I presume you want the trailer to be safe to tow without the motorcycle on it. This means it must have at least 10% of its weight on the hitch when the motorcycle isn't there. This is fairly easy.
When you load the motorcycle, it adds something like half the weight of the bike onto the hitch and half onto the trailer's axle. So you need a tow vehicle that can take this sort of hitch weight - as you Merkans all drive huge trucks (we Brits know this....
), this shouldn't be a problem!
I have sketched out how I would do this. I have made the whole frame in one piece, but you could separate it into a frame and tongue if you want to, but I think you have to have an A-frame tongue to carry the motorcycle safely. You'll see that I end up with a frame that's 15' long overall and allows the tow vehicle to turn to a sharp angle.
I've checked the balance with and without the bike on board and it's shown in another attached pdf. The hitch weight is around 170lb without the bike and 380lb with it (this is with a 350lb bike). If your tow vehicle and hitch are OK with this sort of load, then I don't see a problem.
Having recently written a web page on how to determine the tongue strength required by the Australian trailer rules, I though I'd run this frame through them. To pass the rule with a 2000lb total trailer weight and a 72" long tongue, the main rails need to be 2" x 3" x 3/16" rectangular tube - this achieves 108% of the required strength. As we have been discussing how these rules are a bit strict, I think I'd be happy with 2" x 3" x 1/8" rectangular tube rails as these achieve 78% of the required strength.
For the bike platform, I've shown:
- two 2" x 2" x 3/16" angles set with a 5" gap between them;
- 1" x 1/4" flat bar 'treads' welded under the angles at 4" spacing.
This gives a ramp on which the bike can be washed down without risk of flooding the trailer!
by Niall » Wed Jul 12, 2006 6:54 am 
