PDA

View Full Version : Low speed mod for HF lathes, motor question



johnm
07-08-2007, 02:53 PM
Folks -

Okay, we're getting ready to extend the bed on our lathe so we can do full 8' turnings. We are not yet equipped with a stepper setup, but I do need to find a way to reduce speed on the VS lathe to less than the current minimum speed of 600 RPM. We are turning 4 large kitchen island legs out of solid cherry - more than 6" dia, and a poplar turning that is almost 8" - also solid stock... No room for error and don't need to spin the stock fast at all to do the milling. Any advice on rotation speed or turning advice would be welcome as well.

I was thinking about hooking up a large VS drill motor directly to the back side of the arbor spindle. This would be fairly easy, as the arbor shaft is hollow for the knock out rod, and is already tapped for 1/2" N/C thread. I was going to simply screw in a length of bolt rod with a lock nut and attach the drill motor to this.

Would I run into any trouble having the existing drive motor being "driven" by new setup? I could disconnect the belt, but it's kind of a PITA.

I'll post some pics in a bit, but wanted to get some feedback. Our setup is nearly identical to Wayne Locke's down in Texas.

Thanks,

John

harryball
07-08-2007, 04:22 PM
If you use a belt driven lathe head you should be able to replace a pully to get to the desired PRM's. Now... I'm sure someone could come up with some math that would let you calculate the RPMs if you decrease the motor pully size.

Robert

johnm
07-08-2007, 04:28 PM
Robert -

Yes, but I would rather leave the existing setup in place as I do like having the higher speed option for sanding and finish work. Also, I don't have a great deal of room for replacing the pulleys and couldn't get a larger one on the lathe spindle anyway - there isn't any room. At best I'd end up using a jackshaft setup, and eventually do want to put a stepper on the lathe, so... I'm posting pictures of all this shortly.

John

johnm
07-08-2007, 04:35 PM
Folks -

Okay, I've taken some snaps - with the drill motor attached, I took a tach reading and now would have a max RPM of about 300 with this setup. My low speed would be between 50 to 100 RPM. This feels like a much safer turning speed, even if the motor setup, for now, is a bit of a kluge. With the shaft coming out the back of the motor I can mount a much larger pulley outboard to get my low speeds.

Again, tho' what about damage to the motor or other things on the motor circuit due to the motor being driven by the low speed motor?

Here you go!

John

178
179
180
181

ed_lang
07-08-2007, 04:43 PM
My lathe, a Oneway 2436 has a 3 phase motor and a VFD much like my 4HP HSD spindle on the CNC. I would look around for a motor and VFD. This way you can vary the speed and have the best of both worlds.

I would love to see more pictures of your lathe mounted when you get time.

I have several projects in mind that the indexer or a lathe mounted to the machine would be nice to have.

harryball
07-08-2007, 08:23 PM
Well... like you said, disco the belt. The motor, when driven will become a generator so you would want it disconnected from power at a minimum. I'm not sure of any potential damage to the motor from driving it unless it damages cold bearings or the capacitor inside etc... I know several people that converted motors to generators.

Could you replace the motor with one that turns slower? It would drop your entire range down so you'd loose some off your top end.

Another possibility might be a Variac. It varies the AC power to the motor and would cause it to turn slower. Again, someone more knowledgable than myself would have to tell you if it would damage your motor. I know a guy that made a grinder with a motor and a variac, to my knowledge it is still running.

Robert