[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.
Cheers,
Henry Thomas.
//
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