When I first finished my KR, I used an analog tach from WesTach with a pulse generator mounted to the tach drive on my O-200. I found that tach had a 200 rpm error in it, but if I remember right, it also didn't require any power other than the pulse generator itself.? I didn't discover the problem for a few years.? Had I have found the issue when it was new, Westach undoubtedly would have replaced/repaired it for me.? ? I replaced the Westach Tachometer with an Analog Tach from UMA that also uses a pulse generator, but requires DC power to operate. The UMA tach is precise and includes an internal Hobbs meter that only runs when turning >1800 rpm to record engine time. I used the same type of UMA tach on my SuperCub when I built it except that it has a transducer that screws into the Slick mag to pick up the pulse signals from the rotating magnets in the magneto. That tach is also very precise. I have found UMA and WesTach both to be very helpful when I've had questions or needed support on one of their instruments.? I had planned to use the pulse generator for the tach in the SuperCub as well, but found that it simply would not fit with the oil filter adapter.? UMA was happy to swap out my tach (4 pulses per revolution from the pulse generator) for another new tach that would work with the magnetor transducer (2 pulses per revolution) at no charge.? When I wanted to set the Hobbs time to match the aircraft time when I installed the new tach in the KR, they were also happy to help get that set as well at no charge.? ? On the non-electric VW powered Avid Flyer I built, I used a Tiny Tach mounted on an ignition lead on a Slick Mag. You do have to remove the shielding from the spark plug lead in the area where the Tiny Tach sense wire is going to wrap onto it. The Tiny Tach worked OK and seemed to be accurate, but it seems that the internal battery didn't last very long. When the battery died, I lost the accumulated hours from the unit.? Lots of people have struggled to get the Tiny Tachs to work properly.? The sense wire has to be installed following "Flemings left hand rule of Magnetism", which is going to be different between solid wires like what are used in aircraft and spiral wound wires like what are used in cars.? Since the Tiny Tachs us an inductive sense wire to pick up the pulses from an ignition wire, they are also sensitive to other induced noises, so in some installations, they may not be reliable or may require some shielding to improve reliability.
-Jeff Scott Los Alamos, NM ? ? ---------------------- Dear All, I find myself in need of a new RPM guage.What kind or type do you use or recommend?? I have been researching rpm guages for a week; mechanical, ones that read off of the P lead, ones that read off of both P leads, devices that plug into the vent hole of my slick magneto, so many. ?I would like to spend less than $200. ? Joe Nunley?CW2 US Army RetiredBaker JROTC Instructor?Baker Florida?
