Lightweight Trailer Build

So I need a trailer for the CRX and for numerous reasons it is really difficult to find commercially available trailers for very small and light cars. So I decided to build my own and post up some info for anyone else looking to do the same.

Here is the basic design I am going with:
http://i256.photobucket.com/albums/h...SS/trailer.jpg

The main deck will be 13' long and 6' wide which will fit a Civic, CRX, Miata, and the S2000. I am going to use all box tubing for maximum strength and low weight, and leave the center of the trailer open. For axles I am going to use dual 2000lb torsion axles and tie them into the frame. Why dual axle? I could have easily gotten away with a single axle with a sub 1900lb car. But with a single axle I would have to use heavy duty trailer tires. With dual axle I can safely use much shorter car tires which mean shorter ramps, massively lower CG, and the ability to open the doors over the fenders.

So today I went and picked up most of the steel and tires:
http://i256.photobucket.com/albums/h...S/f3241996.jpg
I am going to build the main rectangular section of the trailer first and then attatch the tongue and axles later.

Then I needed to break in an engine so I took the CRX to pick up the wheels:
http://i256.photobucket.com/albums/h...S/0db691f4.jpg
I think they are 13x4.5. I would have loved to find a nice set of lightweight aluminum wheels but the price of steel trailer wheels was too hard to pass up: 5 new wheels for $100 with tax!

The trailer supply store had a few different styles of wheels to choose from. I asked to go back into the warehouse so I could compare them and figure out which was lighter. They thought I was crazy...

http://i256.photobucket.com/albums/h...S/3b0b0ac9.jpg
12.4lbs is not too bad! From what I have seen 14's are considerably heavier but have much higher load capacities.

The next thing I need to figure out is decking. While aluminum would be nice I think I am going to go with steel that way I can weld it on which will add a ton of strength. Then make the decking super thin and brace (or double up) the 4 areas where the car will rest on.

So I would love some input on this. The two main sections of decking will be one foot wide. My car's maximum corner weight is only 600lbs. What thickness would be safe for the sections that will only be driven across in loading/unloading? What thickness would be safe for the sections that the car will actually ride upon?

Great thread idea, David.

Looks good. Keep the pictures coming.

I was just thinking about white spoke wheels the other day. I had a set on an old Ranger and wondered if they still made them.

I'd think that the best way to determine good deck thickness would be to compare to other trailers out there. They've done the engineering for you.

You could setup a flex test on your own: weld some 1'x1' or 1'x2' squares onto angle-iron frames and drive your car on them to measure deflection. I think that would give you a pretty clear idea of their capacity and how much flex youd be comfortable with.

Would one more piece of tubing down the center of the section where the wheels roll fix the problem for this car and future ones too? I'm guessing then you could use just about anything for the surface.

Ok I just ordered (2) 2000lb dexter brand torflex axles. I went with a 22.5 degree down start angle which should give me a pretty low deck height of around 15.75". I found another brand that had a cool adjustable ride height setup but the prices was more and I would have to pay for shipping. Here are the two styles:

http://www.cityspring.com/uploads/im...onAxle_GDC.jpg
http://www.leeagra.com/images/torflex-header.png

One of the issues I have run into is brakes for 2000lb axles are expensive and harder to find. The far more common 10" brakes (typically under $100) won't fit only 7" brakes will work ($200). I tried to figure out a way to make the 10" brakes fit, the backing plates will bolt right up so it's just a matter of finding an 1 odd size bearing. But I don't have time to reinvent the wheel so I ended up buying one axle with brakes and one idler. I can always add brakes to the other axle later but with a car/trailer that are this light I might never want to.

Here is what I found for current prices on 2000lb torsion axles:
Bare axle $194
Idler axle $225
With brakes $365

7 inch brakes look tiny!
http://www.randpcarriages.com/ebay/brakekit7.JPG

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Originally Posted by onething

Would one more piece of tubing down the center of the section where the wheels roll fix the problem for this car and future ones too? I'm guessing then you could use just about anything for the surface.

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Good idea! I have thought about the same thing. If spanning the full 1 foot doesn't work that may become the backup plan.

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Originally Posted by Davidss

Good idea! I have thought about the same thing. If spanning the full 1 foot doesn't work that may become the backup plan.

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Can I get that in writing? Oh, I guess it is.

I guess cost and weight are the down side.

Have you looked at or thought about leaving the rear of the trailer open? This would make it easier to attach axle straps and tie downs. I've seen it done and it seems to work well.

http://www.reliablecustomracingtrail..._trailer01.jpg

I am planning one too, and plan to use the rear open space to store my ramps.

