[python] Re: Climbing and test rides

That is a good thing to hear.  My friends and I are planning to ride back
and forth to work and there are a few small hills and a couple nasty ones.
I was concerned with hill climbing on the python as it's hard going on a
couple of the hills even on my trike.  Low speed (like, 3 or 4 kph) handling
was a point of interest for me with the python.

A picture of the handle bars we mounted on the one python is here:
http://bikes.jkcc.com/python%20md%20extension%20and%20bars.jpg
As mentioned prior, the handle bars ended up being a distraction and made it
more difficult to ride the python when my friend actually tried to use them
to help steer.  They were simply pieces of galvanized steel tubing used for
electrical conduit.  The sockets were small pieces of 1" square box tube
with a slit in the side and a pinch bolt.  As the bike could still be ridden
without them, we opted to remove them and raise the seat 2" instead.  You
can see the 2" extension piece in this view too.

Another picture of the seat extension is here:
http://bikes.jkcc.com/python%20md%20seat%20extension.jpg
The extension is a short piece of 1 1/2" box tube, with a short piece of 1"
box ube welded to the top of it to mount the seat to.  The rear seat post is
long enough that we simply raise it a couple inches to keep the seat angle
roughly the same.  The seat extension was bolted on so that the rider's
weight would tend it to try to push it down and to the rear, so two 1/4"
bolts holds it very firmly wihtout having to weld it in place.  The idea is
that once the rider becomes steady or confident enough, the extension can be
removed and the seat can be lowered back to the original position.

So, why the extension in the first place?  Well, in non-technical terms, I
envision the "balance" envelope as being a large "V" shape (when looking at
the bike from the front or rear) with the point touching the ground at the
tires.  If the CoG is very low, the bike doesn't have to tip side to side
very much before the CoG is outside this "V", and you lose control and tip
over.  I figured that if the CoG was raised, this would not only allow the
CoG to travel further before it got out of control, but the extra movement
distance would mean you could "feel" the tipping a little easier, and allow
the rider to make less precise corrections to regain balance.

How did the extension work?  Like a charm! :)  I was amazed at how much the
handling changed by raising the seat 2", while leaving everything else the
same.  My friend who could already ride it, looked far smoother and he
commented on how much easier it was to keep control.  He was practicing
figure 8's and doing very tight turns both with and without clipless pedals.
For me, while I couldn't ride or balance the python at all before, I found
that I could now ride a few feet balancing myself and I could actually
"feel" the balance of the bike now.  This was in one ride that lasted under
2 minutes.  Our other friend who could balance it a little bit before, but
still had big stability problems, and could now ride it too.  We were all
very pleased and very excited at this "breakthrough".

We pulled the first set of handlebars off, and welded a new handle bar mount
to the seat extension so brakes and shifters can be mounted for more
controlled and faster riding (picture will follow).  They are more rigid and
are mounted on the rear half of the python (under the front of the seat),
instead of the front half, like most of the other builders here.
Additionally, using pedal clips on the python also seemed to enhance
control, according to my friend.  While I am too wobbly yet to feel
comfortable with my feet clipped to the pedals, my friend liked how he could
push or pull to either side, from any foot position, during pedalling when
he used his SPDs.  I have dual platform/SPD pedals on my trike so I can use
normal shoes until I feel confident enough, and then I can clip in.

While lots of theoretical conversation, applications and math are fine from
an engineering standpoint, they don't do me much good, unfortunately.  I
need plain information on a particular aspect of the bike, and exactly what
it does, good or bad.  IE, I know that angles higher than about 68 degrees
make the front end feel "light" and too easy to steer(some don't like this,
others do).  Now I also know that the higher the seat, the easier it is to
feel the balance point and learn to ride.  I imagine there is a point where
the seat is now too high, and I also wonder what the BB to seat relation
does as far as control goes.  On my python, I'm going to raise the seat
three inches and see if that has a further positive effect, which I think it
will.  I'll try to experiment a little and see what it does when I get the
seat at 32 or 33cm.  The seat position of the python is similar to that on
high racer recumbents, so, as long as a functional BB to seat measurement is
maintained, has anyone come across any good reasons to have a low python
aside from possible aerodynamic advantages?

With regards to seat height, aside from our pythons just sort of ending up
as low as they are, I wonder if it's worth it at all to shoot for a low
design.  While it is completely dependent on the ability of the rider to
balance, at what rouugh average point is the seat TOO low and both difficult
to learn, and difficult to balance at low speeds while climbing hills (for
example)?  I seem to have a preference for low racers, but in the case of
the python, this seems to be a potentially bad preference.  With the seat
height of my friend's python now around the 30cm height, it seems to be
pretty much in line with the original pythons.  For people with great
balance obviously even a 20cm seat height is ok because others are riding
them, including my friend.

So, with the seat being raised, this now changes the BB to seat ratio, and
my next question would be, how does BB to seat height affect the python
handling?  I imagine that if the seat gets too high in relation to the BB,
when you are pedalling, you will be pedalling "down" to the BB height, which
might push down on the BB and cause the pivot to be slightly unweighted, and
induce handling issues.  ?


> Hello all,
>
> today I rode in a region that I passed with my airbike some
> years ago.
> There is a nice steep hill with a gravel road. I estimate the
> slope about 15%.
> This should be deadly for FWD bents and I remember well
> how impossible it was with the airbike to climb this.
>
> The bigger was the surprise today, when I made it almost
> flawlessly with the P3, which has the same tires and
> gearing that I once had on the airbike.
>
> It seems that primarily the lower CoG is the reason for
> that.

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