LMTV Frame twist

[Cumminscruiser]

I'm just starting to build the box for a camper on my LMTV. I removed the flat bed and drove the rear of the LMTV. I see about 1 1/2" of twist. I know some attach the camper box directly to the rails but has anyone attached the box using air bags?

 

[TNriverjet]

The box on a stock M-1079 has spring loaded bolt mounts to allow for flex. There are several discussions in various threads here on how to mount a box and overcome this flex.

 

[coachgeo]

These trucks flex very little.... but.. your test on how much it flexed is a bit flawed..... cause you removed the weight in back. Flex is far more when it is fully loaded. still though... that "far more" is very little on these rigs..... well at least compared to a Unimog 404 or similar rig that was designed to keep the wheels on the ground via a flexy frame. These days most trucks use suspension engineering to keep the wheels on the ground so frames are much more stiff than the past.

 

[Cumminscruiser]

Agreed it would flex more with added weight.but I don't want to see rippling in the siding .

 

[coachgeo]

Agreed it would flex more with added weight.but I don't want to see rippling in the siding .

See if you can find some chunks of cement or something you can tie down the rails and try it again? Maybe remount the bed and put the weight in it. Then at your test site; before next testing, loosen all but the rear bolts so the chassis can flex underneath the bed? Tighten them all back before hitting the road?

 

[Cumminscruiser]

Well that's interesting, the bed is heavy I think close to 5000 pounds. Because I could not lift it with a 2000 lb chain fall. I don't think the camper will weigh half that. I also would like to soften the ride of the camper which air bags should do.

 

[coachgeo]

maybe the bag idea has been hit in this long arse thread ... good read....... grab a beer (or three) some pizza and binge read

http://forum.expeditionportal.com/threads/25494-pivoting-frames-and-mounting-campers

 

[quickfarms]

I just had the rear suspension of my truck rebuilt to match the weight of the camper and the truck rides so much better now and the camper is not even on it

 

[98G]

Well that's interesting, the bed is heavy I think close to 5000 pounds. Because I could not lift it with a 2000 lb chain fall. I don't think the camper will weigh half that. I also would like to soften the ride of the camper which air bags should do.

It's not that heavy.

Silverstate55 and I loaded one from his trailer to mine, *by hand*.

My tractor is rated 1250lbs. It lifts an end, almost and sort of.

I'm guessing maybe 3000lbs if that.

 

[Shark Bait]

Not much flex, even with the bed on mine.

 

[Reworked LMTV]

I'm just starting to build the box for a camper on my LMTV. I removed the flat bed and drove the rear of the LMTV. I see about 1 1/2" of twist. I know some attach the camper box directly to the rails but has anyone attached the box using air bags?

I thought about this too, but was concerned about lack of lateral movement control. Certainly would be nice to make it adjustable though.

 

[Cumminscruiser]

Yes the bed is super strong and rigid, Now take off the bed and do it again and you will see twist. The question for me is can I take off the 6" channel that sits on top of the frame? Also I'm thinking of using air bags to support the camper and allow flex in the frame when off road.

 

[Cumminscruiser]

Besides figuring out which air bag ti use the lateral movement must also be controlled. My thoughts here is to use two or three pivoting A arms that let the camper box move up and down but not forward and back or left to right.

I was hoping someone on this forum has done it already.

 

[Cumminscruiser]

Here is another fly in the Preparation H... A limit strap or cable or something should be in place to keep the camper from going too far UP. I don't think the A arms will limit that travel nor will the air springs.

 

[coachgeo]

Yes the bed is super strong and rigid, Now take off the bed and do it again and you will see twist. The question for me is can I take off the 6" channel that sits on top of the frame? Also I'm thinking of using air bags to support the camper and allow flex in the frame when off road.

It was ruffly established in earlier discussions that the channel is not so much on top of the chassis....... as being part of the chassis...... but a channel that is under the bed to add rigidity to the bed. Thus yes... it can be removed from chassis. BUTT.... that being said... the channel also acts as a spacer to get what ever your installing on the chassis up above the transmission. That sucker sticks way up above the chassis.

 

[Rebuilder]

Yes the bed is super strong and rigid, Now take off the bed and do it again and you will see twist. The question for me is can I take off the 6" channel that sits on top of the frame? Also I'm thinking of using air bags to support the camper and allow flex in the frame when off road.

I cut the top channels off my 1078 frame. There's a thread in here somewhere discussing it and the conclusion was that the top channels are there for the box and not for the truck. Expect more twist without them obviously. I personally think airbags would be too much extra work for what you end up with. By the time you add all the pivoting supports to keep the box in place you might as well just build a 3 or 4 point mounting system and avoid any potential future airbag issues.

 

[coachgeo]

On some Expo rigs the lateral movement has been controlled with plates attached to Camp box that sit in contact on out side edge of chassis port and starboard sides. They are NOT attached to chassis and do allow the chassis to slide along them in flexion. A Sacrificual plastic sometimes is used to slide along. Plates are long enough to when chassis moves away from camper box in a flex situation that they stay beside the chassis even at full flex, thus preventing lateral movement

Hope that makes since.

Again...... suggest you read thru the link at Expo portal suggested earlier.

 

[Cumminscruiser]

I did go thru the Expedition Portal link and that did test my ADD. Although most of it pertains to other trucks with much more flex that the LMTV. I did like the way the pivots were made, that solved the containment issue. Unless I missed it I did not see the LMTV in there.

 

[Cumminscruiser]

I did see the thread where someone, who really sounded like they knew what they were talking about, mentioned the 6" channel was for the bed.

 

[Rebuilder]

I did see the thread where someone, who really sounded like they knew what they were talking about, mentioned the 6" channel was for the bed.

I can't tell if you're being sarcastic or not but if you read it why did you ask the question again? If you're expecting an engineer from S&S to chime in I think you'll be disappointed.