Anybody build their own 5th wheel?

[Orin Eman]

> The first two signals come from the ignition, and an Analog Devices 1 axis
> accelerometer.  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?  I am going to make a light aluminum frame for the
> wheel that attaches to the rear bumper of the car.  The frame will have a
> photo diode and an LED mounted on it so as to do one of two things:  
>         Illuminate the Photodiode continuously, such that the light beam is
> broken         by the spokes.  
>         
>         Reflect the light off the aluminum rim, which has been painted with
> flat black paint, except for radial dashes every fifteen degrees. 
> 
>         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?   


Why not use a bicycle computer pickup - a magnet (or however many you want)
bolted to the spokes and the pickup coil bolted to the wheel's mount?

Orin.