Quote:
Originally Posted by larsdennert
Imagine the big HDT tractor trailers. They have a pretty short wheelbase on the tractor compared to the trailer. I think there must be more to the wheelbase arguement. Some vehicles are just made for towing and others not so much.
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The big OTR rigs have the trailer wheels located right up against the rear of the trailer. As a result, the trailer can't develop any rotational motion around the wheels, using the wheels as a fulcrum. This is a good thing, from a sway point of view. Of course, it also means that half of the trailer weight comes down on the tractor's rear axle. That's why the OTR rigs have two axles (8 wheels) on the back of the tractor, just like the two axles (8 wheels) on the back of the trailer.
The TM strikes a balance here. The axle is as far back as possible, to minimize the tendency for the trailer to rotate around the axle. But the axle is far enough forward to maintain a manageable tongue weight.
Wheelbase on the tow vehicle provides the abiltiy to resist the rotational tendency of any trailer. Just for fun, imagine a tow vehicle with a 100-foot wheelbase. It is plain to see, I think, that nothing the trailer tries to do could twist the tow vehicle around. Sway would NOT be a problem in that case. Now imagine a tow vehicle with a 2-foot wheelbase. The trailer could yank that vehicle around quite easily, and there is not much the tow vehicle could do to resist it. For a TM, somewhere around 10 feet of wheelbase seems to be the right answer.
Bill