ping sheldon brown - sugg. for frame torsional stiffness test



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Spacey Spade

Guest
Dear Sheldon Brown,

Thank you so much for your web pages devoted to cycling.

I would very much like to see a torsional test on bicycle frames where the frame is held by the
wheel axles, and the deflection measurements are at the bottom bracket due to loads on the bottom
bracket. This would be a simple simulation for in-saddle hammering (when arms are not used). Is
there some test results published already?

For the test you could use a 1" steel bar in the steerer as in a previous test of yours, making sure
to afix the bar on the axis where the front axle would be (and not allowing it to rotate there, but
allowing rotation in the steerer tube... either that or use the same forks on all frames hehe!). You
could even put weights on the saddle and on the handlebars to make it even more lifelike.

Having owned a Schwinn Premis, now a Cannondale, I really appreciate the torsional stiffness from
the Cannondale. On the Schwinn I used to look down and see the bottom bracket swinging from side to
side under load (and the chainring would rub the front derailleur to the same tune if I didn't have
it adjusted right).

Regards,

Spacey BSME
 
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Mitch Haley

Guest
Spacey Spade wrote:
>
> I would very much like to see a torsional test on bicycle frames where the frame is held by the
> wheel axles, and the deflection measurements are at the bottom bracket due to loads on the bottom
> bracket.

Then you would like to see Bicycling magazine's frame test jig, AKA "the tarantula". Back in the
1980's, when Gary Klein and then Canondale were becoming popular, Bicycling published BB deflection
for all bikes and frames they tested. Now they assume the readers are illiterate, so bike tests have
lots of pictures, few words, and fewer numbers. You might get more info on rec.bicycles.tech, this
topic seems to be more suited for that group. Mitch.
 
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Ken

Guest
Mitch Haley <[email protected]> wrote in news:[email protected]:
> Then you would like to see Bicycling magazine's frame test jig, AKA "the tarantula". Back in the
> 1980's, when Gary Klein and then Canondale were becoming popular, Bicycling published BB
> deflection for all bikes and frames they tested.

Unfortunately Bicycling Magazine no longer tests bicycles. Now days they only publish puff pieces or
thinly veiled press releases. They don't want to ******** their advertisers with any level of
criticism.
 
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Spacey Spade

Guest
Ken <[email protected]> wrote in message news:<[email protected]>...
> Mitch Haley <[email protected]> wrote in news:[email protected]:
> > Then you would like to see Bicycling magazine's frame test jig, AKA "the tarantula". Back in the
> > 1980's, when Gary Klein and then Canondale were becoming popular, Bicycling published BB
> > deflection for all bikes and frames they tested.
>
> Unfortunately Bicycling Magazine no longer tests bicycles. Now days they only publish puff pieces
> or thinly veiled press releases. They don't want to ******** their advertisers with any level of
> criticism.

Moved to rec.bicycles.tech, thank you!
 
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Robert Haston

Guest
Hasn't everything?

I can no longer find the line between the media and the ads. Remember GW Bush's heroic post 9-11 (go
out and buy stuff - go on vacation) speech?

All Herald the Brave New World.

"Ken" <[email protected]> wrote in message news:[email protected]...
> Mitch Haley <[email protected]> wrote in news:[email protected]:
> > Then you would like to see Bicycling magazine's frame test jig, AKA "the tarantula". Back in the
> > 1980's, when Gary Klein and then Canondale were becoming popular, Bicycling published BB
> > deflection for all bikes and frames they tested.
>
> Unfortunately Bicycling Magazine no longer tests bicycles. Now days they
only
> publish puff pieces or thinly veiled press releases. They don't want to
****
> off their advertisers with any level of criticism.
 
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