I know what it is, what is it used for?

[gizmocat]

Hi all, I know this is a tacho, a Smiths Venture ATH4 to be precise. I know it's used to measure rotational speed and ft/m /sec surface speed.

It belongs to a friend of mine, passed on from her father, he was an avionics tech. She knows for a fact it was used at Cranwell during the war, where he was serving.

Question is, what specifically would he have used it for? Any ideas?

Bests,
Giz

[grounded27]

Like! it.

[gizmocat]

You've lost me there mate

[jimjim1]

Some guesses

A quick google [Smiths Venture ATH4] suggests that there are still people prepared to calibrate it.

The "cutting and surface speeds" reference visible in the lid might be a clue. A machinist might use it to determine the speed of a workpiece in preparation for cutting.

It might more usually be a reference tachometer used to verify other instruments including of course aircraft tachometers.

[mathy]

just a mechanical engineer'stacho

The extensions have various "feet" suited to the measuring point. For example have you seen the "countersunk" conical hole tapped into the hub of a high speed flywheel? Insert the leg with the rubber conical foot even while it is rotating and it will be "kept" and not wrench your arm off. Can you only see a flywheel rim? There will be a "foot" that is just a plain hard rubber disk. That's all it is... a measurer of rotational speed be it pulley, flywheel or whatever but it has a sensible speed range to stop you poking it where I wouldn't be putting my fingers. For fun look up a tentelometer for measuring the tension in a belt at one end of the scale down to a streaming tape drive at another. All nice mechanical devices but general purpose and not exclusively aeronautical. Still in use.

[gizmocat]

Thanks for the input chaps.