[modeleng] Re: hand tacho.

 I have an older unit, which is an amazing piece of clockwork. Mine has a
built in stopwatch, and only counts the number of revolutions with a counter
(just like the odometer in your car). You then have to calculate the rpm
using the time taken from the stopwatch for the quantity of revolutions.
There is no rpm limit stated, but I wouldn't push it past 2000.... The
stopwatch starts the moment the drive piece (spring loaded) is pressed in
farenough to drive the counter, and stops the moment the drive disengages.
To reset the stopwatch and the counter, the knob on the end is turned, which
also winds the stopwatch up. I usually take a reading for 60 seconds just to
make it easier on my brain, and, 2, or 3 minutes to get a precice reading. 
Cheers,

Phill.

--------- Original Message --------
From: modeleng@xxxxxxxxxxxxx
To: "modeleng@xxxxxxxxxxxxx" <modeleng@xxxxxxxxxxxxx>
Subject: [modeleng] Re: hand tacho.
Date: 17/09/07 22:14


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[1]
[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.
>
>MODEL ENGINEERING DISCUSSION LIST.
>
>To UNSUBSCRIBE from this list, send a blank email to,
>modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject
>line.
>
>MODEL ENGINEERING DISCUSSION LIST.
>
>To UNSUBSCRIBE from this list, send a blank email to,
>modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject
line.
>
>
>
>

MODEL ENGINEERING DISCUSSION LIST.

To UNSUBSCRIBE from this list, send a blank email to,
modeleng-request@xxxxxxxxxxxxx[2] with the word "unsubscribe" in the subject
line.







--- Links ---
   1 mailto:modeleng-bounce@xxxxxxxxxxxxx
   2 mailto:modeleng-request@xxxxxxxxxxxxx
MODEL ENGINEERING DISCUSSION LIST.

To UNSUBSCRIBE from this list, send a blank email to, 
modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.

Other related posts: