Not a dial indicator!

[Sonic EscapeParticipant @sonicescape38234]

I’m sure most of you know what it is, but I’ve never seen a mechanical tachometer before. It’s basically a stopwatch that couples the shaft for 6 seconds to some sort of mechanical counter. Interesting. And I really needed something like that.

 

[Clive SteerParticipant @clivesteer55943]

It looks as though it is a true revolution counter where the spindle is allowed to index the pointer for a given time period to indicate the revolutions per minute. The timer controlling thee indexing probably has a balance wheel and escapement and its energised by pushing the button and runs for a set time number of escapement cycles and whilst running allows the spindle to index the pointer. This is similar to the way the Jaeger chronometric type of speedometer works.

Clive S

[BazyleParticipant @bazyle]

very fancy. Mine just counts the revs while the operator provides the timing squinting through the window at the church clock.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I have a similar one, but it doesn’t make any ticking noise.

Regards Nick,

[Michael GilliganParticipant @michaelgilligan61133]

Hasler patent for you, Nick:

https://worldwide.espacenet.com/patent/search?q=pn%3DCH64968A

Nice looking instrument !

MichaelG.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi MichaelG, thanks for the link. It is a nice instrument, and it works very well, it weighs 209 grams, and is quite comfortable to use. There a quite a few on ebay, that are not a lot of money, but I had this one given to me for doing a 10 minute small job for an old workmate.

Regards Nick.

[Michael GilliganParticipant @michaelgilligan61133]

Drifting [as has MEW] into locomotive matters … some readers might also like to see this 1901 patent by Hasler:

https://worldwide.espacenet.com/patent/search?q=pn%3DGB190118432A

MichaelG.

[Gerard O’TooleParticipant @gerardotoole60348]

Many Motorcycles fitted Smiths Chronometric Speedometers and Speedometers. Up to the mid 60’s I think, when they moved to the magnetic type.

One peculiarity, which might be shared by your instrument, was that the needle would jump to the correct reading at regular intervals rather than a smooth transition.

This video shows the motion https://youtu.be/aFSeAZnpORo?si=gR_gErLgrflWch5Y

 

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