On Wednesday 21 October 2020 18:54:59 John Dammeyer wrote: > Hopefully the attached photo makes it through. Here's the MC60 > running the 1.5HP 100VDC brushed CW rotation treadmill duty motor. > > Measuring the pot wiper without the flywheel fan weight it starts to > turn at about 0.8V and can be slowed down to about 0.55V before it > stops. > > With the pot all the way over and 12V on the wiper it's spinning fast. > I'd guess 2500 to 3000 RPM. > > Now with the flywheel it doesn't have the torque to start until about > 1.1V is applied. At that point it can be rolled back to about 0.8V > where it turns slowly but very little torque. > > Back when I had a Sherline to play with we found similar issues with > the DC spindle motor. Having a 2:1 reduction made it possible to > thread at lower speeds and still have reasonable torque. > > Since the motor is marked CW I don't know how well the brushes or > commutator would stand up to CCW rotation. It could also be rated > that way because the flywheel/fan is screwed on with a left hand > thread. So turning in the other direction could cause the flywheel to > escape. Kind of like the face plate or chuck on my South bend if run > in reverse.
I drilled lengthwise between the fan and shaft an inserted some set screws. Held for about a year before it crushed the screws and screwed the shaft up. I did essentially the same with a slightly different motor, and added a limit3 so slow the speed ramping, and I've had no similar problems in several years now. Jon's pwm-servo amp needs to be gentled just to save drive parts on TLM. I'd estimate top motor speeds are around 8 grand. 3/1 belt geardown between the motor and the countershaft thats driving the timing belt pulley that drives the 2 speed spindle. With ball screws, a 5" chuck, no compound and tapered gibs, a good qctp, its a wholly useable machine now. Its about 25 yo now. My first machine long before I discovered linuxcnc. > Back when I removed the flywheel the first time I had to use pliers to > grab onto the back end of the shaft as it's a bit marked up. I think > If I wanted to put an encoder on this motor I'd have to pull the > armature and turn that stub down to something that would fit into the > extra US Digital encoders I now have lying around. Wouldn't take much > to then use one of my spare HP_UHU drives, GECKOs or STMBLs to test > how well this motor really works in closed loop. It's been sitting > around for probably 15 years now. Eventually I'll get around to it. > > So kudos to the MC60 controller. It does the job as an open loop > controller. But at low speeds it's lacking in torque. I think there > might be some back emf sensing because at low speeds grabbing onto the > shaft creates a louder hum from the motor. Not sure if that's because > it's trying to make it stay at the set speed or if slowing it down > causes the windings to draw current for a longer time as each tab on > the commutator is under the brush for a longer time. > > John Dammeyer > > > -----Original Message----- > > From: Gregg Eshelman via Emc-users > > [mailto:emc-users@lists.sourceforge.net] Sent: October-18-20 9:40 PM > > To: Enhanced Machine Controller (EMC) > > Cc: Gregg Eshelman > > Subject: Re: [Emc-users] driver for a DC motor for a BS-1. > > > > What many people use for those high voltage DC treadmill motors is a > > MC2100 controller. Those are used in the fancier treadmills that > > have buttons to tick the speed up and down.There are many schematics > > and other info on how to build a potentiometer controlled PWM > > circuit for these or an interface to CNC for speed control. > > > > Cheaper ones with a rotary knob or a slide control most often have > > an MC60 controller. These may or may not work as a spindle driver, > > depending on how the circuitry is setup. Control is as simple as > > properly connecting a potentiometer. One I tried was setup to not > > start the motor until the knob was up to 50%, where it'd slam on at > > 50% speed. Then if it was slowed down too quickly it'd shut down > > until it was power cycled. I sold it for a decent price, presumably > > to someone needing it for a treadmill, because in the listing I > > detailed all the reasons it *was not* useful for a machine spindle > > control. > > > > The MC60 is an SCR controller and it makes the motor quite noisy and > > torque suffers at lower RPM. > > > > On Sunday, October 18, 2020, 12:42:32 PM MDT, John Dammeyer > > <john.damme...@shaw.ca> wrote: > > > > Way back in 2003 I started a project to control the surplus tread > > mill motors I had acquired.� At that time I was still just casting > > parts for making my Gingery Lathe and thought about making my own DC > > Servo motor controller. > > > > http://www.autoartisans.com/MotorDrives/MOTOR1-5.JPG > > > > The first prototype had a bunch of problems and then regular paying > > work took over, I needed the bench space and never revived the > > project.� > > http://www.autoartisans.com/MotorDrives/REVA0059.JPG > > > > The controller was the MC33030 > > > > http://www.autoartisans.com/MotorDrives/MC33030-D.pdf > > > > Knowing what I know now I'd never use this device but back then... > > > > John > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
