Weird M939 20 foot bed... Insulated/shielded?

[CUCVFAN]

I got this bed to use as a bridge over my stream. While stripping it down, I noticed that there were some holes in the bed that did not go through to the bottom.
On closer inspection, it appears that the stock bed floor has 4 panels ( that are approximately 1.5" thick ) on it that are fully welded together. The panels appear to be constructed with outer skins of sheet metal containing a piece plywood, apparently sandwiched between 2 layers of some sort of gritty rock-like substance.
The tailgate hinges are welded higher than normal to make the tailgate match this raised floor.
It appears to have had a shelter in it, so I'm not sure if this floor was for thermal insulating of if it is some sort of radio /EM shielding floor?
Does anyone have any clue what this bed floor is/was for?
Looks like the truck last belonged to the 11th Air Defense Artillery Brigade, based on the painted-over bumper numbers.

 

[CUCVFAN]

Since this is a 20' bed, I looked around at the recently/previously sold M927s and they all appear to have the same raised floor. I could not find any good pics of the rear any M814s to see what they have, but my recollection is that they are plain steel bed bottom.
Can anyone with a M927/M928/M814 confirm what their bed floor looks like?
Still wondering about its purpose...

 

[CUCVFAN]

Here are some that appear NOT to have the raised bed followed by some that do. It's hard to tell on the camo bed, but generally, the bottom of the tailgate aligns to the bottom of the reflector on the raised versions (except the ratty bed, but it has had tie-downs added, so the reflector was moved anyway).

 

[juanprado]

Interesting, I wonder if the marines with the ISO beds had it also?

 

[Two Stroke Madness]

Since this is a 20' bed, I looked around at the recently/previously sold M927s and they all appear to have the same raised floor. I could not find any good pics of the rear any M814s to see what they have, but my recollection is that they are plain steel bed bottom.
Can anyone with a M927/M928/M814 confirm what their bed floor looks like?
Still wondering about its purpose...

My M814 also has the thicker bed. I noticed it a few years ago, but have not had any luck finding out why.

 

[simp5782]

Different manufacturers of beds.

 

[USAFSS-ColdWarrior]

Very interesting.

I'll be checking a couple of trucks nearby to see what beds they carry.

 

[CUCVFAN]

Different manufacturers of beds.

I'm sure there are multiple manufacturers, but I don't think that is the only explanation for this difference.
As I said, these panels are welded together and are on TOP of the normal floor. There were a few holes in one spot of my bed where it appeared to have been torched to remove something. Looking closer, it appears that the holes may have just been punched or rusted. When I dug into the area with a screwdriver and pryed back the top layer of metal (which is NOT thick - *maybe* 18 gauge?), I found a bunch of gritty material under the top layer of metal, below which there was wood. There are two holes all the way through the bed in the front, which I will investigate further and report back. I might just drill through with a holesaw and see what it looks like...

Knocking on the floor with a hammer has a slightly "hollow" sound except near the edges of the panels. The outer edges appear to be box tubing, extending about 2" in from the edges. I guess this explains why it could be welded solidly together without any risk of the wood inside burning at all.
The top layer of metal will "oil-can" when I walk on it in some spots.

I could see a bed being reinforced for some special purpose, but these panels are not very tough. If you get a hole, water will get in and rot the wood and rust the metal from the inside out, not to mention freezing and splitting. There would be no reason that I could see to just add these panels to a standard bed without them having some specific purpose that made it worth doing.

 

[VPed]

My bed has a single layer of 3/16 “ or so-thick metal

 

[CUCVFAN]

I definitely think this bed would not have been procured for hauling standard palletized cargo. One errant nail sticking out of the bottom of a pallet, and the top layer of these panels gets torn up, with no simple repair.
So, thinking more about this and looking at the bumper numbers of some of the other trucks that I found having these beds, it seems several were also from the 11 Brigade.
Given they deal with missile systems, my new theory is that this could be more of a vibration reduction system than a shielding or insulating measure. It makes the bed much "softer" for sure.
If the shelter in this truck had been for missile control or something, I'd guess that taking care of the electronics (even if they are already individually vibration isolated) would be a high priority.
I might just call the unit and see if I can find anything out about it.

