Lightweight Trailer Build

[Davidss]

Update! I got a killer deal on some 14ga steel diamond plate at the local metal yard. It was already cut up into a bunch of 4 foot by 14 inch pieces which are perfect for the decking. And as they were already cut up I got them for drop steel prices ($0.55 a pound!). I ended up buying every piece they had as I'm sure I can find uses for cheap diamond plate lying around the shop!



Also my secret weapon came in the mail:

You are looking at a 100 pack of roll cage gussets. These will add a TON of strength and weight almost nothing. I plan on using as many as I can! Total cost for all of them was only $35 shipped.

So now that I have all the parts I actually got to work today. I am going to build the outer rectangle of the deck first, then add the bracing, then attatch the tongue, and finally the decking and axles. I almost got through with the decking frame today (ran out of mig wire). In it's current state 2 people can still pick it up.


Gussets!!!


I have never built anything of this scale before so I was figuring things out as I went. I started by tacking up the outer rectangle. A great tip to quickly square the frame is to measure the distance from opposite corners (front left/back right and front right/back left), and get them to equal out using a ratchet strap.

I consider myself a decent welder but I'm not great at welding uphill/downhill/etc. So I just kept flipping the trailer frame over and on it's side to weld everything at my preffered orientation. With some careful planning in only took a few full rotations.

Here is a closeup of a typical weld. I learned mig on my own, so are these are good/bad?:


I also found a spreadsheet made to calculate tongue weight. It was designed for teardrop trailers but I modified it for car haulers. Here is the link:
https://docs.google.com/spreadsheet/...UJMWmxvZ0dsRVE
To edit it you will need to save a copy. If anyone knows of an easier way to host a spreadsheet that people can edit but can not save let me know. Also please note that the spreadsheet is setup for single axle. It will give you a good idea of a starting point of a dual axle just assume the tongue weight number it gives you is high.

[Davidss]

Because you are carrying a dynamic load (cars move a round alot more then normal cargo because of the suspension), I would run the center tongue spar back to the second cross member. I would also run the triangular tongue braces back to under the main frame to second crossmember as well.. This will allow the solid steel to support the weight on the front cross member and reduce the chance of the welds breaking loose from fatigue.

Even if you use a fully boxed, heavy gauge beam for the header, that is a lot of stress isolated on a single piece of metal. If you let the tongue reach underneath the first cross-brace/ header piece and tie onto the outer stringer on each side just ahead of the second cross-brace junction (welded at every intersection), you will be able to distribute the stress over a lot more metal and have no worries about the tongue as a weak point. Added plus: triangulation. Second added plus: you can design a little rear-tilt to the trailer deck for easier loading. Refer to HudsonHawk's excellent camp trailer thread for photo instructions about fish-mouthing the tongue spars for an attractive finished look.

Another option that would allow more clearance for a low-to-the ground trailer would be to build it as you have drawn, weld the tongue junction, and get some 3" or 4" x0.25 flat bar and wrap it around the outside corner on each side. If you fully weld all of the edges with about a foot along the stringer and a foot along the tongue spar, you could distribute some of the stress away from that single piece of metal. Add some flat gussets on the top and bottom for even more bracing if you like. This is weaker than my first suggestion, but stronger than nothing. Benefits: lower weight, cleaner lines, and more ground clearance.

A third option (after typing the first two, I think this is my favorite) would be to cut your tongue and stringer to be welded together first. Gusset both sides of the junction with flat bar like in option 2 and then add the header/cross bar to the inside of your sandwich plates. This would be strong, sleek, light, and offer plenty of ground clearance. You could still use a heavy duty header and weld your center tongue spar to it with a butt-weld.

Also, I think seam-welding some diamond plate on top of the stringers will have plenty of triangulation effect. If this is your decking material of choice, just K.I.S.S. and use some angle-iron to brace under the deck.

Big thanks for the awesome input! After reading these posts I put a lot of thought into this over the last few days. Ultimately I don't want to change the basic design of the trailer. The design the Stan originally came up with incredibly simple and easy to build. But I am definitely going to add at least 4 tongue braces and use some of the diamond plate to wrap around the tongue. In addition I am going to completely box in the bottom of the tongue and most of the top. This should add a ton of triangulation and make a nice little 3 inch deep storage area!

[sammm]

Those welds look great to me! What welder are you using?

[black roadster]

Yep. Nice looking welds. I've seen better but not much better welds. I've also soon worse welds and they were much worse than yours. I'll give you an A- for welding. They're a lot better than mine.

[Keifersmith]

If you've never been to Westex Iron & Metal Company in Fort Worth (http://local.yahoo.com/info-18862319...any-fort-worth) it's also a great place to pickup metal scrap. They're a recycler in addition to selling new/used materials. I've bought a lot of stuff there for various projects. The place is pretty well organized and the workers are really helpful.

