index.php/t-6209.html
-
Very interested in air springs for my generator also!!!
This part is made by a number of manufactures:
- Firestone W01-358-7001
- Numatics ASNS11-1-1
- Continental FS-50-5-ci
- Goodyear 1B5-500
Other interesting URL's:
https://www.mrostop.com/w01-358-7001-firestone-single-convoluted-air-spring (https://www.mrostop.com/w01-358-7001-firestone-single-convoluted-air-spring)
https://www.mrostop.com/fs-50-5-ci-1_4-npt-ca-continental-bellows-style-single-convoluted-air-spring (https://www.mrostop.com/fs-50-5-ci-1_4-npt-ca-continental-bellows-style-single-convoluted-air-spring)
https://www.phoenixvibrationcontrols.com/wp-content/uploads/2017/08/FS-50-5-CI.pdf (https://www.phoenixvibrationcontrols.com/wp-content/uploads/2017/08/FS-50-5-CI.pdf)
https://www.asco.com/ASCO%20Asset%20Library/numatics-air-bellows-catalog.pdf (https://www.asco.com/ASCO%20Asset%20Library/numatics-air-bellows-catalog.pdf)
https://www.asco.com/ASCO%20Asset%20Library/numatics-airbellows-asns11-1-1-catalog.pdf (https://www.asco.com/ASCO%20Asset%20Library/numatics-airbellows-asns11-1-1-catalog.pdf)
In my case the following part looks very, very interesting:
(https://www.crystalpoint.com/cpdownloads/public/outgoing/Freds/airbagmount3.jpg)
https://www.radwell.com/en-US/Buy/FIRESTONE/FIRESTONE/W02-358-3005 (https://www.radwell.com/en-US/Buy/FIRESTONE/FIRESTONE/W02-358-3005)
https://www.mrostop.com/w02-358-3005-firestone-reversible-sleeve-air-spring?utm_source=octopart&utm_medium=cpc&utm_campaign=octopart%20Shopping (https://www.mrostop.com/w02-358-3005-firestone-reversible-sleeve-air-spring?utm_source=octopart&utm_medium=cpc&utm_campaign=octopart%20Shopping)
-
Do those have lateral stability?
Do they hold air even when the bus is not aired up? Would hate to have to run the bus just to be able to air up the generator air bags.
Interesting idea though, if they add enough isolation to make worth the effort.
I don't think so, some installations that I have seen have metal cage with a air gap to stop movement as a backup.
-
I also have a 20KW PowerTech generator.
Mounted differently, it shares the driver’s side first bay with the Mini Split.
It is mounted on a Slide out rack and uses small airbags, the slide out mount and Airbags were with it when I got it.
The Radiator Fan came configured so that it blows out, I cut some holes in the Bay door, the one in front of the generator has the same square inches as the Radiator, There are also holes cut in the floor under the Generator head for incoming air.
Everything works great.
The problem I am experiencing is when I am driving with the Baydoor closed after about 5 miles at interstate speeds the temperature starts to go up and the high heat sensor will kick the Generator off, approx. 210 – 215 degrees.
If I drive with the bay door open, no issues at all (except people pulling up beside me and telling me the Bay door is open)
I noticed in your first pictures a Blower, I am thinking if I have one of those pulling air up through the floor it will create a positive pressure inside the generator bay and overcome the pressure gradient created on the outside of the door at interstate speeds.
Could you tell me where you got that blower and the CFM if you know it?
(http://www.peterbylt.com/mci96a3/generator1.jpg)
(http://www.peterbylt.com/mci96a3/generator3.jpg)
(http://www.peterbylt.com/mci96a3/generator2.jpg)
Peter
-
Not surprised there is a problem. Need the air to flow through somehow. And radiator sealed against air inlet so air doesnt go around radiator instead of going through.
-
I was there this evening when he installed 4 new generator air bags. Tag says the old ones were 1992, except one the prev. owner replaced a few years ago. While there, looked over generator. On the exhaust at the engine, there is a circular container about 12 to 14 inches in diameter and about 3" thick. It is made of cast iron. On one side, the exhaust comes out via insulated flex pipe and terminates back of compartment to black iron pipe that goes up through roof. Little flapper on outlet. No noise at exhaust. Btw, the engine has a little turbocharger. No radiator in compartment, so must plumb to engine radiator. Is on a slide out. Engine sits in compartment just behind left front wheel and is parallel to coach.
-
Those are all great points to consider. I've drawn up a sketch of what might work. Let me know what you think. The first bay would have the squirrel cage fan pulling in fresh air (from the side through the door or through the floor?) through the radiator. The air would go past a few switch backs with sound deadening material. It would then enter the generator compartment, which will also be lined with deadening material. The air would then exit the generator compartment through a switch back and into what is now the AC bay and back to fresh air. Would such a design work with keeping the gen cool and also keep it silent?
Openings have to go around corners to suppress sound.
Creating a series of switchback cavities, with enough cross section to satisfy the particular air flow needs of the equipment is the challenge.
Sound deadening material lining the switchback takes all the bounce out, and silence will be lovely.
Switchback cavities consume space, but the silence of operation will make you forget soon enough...
Happy coaching!
Buswarrior
-
It is all in the space you build into the corners. Every dimension of every corner has to be chosen respecting the cross section/area that is required to allow enough air to pass by.
You don't want to reduce your 6 lane road to a single lane going around the corner...
The whole thing, fans included, have to be inside of the switchbacks. Fan noise is a shocking amount of the noise coming from a generator.
Happy coaching!
Buswarrior
-
As far as the design, what are your thoughts? Should the radiator fan pull from the below or from the side?
