a new motor speed

[Ken S]

I downloaded the Tormek handbook on my iPad today. I had done it before, but needed to clear space. i was doing some research on the stone grader when I noticed the T7 speed, which was listed as 90 RPM is now 90 RPM, 100 RPM in US. i suspect the difference is due to the US current standard of 60 Hertz vs the European standard of 50 Hertz. This will give the T7 a slight boost in the competing surface feet per minute debate. Realistically, I don't feel this difference has any real significance, however, as the chief advocate of the T4, I did not want anyone to think I was withholding evidence.

Ken

[Rob]

Saw the T4 for the first time at a show on Friday.  Rather more diminutive than I had expected, especially sat next to a T7 as the A to B comparison was striking.  But it was robust and functional. I wonder what I might have decided if I was purchasing from new again now?

[Ken S]

Interesting comment, Rob.

While I seem to be the forum cheerleader for the T4, I actually am quite content with the T7 (until I have to move it).

Rob, you have made the one point where I believe the T7 has the advantage. When sharpening a gouge, the wider grinding wheel (50mm versus 40mm) seems a point in favor of the T7. The T4 can certainly sharpen gouges, however, the wider flight deck of the T7 is a luxury. Either is wider than most dry wheels. For anyone turning with a full size lathe, I concede the T7 carries the day.

For just about every other use, I still contend the choice should depend on where the Tormek is used. In a full size shop with a sharpening station, I would go with the T7. For those of us who work in smaller and more nomadic quarters, the T4 is very nice. Good observation that the T4 is both robust and functional. Either will do the job, and either uses all of the same jigs. There is no bad choice.

Ken

[Jan]

I downloaded the Tormek handbook on my iPad today. I had done it before, but needed to clear space. i was doing some research on the stone grader when I noticed the T7 speed, which was listed as 90 RPM is now 90 RPM, 100 RPM in US. i suspect the difference is due to the US current standard of 60 Hertz vs the European standard of 50 Hertz. This will give the T7 a slight boost in the competing surface feet per minute debate. Realistically, I don't feel this difference has any real significance, however, as the chief advocate of the T4, I did not want anyone to think I was withholding evidence.

Ken

Ken, you have opened an interesting question. 

The RPM of our Tormek grinders should be proportional to the current frequency. Assuming the same reduction gear ratio, than the RPM in US should be:

RPM _US,60Hz =  RPM _EU,50Hz * 60 Hz / 50 Hz.

It means: RPM _US,60Hz =  90 * 60 Hz / 50 Hz = 90 * 1.2 = 108 RPM

The theoretical 108 RPM for US is not in agreement with Tormek handbook 100 RPM for US. The question is why?

It would be nice, to measure the real T7 RPM in US. Ken, do you think you are able to count the number of revolutions per minute of your T7? It is a challenging task, it revolves quite quickly.

Even more difficult it would be for your "protégé" Tormek T4.

Jan

[Ken S]

Jan,

In my slightly younger days I collected machinist tools. It was a hobby interest inspired by inheriting some tools from a machinist born in 1863.  Starrett makes two speed indicators. They operate on the principle of a revolving shaft turning a calibrated wheel. They are simple tools which have been in Starrett's catalog for many decades. At one time they were plentiful on ebay.

Alas, these were two of the few machinist tools not added to my collection. However, if I locate an inexpensive one for sale, I will try to acquire it. The shaft would be held against the rubber drive wheel for a measured minute. A simple procedure.

I will also contact Sweden and see if they have a more technical, precise motor speed.

Ken

[Jan]

OK, Ken. I have found a detailed description of Machinist Speed Indicator on you tube. That is probably the tool you have in mind, and which will be suitable for our task.
https://www.youtube.com/watch?v=4RLnwgp6YcM

Jan

[Rob]

My question would be "why" do you care what the RPM is?

[Elden]

   Where is your sense of adventure, Rob? I believe Ken was trying to be fair to the T7 superiority versus T4 mentality that appears to be predominate on the forum in regard to comments he has made.

[Jan]

My question would be "why" do you care what the RPM is?

Man cannot live by bread alone, Rob.

Since time immemorial people are looking for an answer to the question "Why is it so". We are interested in finding out the truth. Perhaps it is enough in itself? The topic is not of crucial importance.

Jan

[Ken S]

I am of two minds about motor speed. The old telephone troubleshooter in me places high value on Ohm's Law and is interested in such things as motor speed. And then there is the other more Neanderthal part of me which is just glad I don't have to do the work by hand and is grateful for any motor speed.

We live in a world of adventure and practicality.

Ken

[Elden]

Jan, my old Super Grind clocked in at approximately 93 to 94 rpm (+/- 10% error margin  ) according to my count. Actually, I threw that error margin in as a pun.

[Jan]

Thank you Elden for posting the RPM of your Super Grind. 

Jan

[Herman Trivilino]

I suspect other factors besides just the frequency of the voltage affect the rotation rate. Voltage and grindstone weight are probably the big ones, and motor temperature, too. Should be easy enough to find out. All you need is the right equipment.