I also plan to get the 5-4.5 pattern, and use Ford wheels.
also have the option for vintage mags or such.

Ranger wheels have small center holes and won't fit over the hubs on some.

Leaving the back open seems like a neat idea. If you added, lets say, a 1"x2" rectangular tube diagonally, front to back, to each of the outer sections it would support the wheels, and, stiffen it enough you could probably leave the back center section open. Should be about a wash on weight.


Jim

I would leave the center open all the way to the front. Then use small cross members about every 8 inches under the sections for the wheel tracks. No need to have the center section covered if you are that concerned about weight.

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Originally Posted by davidss

i am going to use all box tubing for maximum strength and low weight, and leave the center of the trailer open.

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My thoughts are similar to the previous mention of supporting where the wheels will be. You can then use 18 ga CRS over this, with Alum down the center (bonus: racing stripe!).

Triangles are your friends.Attachment 5536

That looks a lot like my design that Andy Hollis now owns. Andy's trailer has some additional 1/8" x1.5" steel straps under the tires, but the best solution is to just use a heavier deck material, it will strengthen the whole trailer. My design was to have wood ramps that slid underneath the deck and also helped support the tires if the deck bowed too much. Early ferro-composite construction! The flaw there is the ramps can get trapped sometimes.

Do you have plans to brace the junction between the tongue and the bed?

I built an 18' car hauler after my old one was stolen. If the trailer will be used exclusively for hauling cars, just put two runners where the car's tires will go and leave the center deck free. On mine I used C-channel for the main frame and 2x2 angle iron side to side spaced pretty wide 16 or 24" centers (possibly 12, but it seems like they were pretty spread out), no secondary front to back runners. The heaviest thing hauled on it has been a skid steer at around 7,000 pounds. The deck flexed but it seems to have rebounded just fine. It's easy to go down the extra strength road but it isn't necessary especially if you have an eye toward keeping it light. My ramps store under the deck but don't hang below the bottom of the frame. I cut holes in the C-channel at the back and they slide in - the angle iron had to be notched a little for the ramps to clear too. One of the nicest features on my scratch build is the storage. I closed the tongue in and put a bottom on it and a hinged lid. All the straps, chains, etc go in there.

I can't tell what kind of wall thickness you have there, but it appears to be plenty substantial. I'd skip the secondary front to back runners unless you're just going to leave the entire center section completely bare, in which case it'd be nice to have it supporting your decking and you could probably leave the side to side braces out entirely (assuming your runners are going to be around 12" or so). Maybe include a couple where your tires will be parked. Then just get the thinnest diamond plate they have available. Welding that in will sure things up quite a bit, even if it's relatively thin. I like that notched tail for a dedicated car hauler. Mine is multi-purpose so I left a full deck and tail. I used those same type of axles to get a low ride height, which is why I didn't employ a "dove tail" - too much dragging.

I'm concerned about the axle placement though. They appear to be centered on the main section of frame. They oughta be further back so you can get some tongue weight which will make it tow much more nicely. It'll also help prevent dragging. I'd find a good, "off the shelf," car hauler and scale the axle placement based on that.

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Originally Posted by Webspoke

That looks a lot like my design that Andy Hollis now owns. Andy's trailer has some additional 1/8" x1.5" steel straps under the tires, but the best solution is to just use a heavier deck material, it will strengthen the whole trailer. My design was to have wood ramps that slid underneath the deck and also helped support the tires if the deck bowed too much. Early ferro-composite construction! The flaw there is the ramps can get trapped sometimes.

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It's no coincidence. I considered a number of designs but kept coming back to some pics I took of the Hollis trailer last year. Your design is really simple to build and there are a few other elements that work with my car really well. If you have any tips on improving the design I would love to hear it!

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Originally Posted by Flyin96M

Have you looked at or thought about leaving the rear of the trailer open? This would make it easier to attach axle straps and tie downs. I've seen it done and it seems to work well.

http://www.reliablecustomracingtrail..._trailer01.jpg

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Maybe I'm missing something but If you leave the back of the trailer open that would make it massively weaker.

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Originally Posted by TexasStig

Triangles are your friends.Attachment 5536

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I like that. I don't think I would go that far with triangles but even angling the tire braces by 10-20 degrees would be stronger overall with no downside.

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Originally Posted by boisking

Do you have plans to brace the junction between the tongue and the bed?

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I am going to use stronger steel there and at least partially (or possibly completely) box it in.

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Originally Posted by Davidss

I am going to use stronger steel there [the tongue junction] and at least partially (or possibly completely) box it in.

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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.

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.

A+ thread.