C
On Thu, 31 Mar 2005 02:14:35 GMT,
[email protected] wrote:
>Carl Fogel writes:
>
>> If the dented rim is a fraud of some kind, how was it produced?
>
>> That is, would a normal rim crack like that when bent out on one
>> side with a suitable soft-jawed tool that left no marks (doubtless
>> available under the counter from Harris Cyclery's Covert Operation
>> Catalogue), or would it just bend without the crack?
>
>This is the usual form f a rim that encountered an object, like a
>piece of RR ballast (granite) off center of the tire. I have several
>rims that were fatally dented like this on one side in my collection
>of scrap rims. The difference is that I didn't concoct a story that
>it was the result of moderate inflation pressure and then call
>everyone who doubted that a jerk.
>
>> Would the speed of the bending determine whether it cracked?
>
>No.
>
>> That is, would a real impact cushioned by a tire at high
>> speed tend to rupture, while a fake "impact" produced by a
>> comparatively slow twist with a pair of soft-jawed
>> channel-locks would leave no crack?
>
>That is completely out of the question from my experience with such
>dents. You can't make them that smooth without a tire on the rim and
>exerting a radial overload.
>
>The speed of the bicycle in conjunction with weight on the wheel,
>needs to be only great enough that the inertial load will bend the
>rim. This is not hard to do at speeds of even 15mph, although higher
>speed ensures success. Curling the edge of a rim cannot be fatigue
>related.
>
>[email protected]
Dear Jobst,
Maybe something is wrong with my crude experiment, but . . .
I just introduced an old 27-inch steel rear rim with weep
holes to my bench vise and bent five sections of the rim
sections, some with the narrow end of the vise, some with
the wider normal grip.
Even with four inches of the rim bent out at 90 degrees to
the spokes, there's no cracking, inside or out. Not even
when I bend a section with a rusty weep hole.
Maybe an aluminum rim cracks or ruptures more easily than a
steel rim? Or maybe the hollow double-wall design affects
things?
The bends are much more dramatic than the originals:
http://home.comcast.net/~carlfogel/download/rim_nite.jpg
If there's interest, I take some pictures, but it's just an
old steel rim with sections of one sidewall bent flat and no
cracks.
Carl Fogel
[email protected] wrote:
>Carl Fogel writes:
>
>> If the dented rim is a fraud of some kind, how was it produced?
>
>> That is, would a normal rim crack like that when bent out on one
>> side with a suitable soft-jawed tool that left no marks (doubtless
>> available under the counter from Harris Cyclery's Covert Operation
>> Catalogue), or would it just bend without the crack?
>
>This is the usual form f a rim that encountered an object, like a
>piece of RR ballast (granite) off center of the tire. I have several
>rims that were fatally dented like this on one side in my collection
>of scrap rims. The difference is that I didn't concoct a story that
>it was the result of moderate inflation pressure and then call
>everyone who doubted that a jerk.
>
>> Would the speed of the bending determine whether it cracked?
>
>No.
>
>> That is, would a real impact cushioned by a tire at high
>> speed tend to rupture, while a fake "impact" produced by a
>> comparatively slow twist with a pair of soft-jawed
>> channel-locks would leave no crack?
>
>That is completely out of the question from my experience with such
>dents. You can't make them that smooth without a tire on the rim and
>exerting a radial overload.
>
>The speed of the bicycle in conjunction with weight on the wheel,
>needs to be only great enough that the inertial load will bend the
>rim. This is not hard to do at speeds of even 15mph, although higher
>speed ensures success. Curling the edge of a rim cannot be fatigue
>related.
>
>[email protected]
Dear Jobst,
Maybe something is wrong with my crude experiment, but . . .
I just introduced an old 27-inch steel rear rim with weep
holes to my bench vise and bent five sections of the rim
sections, some with the narrow end of the vise, some with
the wider normal grip.
Even with four inches of the rim bent out at 90 degrees to
the spokes, there's no cracking, inside or out. Not even
when I bend a section with a rusty weep hole.
Maybe an aluminum rim cracks or ruptures more easily than a
steel rim? Or maybe the hollow double-wall design affects
things?
The bends are much more dramatic than the originals:
http://home.comcast.net/~carlfogel/download/rim_nite.jpg
If there's interest, I take some pictures, but it's just an
old steel rim with sections of one sidewall bent flat and no
cracks.
Carl Fogel