[python] Lean Steer Python/Hipparion Trike

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.

Cheers,

Henry Thomas.

//

JPEG image

GIF image

GIF image

Other related posts: