Drill Press - Treadmill motor conversion

[bubinga]

Rick M, was that set up on You tube also?
I think I ran across it before.

 

[Rick M]

Correct. The usable range on my motor was 2.5-12 volts. The extra resistor to set the minimum to 2.5 and only affects the low end. The max is still 12. This design keeps the motor in an operating range of about 100 to 7000 RPM.

If yours is using the MC60 and a 5k pot, then a 1300 ohm resistor will be about right. Or just use another pot to set the minimum to whatever you want. For a lathe it's unlikely that you will need the super slow speeds.

I also used a 3-turn pot to make the knob less sensitive. 3 turns from slow to fast instead of 3/4 turn.

Okay, I was wondering what effect a pot other than 5k would have. The first treadmill I got was a very old one and had a 5k pot so that's what I used on all my motors. I don't really need slower speeds on my Craftsman, current range is ~240 - ~3000. Motor for the Delta will use an MC60. Motor on the Craftsman is using some other PWM, can't remember the model (it's the red one in the link I gave).

Rick M, was that set up on You tube also?
I think I ran across it before.

I have videos on youtube, they don't show much detail on the motor but they are there. I will shortly be converting another lathe to DC and intend to document the process (such as it is) a little better. And make a better video on the strobe tachometer.

 

[bubinga]

yeah, l saw it somewhere online,
I am getting ready do do my 10" logan metal lathe spindle next.
l just did the wiper motor conversion for the lead screw drive.

 

[doan]

Okay, I was wondering what effect a pot other than 5k would have. The first treadmill I got was a very old one and had a 5k pot so that's what I used on all my motors. I don't really need slower speeds on my Craftsman, current range is ~240 - ~3000. Motor for the Delta will use an MC60. Motor on the Craftsman is using some other PWM, can't remember the model (it's the red one in the link I gave).

In the case of the MC-60, the pot is just a voltage divider. "H" is always 12v and "L" is always ground (0V). "W" is connected to the wiper of the pot. When the pot is turned, the voltage at "W" will change to some value between 0 and 12.

With a 5k pot the current will be 2.4mA. Changing that value of the pot will not change the speed range since the highest will always be 12 and the lowest will always be 0. A larger total resistance will lower the current and smalerl will raise the current. So, it doesn't have to be exactly 5k, but if you vary too much it will cause problems.

 

[Rick M]

In the case of the MC-60, the pot is just a voltage divider. "H" is always 12v and "L" is always ground (0V). "W" is connected to the wiper of the pot. When the pot is turned, the voltage at "W" will change to some value between 0 and 12.

With a 5k pot the current will be 2.4mA. Changing that value of the pot will not change the speed range since the highest will always be 12 and the lowest will always be 0. A larger total resistance will lower the current and smalerl will raise the current. So, it doesn't have to be exactly 5k, but if you vary too much it will cause problems.

Lots of discussion on the web about treadmill motors but not many who understand the electronics involved, thanks for the info.

 

[srmofo]

Re: Drill Press - Treadmill motor conversion - COMPLETE

PROJECT COMPLETE

I ended up using a old (1945) Sun Dwell/Tach meter for the control box. This was my grandfather's and I had set it aside for restoration, but it was too far gone. The Dwell meter was beyond repair. I repurposed it instead - another cool old box saved from a landfill.


Two switches went in the hole where the dwell meter was. One for AC power and one to the motor drive. The selector switch on the far right get replaced by a 5k ohm 3-turn pot for speed control.


I calibrated the tach to match the actual spindle RPM, including using the 1000/5000 RPM switch. With the current pulleys, I have a usable range from about 40 RPM to 2700 RPM. The meter is active whenever power is on, so I can see what the speed is before turning on the drive.


.

Im currently doing a drill press conversion myself. I really like what you did with the dwell meter and it got me thinking. I have a dwell from the 80s that was my fathers. Its a ugly cheap plastic actron though, but I could still use the guts and put it in my own box. Here is an identical model:
http://www.ebay.com/itm/Vintage-Act...w-Box-and-instructions-untested-/221461763571

I opened it up and although its not as primitive as yours its still an analogue device so I assume it can be converted to measure the motor speed and then calibrated to match spindle speed.

I know dwell meters are basically duty cycle meters, and since you stated yours shows the speed anytime the power is on Im assuming it was hooked to the pot. Do dwell/tachs just measure amps and then get scaled to the meter?

Can you explain how you hooked yours up and the principle behind the dwell meter/tach?

*I have never set dwell so I have no idea what they are physically measuring.

 

[bubinga]

l think dwell is the % of time the points are closed?

 

[srmofo]

l think dwell is the % of time the points are closed?

Yes but it is measured at 2 terminals on the coil. What is being measured?

 

[doan]

Re: Drill Press - Treadmill motor conversion - COMPLETE

Can you explain how you hooked yours up and the principle behind the dwell meter/tach?

Sorry, I lost track of this one......

Mine was a tach/dwell meter, but I completely gutted it and used only the meter itself. At the end of the day, all analog meters measure current, and then are converted to whatever you want to do.

To calibrate for RPM, you first need to know what the full scale current is. A normal value is 500uA.

