Following things I noticed (I could be mistaken!)
The forces on the pads of the swing arm (item 39) and thus the rod
links are very high. There is a lever between swing arm and pad. And
the force on the pad will be about 360 / 60 = 6 times as high as the
force on the wheel. Just to keep the swing arms in place the rod links
will have to work hard.
Even if this is not a problem strength wise, it could be a problem
because there can occur low frequency oscilations (is it called
shimmer? because of the sloppy feel), and may the effect on speed
Did you consider using an aluminium seat, you can save weight there.
The seat is now 2.6 kgs. A alu seat is about 1kg.
otherwise a very nice design! :-)
Henry Thomas wrote:
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:
FW-Axle 125 (Sachs)
BB-BOS 950 (Back of Seat)
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.