John S. wrote:
> Joe wrote:
>
>>I got really curious about this, and studied it for a long time (I'm an
>>engineer). There was a good thread on this at woodall's RV forum. I have
>>found no frank discussion of it by anybody who has broken it down into its
>>component forces. It's hard to explain it using ASCII here. But my opinion
>>is this:
>>
>>First off, it's clear that trailers can amplify their swaying until you
>>crash. They don't do it all the time, but they can, and that's what
>>interests me. They have no power of their own to bring to the table. The
>>energy to do this comes from the tow vehicle. The trailer sways like a
>>pendulum, sort of (I admit the forces holding a trailer back are not exactly
>>like gravity in this analogy). A pendulum can be powered by a wide variety
>>of motions. One of those motions is moving the pendulum's pivot point side
>>to side. I think this is the motion we want.
>>
>>The forces on the trailer come from its tires and the tow vehicle. I was not
>>interested in any other forces. "front loaded" trailers are trailers where
>>the center of gravity is in front of the tires. When the tires are pushing
>>the trailer sideways (during sway), the center of gravity is in front of
>>that force. Since the side force doesn't go exactly through the center of
>>gravity, the weight of the trailer pushes sideways on the tow vehicle.
>>
>>The inertia of the swaying trailer pushes the tow vehicle from side to side.
>>The difference in loading is simply this. If the center of gravity is in
>>front of the wheels, it pushed the tow vehicle one way, and if it's behind
>>the wheels, it pushes the two vehicle the other way. One cancels the sway,
>>and the other amplifies it.
>>
>
>
> I don't know if amplification is the correct term. Poor loading will
> increase the sensitivity of a tow vehicle and trailer to winds and side
> drafts from big trucks, but I don't understand how the forces could
> actually be amplified. In my experience the side-to-side swaying is
> amplified or increased by the driver trying to offset the swaying by
> steering out of it.
>
This is true and just about all trailer sway issue start with tow
vehicle stabilty issues. (tires and suspension not up to the extra load
on them)
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