leveling jacks(while the bus is up)

[mc8 tin tent]

  Thanks to all with the help on replacing the air bags.
Now that I have the bus all jacked up and blocked up now seems like a good time to install the hydraulic cylinders for leveling, I was thinking of using a two way cyl. 24" long 3.5 dia. 1 1/2 ram and a 8x10"x5/8 plate for a foot pad. My thought was to secure the cyl. using a set off bracket on to the front jack post (on each side) and another bracket on the top of the cyl.(5x10x5/8) to spread out the weight on the air beam. My thinking is keeping the weight off of the deflated air bags may make them last  also it would very handy to have in case of a flat on the road,and also with servicing the bus.
 Oh yes 77 MCI.
  What do you think???
  Thanks Dwayne

[rv_safetyman]

Dwyane, when I planned my jack system (still only have the rear cylinders on), I did quite a bit of looking/thinking about the size of the ram.  Getting the bore size to lift the bus is no problem, but I was very concerned about lifting the bus very much with a small diameter rod size.  Don't remember too much from my engineering school days, but "column strength" and how easy it is to bend a rod on this type of application really stuck in my mind. 

I have documented my system on page four of my bus project pages (http://www.rvsafetysystems.com/busproject4.htm).  You will see that I chose a cylinder with a two inch rod:  "The cylinders are Northern Tool (northerntool.com) part number 902424.  They have a 4 inch bore, 2 inch shaft, and 24 inch stroke."

I used this system to really put the bus in the air when I had to remove the rear end pumpkin and it seemed to be very stable.  I would have been paranoid with a rather spindly 1.5 rod.

Jim

BTW, I have been on my soapbox about thread titles.  We really need to make sure our title is searchable and conveys the specific question.  There have been so many new threads lately that many of us must pick and choose those that we have time to read and/or contribute to.  You may want to add the term "leveling jacks" to the title so that folks know what help you need.      Only the thread creator (or the moderators) can change the title that appears on the main forum page.

[Dreamscape]

Hi Jim,

I checked your site and I have a question.

What happens when you have a piston seal problem and it leaks by, how are you going to hold the ram up? Won't it drift down? Will the check valves in the control valve do it? What happens when a check valve goes bad?

Not trying to pick you apart  , as I have thought about building a system myself someday.

Paul

[rv_safetyman]

Hi Paul. 

As you point out, most jack systems have a return spring to keep the ram in the "up" position.  My cylinders are two way, so the valve tends to keep the cylinder up. 

My cylinder does drop a bit over a very long time (has dropped about 2 inches in the last year or so).   My plan was to simply retract it again with the pump as needed.  Only problem is, I have been using a hydraulic pump that I have in the shop (and don't carry with me).  I have a 12V pump waiting to be installed. 

I don't really plan to use all 24 inches of lift, but if I did, I am not sure what the spring would look like.  I think it would be hard to get a spring that would hold the cylinder up if I lost a hose and still extend 20 + inches.

Jim

[Dreamscape]

Jim,

Where did you get the 12v pump?

I was maninly thinking that if you are driving down the road and a cylinder problem occured, how would you know?

I have used magnetic switches on cylinders that would let you know when it came off the switch, but the piston would have to be differant for the switch to sense it. I don't the cylinders you have would allow that.

Paul

[rv_safetyman]

Hi Paul

I bought my pump on ebay.  The title was:  Haldex 12V DC Power Unit Single-Acting Mod# 1261009

I paid $149.  This pump is also sold by Northern Tool.  I think they get $279.  The pump does not have a valve, but we don't need one, since my system uses its own valve

My thought on having the cylinder drop was that I would rig up a cable to hold it in place.  I think you would know if it dropped down

Now you have me worried

Jim

[Dreamscape]

Jim,

Not to worry you, but pose some questions so if someone has a fix they would let everyone know.

A cable would work, but I was thinking of some kind of spring catch that you could disengage or engage with a rod, it would be attached to the cylinder, with the catch on the foot. Dunno.

Paul

[Stormcloud]

If using a 12V pump, could you not install a micro-switch circuit on the ram that would start the pump when the ram 'leaks down'?
Similar circuit could be used with indicator lites to let the driver know when this is happening.

I also like the idea of hydraulic levelers, but it's gonna have to wait it's turn.

Mark

[Hartley]

Garage door springs can be cut to length to hold the cylinders up.
( Just a thought ) they have lots of stretch and pull.

[mc8 tin tent]

Jim
Thank you. I did rename The topic  you are correct this will make it easy to locate and reply to.
   You also made a good point on the cyl. ram dia. of 2" over 1 1/2 ,I also plan on using using return springs and a magnetic reed switch as a fail safe.
   Dwayne

[Sam 4106]

Hi Dwayne,
I can't comment on the 5/8" plates you plan to use on top of your jacks, but 5/8" plates for foot pads seems like overkill to me. I think 3/16" plates with gussets from the center to the corners would be adaquate. Unless, of course, you already have the 5/8" plates. I tend to use materials that I have, rather than buy new material, even if it is over kill to use the material I have on hand.
Good luck, Sam 4106

[Dallas]

Dwayne,

why not look at the feet on a semi trailer.. many of the trailers I hauled had over 100,000 pounds on board, but used the same feet as the drybox (Van) trailers and reefers (refrigerated) trailers.

the only t6ime there was ever a problem was when the mighty Mississippi decided to encroach on a construction site I was at.. sank the trailer up to the frame and I had to get 3 twin boom 3 axle wreckers to get me loose.

Oh, yeah,, total weight was 16,500+/- for the tractor, 17,200 +/- for the trailer and 8,000 pounds of styrofoam insulation.
41,700 on 5 axles and 18 wheels.

Dallas

[jjrbus]

 I personnaly would want bigger plates.  The single rear axle on my MCI5C weighs 18,620 lbs I would guess there is about 80 square inch of tire contacting the ground. That is a total of 320 sqare inches vs your 160. My tires have sank about 2 inches into the sand in 2 months.
 The commercial systems use a 100 sqare inch plate.           
 
 http://www.bigfootleveler.com/levelingsystems/classa.php

 Being a true bus nut I would want to be able to lift the bus in quicksand, so I would want as big as would fit there.
                                  Jim
 

[mc8 tin tent]

   Thanks for the reply guys
I chose that size of plate because that seems to be the largest plate that I can get in the space without hitting the wheels or the bottom of the baggage compartment , I used the 5/8 thick plate because i didn't want to use gussets to reinforce a thinner foot.
   Dwayne