Don't ask me! You're the smart one! :-)

I think that some really smart guy would say something about sticking a rare earth magnet somewhere as a pickup, and then some sort of chip, and some sort of counter circuit, and some sort of display. It was really easy for the Electrical Engineering geniuses on the Prius groups, but it made no sense to me.

Personally, I'd be searching junkyards for an old timey mechanical tach, and then figuring out where to hook it to the motor...

Oh, and great news on the torque monster...

Yay for 700th post, looks like everything is going okay for you, darin.

This thing is ending up so cheap, perhaps you can upgrade it's range/top speed a bit?

One thing I was thinking: just attach a tiny dc motor (or a magnet and coil pickup) to the drive motor's end shaft and calibrate its voltage to the motor RPM (which we can back-calculate based on vehicle speed, knowing the transmission ratios). Then make up an analog volt gauge that ties it all together....

If the car came with a tach, then it probably is an analog votmeter. The way they worked with mechanical points is that the low voltage coil wire would send pulses to the tach. Inside the tach is a capacitor with a bleed resistor. The pulses would charge the cap and the resistor would discharge the cap. The faster the pulses charge the cap, the higher the voltage and resulting needle indication. As the pulses slow down, the continuouse discharge through the resistor allows the voltage (and needle) to fall. It's so simple that something similar must exist on electronic systems using a hall-effect device that gives the ECU it's engine position information. The ECU probably sends a cleaned-up pulse from the hall-effect device to the tach (that's my guess).

Since there's no ECU, you may be able to simulate the pulses by using an optoisolater which is a colocated LED and photo-transistor with a small separating gap between them. Mount the optoisolator close to a rotating part of the motor (like the coupler) and some kind of shutter glued to that part so that as the 'fin' revolves, it interrupts the gap. To avoid balancing issues with the rotating mass, the shutter should be made out of something opaque but lightweight like a small piece of aluminum flashing. The tach is calibarated to a specific number of pulses per revolution according to the number of cylinders the ICE had. You would want that same number of interruptions (pulses) per revolution. Does any of this make any sense??

Yeah, that makes sense. Unfortunately neither the red or blue cars had tachs. I'm pretty sure some computer mice used optocouplers connected to the ball to detect movement - was thinking if I were just a bit smarter/more motivated, I could hack one of those to do something useful :)

Say... how's the Healey?

The Healey patiently waits. My oil pressurization attempt didn't work (20W50 with stabilizors was too thick) and I seem to need to rebuild the starter...but the lakehouse has a new roof and life goes on... ;)

So... is a junkyard tach an option? If so, I'm fairly certain you could make one work. The advantage (besides asthetics of an oem part) is the nice big 270 degree sweep of a tach movement. Also, if the inertia of the movement is high enough, you can skip the capacitor and resistor I mentioned above. See this most helpful article: https://www.4crawler.com/Diesel/Cheap...x.shtml#Theory

Cool - thanks for the link. Glad to hear about the new roof too :)

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hello,this is my first post on this forum and i would like to hello to everybody.after reading what's been done to build the forkenswift I too are considering the same sort of project,while looking through the US ebay sight I came across the listing which I thought might be of some interest to somebody.
https://cgi.ebay.com/ebaymotors/ws/eB...2757298&rd=1,1
anyway all the best,cheers---palu

Hi Paul - welcome to the site.

That motor would be fine for a large vehicle - it's a beast @ 375 lbs! (I thought the Torque Monster was heavy @ 240.) The main challenge would be finding / making a controller for it, since the field is separately excited, rather than the more common series setup (some people run 2 controllers - one for the armature, one for the field. You can also buy dedicated Sep Ex controllers).

The shipping cost will be the other big challenge.

Funny: I've had 3 inquiries about the Torque Monster since receiving the deposit for it. Which makes me think that, as usual when I sell stuff, the price was probably a bit too low :o

So I had to replace the Healey starter. It was a crude little series-wound motor that could be rebuilt, which I attempted, but the commutator was WAY out-of-round so I surrendered after almost a day of effort. Maybe I'll log it as training for some future EV work. :)

As for the rest of it, it'll have new: carbs(x3), fuel & water pumps, belt, door latches & strike plates, trunk lock (its the only thing that does lock), hoses, thermostat, cap, rotor, condensor, plugs, points(x2), and fuel filter. Rebuilt starter, speedo, temp/oil combo guage, gas tank, and a whole lot of et cetera.

BTW, congrats on your 4,000th post. ;)