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[BlazingPenguin]

One of these items recently appeared at our club:

http://cgi.ebay.co.uk/Starrett-rev-counter-indicator_W0QQitemZ320300188641QQcmdZViewItem?hash=item320300188641&_trkparms=72%3A1298%7C39%3A1%7C66%3A2%7C65%3A12%7C240%3A1318&_trksid=p3286.c0.m14

Does anyone have any idea how to use one properly?
It looks just the ticket for using on our steam and electric engines perhaps.

[bogstandard]

I would give it a miss if I was you, it is really for the lower ranges unless you want to sit there for a few minutes counting how far the dial goes around in conjunction with a stopwatch.

This instrument is a fairly old mechanical design (turn of the 19th/20th century), you would be much better of either going for the machine setting variety with rotary friction input (rather expensive), or the much cheaper digital ones for modelling (aeromodellers use them for setting up and checking ic engines). But the digital ones  tend to work on a strobe priciple, the prop blades passing in front of the sensor giving the input, also they can't be used accurately under flourescent light.

Hope this has helped.

John

[BlazingPenguin]

We have it already John....we didnt have to buy it!

As far as I could work out, if you time it for 15secs on your watch, multiply the figure by 4x and that 'should' be the revs of that particular shaft etc.
If it was whizzing along then time by 10 secs etc.

I just wanted to know if there was a 'proper' way to be doing it?

[Peterm]

I have a little rev counter called a Digital Mini Tach.   It is powered by a 9v PP3 battery and can be switched between 2 and 3 bladed propellers and reads up to about 20 thousand rpm.  Uses a light sensitive system, I think it was designed originally for model aircraft, but works well on the bench with my boats.   Got it on ebay from a model aircraft shop.   Pete M

[bogstandard]

BP,

I have seen the destructions for one somewhere, I will see if I can find it.

PeterM,

That is the one I use, but it is affected, as I said, by flourescent lighting. Just turn it on, under such lighting and it will give a reading all by itself. Something to do with the frequency the lights run at.

John

[bogstandard]

I knew I had seen it somewhere, here is an abridged version of how to use.

1) You'll notice a small button (looks like a rivet head) at about the two o'clock position on the rotating wheel.  With a finger held lightly on the wheel, that button allows you to count complete revolutions of the wheel.

2) Dial is marked clockwise and counterclockwise depending on which direction the shaft is turning.

3) Zero the counter, touch tip to spinning shaft, time it for one minute and you have RPM displayed.

I don't think it was designed for very high speed running.

So it looks like the 15 second way you are doing it, is acceptable, but might be a bit less accurate than the full one minute running time (say 1/2 second error for disengage). The 10 second multiplied by six would be pushing the accuracy a little.

Hoped this has helped.

John

[BlazingPenguin]

Thats great John...we seem to have worked it out then, apart from the what the stud was for and you have explained that for us.

It looks a great little piece of kit, they seem to sell ok on Ebay, but this one aint going nowhere except back into the toolbox of the engineering section.