On Thu, Sep 16, 2021 at 08:39 PM, OldToolmaker wrote:
I contacted KB tech support and was told to turn the potentiometer all the way CCW before turning the motor on as it could be damaged if set too high.
I am assuming I can turn it up as required once it is on. Am I correct in assuming this may be a bit of a risk to the motor as it would be easy to slip up and ruin the motor?
I would start with both MAX & MIN speeds set to zero, or as low as they go. Try varying the motor speed - if it moves at all it should be from standstill to a low speed. I would then turn the MAX speed up gently, until the revs are in the right sort of range, then pause for thought. How can you check the MAX is right for the motor? The output to it will almost certainly be pulsed, so you would either need an oscilloscope or a true RMS voltmeter to check, and I would guess you don=t have either. There are low cost pocket scope/meters out there which do both, but I'm not sure how good they are or how easy to use. The other way would be to check the motor revs, and see if it is anywhere near the rated maximum speed on no load. Rev counters can be electronic, optical, but the old mechanical types may be possible if you have any small gearboxes handy. Using a gearbox with, say, 100:1 reduction, you apply the input to the motor shaft with a bit of rubber as the coupling - just press it on - and then cunt the output rotations while timing it with a stopwatch, or just a clock with a second hand. An assistant to give Start & Stop commands would be useful.
This is a truly antique version:? . I have seen similar ones offered at tool sales, and there is nothing wrong with them in spite of being old tech. Apart from anything else the batteries don't run out!
The pointed is pressed into a recess in the end of the shaft - I assume from a centre drill - and taken out after standard time - I'm guessing ten seconds - and the number indicates the RPM, probably sufficiently accurately for your purposes. So what have you got kicking about the workshop that could be used? I have some small 100:1 worm boxes, but I think the postage to you would be a bit too much.
The remaining worry is that the maximum voltage applied to the motor - the peak voltage of the pulses, not the average voltage - may be too high for the motor insulation, or for the commutator. I tested a brushed motor one day by plugging it into the mains, 230 V here, and it went round very fast with a ring of arcing around the commutator. It was a 110 V motor. Actually it could have been just what you need, but we binned it years ago, and see the note about postage, above.
