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On The Lead Lap
Posted 06 August 2016 - 12:08 PM
So I picked up what appears to be an unused vintage Tradeship slot car motor tach. In its box, but no instructions.
I have no idea if, when sold back in the day, these were accurate.
Anybody have any idea how these are used? Better yet if anyone has instructions to scan and send, so much the better!
Thanks!
T
Headmaster of the asylum
Posted 06 August 2016 - 01:44 PM
Neat snag, Todd.
You might take a variable speed drill (a small Dermel would be ideal), chuck an appropriate shaft in it to connect to what looks to be a spring connector on the tach, and see what you get when you spin it up carefully.
Just for curiosity's sake, where did you stumble on this? eBay or somewhere else?
Gregory Wells
Never forget that first place goes to the racer with the MOST laps, not the racer with the FASTEST lap
Posting Leader
Posted 06 August 2016 - 02:13 PM
I wonder how many the guy has. I have seen them on eBay for a couple weeks.
I wondered if it is designed for a big open pole motor and used a rubber band to drive the shaft and measure RPM.
Matt Bishop
Headmaster of the asylum
Posted 06 August 2016 - 02:49 PM
Thanks for answering my question to Todd, Matt.
Here's a better pic of the 'face' from one of the three or so sold listings I spotted.
One hopes that the markings have a multiplier (i.e. 3,000 = 30,000) or its not going to be a very useful device with any current motor.
Gregory Wells
Never forget that first place goes to the racer with the MOST laps, not the racer with the FASTEST lap
On The Lead Lap
Posted 06 August 2016 - 06:29 PM
I guess it's like an old car speedometer. A magnet spins inside a metal can and creates a torque by means of Eddy currents. A spiral springs counterbalances the torque created. The higher the RPMs the higher the torque and the needle deflection.
I doubt it would have any kind of means of changing the range.
Because light travels faster than sound, some people appear to be bright until we hear them speaking.
Backmarker
Posted 06 August 2016 - 11:33 PM
It attaches directly to the motor shaft. They came with two spring couplers, one for .091" and one for .078".
Set the dial to 'red line' which is zero.
Run motor for exactly 60 seconds.
Count the number of times the pointer goes around (clockwise only) past 'red line' in the exactly 60 seconds.
Multiply by 3,000.
Add the number shown by the pointer on the dial to the total.
The sum of the total of the 3000s counted plus the number it stopped at after exactly 60 seconds is "the revs."
Example: Pointer passes zero 10 times in 60 seconds and then stops at 2250. The RPM rating is 32,250.
That's it!
On The Lead Lap
Posted 07 August 2016 - 07:20 AM
Thanks! This did indeed come with the couplers.
Headmaster of the asylum
Posted 07 August 2016 - 09:00 AM
I guess it's like an old car speedometer.
Based on 88honcho's post, this is not so much a tach as a revolution counter, so it must be simply a reduction gear train. Counting the number of revs in 60 secs (a minute of course) gives RPM.
Gregory Wells
Never forget that first place goes to the racer with the MOST laps, not the racer with the FASTEST lap
Posting Leader
Posted 07 August 2016 - 11:35 AM
Matt Bishop
Posting Leader
Posted 07 August 2016 - 06:41 PM
It attaches directly to the motor shaft. They came with two spring couplers, one for .091" and one for .078".
Set the dial to 'red line' which is zero.
Run motor for exactly 60 seconds.
Count the number of times the pointer goes around (clockwise only) past 'red line' in the exactly 60 seconds.
Multiply by 3,000.
Add the number shown by the pointer on the dial to the total.
The sum of the total of the 3000s counted plus the number it stopped at after exactly 60 seconds is "the revs."
Example: Pointer passes zero 10 times in 60 seconds and then stops at 2250. The RPM rating is 32,250.
That's it!
Good thing there are still a few guys out there that can pull this kind of information out of their @%$ and post here.
Thanks Nicholas 
