[python] Re: Python report, and circular tubes
- From: Dirk Bonne <dirk_bonne@xxxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Mon, 31 Oct 2005 21:11:01 +0100
On 10/31/2005 06:03 PM, Ghislain PILLET wrote:
> Hello Dirk,
>
> Some extra informations to restore confidence in our mind's readers,
> about a flexy python I would ride ! (: >)
>
>
> Forward part of my 20" python is made of steel 30mm x 10 x 1,5.
>
> For the the aft part, I used :
> - Central part, steel circular tube diameter 42mm outside, wall
> thickness 1,5mm
Aha! Thats the reason. I have only a 30mm square tube. OOnly when I put
an extra rib under it it became aceptable.
> - Rear fork, steel circular tube diam. 22mm outside, wall thick. 1,2mm
>
> I'm quite pleased with the stiffness of the bike. It's quite ok for my
> 80 kgs.
>
> > 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
>
> Alternative to aluminium could be carbon ! I might try some day.
>
> > 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.
>
> Thanks for opening my eyes : 10mm x mm , 0,11kg/m, is the section you
> plan to use for your new version.
> Your updated website gives me plenty of informations,
Well, thanks. Such a frame allows some calculations to be made, but
problem is what to do with them. In principle 100kg load is enough, but
what happens when riding over a pothole. I would asume, it in a way
loads up certain (other) parts of the bike. But how big a forces can be
expected here? So I design the bike to hold for what, 200kg? 300kg? a
ton? Obviously the more safety the more heavy the bike will get.
> and opens a path towards a composite fabrication. Carbon laminated, or
> carbon pipes glued in aluminium inserts ?
Please, go ahead >:-)
Dirk
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