An other point of worry is the low seat angle. The flatter the seat is the
more difficult it is to ride the bike. I would increase that angle to at
least 30 degrees, and when you still need to learn riding it probably 40
Op di 28 aug. 2018 om 07:24 schreef Paul Cartwright <
I built a crude test version with the unicycle type of front wheel, like
It is a problem having the pedals so close to the pivot, because as you
surmise, the front wheel wobbles side to side. I tried a number of
different configurations, and made a rather heavy bike that had all sorts
of adjustments possible.
I ended up building the bike in the attached photo. This bike is easy to
ride, even with no hands, because one's legs tend to keep the bike going in
a straight line. It can also do tight figure eights at slow speed. Note
that the pedals are well forward of the front wheel axle, and the pivot is
under the seat. The short wheelbase puts the right weight distribution on
the wheels, about 60% front/40% rear, which is important in hill climbing
with front wheel drive, and it feels super stable at high speeds.
My bike also has an adjustable elastic "steering damper" that is critical
in compensating for front "wheel flop".
This eliminates any residual side to side motion, and makes the bike easy
to ride. Without this device the bike is much harder to ride.
I think it may be difficult to ride the bike as you have drawn it. But
nothing like building a quick prototype to find out!
On Mon, Aug 27, 2018 at 10:29 AM, Vincent Bashandy <
Yeah the pedal-strike is also a thing I’m worried about. I chose the
biggest possible wheel and only 150mm cranks, maybe the cranks should be
even smaller. It was also my plan to build a simple prototype with just a
single speed like the unicycle, but it’s not so easy to find a unicycle
with a 28 inch wheel 😊.
To cope with different rider sizes I was thinking about an adjustable
seat. Not for the race version, which has everything fixed and is made to
fit the rider.
I don’t know about understeer, something in me tells me it’s more
convenient to have a normal bicycle steer. It’s probably more aerodynamic
too as the front surface can be bigger with your arms dangling on each side.
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*Verzonden:* Sunday, August 26, 2018 10:34:25 PM
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*Onderwerp:* [python] Re: Would my design work?
I have ridden the KerVelo last year in Germersheim for a few meters and
not being used to recumbents back then this was the first one I could ride
without tipping or feeling unsafe.
The only downside was that small turns cause pedal-strike quite easily.
I could imagine that your idea works, but not sure how it feels.
What about building a quick and dirty prototype without the hub gears -
just using a rigid axle from a unicycle?
If this is rideable (you can let someone try who can ride a Python or try
to learn it yourself) - you can go from there.
This looks very interesting to me. The thing I liked with the Python
right from the start is the simple concept and the compact drivetrain.
You idea is even more compact and simple - only probably harder to learn
than the KerVelo.
One more thing: Adjusting to different rider sizes probably means
telescoping the front section / front wheel from the pivot.
This is not necessary if you build it for yourself of course…
I would also consider putting the handlebars beneath the seat. This is
more relaxing and even simpler to build.
Just attach them to the front section near the pivot.
Good luck and keep us posted!
Am 26.08.2018 um 20:37 schrieb Vincent Bashandy <vincent.bashandy@xxxxxxxxxxx>:
market rather than not being technically possible. In fact, as ‘drcorle’
Thanks for your feedback. That hub gear is a matter of not being on the
said, it does already exist.
never driven a Python, does it require a lot of power to steer? In my
The second issue is a good point, haven’t thought about that. I have
design it would require about twice the force of a regular Python. This
problem could either be solved by power steering, or by moving the steering
pivot under the seat, but I don’t know what such a big trail does with the
Karl McCracken <karl.mccracken@xxxxxxxxxxx>
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Verzonden: Sunday, August 26, 2018 5:47:26 PMwith cranks like that instead of a single drive sprocket. So you've no way
Onderwerp: [python] Re: Would my design work?
I'm not sure this would work.
The main problem is that hub gear - I don't know of one that'll work
to get power from your left leg and into the hub.:0/
Python layout, your legs have a nice long lever to act on, and crucially
The next issue is the steering torque required. With the "standard"
this is well beyond the wheel's contact point. Your setup doesn't have
this, and I'm not convinced that the handlebars will help.
behalf of Vincent Bashandy <vincent.bashandy@xxxxxxxxxxx>
It is an intriguing design though, so don't give up on it yet!
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Sent: Sunday, August 26, 2018 3:32:20 PMover some problems regarding the steering system. Then I came across the
Subject: [python] Would my design work?
Dear everyone and Jürgen,
Lately I got an idea in my head for a recumbent bike but I stumbled
website about the Python Lowracer which convinced me that a bicycle with a
steering pivot far behind the center of the wheel was actually possible, so
I began modelling my idea. Now the first version is finished and I consider
building it, but first I need to know if this design would be
stable/ridable. Is it worth building it?
directly on the front wheel, using a hub gear to get gear ratio’s. I also
The design is different in all other python’s in that it has pedals
added a steer for stability aiding purposes and as a place to put your
hands on. This version is intended as a racer, as you can see in the first
seat angle is 20 degrees.
The dimensions can be seen in the second image.
The front wheel 28 inch, the rear wheel 20 inch. Crank length is 150mm,
you have to steer hard, but there are solutions to this. Also according to
Now, the main question is, would this work?
My main concern is that the legs could strike the steering column when
the Open Bike wiki, the Pedal-Steer interference would be bad because the
steering pivot is not under the hip of the driver. This could be solved by
moving the pivot to the seat - and this would also solve the steering
column striking problem – but this would give a trail more than twice as
big as it already is now. This would make it completely unridable, right?
I would like to hear your opinion on this :D.
Vincent Bashandy, Netherlands
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