LMTV Frame twist

[Ronmar]

Interesting thread read. Out of curiosity, how is the factory M1079 Van body attached?

4 anchor pockets(3x5”?) welded to the upper 6” frame channel near front and rear. The rear crane lift point is also incorporated into that upper channel just forward of the rear wheel. The box is attached to a box tube subframe that has 4 feet that rest in the pockets on 1/2” rubber pads. There is a large bolt hole down thru the middle of each foot/pocket. Two have nuts and bolts, the other two have long bolts with captive springs. I looked up what I thought was the spring specs once upon a time. If I recall correctly, they have a little over 2” of total compression @ ~1000#/in rate…

i bought a M1079 cab and chassis at auction. You can see the remnants of my pockets(cut the walls of the pockets off flush with the top of the frame) in this pic…

 

[Mavcaster]

4 anchor pockets(3x5”?) welded to the upper 6” frame channel near front and rear. The rear crane lift point is also incorporated into that upper channel just forward of the rear wheel. The box is attached to a box tube subframe that has 4 feet that rest in the pockets on 1/2” rubber pads. There is a large bolt hole down thru the middle of each foot/pocket. Two have nuts and bolts, the other two have long bolts with captive springs. I looked up what I thought was the spring specs once upon a time. If I recall correctly, they have a little over 2” of total compression @ ~1000#/in rate…

i bought a M1079 cab and chassis at auction. You can see the remnants of my pockets(cut the walls of the pockets off flush with the top of the frame) in this pic…

View attachment 937422

Ronmar it looks like here the large forward lifting cross member has been removed. Do you know if that part is solely for lifting or is it there for frame support as well?

 

[Ronmar]

I don’t see it really supporting the frame all that muck as it is narrow and mounted perpendicular to it. Because the engine and trans is located there, trucks don’t typically have any re-enforcement there. Looking at it as a whole, it probably weakens more than it would support as they had to drill a lot of holes(6 in each frame rail) to bolt it in place with enough fastener shear to support most of the vehicle weight(its just forward of the CG) when lifting…

 

[aw113sgte]

It will obviously strengthen that area, however it may also cause stress risers due to the increased stiffness. Crossmembers are needed and there is a large variation between FMTV models.
There will likely be more stress on bushings, but less stress on the frame.

 

[Mavcaster]

Yeah thanks Ronmar, I was considering removing mine but think I’ll just not go down that road. I saw a video awhile back where the controls for an electric hydro pump was mounted in one of the ends. Anyways I would need to fab another way to mount coolant res and cab leveling switch, etc


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[Shakkles]

The wripling on the panels in this picture is my concern. Not sure whats going on here, but the seams look like they are separating...

I like the idea of composite for the clean panels, but don't want the added 'torsion' frame. for many of the reasons stated in this thread. height, torsion frame putting pressure where it wasn't designed to be.

i'm torn on what the right answer is and what direction i'm going to go. I've talked with several folks and looked at a lot of the designs, I just can't figure out how to keep the 'skin' clean and not wavy using metal.

I've think I've settled on my 'thermal transfer' solution for metal. Spray cork. Used in marine applications. I'm going to use it on the cab as well. Lots of good videos out there on this

Height and easy entry/exit are key design criteria. I don't know what it's called, but i'm calling it 'school bus entry'.
View attachment 937214

I don't see any "panel rippling" in that picture my man. I do see a lens flare artifact. Is that what you're seeing and thinking it's a physical defect on the truck or am i mistaken?

 

[Ronmar]

Yeah thanks Ronmar, I was considering removing mine but think I’ll just not go down that road. I saw a video awhile back where the controls for an electric hydro pump was mounted in one of the ends. Anyways I would need to fab another way to mount coolant res and cab leveling switch, etc


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Well I needed the room for my habitat, so the cooling system and oil fills were getting re-engineered anyway. I actually wound up fabbing my own front wall truss that bolts in the same location, only down at the floor level, arching close over the top of the transmission. I even re-used the same lower cross-member channel. The original truss I welded to the back of the upper frame to extend the floor structure 18”

i designed my own cab suspension system using more commonly available bags and shocks, and relocated the height control valve down to the left frame right behind the power steering reservoir.

 

[coachgeo]

PS- this thread started before their was a forum in here for building MV trucks into RV's. There may be similar discussion over in that now on this topic

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