Segmented partly-removable LMTV bed?

[wandering neurons]

A crazy thought for the crowd.
Here I am with a fleet of vehicles, including my M1081 and a fifth-wheel camper. I'm racking my brain on ways to be able to tow the camper, short of buying a -350/-3500 or larger truck (the fifth-wheel empty is 12k+ lbs). Part of this plan is an excuse to add high-speed gears, a 290hp turbo and tweak the fuel on the LMTV. (Whadda' do we need? More power!)
Biggest problem is the height of the bed. This has been covered several times before and the normal solutions seem to be: Get a different truck (M108 or remove the entire bed and leave it behind while towing. But if I'm moving, it's a little hard to drop the bed, tow the camper, then go back for the bed.
So - how about cutting the bed and intermediate frame into three sections (crosswise)? First cut would be just behind the cross-bed storage bins, and the second cut about halfway back from that. Punch out the Huck bolts for the rear and middle sections, replace with Grade8 nuts and self-locking bolts. Have to do something with the airdrop equipment, rear bumper/lights, and splash guards.
When ready to tow, use camper jacks or similar to stack the rear and middle sections into the forward section and chain/strap in place. Drop in gooseneck ball or an Anderson-style fifth wheel setup. When done towing, remove ball or hitch, and relocate bed sections and re-bolt into place.
Height might still be a little more than a normal pickup bed, but could be remediated with some creative engineering.
I think that there would be enough clearance between the stacked bed segments and the front of the camper, but will measure and mock up, especially for turns. Additionally, the ball or hitch may be a little behind the axle to accommodate, or use a slider fifth wheel hitch.
Am I nuts, or might this be a practical solution?

 

[coachgeo]

sounds like it would work..... but also sounds like a more logical solution would be too build a rack you can drive truck thru the middle of and stop when it matches bed. Use lengthened air lift arm pulled out so bed now can rest on the rack on these arms. Add similar thing up at front of bed and do same thing. a few smart placed atv 2ton winches to then squash the suspension down.... maybe along with dropping to lowest air in ctis... and drive out from under her.

Other option is a rack you back up too... rack has rollers like on boat trailers.. at one end is a winch... you pull it off with winch onto rack. same winch and cable thru an eye and pulley mounted center front by air cleaner/spare tire holder and back to bed.... use it to pull the bed back onto truck for re-mounting. grease to help it slide?

your goosneck can be hanging on a chain or a gantry orr? you drive under and install.

 

[tobyS]

Why not put a trap door in the bed and mount a fifth wheel ball down at the frame. Then make the hitch on the trailer adjustable down to it. I'm doing the hidden ball on my M35A3 4x4, putting it about 10" behind the axle. Ball is rated 17,000#.

 

[coachgeo]

Why not put a trap door in the bed and mount a fifth wheel ball down at the frame. Then make the hitch on the trailer adjustable down to it. I'm doing the hidden ball on my M35A3 4x4, putting it about 10" behind the axle. Ball is rated 17,000#.

Really good idea Toby. If needed could potentially be a door that opens a trough that runs from the ball all way back to exiting out at rear of bed? then one would not have to raise the trailer additionally high to get up above bed height before dropping back down to the level of the ball. Trough would allow trailer to glide in at height just above ball then be dropped into place. Might have to refigure a cross supports or three on the bed but that is doable.

in any of these have to figure out how to deal with rear shock mounts and how to deal with the load valve that adjust the brakes. these all attach to rear of bed. (with that in mind.... finding way to squash rear suspension while mounting trailer might be easier.)

 

[tobyS]

You don't need a trough, all you need is the one hole about 12" x 14" or so in the bed and a plate to cover it (nicely fit) when not in use. The trailer would be a square in a square and pin in place, so it would go up and clear the bed. You need a properly mounted hitch plate to the frame. Mine is under construction, not complete but I'll get a picture.

Take a look at this style. https://www.etrailer.com/Gooseneck-and-Fifth-Wheel-Adapters/etrailer/KPG5-Q30.html

I like that !!!

 

[tobyS]

Here is the start of mine for some ideas. The web of that channel is about 7/16" and outside will have aheavy angle welded to it and bolted to the side of the frame. The frame on this truck is getting a 3 x 11" x 1/4 x 10' plate before the springs are put on and reassembly starts, so the outer part will be fit when the frame plates are finished installed.

A similar assembly would work on your LMTV with adjustable hitch on the trailer. Like this:

https://www.etrailer.com/Gooseneck-Trailer-Coupler/Bulldog/BD1289030300.html

On the third picture, the plate that will attach the bed (sticking out) is at the new CL of the axle. The ball is about 10" in the rear of the axle (and not welded or bolted on yet). A load will be offset by the heavy Cat engine.

 

[olly hondro]

I was thinking of segmenting the bed for different reason: so it would flex abit. The lore is that skid, or subframe is there so the bed DOES NOT FLEX...but I want it to.

 

[Derrickl112]

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[wandering neurons]

Well, removing the entire bed is feasible, if I travel cross-country, the bed is still where I started from. Or if I go somewhere for a shorter period of time and want to use the truck as a truck, not a tractor, I don't have the bed. The idea is that the bed travels with me in pieces, to be reassembled at the destination when the fifth-wheel is disconnected.
But some good ideas on pulling the whole bed...

sounds like it would work..... but also sounds like a more logical solution would be too build a rack you can drive truck thru the middle of and stop when it matches bed. Use lengthened air lift arm pulled out so bed now can rest on the rack on these arms. Add similar thing up at front of bed and do same thing. a few smart placed atv 2ton winches to then squash the suspension down.... maybe along with dropping to lowest air in ctis... and drive out from under her.

