[python] Re: Test ride
- From: "25hz" <25hz@xxxxxxxxxx>
- To: <python@xxxxxxxxxxxxx>
- Date: Thu, 21 Apr 2005 19:33:40 -0400
After looking at your picture, perhaps the problem is you are seated a
little too low, and the BB is a little too high? While a high BB is
"doable" on a trike or a bent that has more conventional steering, perhaps
the combination of 60 degrees and the high BB make it too tough to swing the
legs and twist the hips in a more upward direction? Raising the seat 5 or
10 cm would add to the balance "feel" of the bent as well as give you more
time to notice the need for steering corrections. At the same time, it
would lower the BB in relation to your seat and change the angle of the
forces you're putting into it for steering input. Instead of pushing up and
to the sides, the lower BB would move your effort to a closer horizontal
position, which might make it easier to steer?
We took MD's python yesterday, and I added another 1" extension to the seat
so the seat height is now around 33cm, and you guessed it, it's easier still
to ride it. Today, my friend is smoother and was riding quite fast on it
due to the addition of handlebars, brakes and shifters, but only on the
flat. No hill climbing or high speed data on it yet til he feels more
confident on it. My other friend who could "almost" ride it, WAS riding it
after the adjustment. I didn't attempt it because me knees were pretty
sore, but I think we have another python convert, which is a GOOD thing :)
I also took out the adjustable seat angle and used a 1" dia piece of
aluminum tubing to act as the rear seat support. Seat back angle adjustment
is nice, but I think they like it where it is, so I took out the steel
adjustable post and put the aluminum rigid one in - saved a couple grams :)
Now, the seat height is just slightly higher than the wheel axle (which is
where P1 and P3 seem to have the seat) and the BB is very close to the seat
height as well now - with seemingly no adverse effects from the raised seat.
My friend is going away and taking the bent for the weekend, and depending
on his "report", I might notch the main frame tube, and change the angle to
~65 degrees because he feels he'd like a "heavier" feel to the steering. I
keep telling him to put more time into the python before passing final
judgement. We'll see how it goes.
> After spending some time last night fine-tuning the alignment, I test rode
the new bike this morning and I think that the pivot angle is just too
small. The front ends falls/turns rather easily side to side and the
response to steer is _very_ slow. I could not possibly turn the front fast
enough to bring the bike back under the center of gravity once it started
going over. It would probably be ridable at higher speed, but not starting
out, or any low speed.
>
> wheelbase: 131cm
> pivot: 59.5
> trail: 23cm
> seat height: 27cm
> BB height: 52cm
> http://rjs.org/gallery/python_1.jpg
>
> I attached handlebars to the seat tube, but they only helped a little and
added mass to the front end, which increases flop. (I clamped the old steel
seat post back into the cut-off tube upside down; the 1" handlebar stem fit
inside the post perfectly.)
>
> I'll next increase the angle to ~64 degrees and shorten the wheelbase
1-2cm at the same time. Trail will increase to ~25cm.
> It is very comfortable, though :-)
>
> Ray
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