So, if you're going to drive the meter off the 0 to 12v input of the MC60 controller, you want it to go to full scale at 12 volts.

Volts = Amps X Resistance

So,

12 = 500uA X R

R = 12/500uA = 24k Ohms

To make it easy, you could buy a ~50k pot and just adjust the pot until you get full scale on your meter when your MC60 is set to maximum speed.

The meter and 50k pot would be connected in series across the L and W terminals.

L ----- 50K pot ----- meter ----- W

You basically just made a 12v meter. If you want to calibrate the numbers on the meter scale to motor or spindle RPM, just change R until you get the desired reading.

Hope that helps. Take a picture of the guts of your dwell meter if you need more help.

 

[srmofo]

big thanks to doan for straightening me out.

Still dont know why I didnt think to just use the meter and leave the guts alone.

Im using the mc-45 which is pulling about 1mA @ 11.5v across the speed pot. Crunching some numbers I end up with about 11k ohms needed for my meter.

I started high with a series of 3 10k resistors in series and a 10k pot. I reduced the pot each time before removing a resistor and turning it back up. Once I got close to the correct value the needle started moving. I adjusted it up to the top with the speed pot all the way up and then started playing with the speed pot. total resistance across the meter is right around 10,130 ohms. Now I have full range on the meter.

I still need to calibrate the spindle speed pot but I cant do that until my optical tach shows up tomorrow.

I was going to calculate it by the pulley diameters and stated motor speed but it seems silly to do all that theoretical math when I can just take an actually reading of the spindle speed and adjust the resistance on the speed pot accordingly.

Maybe Ill post a build thread once I get a little closer to making this all happen in a few weeks. Right now I need to finish up a 25 page literature review that I have been slacking on all summer

 

[macgee]

Re: Drill Press - Treadmill motor conversion (UPDATED)

The wife was going to sell the old treadmill for $50. I said "that's less than a new drill press motor, I'll take it appart."

1.5 HP motor - 0 to 6700 RPM

MC-60 PWM controller

Test bench

The old treadmill control has 10 discrete speeds from 1 MPH to 10 MPH. This is about 550 to 5500 RPM. Although I'd like to keep the digital control, its a one piece board, and I don't need the rest of it. I'll probably just replace it all with a 10K ohm pot.

Is there any advantage to leaving the flywheel on? Mine is setup for a poly-V belt, I could just put a poly-V pulley on the drill press (Craftsman 1500

I'm resurrecting this thread to say nice job Doan, you made a thread worthwhile and readable. I have a Vintage Delta drill press giving me issues and been thinking of doing what you did to get more reliability and more rpm range.

I'm seeing more and more treadmill motors and there controllers for sale.

Again, thanks for posting this.

 

[nine4gmc]

Macgee, there is not a week that goes by that I don't see a treadmill on the curb for free. Keep an eye out when you are driving around, also check the free section on CL.

 

[Ed ke6bnl]

I picked up a free treadmill and fired it up worked perfect and sold it for $200, but I have two motors in the garage for projects, wind generator and for my wood lathe.

 

[shortykorte]

I would like to add this find. Haven't check if it works but it is cool looking.

 

[macgee]

Macgee, there is not a week that goes by that I don't see a treadmill on the curb for free. Keep an eye out when you are driving around, also check the free section on CL.

Nine's,

I totally agree, I see a lot of them as well in alleys and on CL but I'm seeing the motors for $20 which to me makes it worth alone for not having to haul it home, dismantle and then haul the carcass away.

I do see guys now on eBay selling complete setup's with motor, DC controller and
wires for projects but they are not selling so cheap.

Two switches went in the hole where the dwell meter was. One for AC power and one to the motor drive. The selector switch on the far right get replaced by a 5k ohm 3-turn pot for speed control.

I calibrated the tach to match the actual spindle RPM, including using the 1000/5000 RPM switch. With the current pulleys, I have a usable range from about 40 RPM to 2700 RPM. The meter is active whenever power is on, so I can see what the speed is before turning on the drive.

I wonder what other type of tachometer gauges could easily be used (usually need 0-3,000 rpm). Could be cool using NIXIE TUBES to display the RPM's.

 

[macgee]

If possible, I have four Questions that hopefully could be answered by the ones with knowledge & experience:

Is there an ideal treadmill motor spec for drill press's? I see wide varying specs for different treadmill motors, The RPM's are much higher than the standard 1725 rpm AC motors.

I'm also wondering how hard would it would be to get the desired RPM range of 100 rpm - 3,000 rpm and at the desired torque within the desired RPM's ?

Is this programed within the MC-60 controller board (2.5v-90v?) or does the type of treadmill motor also matter? Is there also needed a particular pulley size that differs from typical drill press motor pulley's? Or are others things needed in additional to the pulley and controller board to attain proper drill press speeds & torque, especially the slow speeds?

Greatly appreciate any knowledgable info that can be provided and sorry if these questions seem rudimentary but just trying to fill in the gaps of info I can find. I must say out of all the info I found online it's nice to find a thread with posters who actually understand both DC systems and drill press's.

 

[Rick M]

My treadmill motor runs ~250 - 3000 rpm. I believe the mc60 is adjustable although I have no need so haven't messed with it.