Other option is a rack you back up too... rack has rollers like on boat trailers.. at one end is a winch... you pull it off with winch onto rack. same winch and cable thru an eye and pulley mounted center front by air cleaner/spare tire holder and back to bed.... use it to pull the bed back onto truck for re-mounting. grease to help it slide?

your goosneck can be hanging on a chain or a gantry orr? you drive under and install.

 

[wandering neurons]

Also thought about, but on a regular fifth-wheel camper the overhang is usually around five feet, just enough to clear the rails on a non-lifted pickup truck. So the overhang would barely clear the bed, and I'd have to really jack up the front of the fifth-wheel to get the hitch into place, and they're not small. The trap door would be pretty big to accommodate the rotation and vertical movement of the pin box on the underside of the overhang. But if the pin box were modified to accept a ball, not the normal pin and saddle, that might work.
Interesting potential!

Why not put a trap door in the bed and mount a fifth wheel ball down at the frame. Then make the hitch on the trailer adjustable down to it. I'm doing the hidden ball on my M35A3 4x4, putting it about 10" behind the axle. Ball is rated 17,000#.

 

[coachgeo]

I tried the trap door option for a while, raising the trailer extra high to clear the bed was a pain.....

twas my point earlier... thus the trough idea.

 

[wandering neurons]

Nice rig, something I'd considered as an option.
Cutting the bed into 3rds versus half - 3rds would allow more clearance between bed and overhang, but you're right, would also shift weight forward. Could be compensated by moving the pin or saddle behind the axle, though might cause stress on the overhang and change handling. But something to investigate. I need to make some measurements...

I tried the trap door option for a while, raising the trailer extra high to clear the bed was a pain. Clearance between the trailer and bed was also tight. I ended up going with something that had a clear opening to the rear like the hauler beds used on pickups. How much tongue weight does your camper have? You may be able to get away with only cutting the bed in half, and moving the GN/5th wheel further back since there would already be more weight on your front axle from the stacked bed sections.

 

[coachgeo]

.... The idea is that the bed travels with me in pieces, to be reassembled at the destination when the fifth-wheel is disconnected. ...

that makes absolute sense. Go for it. You could make the moving sections a bunch lighter if your really never going to put into the bed something that needs as much overbuild strength put into these beds. Rebuild the to be moved sections out of something much less lighter.

 

[wandering neurons]

Unimogs are known for their frame flex, and anything mounted to the frame behind the cab must be three-point and flexible, not rigid! As for the Steyr 12M18 and LMTV, hard to say. Flex could go both ways - allowing more wheel travel overall, but possibly stressing the frame causing cracks. I wonder what the differences in steel and hardening are between the Unimog and LMTV?
Then again, a sectioned bed may force the flex into specific areas and cause induce stress in a limited area. Main reason that windows in commercial airplanes have round corners - induced stress risers.
That could be bad. Thanks for putting that into the equation!

I was thinking of segmenting the bed for different reason: so it would flex abit. The lore is that skid, or subframe is there so the bed DOES NOT FLEX...but I want it to.

 

[Derrickl112]

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[wandering neurons]

Bedtime for Bonzo here. Some interesting ideas. Between now and the weekend (weather permitting), I'll get some measurements on the camper overhang height and length, and LMTV info. I won't be able to use my camper specifically, it's wrapped with sheeting for winter weather. But will get close.
Stand by for more! And thanks for the interesting ideas. I like the hidden gooseneck ball, but need to check clearances.

 

[wandering neurons]

Have seen this posting and like his setup. But he's either running an A1 or there's something totally custom with the rear of his rig. The hitch is waaaaaayyyy different than any LMTV I've seen so far. And while it works for a gooseneck, may not work for a fifth-wheel camper, without modifying the pin box or using some kind of adapter. And still worry about overhang hitting the deck.

Have you seen this set up?
https://www.steelsoldiers.com/showthread.php?139687-LMTV-pulling-a-Gooseneck&highlight=
The hitch is well behind the rear axle and the trailer probably weighs around 20K loaded. It’s been about 3 1/2 years since he did the mod, it wouldn’t hurt to pm Justin to see if he’s had any issues.

 

[coachgeo]

Unimogs are known for their frame flex, ...!

IMHO for last couple decades they have chassis flex not much more; if any more for that matter, than other large commercial trucks in the same class. Just nostalgia, assumptions, and salesmen after profits still driving the usage of super flexy sub frame for camper boxes. Captured spring mount systems like the M1079 is growing more and more as this realization is starting to set. Not sure Unimog itself even use beds etc. with built in pivoting sub chasses themselves these days. The 404 long ago was the flexiest. It has gotten less and less ever since. Their is more flex in built into suspension.... less in chassis.

 

[Derrickl112]

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[olly hondro]

that makes absolute sense. Go for it. You could make the moving sections a bunch lighter if your really never going to put into the bed something that needs as much overbuild strength put into these beds. Rebuild the to be moved sections out of something much less lighter.

I like it.