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

  • From: "dirk@xxxxxxxxxx" <dirk@xxxxxxxxxx>
  • To: python@xxxxxxxxxxxxx
  • Date: Thu, 7 Jan 2010 14:30:19 +0100 (CET)

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

> 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!
> Stefan
> address is 
> http://www.free-archers.de/files/galleries/246/recumbent%20trike%20variants.jpg
> trike

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?)


Attachment: python-trike_D+E.jpg
Description: JPEG image

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