Hi there,
I think it looks a neat design, but there are three key factors:
1/. You need to loose the handlebars
2/. Move the seat over the pivot
3/. You need the crank forward of the wheel, to enable good directional control
I would work as it is as a trike, but not with two wheels, where balance and
control are critical. I also think the seat is way too reclined for a
comfortable neck position.
Hope this helps?
Best regards,
Neil.
________________________________
From: python-bounce@xxxxxxxxxxxxx <python-bounce@xxxxxxxxxxxxx> on behalf of
Jaculus <jaculusbent@xxxxxxxxx>
Sent: 28 August 2018 11:19
To: python@xxxxxxxxxxxxx
Subject: [python] Re: Would my design work?
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 degrees.
Op di 28 aug. 2018 om 07:24 schreef Paul Cartwright
<paulcartwrightx@xxxxxxxxx<mailto:paulcartwrightx@xxxxxxxxx>>:
Vincent,
I built a crude test version with the unicycle type of front wheel, like the
Kervelo.
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!
Paul
On Mon, Aug 27, 2018 at 10:29 AM, Vincent Bashandy
<vincent.bashandy@xxxxxxxxxxx<mailto:vincent.bashandy@xxxxxxxxxxx>> wrote:
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.
Greets,
Vincent Bashandy
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Van: python-bounce@xxxxxxxxxxxxx<mailto:python-bounce@xxxxxxxxxxxxx>
<python-bounce@xxxxxxxxxxxxx<mailto:python-bounce@xxxxxxxxxxxxx>> namens
Christian Winkgen <christian.winkgen@xxxxxxx<mailto:christian.winkgen@xxxxxxx>>
Verzonden: Sunday, August 26, 2018 10:34:25 PM
Aan: python freelists
Onderwerp: [python] Re: Would my design work?
Great idea.
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!
Cheers,
Christian
Am 26.08.2018 um 20:37 schrieb Vincent Bashandy
<vincent.bashandy@xxxxxxxxxxx<mailto:vincent.bashandy@xxxxxxxxxxx>>:
Hi,
Thanks for your feedback. That hub gear is a matter of not being on the
market rather than not being technically possible. In fact, as ‘drcorle’
said, it does already exist.
The second issue is a good point, haven’t thought about that. I have never
driven a Python, does it require a lot of power to steer? In my 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 ridability??
Greets,
Vincent Bashandy
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<python-bounce@xxxxxxxxxxxxx<mailto:python-bounce@xxxxxxxxxxxxx>> namens Karl
McCracken <karl.mccracken@xxxxxxxxxxx<mailto:karl.mccracken@xxxxxxxxxxx>>
Verzonden: Sunday, August 26, 2018 5:47:26 PM
Aan: python@xxxxxxxxxxxxx<mailto:python@xxxxxxxxxxxxx>
Onderwerp: [python] Re: Would my design work?
Hi -
I'm not sure this would work.
The main problem is that hub gear - I don't know of one that'll work with
cranks like that instead of a single drive sprocket. So you've no way to get
power from your left leg and into the hub.:0/
The next issue is the steering torque required. With the "standard" Python
layout, your legs have a nice long lever to act on, and crucially 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.
It is an intriguing design though, so don't give up on it yet!
Karl.
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<python-bounce@xxxxxxxxxxxxx<mailto:python-bounce@xxxxxxxxxxxxx>> on behalf
of Vincent Bashandy
<vincent.bashandy@xxxxxxxxxxx<mailto:vincent.bashandy@xxxxxxxxxxx>>
Sent: Sunday, August 26, 2018 3:32:20 PM
To: python@xxxxxxxxxxxxx<mailto:python@xxxxxxxxxxxxx>
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 over some
problems regarding the steering system. Then I came across the 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?
The design is different in all other python’s in that it has pedals directly
on the front wheel, using a hub gear to get gear ratio’s. I also 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 image
The dimensions can be seen in the second image.
The front wheel 28 inch, the rear wheel 20 inch. Crank length is 150mm, seat
angle is 20 degrees.
Now, the main question is, would this work?
My main concern is that the legs could strike the steering column when you
have to steer hard, but there are solutions to this. Also according to 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.
Greets,
Vincent Bashandy, Netherlands
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