[modeleng] Re: hand tacho.

Julian

Back when I used one of these, the "points" were presented to the end of the
shaft being measured and the Tacho read directly in Revs Per Minute (RPM).
There were a couple of rubber "points" male and female cones plus a metal
"point" shaped like a pyramid.  They had two slots that fitted over the
shaft and onto two pins to give positive drive.

Within the "kit" of attachments there was also a rubber wheel.  It was used
to measure the peripheral speed of a wheel, shaft, etc.  Can't remember what
size it was, but I do remember it was marked with a conversion factor.

Anyway, it's relatively easy to work out if you measure the diameter.
Supposing it's just under 4", the wheel would give you speed in ft/min. Good
old Pi*Dia (Circa 3.142 times a little less than 1/3 foot)

IIRC as well, there were warnings about exceeding the max RPM in any range
as there were gears inside the tacho to allow measurement of low speeds and
these would have been damaged if it was on that range and used for too high
a speed.  Dragging the memory banks further, I think the one we used had 30,
300 and 3000 RPM (ft/min) ranges.

Hope this is of use to you.

Andy

-----Original Message-----
From: modeleng-bounce@xxxxxxxxxxxxx [mailto:modeleng-bounce@xxxxxxxxxxxxx]
On Behalf Of Julian
Sent: 16 September 2007 14:59
To: models
Subject: [modeleng] hand tacho.

Hi,
I have just bought an old-ish hand tachometer. It is a Smiths Industries 
"Venture" ATH6. It came with no instructions so I don't know whether it 
measures ft/sec or ft/min or rpm. Does anyone have any instructions for 
one of these? If so please can you scan and email to me. It looks to be 
around 70's 0r 80's as it has an 01 number for London. Belonged to an 
old engineer who died and his son sold contents of shed. Never been used 
as the unit was still sealed with the factory way seal.

Julian.

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