[python] steering pivot
- From: Rhisiart Gwilym <Rhisiart@xxxxxxxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Sun, 17 Sep 2006 13:20:34 +0100
Siwmae Jurgen and all python keepers!
I've been lurking on the list for sometime, picking up extra
knowledge of pythons, beyond what I've learned already from the
websites of the trail-blazers. I have to say that I just love the
pythons, and I'm really impressed by the innovative -- and obviously
highly practical -- technical solutions pioneered by the first goers
-- especially Jurgen's designs. P3 is a honey!
Before I ran across the python saga, I had been working on the design
of a self-build centre-steer bent. I assumed it would have to be a
flevo clone, because like everyone else I assumed that negative trail
wasn't workable. Then lo and behold! Jurgen and colleagues are
proving -- with lots of successful mileage -- that it works in
practise. In the end I'd sooner go for a python than a flevo, because
the steeper steering angle allows a more convenient geometry. And of
course flevos seem to need steering dampers.
The other thing that caused me a lot of doubt, until I found the
python material, was the steering joint. I thought I would have to
buy a flevo joint. But then, as I'd wondered for some time, the
python masters pioneered using a BB joint. And they confirmed also
that cottarless cranks work fine as linkages between for and aft
parts of the bike. Also, my engineer's instinct has always preferred
a swinging joint shackled on both sides rather than one.
So now I'm a bit checked. From what Jurgen said in the BB
joint-survey posts my original doubts about the cup bearings in a BB
set being sufficiently beefy to act as steering head bearings has
some justice. But then again, Jurgen reckons that P3's joint, which
has a sealed unit, is up to the job. And Ray says: "I found that my
ball/cone BB needed adjustment to keep zero play, but it was also
very easy and accessible. I bet that the stamped outer race deforms
under python's heavy loads, whereas the cartridge type is harder
material."
So what I'm asking here is: in the light of all you intrepid
pioneers' actual road experience, is the BB steering joint a good
practical solution, or should I go back to looking for something
beefier? Obviously I'd sooner go with the BB, as it's cheap and
off-the-shelf available, and Jurgen seems to have created an
eminently simple, practical linkage solution. But is the BB really up
to it?
I should say that I use my bikes a lot, as heavy duty work-horses,
including carrying substantial loads, and not always on smooth tarmac
surfaces.
The other point I wanted to mention is that my home-made has been
designed for orthodox pedalling in the recumbent position, or
alternatively for rowing in a more upright position on the same seat,
with back unsupported, to provide a lot more upper body workout than
pedalling can.
Cofion gorau i bawb, Rhisiart Gwilym
"What should we all do to help Gaia, and +all+ her children? Plant
trees incessantly, and learn to grow our own food. And struggle for
deep-green ecosocialism."
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