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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.

Don,
I have the manual. I understand what you are saying and I will look at that as soon as I have the motor in hand. Everything you said makes perfect sense and I am sure I can adjust the trim pots. I will keep in touch.?

Dick
--
http://www.homemadetools.net/forum/?OFF-SET-tailstock-center-65965#post105972
?SMALL TURRET TOOL POST PLANS?
?LARGE TURRET TOOL POST PLANS
?MINI-LATHE CARRIAGE LOCK PLANS
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?QUICK CHANGE LATHE TURRET
?MINI LATHE COMPOUND PIVOT MODIFICATION

Dick:

Short answer - YUP.? You definitely want to keep that knob turned down at first.? Turning it up too high will let the magic some out of the motor.

Here's a possibility, that drive has trim pot adjustments for the MAX and MIN speeds.? I'm not sure how MUCH adjustment is allowed but it never hurts to try it.? Did you get the User/Installation manual with the drive?? If not it's available on-line - just Google kb drives manual.? It's a 16 page PDF and it's pretty self-explanatory.? The factory defaults supposedly have the MAX trim pot set to rated speed and the MIN speed set to 0 - they both should be turned all the way, one way or 'tuther.? This will let you set the upper and lower limits for the motor speed.? I'd check what the MAX trim pot is currently set to, and then with the motor running try turning that guy the other direction and see what it does.? You should get an immediate response out of hte motor.? You MIGHT have to cycle power to the drive, but I doubt it since you're adjusting an actual device.? Who knows, it might actually let you limit your max speed to what you want.? That way you still have the full Min to Max range of adjustment available on the speed pot.? And, you are taking advantage of some the drive's capabilities.

Don

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??
Dick
--
http://www.homemadetools.net/forum/?OFF-SET-tailstock-center-65965#post105972
?SMALL TURRET TOOL POST PLANS?
?LARGE TURRET TOOL POST PLANS
?MINI-LATHE CARRIAGE LOCK PLANS
?SMALL QC TOOL POST PLANS?
?QUICK CHANGE LATHE TURRET
?MINI LATHE COMPOUND PIVOT MODIFICATION

Dick:

If there's a nameplate on the motor it will usually list the FLA (full load? amps) of the motor - HP or KW might also be listed on the nameplate.? From the FLA and the motor voltage you can get a ROUGH idea of the motor wattage.? Failing that, see if there is a manufacturer's name and/or model number stamped on the motor someplace.? I've used those to dig up the manufacturer's motor data before.? If the seller is unwilling to do that for you, I'd move on to another seller/motor.

You'd be surprised how much info you can find if you ask Google the right questions.

Don

Thanks, Clark!
I have one more question to ask. How does one determine the wattage of a dc motor if the seller doesn’t know or is unwilling to find out. I want to find a 24 volt permanent magnet dc motor about 150 watt.
Dick
--
http://www.homemadetools.net/forum/?OFF-SET-tailstock-center-65965#post105972
?SMALL TURRET TOOL POST PLANS?
?LARGE TURRET TOOL POST PLANS
?MINI-LATHE CARRIAGE LOCK PLANS
?SMALL QC TOOL POST PLANS?
?QUICK CHANGE LATHE TURRET
?MINI LATHE COMPOUND PIVOT MODIFICATION

I think a footpedal speed controller can be added in a similar way to that resistor but to different legs of the regular speed knob. I’d looked at different footpedals that I thought might be adapted, I can’t remember if I found a good one that would work that way that was also cheap. For the Consew branded brushless motor I mentioned earlier I replaced the insides of a sewing machine pedal with a circuit supplied with the Consew controller.

I have one of these, noisy and not that powerful. I have been using a XD3420 12v DC 3000 rpm on my Unimat SL. It fits in no mods. Not as powerful as the scooter motors.

On Thu, Sep 16, 2021 at 09:26 AM, luifri@... wrote:

. Ebay

> 363151138130 is offering

ebay - not found..

Works for me from UK. Searching for "775/795/895 dc 12v" brings up some suppliers of all three motors.

Zitat von "Keith? S. Angus" <keithsangus@...>:

> It looks like a range of small high power, probably high revving (no
> real figures given), motors are emerging from China. Ebay

It looks like a range of small high power, probably high revving (no real figures given), motors are emerging from China. Ebay 363151138130 is offering three variants, although I'm not sure what the real difference is. I've ordered one for my Basic/PC. It should fit in the available space, and I have a cheap speed controller on the shelf that should be OK for it. They talk about a starting current of 15 amps, and needing a 360 watt power supply. Well, we'll see. I will look again at a soft-start circuit, so it ramps up to speed in about half a second, and see what can be done about resistive braking, but not all at once. I'd like the actual speed control to be mechanically chunky, regardless of the electronics, and maybe introduce some non-linearity so control is more sensitive at low speeds. The aim would be to do it right first time and be glad I did for a long time to come. I will report back once it arrives.

Dick:

If you're talking about the horsepower resistor, that tells the KB drive what the current limit to the motor should be set to.? It also tells the drive how to respond to a varying load, at least it gives the drive a rough setting.? There are pots on the board that allow fine tuning of the drive if it's not performing to your satisfaction.? Fuse the drive appropriately and it should last you a lifetime.

Be sure to REALLY thank whoever gave you that drive, your set-up would cost you a couple hundred bucks to purchase new off the shelf.

Don

Clark,
Now I get it-it is the resistor that limits the voltage available to the motor. So even though my KB motor control is 90 volts the resistor used sets the upper limit. I am learning a lot on this forum about electronics. Thank you very much! My eyes and brain are beginning grasp this.
Dick
--
http://www.homemadetools.net/forum/?OFF-SET-tailstock-center-65965#post105972
?SMALL TURRET TOOL POST PLANS?
?LARGE TURRET TOOL POST PLANS
?MINI-LATHE CARRIAGE LOCK PLANS
?SMALL QC TOOL POST PLANS?
?QUICK CHANGE LATHE TURRET
?MINI LATHE COMPOUND PIVOT MODIFICATION

You need the horspower resistor, I believe that tells the drive how to set-up some of its' electronic limits.

On Sat, Sep 11, 2021 at 06:10 PM, OldToolmaker wrote:

It's been a while since I did a project using a KB drive, but I remember that some units could be run on either 120V or 240V.? When operated on 120V you got a 0-90V output, and on 240V you got a 0-180V output.? You need to be sure your motor matches that voltage rating.? A regular 12VDC or 24VDC motor won't work that well, you'd have to limit yourself to the bottom 10%-20% of the drive output.? (Anything over that and the magic smoke would be let out of hte motor.)? That being said, if you've got the right motor to go with the drive then you've got yourself a nifty little set-up that'll run reliably for years.? I've taken out 20-30 year old industrial equipment that had KB drives in them and the drives were still running strong.? The mechanicals were completely worn out, but the drives were still good.

Don?