[python] Lean Steer Python/Hipparion Trike

  • From: Henry Thomas <whpthomas@xxxxxxxxx>
  • To: python@xxxxxxxxxxxxx
  • Date: Thu, 04 Jan 2007 02:40:32 +1000

Hi Pythonauts,

This is my first opportunity I hope to contribute something meaningful to this great forum.

I got the recumbent bike building bug about a year ago, but living on a sugar cane farm (near Bundaberg in Queensland - Australia) I found the off road handling around the farm somewhat lacking. I looked into trikes, but for stability they need to be very low, and tufts of grass here will rip a derailleur clean of a bike. So I started investigating ways to raise the center of gravity of a trike by allowing it to lean independently of the steering.

My first prototype (Prototype-A.jpg attached) wasn't ultimately successful, aside from being heavy, the BB was too high and it suffered from wheel flop on sharp corners causing uncontrollable over steer. So I set off on a journey across the Internet to learn all I could about bicycle geometry and consequently came across many of this forums contributors sites like Jürgen's, Dirk's and 25mhz's. It got me thinking that their must be a way to design a trike that could lean, but like the python also have static stability that was self centering.

So I played around with many designs and simulated their geometry (Tilt-Geometry.gif attached). Finally I have settled on one (Jetrike-3D-View.gif attached), which I plan to start building next week. It raises the seat height by 30-40mm on a 30 degree tilt, which will push it back to neutral, yet be easily over compensated by leaning to either side.

I have drafted detailed plans with a cut list which anyone who is interested can download form http://jetrike.com/Jetrike-Plans.pdf

[In the design an M8 tie rod links the rocker arm to the swing arms, but these are not shown.]

I plan to take photo's and maybe even some video's of the trikes construction and post them to the site as I go.

The specs from the design table are as follows:

Pivot-Angle 55
Wheelbase 1230
Trail 250
FW-Radius 254
FW-Axle 125 (Sachs)
RW-Radius 254
RW-Axle 100
BB-Height 400
BB-FWA 380
BB-BOS 950 (Back of Seat)
Seat-Width 450
Seat-Height 240
Ground Clearance 105

I would be grateful if some of you could review my design and see if there are any glaring mistakes.

For the materials I plan to use high strength 316 stainless steel, mainly because it is the only steel I can get in a 40 x 20 profile. I could get 40 x 10 in mild steel, but I would have to purchase a ton, which is a little outside my budget. We have a good machine shop on the farm so fabrication and welding shouldn't be an issue.

I look forward to reading your comments.


Henry Thomas.


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