Building 2-car trailer

[racer-025]

I've started building a 2-car trailer for two ITA CRX's. The trailers specs are:
- 24.0' X 6.5' deck
- tandum 3500# axles with brakes on both
- leaf spring over axle suspension
- 15" wheels with load C rated tires
- 2x4 box frame (2 on each side for car wheels)
- 2x2 cross bracing
- 1/8" plate on wheel tracks only
- tongue 2x5
- 2-5/16" 10,000# ball
- load distribution hitch
- break away kit & brake controller

I'll fill you guys in on the details, and how it hauls if your interested.

[BMW RACER]

I'd think about going to triple axles. A little more reserve load capacity. Have you looked into those torsion axles? I have them on my TPD. They seem to work fine and look a lot easier to mount.
Keep us posted.

[racer-025]

I already have the two 3500# axle assemblies. I think the total gross weight is around 6000 pounds so I think it should be OK. I'm not sure on the C rated tires. May have to go to D or E but time will tell.

[wally]

If you are building a steel 2 car trailer, I would recommend (2) 5200 axles. By the time you figure in the weigth of the trailer, you are close to the capacity of the axles. Bigger axles means bigger brakes, bearings and tires.

Wally
Trailer World Inc.

[apr67]

Get two big axles. Go with oil bath bearings, and brakes on both of them. Torflex are the only way to go.

[JohnRW]

You need bigger axles. My 18' steel open deck trailer is over 1800lbs. all by itself. You need a lot of steel to keep the side rails of a 24' from flexing and cracking.

What is your weight budget for the trailer alone ?

[MMiskoe]

Why box tubing as apposed to C-channel? Channel has a better strength to weight ratio than tube. Compare the "I" and pounds/foot numbers in the steel books. Cheaper too.

It may not be an issue, but box tubing needs its ends capped to keep road salt out, channel has no internal surfaces to worry about.

Paint, paint, paint. Send it out for sandblast prior to wiring & axles. Call up a real paint distributor for their recommendation on primer & top coat. Do it right, do it once. Just did mine w/ a Sherwin Williams epoxy eurothane - looks great & very tough.

Measure your door bottom heights, try to make sure they will clear the fenders when the car is on the deck.

[racer-025]

Weight of trailer estimated at ~1800. 2 crxs at ~2000 = ~5800. So I'm hoping to keep it under ~6200 GVW. I'd like to build it with Torflex but I already have the 2 axles. Worst case I add another similiar axle if it gets over loaded.

I built another trailer (single car - no suspension) using channel, but had undesirable results. The channel kept cracking. This time I figure 4-2x4 box "should" do it.

MMiskoe,

I don't really want to paint this trailer. I am planning on having it hot dipped galvanized.

I put a PDF drawing on my website. Check it out and let me know what you think....
(don't all download at once, lol, it is on geocities w/ not much bandwidth)

www.geocities.com/mcnuttracing/bamtrailer.pdf

[chuck baader]

Nice drawing. Comment: personally, I would move wheels back about 18" leaving enough room to open door on rear car. Serves two purposes...makes trailer more stable pulling, and keeps more weight between the wheels and tow vehicle--less cantilevered load on the rear of the trailer.

I assume you will be using a class 3 load equalizing hitch with torsion bars? Very strongly recommended. Good luck, CB

[MMiskoe]

I didn't mention galvi because of the cost. It is by far the best way to coat something that will be outside. I've seen other trailers done that way.

Cracking of the C-channel is odd. Seems to me it would only do that if it was being flexed repeatedly, especially outside its elastic range. If the sections of tube you've selected are too small, they will do the same thing. What were you thinking for wall thickness?

[BMW RACER]

Are you going to carry your cars like in your plan? How about putting them nose to nose? That way the weight is more towards the axles. You might be able to make the trailer shorter, remember all you need is enough length for the wheels, I used to tow my 2002 on a 10' long trailer.
Keep us posted.

[racer-025]

Chuck,

I'm not sure on moving the wheels back any further, because of the long span between the hitch and the wheels. Wouldnt that put too much weight on the hitch?

My 2500 van has a class III while my motorhome has a class IV. I do have a 10,000# weight dist hitch that I can use on both.

MMiskoe,

I think the C channels cracked because of no suspension X trailer running empty many times X rough roads. I do have a backup plan if there are too many stresses on the frame.

BMW,

I've considered nose to nose, and that may be the wiser idea, especially with my van. I think they could go either way using the motorhome. I wanted to keep the deck at 24' in case I change to a longer race car. I've been racing the CRX for many years now, but the Integra is longer.

BTW, I have 2 identical CRX's as shown.

[chuck baader]

025..If you have the 1000#+ torsion bars for the hitch, you are far better putting the most weight you can between the car and trailer wheels. Look at a commercial truck and where the rear trailer wheels are in relation to the load. Good luck, Chuck

[irondragon]

I think that two 3500pd axles will not provide sufficient capacity. Better to get get a pair of 5K pd axles. The tri axle arrangement will cause tire scrubbing, difficult manouevering and 50% more maintenance.
Also, the 2x4 tube sections seem too light. Please consider using 2x6 unless you plan to use a built up deck edge or rail to add section.
Don't know if you've had experience w/ hot dip galvanizing but you will have to put a 1/4" diameter vent hole in every closed piece of tube. Tiny amounts of moisture or even moist air will cause explosions when hot dipped. I have seen molten zinc blown onto the roof sixty feet above the dip tank.
Matt Miskoe is correct that C sections offer better I per pd but the assymetric section can cause weird flexures at the flange edges.
Best Regards - Bill Miskoe

[wally]

Here's some pictures of a 2 car trailer.

Wally
Trailerworld.com

http://www1.trailerworld.com/Content.aspx?...eContentId=1425

[wally]

BTW that trailer tip's the scale at 2070. lbs!

Wally
Trailer World Inc.

[alfa]

So what's that trailer go for, wally?

[wally]

The 30' 2 car track model sold for $8900. The owner hauls two Civic SI's for Solo II racing. The trailer with the two Porsche sold for 14K, it was loaded with a lot of options.

Wally
Trailer World Inc.

[irondragon]

I ran some numbers on the 2x4x1/4 tubing. Statically you are OK. Max fibre stress at about 17ksi. Yield probably at 45 ksi.
However this doesn't look at dynamic loads which are hard to determine being dependent on things such as % unsprung weight (low in your case) and spring damping rates.
But I think you will experience gradual yielding over time with these sections, particularly if the suspension ever bottoms.

If you were to use 2x6x3/16 tube you would increase stiffness by a factor of 2.4 and weight would go up 6%
2x6 - I=11.1 W= 9.42 pd/ft
2x4 - I= 4.69 W= 8.81 pd/ft
Best Regards Bill Miskoe

[chuck baader]

025..I'm with Bill -- use the larger section. You (per my rough estimate) are over 2000# just for steel for your trailer. I will be very surprised if your road weight is under 6000#. You also need to look at higher load range tires than standard automotive...i.e., real truck tires. The axles should be fine, but I would seriously consider a third. When engineering a structure such as this, I always used a 50% safety factor. Haven't look at the stresses involved with the static loading of your bridge, but with dynamic loading I would look hard at a greater safety factor. This should muddy the water somewhat. Have fun, Chuck