-
JC if you are going to the trouble of those switchbacks it isn't much more trouble to add tuned quarter wave cavities and those can have a profound effect on sound levels. Lincoln uses them in their engine intakes. All you need to know is how big to make them, and to nail it down you should make friends with an audiophile. Often the sound man at a church is such a person. He may have a meter which samples the sound spectrum and can tell you the frequencies that are loudest. From the center frequency you can determine the quarter wave length and from that include trap(s) in your design. If you cancel out just the loudest couple of bands the rest should be fairly easy.
Jim
-
Line an intake box with lead or use a car muffler. Go look at a Prevost xl Marathon coach and see how they did it. The compartment intake goes through some sort of baffle on end of compartment and exhaust is directed into a cast iron circular chamber.
-
Hi Jim
I'm not sure what a "tuned quarter wave cavities" are. Could you be more specific? The suggestion on using a meter is a great one. Thanks
JC if you are going to the trouble of those switchbacks it isn't much more trouble to add tuned quarter wave cavities and those can have a profound effect on sound levels. Lincoln uses them in their engine intakes. All you need to know is how big to make them, and to nail it down you should make friends with an audiophile. Often the sound man at a church is such a person. He may have a meter which samples the sound spectrum and can tell you the frequencies that are loudest. From the center frequency you can determine the quarter wave length and from that include trap(s) in your design. If you cancel out just the loudest couple of bands the rest should be fairly easy.
Jim
-
JC, I think I explained it in an earlier post maybe in this thread but it's the old idea that opposing waves will cancell each other out. So what you do is make a dead end that is 1/4 wave in length at the point where the air path makes a bend. In other words it is an extension beyond the air path. The dead end reflects the wave back and by the time it gets back to the junction it is 180 degrees out of phase and cancels the incoming wave.
Now if it worked perfectly it would completely cancel every other wave in theory at least. Even that is going to do a lot more than just square corners. But I suspect that with some damping it might do much better.
Jim
-
So let's think about this. If you have a pulse and you use it to cancel the next one what does that do to the first pulse? Doesn't it cancel it too? Seems it would. Probably depends on how the exit feed was constructed. I don't know all the answers here but certainly someone does and I'm sure you can find it on the web. I do personally know at least one guy who built wave traps to get rid of a drone in his exhaust and said it worked very well. He simply attached it using a "T"and a 90 so it ran along the pipe. Personally I think I would use a tall narrow slot right at the cancellation point with enough throat area to handle the airflow without it having to speed up too much. It might be an advantage to angle it towards the reflecting wall or it might not.
Now one thing you can do is play different frequency tones from a google search and it should be fairly easy to match the sounds from your genset. My guess, it'll be somewhere not too far from 200 hz that you hear the loudest noise. The wavelength of 200 hz is 150 cm or 59", so 1/4 wave for 200 hz would be 14-3/4". Well within reach for this construction.
BTW, all this info is an easy google search away.
Jim
-
So I think I understand better. Basically I would measure the generators frequency and find out at what hertz it's the loudest. Then I run the equation to see how many inches is the quarter wave. Then I build the box with the switchback however many inches the quarter wave equation dictates. Line the switchback with some acoustical foam and in theory it should cancel out most to the sound but not restrict air flow. Am I understanding the concept, or am I way off?
I found this pic that I thought was interesting how the do the air intake and exit. What are your thoughts?
So let's think about this. If you have a pulse and you use it to cancel the next one what does that do to the first pulse? Doesn't it cancel it too? Seems it would. Probably depends on how the exit feed was constructed. I don't know all the answers here but certainly someone does and I'm sure you can find it on the web. I do personally know at least one guy who built wave traps to get rid of a drone in his exhaust and said it worked very well. He simply attached it using a "T"and a 90 so it ran along the pipe. Personally I think I would use a tall narrow slot right at the cancellation point with enough throat area to handle the airflow without it having to speed up too much. It might be an advantage to angle it towards the reflecting wall or it might not.
Now one thing you can do is play different frequency tones from a google search and it should be fairly easy to match the sounds from your genset. My guess, it'll be somewhere not too far from 200 hz that you hear the loudest noise. The wavelength of 200 hz is 150 cm or 59", so 1/4 wave for 200 hz would be 14-3/4". Well within reach for this construction.
BTW, all this info is an easy google search away.
Jim
-
Is that a correct description?
So I think I understand better. Basically I would measure the generators frequency and find out at what hertz it's the loudest. Then I run the equation to see how many inches is the quarter wave. Then I build the box with the switchback however many inches the quarter wave equation dictates. Line the switchback with some acoustical foam and in theory it should cancel out most to the sound but not restrict air flow. Am I understanding the concept, or am I way off?
I found this pic that I thought was interesting how the do the air intake and exit. What are your thoughts?
-
Sounds to me like it ought to work.
Jim
-
Does your setup kill most of the noise? What do you mean when you suggest you would do something different with the exhaust? You also mention the intake. Is it too small? Not enough air flow? Does your gender overheat?
Sorry that I didn't see this until now, so let me answer so it's at least saved for perpuitity.
As far as my gender overheating or being too small, I think you'd have to ask my wife about that. ;)
The doghouse does kill quite a bit of the noise, though I've never measured it, and/or compared it to closing the bay door without the doghouse, since I've never had it installed as such.
I will say that it's considerably quieter, and is comparable to a car engine in terms of noise when it's all buttoned up.
As far as the exhaust - I would put on a silencing muffler, and probably run it all the way to the back of the bus (to get the exhaust away from the side windows).
I'd also move the air intake and air flow exhaust further apart. I was making some compromises to make it fit, and it was a mistake. I deal with it now by putting a flap between the two every time I go park out in the desert, which is every year, to make sure it doesn't suck in too much of the hot air flowing out. Climbing under the bus twice a year isn't a huge cost, but it would be nice if it had been done better. The genset also comes sitting on two small airbags courtesy Wrico.