[python] Re: frame flexibility

Hi all,

I just point-welded -as an experiment- another 30x30x1.5 under the rear tube. The rear tube was already a 30x30x1.5... So the total height is now 60mm.

The frame stiffness has become much better! 8-o

Before welding that tube onto it, I put the whole bike in the bench-vice, I could visually see the tube bending when I applied presure on the BB. I would never have expected that a 30x30x1.5 tube like that would bend so much.

Well not all flexibility has gone, but it is much better. I still hope to be able to remove the rest, but I have first to find out where it is coming from.

The 30x30x1.5 that I now welded on isn't going to stay there. I plan to replace it with a seat-stay tube about 50mm below the main tube.

Dirk

Dirk Bonne wrote:
Torben Scheel wrote:


-----Original Message-----
From: Dirk Bonne <dirk_bonne@xxxxxxxxxx>
To: python@xxxxxxxxxxxxx
Date: Sun, 12 Dec 2004 13:03:01 +0100
Subject: [python] Re: frame flexibility

 > Jürgen Mages wrote:
 > > Hi Dirk,
 > >
 > > at first glance I would blame this on the 30x10x1 tubing.
 >
 > If it were only true! It is 30x10x1.5 :-)
 >
 > > Does Torben, who uses the same material has flexing?
 >
 > yes, please, test it out!
I have extensive "flexing" from the flevopivot mount to the rear frame clip-mounted), so I can't determine if anything else are flexing until that is fixed.

Already fixed that! ...unfortunatly :-(

I could feel the U-profile bending under my weight, when mounting the bike. See picture attached for what I did --it is a mean looking pivot now. It still needs side plating (rost/dirt prevention).

> I would suspect the Dirk's pivot (the flat plates) after
seeing his weldings (good!). On my bike the rear fork (a pleonasm? The fork!) is the weakest point - I'm fixing that with 10*10*1 tubing from dropouts to seatmount.

Does this mean you will make the seat unmovable? I am also beginning to suspect the innocent looking rear part.

I'm going to make a tube that fits the flevoaxel exactly in a lathe, and braze it in the rear frame, but maybe I can't

When I saw your python, you were not using the parts 25, 26, 47 and 27 (numbers taken from the drawing you posted). My experience with the flevo is that these are really important to completely eliminate flexing in the flevo pivot. And it prevents the holes from elongating becuase the axle does not rattle anymore in these holes.

eliminate every last bit of flexing. I wonder if flevobike have the same problem - I used mild steel and the flevo way with enforcements plates : http://www.hpv-klub.dk/selvbygger/Flevoracer/e-fr09.gif - the holes in the rear frame are bound to be eliptical in time.
 
Cheers'
Torben



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