Not an expert on these things but it sounds like the little VDO was loading the mag down, probably a low resistance movement or breaking down. 4 options are to 1. try adding an in-line resistor of increasing value. If you get to the stage where the engine is smooth and the tacho is still accurate you've had a win. The analogue gauge actually "counts pulses". It has internal transistors that "average the power going to the needle movement based on the frequency of the pulses and only requires 6v or so to work. 2. get a higher impedance ($$$) analogue gauge, 3. buy a digital tacho, you'll probably have to protect it with a high value resistor (if it is not purpose built to operate on a magneto) as these usually work on low voltage. Here is an example. http://www.csharpprogrammer.com/wordpress/?p=8 4. Stay right away from the magneto by build a digital tacho kit from an electronics shop. These have a magnetic (or hall efect) pickup you can attach to the back of your prop hub (put two on for balance)
Good luck, Paul Smith Brisbane, AUSTRALIA pk.sm...@bigpond.net.au http://kr2spacemodulator.blogspot.com/ -----Original Message----- I used a VDO rev counter with the pickup on the deadcut point of one Slick Magneto. There are two on the Limbach. Since I removed the wire from the Magneto the engine is running much smoother. Now how can I measure the engine revs? There is no alternator on the motor. Any ideas? Please help.
