$39 test device for forces on spokes

Quoted message said:

While sitting at my computer, I happened to pick up a roll of a
hundred 39-cent stamps, packed by the US Post Office in a tight
plastic wrapping.

A moment later, I noticed that I was holding the natural enemy of such
packaging in my other hand, namely a ball-point pen.

I can resist anything except temptation, so . . .

Whonk!

http://www.filelodge.com/files/room19/497501/216%2039%20dollar%20test%20wheel.jpg
or http://tinyurl.com/otx8z

If you click on the lower right of the picture in Explorer, you get a
huge view, detailed enough to show the stretch-marks on the plastic
wrapping, indicating tension of some kind.

While expensive, a roll of stamps should eventually be within
everyone's reach.

(I suppose that the post office will sell you a roll of hundred 1-cent
stamps for just a buck, but I must caution you against using cheap
materials.)

Anyway, it's a fun and easy-to-play-with model. Is the plastic
"spoking" in tension? If you push the pen "axle" sideways, then it
certainly is. Apply a load to the pen "axle" and see the upper
"spoking" pull away from the pen-axle while the stamp "rim" flattens
slightly.

I doubt that anything terribly new is happening, but it may provide
harmless entertainment for the usual debate. You could make a bigger
model by stretching some inner-tube rubber across the mouth of a tin
can.

Explaining the details should be a good exercise for anyone tired of
wagon wheels, cast wheels, and pre-tensioned spoked wheels.

I'll fiddle with it after I find a simplification for the Stokes-Boles
equation.
--
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Quoted message said:

While sitting at my computer, I happened to pick up a roll of a
hundred 39-cent stamps, packed by the US Post Office in a tight
plastic wrapping.

A moment later, I noticed that I was holding the natural enemy of such
packaging in my other hand, namely a ball-point pen.

I can resist anything except temptation, so . . .

Whonk!

http://www.filelodge.com/files/room19/497501/216%2039%20dollar%20test%20wheel.jpg
or http://tinyurl.com/otx8z

Wow, look at that naturally high "spoke" count. Apparently, nature
abhors low spoke count wheels!

Earls61 said:

[email hidden] wrote:

Quoted message said:

Quoted message said:

Whonk!

http://www.filelodge.com/files/room19/497501/216%2039%20dollar%20test%20wheel.jpg
or http://tinyurl.com/otx8z

Wow, look at that naturally high "spoke" count. Apparently, nature
abhors low spoke count wheels!

What - "one" is "high"? ;-)

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame

Quoted message said:

While sitting at my computer, I happened to pick up a roll of a
hundred 39-cent stamps, packed by the US Post Office in a tight
plastic wrapping.

A moment later, I noticed that I was holding the natural enemy of such
packaging in my other hand, namely a ball-point pen.

I can resist anything except temptation, so . . .

Whonk!

http://www.filelodge.com/files/room19/497501/216%2039%20dollar%20test%20wheel.jpg
or http://tinyurl.com/otx8z

If you click on the lower right of the picture in Explorer, you get a
huge view, detailed enough to show the stretch-marks on the plastic
wrapping, indicating tension of some kind.

Maybe that's plastic deformation caused as the pen was shoved in. I
don't believe the resulting wheel can be pretensioned since nothing is
actually glued to the pen.

Quoted message said:

While expensive, a roll of stamps should eventually be within
everyone's reach.

(I suppose that the post office will sell you a roll of hundred 1-cent
stamps for just a buck, but I must caution you against using cheap
materials.)

Anyway, it's a fun and easy-to-play-with model. Is the plastic
"spoking" in tension? If you push the pen "axle" sideways, then it
certainly is. Apply a load to the pen "axle" and see the upper
"spoking" pull away from the pen-axle while the stamp "rim" flattens
slightly.

Certainly wheel-building would be easier if all you had to do was ram
the hub in through some plastic wrapping...

Quoted message said:

Explaining the details should be a good exercise for anyone tired of wagon
wheels, cast wheels, and pre-tensioned spoked wheels.

For those tired of wheels altogether, it may also be interesting to
reflect that space elevators use the same principle as the bicycle
spoke. It's the pretension in the cable that stops the orbiting skyhook
coming down to Earth when you winch something up the cable. As the load
climbs up the cable, the stretch of cable behind the load, between it
and the ground, goes a bit slacker, but the tension in the cable above
the load all the way up to the orbiting satellite stays the same.