[python] Re: Python report, and circular tubes.
- From: Dirk Bonne <dirk_bonne@xxxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Sun, 30 Oct 2005 21:52:26 +0100
Hi Ghislain!
On 10/29/2005 03:36 PM, Ghislain PILLET wrote:
> Hello, all !
>
> My 20" Python, 2000 kms now, since may 2005.
>
> Pivot angle 60°
> Trail - 14
> Seat height 29
> BB-seat 20
> Ground clearance 22
> Wheelbase 100
> Weight 13
> BB-FWA 46
> BB-EOS 75
> Front tubing 30x10x1,5
> Wheel Size 20" 20"
> No suspension
>
> Present forward part , tubing only :
> Steel hollow rectangular 30mm x 10mm x 1,5mm - weight 0,872 kg/m
> length required 1,42m = total weight 1,24kg.
> Tested, works ok for me ; however no idea of maximum watts I can put
> on the pedal, or too approximate, if any.
Its very flexi isn't it!? Putting a rib under the backbone will stiffen
it up and extra bits and piece at other places help very much! But
basically I find the material not realistic for a stiff construction.
> Could a next forward part version be :
> Aluminium hollow rectangular 30mm x 10mm x 2mm - weight 0,388 kg/m
> length required 1,42m = total weigth 0,55kg
> Pivot and bottom bracket aluminium.
AFAIK aluminium is about three times as weak too. Do you think this
would hold?
> Comparison with circular tube - ( Hi, Dirk (: :>) a very nice looking
> bike y've designed- I've followed your previous 20" design and I enjoy
> it a lot, it makes dull any other recumbent ! )
I am happy it worked for you, Ghislain! I had the same feeling when I
made my first center steered bike (20" flevo racer)! Even though riding
it was not without problems, one would have had to kick me, to get me
back on one my other one (challenge twister).
> Steel, circular tube 10mm x 1 or 2mm - weight between 0,22 / 0,27 kg/m
> length required 5,25m = total weight 1.31kg
> Pivot and bottom bracket steel.
> (Datas from http://www.matweb.com/tools/weight-calculator.asp)
Hey hey stop!!! 10mm x 1mm is 0.11kg/m. I have updated my website with
some values on stresses on the bike, and will base tube thicknesses on
these calculations. ...but even so I do not really expect it really to
be much lighter then my current bike.
> A good rear suspension will be my next modification as python can
> quickly turn into a wild horse on bad roads. For safety sake first.
> For comfort, second. ( Dirk, no suspension ? do you confirm ? Have we
> been made so differents ? (: :>) )
May be a little more fat at the right place, but else probably not ;-)
Anyway, if the roads in denmark degrade under a certain level I go for
plan B, I'll spend €€€ for a pantour hub (this is a hub with suspension
build in --- don't know how good it works though).
> Probably whith narrower wheels for the performance, and clipless
> pedals.(As long as, just in case, ... I can quickly take the famous
> python safety position : let drop the feet on the ground and let slide
> till it stops, trying not to ly down miserably on one side)
Dirk
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