[python] Re: First test drive
- From: "25hz" <25hz@xxxxxxxxxx>
- To: <python@xxxxxxxxxxxxx>
- Date: Thu, 6 Jan 2005 20:31:51 -0500
> thanks for translating the units into metric system.
Well, being from Canada, I sort of use a mish-mash of both systems every
day. I prefer Imperial for building because all my tools, bits, etc are
still that way.
> I studied your design variations. The bike looks awesome, especially
> the front part and the seat.
> The weakness, that I spotted in the CrMo tube of the rear part,
> already gave in. I wonder if you can notice a similar flexing as
> Dirk http://dirkb.dnsalias.net/python.html
> because with 32 x 1.6 mm (1 1/4" x .064") square tube for the
> backbone you are quite close to his 30 x 1.5 mm square tube.
I played around with round and square when I first started building
bikes/trikes and took the square because it was cheap, easy to get in good
condition, and it was easy to use without a ton of jigging because it always
has a flat side somewhere. The only thing I noticed, was that it is much
more succeptible to torsion/twisting failure than round stock. The way
around this that I found was 2 things. 1) Use more than one angle when I
can, to change the twisting axis' so they work against each other, and 2)
keep the straight sections as short as possible. I think the problem with
dirkb's is that the main spine is so long and so straight. On my trikes,
the twin rails are pretty long as well, but I have two short tube sections
connecting the two rails that turn the twin rails into a rectangle, which
doesn't twist. He didn't have that option so he had to double it up. With
the clone, I asked my friend to watch the frame while I tried to ride it and
aside from a small amount of flex up and down (which I wanted) he said he
couldn't see any major twisting aside from the small cross tube's failure.
With the repairs and CroMo forks on the back now, I'll see how that handles
my crashes. I temporarily put a 27" wheel on the rear as well but might put
the 24" back on during my learning/crashing phase so I don't taco the 27".
> The front wheel dropouts on top of the frame have the two benefits
> of allowing lower seat height and improving the chainline. I have
> the problem that in some gears the chain touches the chain stay -
> you don´t.
> Disadvantage of your solution is, that with a mounted front fender
> or wheel well you cannot simply dismount the wheel for
> maintenance. Maybe your half fender/leg guard is a solution.
To be honest, I never even considered the effect of top dropouts on the
chain line :) I was blissfully unaware of any chainline issues with the
frame even though I have seen a coupe other pythons with notched chainstays.
My main reason was to lower the BB, seat and pivot as close to the ground as
possible. I really like the "lowracer" thing :) I have a design in mind
for a sort of fairing/fender that will have 4 small hardpoints on top of the
rear part of the chainstays so it can be mounted to them. I rarely have to
remove the rear wheels on my trikes so am not too worried about what I have
to do to get the wheel off the python. Every design has its little quirks,
and I'll live with that one :)
Anyway, I appreciate your advice and comments. I hope I can learn to ride
it within the next week if the snow melts enough :)
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