My M762 build (same structure as flatbed M416) - made a gear hauler (solar and fridge updates)

[stbrendan]

Hi all - I'm going to try and document what I have done to a 1967 M762 3/4ton flat bed trailer. Based on my research, a lot would also be applicable to a flat bed M416 trailer.
I got this trailer 2nd (or 3rd... maybe 4th) hand, from a nice dude who had modified it for his own use, and documented it on http://www.ultimateyota.com/showthr...er-Buildup&s=69e7ee37b811853390cf49af17532e7e

So. From where I got it, to where it is now is what I will attempt to show.

I bought it with the intention of turning it into a shed on wheels for offroad/rough road self supported remote camping in California. The family and I like getting away to primitive camping spots, and I wanted to make it easier to do that without all the packing on each end.

I have NEVER done anything fabrication oriented - I am a desk job guy, and taught myself these skills from hours of youtube videos. If I had to do it all over again, I now know that I could have built it a little bit more to my ideal specification if I had started from scratch. BUT--- I got a cool piece of military equipment, already registered with CA DMV, and I didn't have to jump through those hoops, so there are trade offs for sure.

Pic 1 is how I got it.

Pic 2 is how it is now, packed and ready to camp (which will happen ... soon... ish).

Things I want to do in the future include lights/battery/solar/fridge.

Things I have done--- I will document in additional posts.

 

[stbrendan]

By the way, thanks to all those that documented their builds before me, I learned a lot (and borrowed a lot) from your expertise and sharing.

 

[stbrendan]

To get started on my project, I did test welds on scrap steel learning how to lay it down and do some basic fillet, angle and butt joins. My tool was the 20Amp Chicago Electric 170 Flux/Mig model, plugged into the 30Amp dryer outlet in my laundry room, using an expensive heavy gauge extension cord and heavy gauge prong converter. Both are 50Amp rated, so I figure I was still getting all the output I needed, which definitely seemed to be the case based on how much penetration I seemed to be getting on the metal.

Controlling burn through was a challenge on anything under 1/8" thick. I definitely recommend beveling and making sure the weld zone is clean, it helped. I switched to .030 Forney 2lb welding wire for most of the build, and then Harbor Freight had a sale on .035 Vulcan wire which had pretty good reviews, and I preferred the heavier gauge. Since it was all Flux welding- splatter and grind were my constant companions.

The other tools I used a lot were my Dewalt grinder/cut off with Diablo grinding discs and Avanti cut off discs, and a Diablo "Steel Demon" 7.5" carbide blade in my miter saw to chop down the metal and make angle cuts. I also had to use the blade in my circular saw on some of the sheet metal, which worked OK for the 16gauge.

 

[stbrendan]

After getting my hands on the M762 trailer and reviewing what was in front of me, I decided on a 40" wide x 70" long x 36" tall box. I had already figured out I wanted a rear swing out hatch, and doors in front of the fenders to meet my storage an organization goals. I also designed the expedition box around built in drawers (2 drawers- 18 w x 50 L), and a cargo tray on top of the drawers. I figure I might want to do an awning and/or roof top tent, or strap stuff on top, so a rack was in the design too.

I also wanted to change from 5 lug hubs without brakes to 6 lug brake hubs and use toyota rims to match my 4Runner (can share a spare that way, etc.)

Lengthening the tongue to allow better towing and a tongue box for future add ons wraps up the current plan.

 

[stbrendan]

After getting all my measurements and drawing it out, I put together a parts list based mostly on 1/8" in thick steel for most of the frame, an overbuilt 1/4" thick steel tongue extension concept, 14 gauge steel for the rack and misc. frame support pieces, 16gauge steel for door frame, and 16 gauge steel for the walls. Not exactly the lightest material. If I was going to do it again, I figure I would use 3/16" for the tongue extension, and incorporate more 14gauge in the frame, just using 1/8" in key spots.

 

[stbrendan]

Rust removal with wire wheels, followed by priming all over kicked things off.

 

[stbrendan]

The existing tubing on the trailer was 1/8", so it made a good match for all the 1/8" box framing I welded on.

Witness the carpenter square- it was not the squares fault, I blame the operator and the original government contractor for anything misaligned.

 

[stbrendan]

Weld the frame, grind the splatter, repeat as needed.

I used a 3 x 1.5" x 1/8" rectangle tube for the top of the frame - I wanted it to overhang the walls like a lip, plus gave plenty of platform to weld the rack and add the sheet metal for the roof.

 

[stbrendan]

I had to cut holes in the existing metal floor to get to the spot where the tongue rails attach. Word to the novice from one that has been there- a quality step bit is a good investment for drilling metal. Harbor Freight Warrior titanium regular drill bits cut fast ... until they shatter The Bauer step bits were what I bought after hours of drilling. Wish I had bought them first.

 

[stbrendan]

Got help from my dad and sons along the way - here we are drilling for an hour on the tongue attachment holes. And then figuring how to re-attach the lunette holder.

 

[stbrendan]

Doors are... diabolical. I had come up with a door frame concept using 1" angle iron with 3/4" square tubing nested inside the angle iron. I used weld on hinges, and welded the door frames to my box frame. I measured 20 times for every cut or adjustment, and am mostly ok with how they came out. a 2nd hand welding table helped me square things up for precision welding and grinding. I bought some carbide dremel bits from Amazon, they were amazing for getting into the wee corners of door frames.

 

[stbrendan]

Got more help when it was time to attach the sheet metal sides/roof/etc. Neighbor helped me wire wheel and acetone clean the sheet metal, Dad helped me test fit and mount. So - belts and suspenders and safety pins is how the sheet metal is attached. I had heard great things about Sikaflex, so I used a lot of it. But, this is steel, not aluminum, so also put at least a foot of spot weld in corners and convenient spots attaching the sheet metal to the frame (and as you weld next to Sikaflex, watch out for fires!). But then at a later point when I was attaching door handles, I used stainless rivets to attach the door handles to the doors... so I also went back and retrofit some rivets onto the sheet metal walls. So... they probably aren't gonna fall off!

 

[stbrendan]

Put the older son to work rolling on primer inside the trailer.

 

[stbrendan]

I had planned on using plywood on top of steel tube floor rails, but had so much "drop" cuts of sheet metal that I welded some pieces together to make a sheet metal floor. I then put a hardboard piece on top of that to provide a smooth drawer bottom.

 

[stbrendan]

Then I built my drawers, and used low friction UHMW tape to make them move smooth.

Younger son uses the rack as a climbing apparatus.