[Davidss]

Didn't have much time to work on the trailer today. The axles came in so I went to pick them up. Disappointingly they are really heavy. The idler axle is 72lbs and the axle with brakes is 106lbs. The only positive is to all that weight is that torflex axles can be used as a stressed part of the chassis.

With a new spool of mig wire and a fresh bottle of gas I finished up on the gussets and built the tongue. With the frame skeleton finished my dad and I could still pretty easily pick the whole thing up. We estimated 200lbs or so:

Those welds look great to me! What welder are you using?

Lincoln 175 amp but I'm not sure of the model. It says NASCAR on the side so it must be good.

[Robert]

Like TexasStig said, I would add some triangles. At least on the front half, back to the axles. That would add a lot of strength and only a little weight. Squares are a weak shape, triangles are much stronger.

edit
Looking good so far.
(I tend to over design things, so I would triangle the s**t out of it)

[Rogue]

That tongue scares me.

[Robert]

Stress with and without triangles.

[Keifersmith]

That tongue scares me.

+1. I tend to overbuild things but I don't think I'd trust those butt welds between the tongue and the frame. Seems to me there's going to be a lot of stress on those weld joints.

[cone-cerned]

Stress with and without triangles.

+1. I tend to overbuild things but I don't think I'd trust those butt welds between the tongue and the frame. Seems to me there's going to be a lot of stress on those weld joints.

+1

[Rogue]

FYI, This is Keith Tanner's Miata trailer that he has had for years. Its been all over the country.
Kinda underbuilt for me, but can't argue with its durability i guess.

[miataspeedracer]

FYI, This is Keith Tanner's Miata trailer that he has had for years. Its been all over the country.
Kinda underbuilt for me, but can't argue with its durability i guess.

Wow. Not sure I'd trust my car on that...

[Rogue]

[OZMDD]

Have you ever checked out a tow dolly? Not really all that much more overbuilt, and people throw full-size SUV's onthose things and abuse them all the time. Rarely see anything more than flat tires and bad bearings. I think the proof is in the pudding, in that both Keith and Hollis' trailer's have logged tons of miles without incident.

I agree that I'd like to see the tongue extend back under the frame a little more, but I think the design looks sound for the load. My 850-lb rated HF trailer is a joke by comparison. He's only putting 2500-lbs max on that thing, figuring tires, spares, tools, etc.

[general default]

Once you get the wheels and fenders on...
Will it fit through the garage door?

From the prospective of the image it looks close.

[boisking]

That tongue scares me.

+1. I tend to overbuild things but I don't think I'd trust those butt welds between the tongue and the frame. Seems to me there's going to be a lot of stress on those weld joints.

I'm waiting to see what you come up with for bracing. Make sure whatever you do, the idea is to distribute stress away from that transverse header between the tongue and the main rails. You want to mimic a sold rail running the full length of the trailer for maximum strength.

[Davidss]

Yesterdays progress:

I had planned since the start to brace the tongue more than what you guys have seen so far but based on the comments I was getting I decided to go much further with it. I capped off the outside corners, made custom larger gussets, boxed in the bottom of the tongue, and added some significant bracing.

Today's progress:

Flipped the trailer over for the last time and welded the decking on. That is over 50 feet of weld bead so it took a while! Welded on steel decking is the way to go IMHO. In my case it was $100 cheaper, only 50lbs heavier and made the trailer much stronger.

Not much left to go at this point. I will probably have it on the ground by tomorrow.

[Davidss]

FYI, This is Keith Tanner's Miata trailer that he has had for years. Its been all over the country.
Kinda underbuilt for me, but can't argue with its durability i guess.

Here is Hollis' trailer:


It went a quarter miles before it developed a crack. No spectacular failure or crash just a crack that was easily repaired and then back on the road.

Like TexasStig said, I would add some triangles. At least on the front half, back to the axles. That would add a lot of strength and only a little weight. Squares are a weak shape, triangles are much stronger.

This is my personal feeling/rant on triangles. I know triangles are stronger and they will be a great way to strengthen this trailer if I feel it needs it after testing. But there are some pretty big downsides as well. Triangles are really difficult to cut right and fit up properly. I would rather have a rectangular structure where all of the joints are perfectly accurate and fit up well with no gaps so I can put a good strong welds on.

Once you get the wheels and fenders on...
Will it fit through the garage door?

From the prospective of the image it looks close.

It's all perspective. The trailer is TINY in person.

[cwisenheimer]

This is my personal feeling/rant on triangles. I know triangles are stronger and they will be a great way to strengthen this trailer if I feel it needs it after testing. But there are some pretty big downsides as well. Triangles are really difficult to cut right and fit up properly. I would rather have a rectangular structure where all of the joints are perfectly accurate and fit up well with no gaps so I can put a good strong welds on.

While it's true that a triangulated square is better than a square by itself, you've done even better. You built a five-sided box structure and that fifth side is like a reeeeeeally wide (stiffer) triangulation. In addition, it's even stronger because it's not just attached at the ends, it's bonded along the entire perimeter of the square and the entire edge of the fifth side/triangulation.