Next message: ShanicaJII: "Re: lv-ab: Luders 36 Electrical"
If you use a metal strip twisted lengthwise as the impeller, and just
let it out on a line off the back of the boat -- like any taffrail log
-- then all you need to do is find some sort of wheel you can tie the
onboard end of the line to, and the impeller will spin the wheel. By
giving the metal strip more of less twist you can calibrate the speed of
the wheel with respect to the boat's movement through the water. Then
the bicycle pickup can go right on the wheel. That's a good idea about
a bicycle speedo, as long as it doesn't take much force to drive it.
The other idea is good too -- have the line drive a small permanent
magnet electric motor, and use it as a generator. Just hook up a volt
meter to it, and calibrate it, and you have a speedo. Calibration would
be easier since you could do it electronically.
Dick
> How about making an impeller of some sort and trailing it behind the boat on
> a wire, just as the Walker Log does (at 20 times the price)? I think, one
> could measure the output signal of a sensor and make a contraption that
> would do the same without the hassle of a magnet and a large wheel. A small
> DC motor, maybe? Cut off all the brushes except one?
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