[modeleng] Re: hand tacho.

Andrew Houston wrote:

>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
>
>  
>
Hi,
Many thanks....sorted it. Point and cup adaptors  give rpm and wheel 
gives f/min. Tested it on the lathe with digital rpm readout. Its dead on.

Needed it to measure the rpm of various electric motors to then work out 
the gear ratios needed to drive my electric traction engine. Using the 
fan motor off a ford transit van. The shaft turns at 3400rpm so plenty 
of torque thru a good reduction.


Julian.









>-----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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>

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