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Thomas's Tach
- Thread starter animal12
- Start date
- Replies 4
- Views 1,422
thomasutley
Hot Rolled
- Joined
- Sep 10, 2014
- Location
- Oro Valley
There is a fair amount of info in my restoration thread, search this forum for "16 x 60" resurrection" and you'll find that info toward the end of the thread along with a lot of detail on the wiring, controls, and VFD integration within some mechanical adaptations for safekeeping of the sparky stuff as well to improve visibility and ergonomics of the buttons and the tach.
The short version is I ordered the following components and wired them up with a DC power supply and two small custom circuit boards I made at home:
1) GL338-TACH-06-HTZ 3-3/8" Diesel Tachometer (4K RPM) from Speedhut.com. This is a very versatile aftermarket automotive tach that accepts a variety of pulsed/square wave/sine wave signal inputs commonly found on diesel trucks and cars without high voltage spark plugs. You use the supplied programming dongle to calibrate it to a known reference such as a laser tachometer gun pointed at the spindle nose (~$20 from Amazon). I paid a nominal artwork fee to customize the dial face to reflect the graduations and max value I needed for my lathe, I think it was a $40 upcharge at the time). I would guess Speedhut still has my artwork on file for reference if needed. I think the final bill for the tach was around $150 as I recall.
***Edit: looks like this tach is about $145 from Speedhut currently, plus any custom artwork fees. Keep in mind the custom dial art is truly optional as the gauge is calibrated after installation to read the correct value based on your gear toothcount and spindle RPM--you just may not read full scale if, for example, your machine doesn't reach 8K RPM...ha ***
2) GS100701 Geartooth Sensor from the German company Cherry. These run about $30 online from various sources. This sensor comes in a couple of packaging configurations (inline, right angle) and wire lead/connector options for mounting/wiring. Ultimately it uses a low voltage DC power input from 10VDC to 30VDC(?) to convert the Hall Effect magnetic flux of passing gear teeth into a signal the Speedhut tach can use. Both the geartooth pickup and the tachometer can be operated off the same DC power supply at 12V, you just have to pick the right "pull-up" resistor across the sensor inputs to set the source voltage, it's really as easy as buying a $0.50 resistor of the correct value and soldering it across the leads. Instructions for picking the right value are in the Cherry user instructions.
The two components work really well together. Two years in and so far I'm very pleased with the performance. If I had it to do over again, I'd probably get a larger dial with a little different artwork that looks more "vintage South Bend," but from a usability and performance perspective it's working really well for me.
The custom cast iron housings for both the tach and the pickup sensor were just my attempt to make the new tech fit in better visually on and old machine.
Happy to help anybody through the process of setting one up, just ask. I'll even design you up a custom cast iron pattern that you can get CNC carved and cast at your favorite foundry, but that's gonna cost extra.
BTW, the circuit boards are not required, but make the wiring neater with everything else going on around the VFD in the controls box. I still have the etching mask artwork, so I could make boards for someone who's serious about using these components together.
Take care,
Tom
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I did think that your gauge face had a Capt'n Nemo type feel to it! I can't imagine what a better one might look like off the top of my head. I like the early 1930 car dashboard gauges for inspiration.
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