Bicycle computer for speedo, data, and tachometer.

Rev Counters, Speedo's, etc..

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dieselbikin
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Joined: Sun Apr 27, 2008 12:49 pm
Location: United States, Athens, AL

Bicycle computer for speedo, data, and tachometer.

Post by dieselbikin » Tue Sep 22, 2009 5:30 pm

I use a bicycle computer from Walmart as a speedometer and for keeping track of my average and top speeds during test runs. This has been invaluable during testing because I no longer have to rely on seat of the pants evaluations of whether performance was better or worse over a 3 mile course.

I also tried to make one of these computers into a tachometer so that I could keep track of average and top RPM to help evaluate gear, puck, and spring combinations. I had both computer hooked to switch I discuss below. The problem I ran into was that the computer itself does not have the ability to handle more than about 2900 inputs per minute. I even tried my Sendec's transducer which is good for 10,000 RPM with the same results. In other words, the lack of resolution is in the computer rather than the transducer (magnet assembly on the rotating assembly).

Anyway, during testing I used to have to reset my computer at a dead stop. The computer would start recording data as I accelerated from a dead stop and I would look at my avg speed just before letting off the throttle at the end of the course. Unfortunately this did not allow me collect very accurate data for avg top speed. I have installed a small on/off switch on one wire of my computer to allow me to open the computer’s input circuit from the magnet. Now I can reset the computer whenever and turn flip the switch with my pointer finger once I’m up to speed to record average top speed. I ran a test run with it today using this method and ran an avg/top speed of 53/60 mph on section A of leg 2 and 57/60 mph on section B of leg 2. Leg 2 is a relatively flat 3 mile test course. Very happy with progress.

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