Variable speed

[tool fan]

Of course. I knew that, just forgot.


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[DougLA]

The DPDT switch was installed in KB controller on the DC side of current where the KB for/brake/rev switch would go.

[tool fan]

I've had a couple, and I can't understand why, that actually increase the power under a load. So, when I try to slow it down it actually tries to speed up. When I first started using DC 51 control boxes, the motors would respond like that. In fact I had one on a drill press that would blow a 15 amp circuit breaker before it would actually stop working. Those were the good DC 51 control boxes. The new ones do not behave like that at all and the motors can be stalled quite easily.

I've never tried using a DPDT switch with 220 so can't comment. I have had no issues using 110, acknowledging that the motor needs to stop before changing direction.

[DougLA]

I did install a DPDT switch from Princess auto when was testing controller before installation. They did have a $7.00 one but purchased a the $24.00 model as it had a higher current rating. It worked but similarly to your experience not good if didn't wait until came to a full stop. At some point the switch shorted out and was just on all the time. Removed it before really messed up. The KBMD switch has a resistor that helps slow down faster but from what I understand still need to wait.

I did have a P.Auto reversing switch on my Leeson AC 3/4 HP (with a centrifugal switch) simply wouldn't change direction if didn't wait to slow way down. Perhaps safer situation. So not sure how smart it is to have a reversing switch on a DC motor???

Well, before installing I tried stalling motor by grabbing pulley on spinning shaft with heavy gloves. Was able to stop until spun motor shaft up to around 750 and beyond that couldn't hold back. Thus set minimum speed of controller to 750 and with jackshaft low gear that gives a lathe spindle speed of ~200 rpms.

Also KD controller current limit trimpot can be adjusted upward to a point so more current (torque) supplied when under load. Also has something called an IR compensation trimpot so that compensating voltage is supplied to keep motor speed constant at potentiometer setting. Playing around with these helped. Again I know next to nothing re electronics and this is simply regurgitated from KBMD -240D manual.

[tool fan]

I do not have any experience with a KBMD brake/reverse switches. On the lathes that I have converted I have used a simple DPDT $7.00 switch. I've tried flipping it into reverse while running in forward at low speeds and concluded from the sound that it was not a good idea.

A couple of years ago I picked up a used KB electronics control box and was very impressed with it. Not only is all of the wiring contained making it plug and play, the low speed torque was terrific. I ended up selling that lathe but if I remember correctly it had a built in F/R switch, but I could be wrong. Since then I have been looking for a deal on another one, but have had no luck. On ebay they are around $150 US plus shipping. The free MC 60's from old treadmills are almost as good, but require more work.

I notice that you have a jackshaft too. Did you test the low speed torque without the jackshaft?

[DougLA]

Thanks it certainly weighs and sounds beastly. Motor/controller requires 220 wiring and I already had a 30 amp outlet at lathe for a 4000 watt heater - so that part was easy.

I was eyeing those KBMD controllers and at same time that motor became available recently I found this one - so jumped on both. I've also ordered a KBMD forward/brake/reverse switch with a brake resistor through Amazon - will cost as much as controller but gotta have it! I've seen where others have built one from scratch and I have a schematic but I'm afraid I'd kill the controller, motor or myself if attempted! Personally no experience with electronics other than Heathkit stereos I built 50 years ago! Still, will need to be careful to stop before reversing direction so don't blow brushes or armature. Any thoughts?

[tool fan]

You won't have any trouble with torque with that arrangement and the KB electronics controllers are the best. Getting one for $75 is a steal! The motor must have come from an industrial treadmill from a 400 lb and over fitness club , its definitely a beast!

[DougLA]

My recent version of a retro fitted treadmill motor on my Craftmaster. A bit more expensive - 40 pounder DC motor for $50 on Kijiji and really nice KB Electronics DC control from Montreal for $75.00 on eBay. So far works great with test trials - roughing out 12" bowl blank and using a 3" Forstner bit.
https://www.flickr.com/photos/767624...7711215500638/

[tool fan]

Nice work Al!


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[al.m..]

Here are a few pictures of the lathe with the electronics installed in the plastic box.as you can see,there is a extra switch,it's a double pole double throw that allows switching the polarity on the dc side,giving the lathe reverse.i am very pleased with the outcome.there may be a tachometer in its future.

[tool fan]

Where were you guys when I was running a 3400 and later on a Delta!!!!! Excellent conversion and using a DC motor will give better torque characteristics. It's only been in recent years the AC/VFD units have come down in price and now have improved torque. So is it too much to ask you guys to do a blow by blow account and post it in the Tutorials section?
I know there's a lot of new turners who would love to get some good solid old iron and give it a new lease of life at a fraction of the cost of a Onway or Powermatic

Pete

I can do this but it will not be for a few weeks as I am in Hawaii right now . If someone else wants to tackle Pete's suggestion be my guest.

[Roundhead]

Where were you guys when I was running a 3400 and later on a Delta!!!!! Excellent conversion and using a DC motor will give better torque characteristics. It's only been in recent years the AC/VFD units have come down in price and now have improved torque. So is it too much to ask you guys to do a blow by blow account and post it in the Tutorials section?
I know there's a lot of new turners who would love to get some good solid old iron and give it a new lease of life at a fraction of the cost of a Onway or Powermatic

Pete

[tool fan]

Sounds like you got it right. However, your pictures are not showing.

Hi Al, I would be interested in the proper enclosure that you are buying. I usually just build a box to contain the wiring and mount the circuit board as you have under the lathe. Here's a couple of examples.

[Leo Van Der Loo]

Well done Al, happy turning

[al.m..]

A second try at the pictures