 

[juanprado]

there have been many variants of the m927/m928 with specialized platforms. I would concur that your truck bed is used on one of these flavors.

 

[juanprado]

more flavors...

I wonder if there were more specialized variants than troop carriers of the long wheel base. There is also the USMC ISO version of the long bed. I suspect most of those were used for cargo and general hauling.

 

[VPed]

Mine has a drop-side bed which according to the TM, was specifically not produced due to the length. The bed is similar to a deuce bed in that it does not have the taller (and fixed) sides towards the front. In fact, the troop seats from my deuce fit the 927. I have yet to see another like it.

 

[BKubu]

Mine has a drop-side bed which according to the TM, was specifically not produced due to the length. The bed is similar to a deuce bed in that it does not have the taller (and fixed) sides towards the front. In fact, the troop seats from my deuce fit the 927. I have yet to see another like it.

I had one just like that. It was an M928 (converted to A1 with super singles) by the USMC. It had a drop-side bed just as you described. I, too, agree that there are not many around, or at least I've not seen them either.

 

[CUCVFAN]

To follow up on this thread, I drilled through the bed with a hole saw and found that what I though was possibly some sort of "stone dust" must have just been rust buildup from the underside of the top layer of metal in that area.

The construction appears to be as follows: Solid wood (not sure of the actual lumber dimensions) boards were placed directly on the bed floor. I assume that the edges have the box steel as a framework and the planks are in the centers. Then, a layer of relatively heavy sheet was placed over that and welded to the outside framework and bed sides, as well as in the center. The sheet was rusted so much in the other spots, it appeared to be thin gauge. That is not the case.

The images show the cross-section of the hole and core.

I am still guessing it is either insulation or vibration related, but I think it will be coming off this bed so it doesn't rot my bridge from the inside out.

 

[CUCVFAN]

The pics also show how wet the wood was down near the bed floor. Drilling it required cleaning the teeth of the hole saw out regularly because it was so wet. This is why I will be removing it. Hopefully, the lumber will be usable for something else.

 

[CUCVFAN]

Finally got a chance to cut some of this apart. If you have this style of bed, here is what your bed probably looks like inside of what I can only assume was the "cushioning" layer.

 

[CUCVFAN]

The boards were originally nice solid wood and are still partially decent, but are pretty wet and rotting on the end near the tailgate.
The rust under the wood appears to be from the original bed floor. Fortunately, at about 3/16" thick, it still has about 1/8" in the really rusted spots.

 

[71DeuceAK]

Mine has a drop-side bed which according to the TM, was specifically not produced due to the length. The bed is similar to a deuce bed in that it does not have the taller (and fixed) sides towards the front. In fact, the troop seats from my deuce fit the 927. I have yet to see another like it.

That's a rare gem.

 

[CUCVFAN]

Some more info on this thing. I don't think that this particular bed was made this way originally from the manufacturer. The reason is that I found some spots of "filler" under the wood in the rear section. I did not know what it was at first, but when I chipped them out, there were what appear to be prior rust holes in the bed floor that were filled. Not sure why this bed would have been that rusted, unless it previously had this construction and they re-built it, but they filled several holes with the filler shown.

As for construction, It appears they welded 1.25"x2.5", 3/16" wall rectangular tube in an "H" pattern to the stock bed floor. The cross piece is 12' from the front (8' from the rear). The boards were cut to size and placed in the framework, then covered with what appears to be 11 gauge sheet steel, welded to front bed wall, center "H" and the bed sides. In the rear, it was wrapped down around the wood and welded to the floor. The front wood was really rotted bad, even though the rear area had the worse rust.


To make a useful bridge out of this at this point, I think I will drill a few drain holes, knock off the heavy scale, and paint it with some POR-15 or equivalent. Maybe a top coat, too. Then I'll screw some new 2x6 boards down without covering it with any steel, leaving spacing for drainage/evaporation. It should last as long as I need it, but this has been WAY more of a pain than I wanted to deal with...