cbrTodd's Trailer Project

[cbrTodd]

Disclaimer: If you dislike modification of military trailers, you won't like this thread. You have been warned.

I've been working on a project for a while now that I thought I would share with the group. I wanted a trailer to pull behind my M923A2 based camper. I will share more details of the 'need' later, but I wasn't looking for anything particularly heavy duty. I didn't want it to be too heavy or too tall. I wanted it to be easy to see while towing and easy to back up. I wanted it to retain at least a somewhat 'military like' design to match the camper, so generic box trailers wouldn't do. I just couldn't find anything that suited me.

So as no surprise to anyone, I started looking into making something. M105 trailers are readily available and relatively cheap, but they are too narrow to see behind the 923A2 and they are so short that they jack knife really easily (I regularly pull an M105A2 already so I am well aware of this).
Could I fix those issues with some fab work? I thought about widening the bed on one, but that would look silly without doing something to fix the track width of the axle. I had seen where folks had tried to put duals on them, but that ended up with an over legal width condition.

My 'aha' moment came when I found an M105A2 trailer with an M105A1 type axle. The earlier axles use M35A2 style hubs and brakes, which can be flipped the same as is done on trucks to run duals vs singles. I did some measuring and verified that if I flipped the hubs inward and ran duals, the tires would clear the leaf springs and be less than 96 inches overall width.

So if I widened a trailer bed, it seemed like I could stay legal on width and have a trailer the same width as the truck. I figured if I lengthened it too, I could lessen its tendency to jack knife. So I set about procuring another M105 for parts in addition to 2 donors I already had, and commenced disassembly!

Donor #1 pictured having the bed removed to work on the frame:

Donor #2 with a damaged frame being cut up for raw materials:


Donor #3 ready to be worked on:

 

[cbrTodd]

With the frames all separated from the beds and the frame from donor #1 cut apart to get the inner crossmembers and rear frame out that I needed, I set to work on cutting the tongue off of donor #2 right in front of the first cross member, keeping all of the frame rail with it. Donor #3 got the opposite treatment - it got the tongue cut off as far forward as possible and keeping the frame rails with the rear. I then took the two 'long' pieces and used a 'z notch' to join them together, which made a frame about 2 feet longer than the original. I used some of the crossmembers from donor #1 to box in the entire frame from the front cross member forward and then added in another crossmember in the middle of the lengthened section. I now had a trailer frame that was 2 feet longer than it started!

To keep the weight distribution similar, I also added a foot to the back end. I didn't bother with boxing that in since it was behind the axle, but I did do the Z notch.

After that, I flipped the hubs, did a full bearing and brake service, and put donor bed #3 back on it to start the widening and lengthening process.

 

[cbrTodd]

The bed work is what took a lot longer than I expected. I had hoped I could split one down the middle, weld in pieces of donor trailer metal, and end up with a wider trailer. I didn't factor in how rust prone these older M105 beds are. The way they are constructed on the sides, they have a layer of 14 ga steel sitting on top of the 1/8" decking with spot welds holding them together. It collects water and has 'rust jacking' push them apart.

I understand that the original service life was short enough for that to not be a problem, but it meant that I had a lot of repair work to do at the outer edges. It ended up making more sense to rip off the bed rails from the decking surface upwards, extend the hat channel support structure and the decking, and redo the outermost rail surface with new metal.

It was a lot of work, but I ended up with a decking surface that went from 83 inches wide by 110 inches long, to 96 inches wide by 146 inches long. It did involve narrowing the space between the wheel tubs to 44 inches, which wasn't an issue for my intended use, but it is a consideration if you need to haul sheets of plywood or something.

 

[cbrTodd]

Then it was time for the bed sides. Because I cut off the original continuous piece of metal that makes the bed sides and outer rail, I have an extra joint that the original trailer didn't have. From the outside, it won't be obvious. On the front, I used a piece of metal and an extra rail from donor #2 to widen the front panel of #3. I am still working on the tailgate, which has some rust holes that need repairing, even starting with the best of the 3 tailgates I had. But it's looking a lot more like a trailer than it has in a while.


(Yes I used chatgpt to blur the background and not make my shop look so messy! I have spent all my time working in it, not cleaning it.)



Then I acquired another set of sides and bows to work on. All 3 donors only had either no sides or partial sets, but I needed 7 bow sets worth total, in addition to needing them to be taller than normal for my intended use...



That's pretty much where I am at now. I spent yesterday making brackets to add the air tank and relay valve underneath, as this trailer started as a 1-air-line trailer with no break away emergency coupler. I added that to my 'normal' M105A2 a while back, so I already knew how to do that. I have a while before it's going to be warm enough to do any outdoor painting here in South Central Indiana, but bodywork is the next step after I have the situation sorted out with the side rails and bows.

So, if anyone thinks it isn't possible to run dual 9.00-20 on a M105 without modifying the axle tube or being over 102" wide, I can say otherwise. It just requires starting with an M105A1 axle and heavy modifications to the bed! I just made the modifications more significant by also lengthening this trailer at the same time.

I will update this later when I have made more progress, but given that the work in this thread so far is about 6 months of my 'spare time', it might be a bit.

 

[Tinstar]

That was a lot of work.
Should handle anything you throw in there.
Looks good!