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Old 05-07-10, 12:23 PM   #5
martinpaff
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Join Date: Mar 2007
Location: Lincoln, UK
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I've been sitting and pondering some of the advantages and disadvantages of the various layouts...

Everybody whose built a trolley for an engine will be familiar with the problems of a turntable:

1. As the steering turns the trolley becomes unstable at the front, because the effective track narrows.

2. The wheels have to be able to pass below the chassis to get any usefull amount of lock.

Ackermann gets round both of these problems, but unless the front and rear wheels are fairly close, the steering lock can be limited. We frequently see equipment with a bent or broken draw-bar because the lock has been exceeded.

Ackermann geometry could be fun to design, but everything you need to know is on the net. Any slack at all in the system makes the trailer "fish-tail".

Reversing a close-coupled trailer can be an interesting challenge...

Because the drawbar needs to be quite long and quite wide, there is plenty of room on the underside to mount the cable balance bars. I see absolutely no reason why all four wheels shouldn't be braked. I would think the cables could simply pass underneath the pivot point, in a relatively loose loop, and they would work fine. The balance bars would always make appropriate compensation for the cables flexing.

Just random thoughts...

Martin.
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