VINTAGE HANDHELD TACHOMETER

[bob duffer]

Can anyone tell me how this works  ? It is supposed to be from the 30's . Has anyone seen or used one before?

Thanks

 

[keiser31]

If the end of it (dark tip) spins, it is probably held against a tire while the vehicle is up in the air with wheels turning under motor power. Or maybe you just hold it against a fan belt.

Edited January 27, 2016 by keiser31 (see edit history)

[PONTIAC1953]

it's made so that the rubber tip makes contact with the center of a shaft or bolt that's bolted in the center of a shaft (like a bolt securing the harmonic balancer to a crankshaft), and tells you what the rpm's are.

charles l. coker

1953 pontiac tech advisor

tech advisor coordinator

poci

[keiser31]

it's made so that the rubber tip makes contact with the center of a shaft or bolt that's bolted in the center of a shaft (like a bolt securing the harmonic balancer to a crankshaft), and tells you what the rpm's are.

charles l. coker

1953 pontiac tech advisor

tech advisor coordinator

poci

That makes more sense than my guess.

[smithbrother]

I recall they were used for lots of reasons,

I owned one, but as a kid of 15-16, well I didn't keep. My life story, hehe

The tip of mine was hard rubber so that it would grip the rotating motion.

Dale in Indy

[Guest Rp1967]

They use them in the small engine world to set max Rpm

Holding them in the center of the shaft is correct.

[capngrog]

As others have already said, holding the head of the tach and pressing the rubber foot into the center of rotation is the way to use it.  For years, part of my job was testing/certifying diesel engine-driven fire pumps.  We used a similar mechanism (Veeder-Root) which directly counted the number of revolutions which, when using a good stop watch, yielded the number of revolutions over a given period of time (usually 1 minute).  Although, in the telling of it, it seems like a fairly crude method, it was amazingly accurate.  The engines were usually large GMs or Cummins and had an indentation in the center of the crankshaft which would allow placement of the tachometer without too much drama.

 

Cheers,

Grog

[Jim Bollman]

I had a similar looking one, should be around somewhere, was told it was for measuring the PTO rpm on a tractor.

[Larry Schramm]

They were made by AC Spark Plug Division of GM for many years. 

 

The internal mechanism is basically the same as used for mechanical speedometers in the cars. 

 

Just calibrated for shaft RPM speed.  They are for sale with some regularity on ebay.

[Hudsy Wudsy]

If you go to a threshing meet you'll see them in abundance. The guys are forever checking the RPM of their "Hit and Miss" engines. I'm not sure why, exactly.

Edited January 28, 2016 by Hudsy Wudsy (see edit history)

[Guest prs519]

I have a mechanical tach, probably for calibration, similar to this. It also has a 2x and a 4x diameter rubber wheels so

as to keep the rotation at a reasonable rpm. The dial is therefore marked with a few different scalings and one would readthe proper value according to which reduction. I think one could check a shaft or belt or pulley speed, as long as

he could get a good safe surface to meah against. Thanks for the tip that it works best in the center of the shaft. I should add that my tach is much larger than the one the op posted.

[oily rag]

The rubber tip is put against the center of  the shaft. I have used similar ones to determine over loading on production equipment that runs at a consent speed. 

[Mark Shaw]

I have one in the original cardboard tube container... 

 

Like new!

[smithbrother]

Maybe you should take a peek inside the tube, might be someone slipped a rock inside after they stole it. hehe.

Sears had that problem a few years ago, at the drive up return window the customer retuned a drill in the carton, but inside was a brick.

Dale in Indy