Home-grown 5th wheel project

[Daniel R Burk]

Thanks Bruce, Orin, Dan and Peter for the wonderful input.  I'll zip over to the
bicycle shop and get an idea of what the mag pickup looks like.  I might be able
to do just as you suggested and mount a small magnet onto every other spoke.  
There seem to be approx. 36 spokes on a typical wheel so that would be 18
positions
which is one every twenty degrees.  Based on my initial calculations using
36 spokes
on a 26 inch O.D. tire/rim combo, I would get a 1000 Hz signal at approx.
129 MPH.
Thus, with only 18 spokes, I should get a 500 Hz signal. 

I did a quick check on how much time a .100" thick spoke would break my
light beam
if I was monitoring near the edge of the rim. (20.5" dia.)  I found that the
spoke
would obstruct the beam for only 60 microseconds at 129 MPH!! I'd have to
widen that pulse width by either using a 1 shot timer, or by moving the
sensor closer to the 
hub.

        The research continues.

        BTW, I like the idea of correlating the data via integration of
the accelerometer data.  I'll probably load it all
into MATLAB and crunch it in just that fashion.

Cheers!
        --Dan.