Anybody build their own 5th wheel?

[Darrell Norquay]

At 02:07 PM 6/17/96 -0400, you wrote:
>
> The second two are going to come from a 5th wheel that I want
>to make from 10 speed bicycle tire.  Has anyone had any experience with
>making one of these?  
>
>        Does anyone have any suggestions or comments on how I can improve
>this design?   Any suggestions for an LED/Photo-receptor package that is not
>influenced by stray light?   

I think you would be much better off going to a "photo interrupter" type
system than a reflective sensor.  These are sometimes called "slotted
optoswitches" and come in several different flavors.  As long as you use
infrared emitter/detector pairs, ambient light should not affect it too
much, other than possibly direct sunlight.  A small "hood" should take care
of this.  The interrupter style sensor could even be used with the original
equipment sprocket and hub, a much more practical arrangement for what you
have in mind than either magnetic reed switches or reflective optos. 

As some people have stated, detecting a spoke at 120+ MPH would be a real
challenge, and I don't think a magnetic reed switch will activate that fast
either, although a hall effect sensor might work.  The bicycle speedo
approach may also work, but they are not really rated for those speeds, and
you may end up missing pulses.  When was the last time you saw a bicycle
doing 120 MPH? :]

regards
dn