M1088 camper conversion

Reworked LMTV

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Made some more progress today. First order of business was assembly of all the perches:



Next was to trim the upper rails to proper length. These were too awkward to set up on the saw, so I set the saw up on them. Some C- and trigger clamps did the trick, just had to support the free end by hand as the cut finished:


Next was to see how everything lined up, including the section I channeled for the trans mount. Happily, I only measured once and only cut once:


Trans mount notch lined up perfectly


With everything on the truck, I finalized the locations for the spring perches. With the upper rail pinned at the cab end, I have a pair at 5', 9' 6", and 15'. I measured out the rails and started drilling. I clamped the perch into position and using a bushing I made on the lathe, drilled pilot holes in all the appropriate places.

Perch clamped in place with the drill rig in action:


Piloted with a 3/16" bit, opened it with a 7/16" bit, then stepped up to 5/8". Planned on going to 1" and welding in crush tubes to reinforce the rail, but something let the smoke out of the drill and it quit working. I didn't feel like going to Home Depot (just bought the drill) on Black Friday, so I just called it a day. I may get up tomorrow and go.

Despite losing the one battle with the drill, it was quite a victorious day. I've had this design in my head for a long time and had the sketches laid out on the computer for a while as well, but it's nice to see that it all seems to be coming together as desired. Getting the upper rail tied to the lower rail to effectively complete the subframe construction will be a major milestone.

One step at a time though...
I need a mag drill. Seems like one could make one.
 

Reworked LMTV

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Christmas came early, and wrapped in little orange ribbons:



It's the initial supplies to complete the subframe and build the floor:


Upper rails in place, but need to get trimmed:


Also need to get notched out to allow clearance around the transmission mounts:




I had some pieces laser cut to make up the spring perches for the subframe:






Still have a couple of hurdles to clear but for the most part, everything is coming together. It is a very exciting time!
Nice welds.
 

B-Dog

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Just curious what you paid for the large box beams. I need to plan my budget.
For steel budgeting, estimate based on weight. In Denver, as someone in the general public, you can budget about $1.25/lb for structural tubing and get in the right ballpark.

Chris' pricing, compared to Denver anyway was great. Loving the build!!

Are you going to hard mount any of the perches to the frame (w/o springs)?

No, like this, a plate added to what you notched. Sorry for the poor finger drawing
Are you thinking to protect the tranny mount or add strength?
 

Ohiobenz

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For steel budgeting, estimate based on weight. In Denver, as someone in the general public, you can budget about $1.25/lb for structural tubing and get in the right ballpark.

Chris' pricing, compared to Denver anyway was great. Loving the build!!

Are you going to hard mount any of the perches to the frame (w/o springs)?



Are you thinking to protect the tranny mount or add strength?
Strength. That notch, even tho boxed is a significant reduction in strength under flex.
 

ckouba

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Strength. That notch, even tho boxed is a significant reduction in strength under flex.


Are you advocating that I tie it back in to the trans mount? I am thinking that would defeat the intent of the torsion isolation. It would also introduce the flex of the trans mount into the subframe system, if I understand your proposal correctly, which would in turn be constrained by where it anchors to the chassis at the lead end of the subframe. Yes, the notch is a reduction in strength but consider it marginal and not significant after having plated it back in with more 3/16" material.
 

ckouba

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Loving the build!!
Thanks. It is getting to quite the exciting time.


Are you going to hard mount any of the perches to the frame (w/o springs)?
All the perches will be bolted to their respective frame rails. There will be a rigid connection (plate) at the cab end connecting the top to the bottom rail, and all the paired perches will be sprung using rates which diminish along the length of the rails. This should keep any forces transferred across the subframe reasonably comparable over the whole assembly.
 

coachgeo

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Thanks. It is getting to quite the exciting time.




All the perches will be bolted to their respective frame rails. There will be a rigid connection (plate) at the cab end connecting the top to the bottom rail, and all the paired perches will be sprung using rates which diminish along the length of the rails. This should keep any forces transferred across the subframe reasonably comparable over the whole assembly.
so in review- on each side; you fixed the camper to the truck chassis by the cab... from there rearward is three; logically placed, progressively decreasing captured spring attachments between camper and truck chassis?

why did you choose to do camper solid fix by the cab instead of opposite with fix at the truck chassis arse end?
 

chucky

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Are you advocating that I tie it back in to the trans mount? I am thinking that would defeat the intent of the torsion isolation. It would also introduce the flex of the trans mount into the subframe system, if I understand your proposal correctly, which would in turn be constrained by where it anchors to the chassis at the lead end of the subframe. Yes, the notch is a reduction in strength but consider it marginal and not significant after having plated it back in with more 3/16" material.
I dont get it that frame rail is fifty times stouter than it has to be now its the end of the frame there wont be 2 thousand pounds on it at any moment of its life ! If anything slightly twist it will be in the center of the flex and with 3 frame rails stacked he has that coverd with the springs. If these 3 axle trucks flexed that much we would see it in the frame and bed welds when we got them . The military was much rougher on these trucks than we will EVER be and no more than these boxes were putting on them is like a flee on a dogs back. IMHO
 

B-Dog

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All the perches will be bolted to their respective frame rails. There will be a rigid connection (plate) at the cab end connecting the top to the bottom rail, and all the paired perches will be sprung using rates which diminish along the length of the rails. This should keep any forces transferred across the subframe reasonably comparable over the whole assembly.
I think that answered my question. Why the cab end and not in the middle I assume to keep the pass-thru lined up...? Good call on changing the spring rates!
 

ckouba

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Components coming together:



Forgot to pick up washers, so no lock nuts on there either, but they're starting to look like something. Picked up a different drill with a much lower rev range to prevent overheating the drill bits. Hope to finish drilling all the holes and get the perches mounted over the next few days, which means that the subframe will be able to be mounted onto the chassis as well. That will be a big milestone.
 

ckouba

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Recommend you consider a mag drill and annular cutters. Mine made frame drilling so easy. You can rent the drill but have to buy your cutters.
I was put off by the cost of a decent mag drill but renting one never even crossed my mind. Thanks for planting that seed!
 
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