You can reach me at phinishline@yahoo.com for comments, questions, and suggestions.This is another article sent to me over on Bob's 4-cycle forum. All I got for the author's name was, "Irish". If this is you or you know who this is I'd like to know so I can give credit where credit is due. Thanks for the help..... Jamie Webb
enjoy...
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Brad,
This was really very easy if you find the right cassette recorder. Take a digitron tachometer lead and cut it about six inches from the end that connects to the tach. Go to Radio Shack and buy two 1/8" mono plugs. Use mono because that way you won't get the channels reversed between when you record and when you play back. The tach cable is a coaxial cable. Solder the center conducter to the center pin of the plug and solder the sheild to the ground/strain releif crimpable clamp. If you purchase the all metal plugs, they will help sheild the signal from noise. Remember to slide the cover onto the cable before you do your soldering.(just trying to save you some grief that I always seem to do to myself) Then, once I had the soldering done and the covers on I filled the exit hole with rtv silicone rubber around the cable. Now attach your tach sensor to your spark plug wire along with your regular digitron tach sensor with a wire tie or whatever you normally use. You need a portable cassette recorder that has a mike socket and enough output power to drive the input on the digitron. I tried a palm size cassette recorder from sony that didn't have the stuff. It used two AA bateries for a total of 3 volts output. Then I bought a cassette recorder that was the older style(about 8"x5"x1 1/2") It runs on 4 AA batteries or 6 volts. With the volume not quite all the way up as i play the recorded info back into the digitron it works great. The recorder records at the same level, no matter where you have the volume set so don't worry about the recording level.In the original article the author had used a Panasonic 704 or 417 or other which was a micro cassette recorder which of course is smaller but that cost $40, the sony I bought first cost $30 and didn't work and this heavier duty unit also a sony cost $20. If you are an electronics buff you might try making an open collector transistor interface with capacitor coupling to the recorder for playback into the digitron. I think that the digitron has a somewhere near nine volt supply on it's sensor wire which gets grounded out each time the sensor sees a ignition spark. We're using an output from the recorder which oscillates on either side of ground by the ammount of the battery voltage to pull the digitrons sense signal below zero for every time we've recorded a spark. This does work as is but the interface would work with the smaller lower output recorder. It's also neat to hear the recording when you pull the cable to the digitron out of the earphone jack. The other author also mentioned that he had his wife video record the race and as he was pulling onto the track he would simultaneously wave and start the data recorder. That way he could later exactly match his rpm's with where he was and what was hqapening at the time. I had thought that if you could later record the digitron's face over the race in the upper right corner you might learn alot about where your speed is spent and gained. I don't know who thought of this but it's truly one of the best ideas around. It's great for the average racer to improve and learn by but even greater for Dad's who are wondering how to help their kids around the track.
Best of luck to you
Irish [Don't believe in miracles,
You can reach me at phinishline@yahoo.com for comments, questions, and suggestions.