My second build - Project Heep trailer mk2

[MattFromDenver]

So I learned some lessons from Project Heep (2005 LJ Rubicon) trailer mk1, mostly that I should build a trailer for a Jeep LJ like an aircraft, not like a tank, keeping in mind the Weight/strength ratio, rather than Strength/weight ratio. The tragedy of mk1, leading to lessons learned:

1. base frame and 2 crossmembers are 2x3 3/16" wall, exoskeleton is 2x2 1/8"
2. drawbar is adjustable, with 2.5 square 3/16" and 2x2 1/4" tubing, along with 2x3 3/16" a-frame
3. front, sides & tailgate are skinned with 14ga diamond plate
4. never got around to lid and fenders
5. couldn't get the 5/8" hole in the right place, so irrevocably ruined a >$200 AT coupler by welding it to my adjustable drawbar (including rosettes - see theme about tendency to overbuild.)

Empty, this almost bottoms out my timbren 1200# independent suspension. Loaded, it's banging off the frame, and the only travel is by virtue of airing down the 35" tires to 15#.

Plans for mk2 (and my plea for feedback/advice) -

1. scale down the wall thickness on everything - if I use 1/8" for the base frame and 14 ga for the exoskeleton & lid (without changing the tube O.D.,) all the steel (including 14 ga diamond plate lid & front skin,) adds up to ~500lb, which I think is a good sprung weight empty.
2. 1.5" tube & 16-14ga fenders (to match Project Heep and because my buddy's tubing bender is one of my favorite fab tools.)
3. brakes - I only towed mk1 on the highway, which was heavy but handled well, I think anything over 1000# without brakes is potentially scary behind the Jeep. Fortunately, I wired the Jeep with a 7 pin socket in anticipation of running brakes and 12v back to the trailer.
4. fabbed independent airbag suspension

on point #3, I'm thinking about buying a straight axle with brakes at 65" WMS and using that as the back half of a "jig" to fab up the trailing arms, then slicing out the middle to leave the spindles attached to the arms. My logic there is that it not only helps keep things square, true and symmetrical during the build process, but also leverages the built-in camber that the axle comes with, which would subsequently end up built into the interface between the trailing arm and spindle.

Attached are build and aftermath shots of mk1. It would be *perfect* if I ever had to tow a bobcat with Project Heep, but sadly is overkill for my tent and cooler, and likely to be upcycled into parts for mk2 and tool stands for my garage.

 

[highlandercj-7]

I think your springs may have killed the first design. It doesn't look all that heavy, what added that much weight? I have a 2x3 3/16" wall frame on my CJ trailer and it has never gave me issues. I ran Grand wagoner front leafs in it. Held in place with all CJ hardware.

 

[RagnarD]

Sounds like you have a good plan. I too have a list of things I would do differently for round 2.

First on your list should be to build a cart for that welder though

There was another build on here when a standard axle was used in the way you are planning.

ETA: Found the build thread

http://www.expeditionportal.com/forum/threads/67840-My-2-trailers-build

For me, it has been worth it to buy pre-made receiver sections with the hole in the correct place and a collar. Curt makes unfinished from 6" to 4' and they are decent prices on Amazon.

 

[MattFromDenver]

@Highlandercj-7 - I agree about the springs. 2K springs would have cut it (still could,) but I think brakes would be in order at that point. Leaves the possibility of mocking up an independent trailing arm with airbags on the existing trailer, but I think it'll still be a pig. You're right about the basic frame not being out of hand using 3/16 wall tubing, but add to that the adjustable drawbar (~6' of 2x2x.25 nested inside of 6' of 2.5x2.5x.187,) the add'l 2x3x.187 a-frame and the 14 gauge diamond plate for sides, tailgate and front, and I ended up with really noticeable weight behind the Jeep. That 4.0 feels like it makes all of about 11 horsepower above 12,000 feet, so I'm inclined to keep the weight as low as possible.

@RagnarD - yes, I have a build ordering problem. Welding cart and table with vise are ahead of mk2 in the queue Thanks for the link.

 

[toyrunner95]

Diamond plate is heavy. Use sheet metal. I used 1x1 to build my truck bed. I could lift the frame easily. Airplanes are light materials properly braced. Use physics not brute toughness. Why do you need such heavy duty uprights? Make your base square and tongue heavy then fit your storage area on top. Use lighter materials and more braces.

 

[MattFromDenver]

@toyrunner95 thanks for the info. It was easy with the first build to start burning metal and build a tank. I figure the trailer needs to be no tougher than the vehicle towing it anyhow. Made the decision yesterday to substitute aluminum diamond plate for the skin, it'll look better, ends up between 1/3 (.063) and 2/3 (.125) the weight of the 14ga steel skin. $$ but the idea is to actually use mk2 more than once before up cycling it into shelving & tool stands.

Still working out all the little gremlins before I start cutting metal, then allowance from the powers that be to build yet another trailer in the garage, and then off to the races.

 

[toyrunner95]

Look at utility trailers online. You will notice that a lot of them use bead rolled panels. Making the metal stronger and eliminating the need for a lot of bracing. Even adventure trailers uses bent sheet metal not a frame.

Also look into the dimensions of the trailer. I would focus on the corners. I used to be a heavy equipment mechanic and we would put catwalks around the excavator houses to prevent them from getting all beat up when wringing around trees. Put the metal where you need it. Put the engineering where it belongs.