Flexing your chainwheels (vintage style)

ALL substances strain under stress. Often the displacement is not visible.
If you see elastic deformation as 'inefficient' then visible strain will be
undesirable.

"Bob" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Do all chainwheels/crankarms flex if you push hard and not really
straight in line with the crank ?

I've noticed that I can flex my TA 3-arm Professionel chainwheels
moderately easily by pushing hard and (incorrectly) not in a
direct line with the cranks. Actually, the noise I hear helps get
me back in line :-) I thought this might be a 3 arm crankset issue.

But, I've also noticed that my Stronglight 93 - which is a 5 arm,
highly distributed structure with reenforcement bars concentrically -
can be flexed in the same way if I really get on it. Perhaps not as
severe as the 3 arm TA, but still flexing. From an engineering
structure viewpoint, the 93 with the proper rings looks almost
ideally built to be rigid, but it still flexes.

So... do all cranks have this issue ? Are more modern cranks better
at this? Other designs better ?

Doug Huffman said:

ALL substances strain under stress. Often the displacement is not visible.
If you see elastic deformation as 'inefficient' then visible strain will be
undesirable.

Yeah... but do your chainwheels bend ?

Yes, ALL chainwheels elastically bend.

"Bob" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Doug Huffman said:

ALL substances strain under stress. Often the displacement is not
visible.
If you see elastic deformation as 'inefficient' then visible strain will
be
undesirable.

Yeah... but do your chainwheels bend ?

Doug Huffman said:

Yes, ALL chainwheels elastically bend.

I guess my question is "do they bend enough that it affects
operation?" - ie you hit the sides of the cage with the
chain? Or are some fairly resistant to bending in normal operation ?

Bob said:

On Tue, 6 Sep 2005 18:14:20 -0400, "Doug Huffman"
<[email hidden]> wrote:

Quoted message said:

Quoted message said:

Yes, ALL chainwheels elastically bend.

Quoted message said:

I guess my question is "do they bend enough that it affects
operation?" - ie you hit the sides of the cage with the
chain? Or are some fairly resistant to bending in normal operation ?

Chainrings rubbing on the derailler is often related to frame flex, not
flex in the crank or chainrings. I have had chainrings rub, and larger
folks are more prone to have the problem.

If you tell us a little about your frame and your dimensions, someone
here might be able to share their experiences with a similar bike. And
you could do some experimenting by switching cranks on different bikes
to see if it's the frame or the crank that's flexing. My money's on the
frame, but just about anything is possible....

--
Dave
dvt at psu dot edu