[python] The old qustion of PSI

  • From: Howard Stevens <hstevens94@xxxxxxxxx>
  • To: python@xxxxxxxxxxxxx
  • Date: Thu, 17 Jun 2010 21:46:48 -0500

Hi Pythonites.  Like some others I have some problems with PSI with my
Python-like trike.  The steering pivot is 100mm in front of the line of my
hips and I cannot get it closer than this with my design.  I have tried
bungy cords which make it quite rideable but when peddling up hills the
PSI becomes more noticeable, despite paying attention to pedalling style and
gearing.  My idea is like the old motorbike dampers which reduced movements
by increasing the friction of the joint movements.  (see the attachment) By
having a hollow pivot pin with a cam lever and skewer with a nut on the
lower end, and adjusting the nut at the lower end of the pivot screw you
could adjust the amount of friction and hence movement needed, but avoiding
any locking which could be dangerous. By releasing the cam lever at the top,
all the friction would cease and so you could easily turn.  The friction
would be between the bottom aluminium plate and the carbon fibre base of the
front wheel housing.  The old motorbike dampers had a couple of bronze
plates as well, which I understand made good friction plates.  Another thing
I mentioned was the idea of putting a wide tyre on the front wheel, thus
giving increased traction for pulling on hills and for braking. The extra
rubber to road contact would also make the wheel less likely to wobble,
according to some experimenters.
So any comments ?  Happy cycling  Howard Stevens

Attachment: Front pivot and friction damper.jpg
Description: JPEG image

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