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I'm trying to design a single wheel trailer for my underpowered VW, much like this one.

Unlike a conventional trailer, it is attached to the car at two points. To prevent the wheel from dragging, it has a swivelling mechanism. Those are hard to come by, so I'm going to build one myself.

I'm not a mechanical engineer by trade, so the questions I have are probably quite basic:

  1. With caster wheel wobble in mind, should the wheel swivel freely, or is some friction desirable?

  2. What kind of bearings should be used for the swivel point? There is definitely an axial load, but is the radial load considerable?

  3. What would be the most effective geometry? How much trail/rake? Is this something I just have to experiment with?

706Astor
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Willem-Aart
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2 Answers2

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There appears to be a big fundamental problem with this design in that the trailer is not articulated. While this will indeed make it easier to reverse, in some circumstances it is potentially dangerous as whenever you turn a corner the rear of the trailer will swing out into the adjacent lane or footpath.

I'm pretty sure that this wouldn't actually even be considered a trailer under EU regulations and in any case they are required to be connected to the towing bracket using an approved ball hitch.

There is also the issue that this arrangement effectively couples the mass of the trailer to the rear of the car in the yaw plane which is going to have a very significant effect on its handling in addition to the effective increase in the rear overhang and is likely to be considered a modification to the vehicle itself in the EU and as such would require individual type approval.

Chris Johns
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I have a trailer just like this one for my wife who has trouble backing an ordinary trailer. To prevent wheel wobble at speed , I use a motor bike steering damper. The trailer is attached to the conventional tow bar with a spreader attachment to provide 2 fixing points and can pivot up and down.

John Markworth
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