[python] Re: Python trike plans [approaching things from the back (D+E Variant) ]

  • From: Rhisiart Gwilym <Rhisiart@xxxxxxxxxxxxxx>
  • To: python@xxxxxxxxxxxxx
  • Date: Thu, 7 Jan 2010 23:44:44 +0000

Hi Dirk,

Do you mean Dennis Renner when you speak of a French (?) guy? You seem to be describing this vid:


This +might+ be an easy-ride FWDRWS, or it might be a centre-steer, with the articulation right at the back of the centre section. Certainly, the rider is sitting on the front part.

Dennis also sent me some still pics of his Mark1 and Mark2 versions. He says the Mark1 isn't easy to ride, but he got the geometry right on the Mark2, and you can see from the vid how easy it is to ride.

I think I've attached the pics that he sent me, but not sure if I've done it right and they'll come out for you. Will try another way if not.

Incidentally, Dennis says that the wheelbase of the Mark2 is 40 inches, and the steering-axis angle is 71 degrees.

I've been wondering if this geometry would work well for a trike too......

Cheers!   RhG

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Stefan Bartels <sbartels@xxxxxxxx> hat am 23. Dezember 2009 um 20:50 geschrieben:

 Dear folks, after a pause caused by illness and hard work I now have all
 the wheels and materials together to begin building my trike.
 I can do three variants which I made sketches of. In the third version
 the seat swings on the beam, the others are a bit more conventional.
 Where should I put the hinge? Which design will be most stable and have
 an acceptable turning radius?
 All three wheels are to be 20".
 Your ideas and advice would be most welcome!
 And have a happy Christmas!

 address is


Hi Stefan,

i kept thinking about trikes as well. Attached is a drawing with variants called D and E, extending your version C and keeping georges suggestions in mind. In your C version, the rider is sitting completely on the front part, which means he will tilt to the inside of the corner, shifting his body mass sidesway an down, which is good. However, i believe ifthe pivot is pointing forward in an angle this flat, with most of the mass on the front part, you will experience flip over like behauviour, when cornering. In my variants, i moved the pivot a lot towards the rear. I could be pointing forward(E) or backward(D). The pivot could even be as close to the rear axle, as (E), because of the two wheels in the back. However, this would leave a short distance to the rear axle probably resulting in poor steering behaviour (big turning circle). So in this respect, the pivot should be somewhere towards the middle ofthe frame, while keeping you and your seat attached to the front part. If you neglect stearing stability for a moment, is should not matter much, whether the pivot axis points forwards or backwards, as long as the pivot is lower than the horizontal line between the two wheel centres. In this case, the pivot lifts up when cornering, resulting in the python like correcting force of a centre steered recumbent. Since the rear part does not tilt, due to the two wheel, when cornering, your probably would want to lean over more. So in a way, you will be facing the problem of lean-steering at the same time. Whith the angle of the pivot, you can influence, how much you want to tilt during a given turning cycle at any velocity - as well as the bevorementioned amount of pythonlike vertical pivot movement, which defines the correnting force to straighten the bike. Therefore, i put in two handlebars attached to the rear part and pointing forward on either side of the seat.
Grabbing these, you can control the steering while also leaning.

This is my best bet, whithout having build anything vaguely near this design :-) A couple of month ago, there was a youtube video from a french(?) guy, who had build a python with pivot closer to the back with steering bars attached to the rear i believe. (Are there actually some drawings somewhere?)


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