Clausing 8520 DC motor w/ MC-60 controller

[gajunkie]

So far, so good. Still in the 'discovery phase" however. Did some light machining on aluminum, so far, and also a cut through some brass with the slitting saw...was slow going on that because I'm getting a bit of belt slippage on the motor pulley. It might be a hair on the small side for the segmented belt. Also the ratio I settled on for now favors the high end range...goes up to 4000 RPM on the spindle speed. I could swap the belts and move the motor up a bit, but I'll see how it goes. Still not settled on utilizing the intermediate pulley, and may go direct eventually.

I did discover during all this that my spindle was getting a bit warm after running for a bit. Not hot, but warm enough to figure my bearings might need replacing. I'll post that stuff on my other thread, though.

Tach is working good after glueing the magnet to the bottom of the spindle pulley...should it hold indefinately, that'll be its final resting place, though my hopes aren't that high.

Mounting the motor was fairly simple with a couple angle iron pieces, using the original motor mounting brackets. It'll go up about another inch if I need to, but woul've been more difficult to get it up high enough to utilize the original A/B range pulley options, so I'm trying this for now. Also, I'm reluctant to modify the original clausing motor pulley to fit the new motor...just in cas I ever go back to an AC motor. The choke (?) that came with the motor setup was mounted there after realizing it wouldn't fit in the control box, and was better than hanging it from a zip-tie like I had at first

Time will tell...

 

[Zertsman]

It'll be interesting to see how it runs without the fins on the flywheel cooling the motor.

Mine is running great. I haven't used any other pulley combinations, so i'm topping out around 2300 RPM I think. At this lower range, digging into aluminum with a 1/2" endmill hasn't been an issue. Still haven't added the choke although I probably will.

I put new bearing in mine and may have over lubed them. Spindle is warm, but nothing I can't hold indefinitely by hand. Motor stays cool as well. I did not wire in the temperature circuit as you did.

They are really nice machines.

 

[RJSakowski]

Mill spindles will run warm to the touch. Spindle bearings are usually set with a preload to reduce free play and there is friction and heating as a result. Depending on the spindle design, it is often recommended that bearing preload be adjusted when the spindle is warm. This is due to thermal expansion causing the spindle to grow and change the bearing preload. As a result, the bearings will be looser than optimum when cold. Some spindle configurations address this by using Belleville washers to take up the change in length. Other designs use opposed angular contact or tapered roller bearings on one end of the spindle and a floating bearing on the opposite end to minimize thermal expansion.

A properly adjusted spindle will be warm but not too hot to comfortably touch after ten or so minutes of operation. Note that spindle growth will increase with increased load and higher rpm.

 

[Zertsman]

Thanks for the info. I put in the correct Angular Contact bearings. There are some here that say too much grease can cause them to run too hot, so I've been watching.

 

[mattthemuppet2]

View attachment 396854

Purchased from @mattthemuppet2 's ebay store...

-Bear

So far, so good. Still in the 'discovery phase" however. Did some light machining on aluminum, so far, and also a cut through some brass with the slitting saw...was slow going on that because I'm getting a bit of belt slippage on the motor pulley. It might be a hair on the small side for the segmented belt. Also the ratio I settled on for now favors the high end range...goes up to 4000 RPM on the spindle speed. I could swap the belts and move the motor up a bit, but I'll see how it goes. Still not settled on utilizing the intermediate pulley, and may go direct eventually.

I did discover during all this that my spindle was getting a bit warm after running for a bit. Not hot, but warm enough to figure my bearings might need replacing. I'll post that stuff on my other thread, though.

Tach is working good after glueing the magnet to the bottom of the spindle pulley...should it hold indefinately, that'll be its final resting place, though my hopes aren't that high.

Mounting the motor was fairly simple with a couple angle iron pieces, using the original motor mounting brackets. It'll go up about another inch if I need to, but woul've been more difficult to get it up high enough to utilize the original A/B range pulley options, so I'm trying this for now. Also, I'm reluctant to modify the original clausing motor pulley to fit the new motor...just in cas I ever go back to an AC motor. The choke (?) that came with the motor setup was mounted there after realizing it wouldn't fit in the control box, and was better than hanging it from a zip-tie like I had at first

Time will tell...


View attachment 397664

looks fabulous, nice work! I'm sure you've already discovered it, but you'll really enjoy having variable speed on your mill. Couldn't imagine mine without it The belt slip is unfortunately one of the downsides of having to use such a small pulley on the motor - you don't get much belt wrap and low motor speed/ high torque use will see it slip. Only solution with your set up is to put a larger pulley on the motor and change position/ belts to get you back to your desired speed range. I have this issue on my drill press, but there isn't much I can do about it due to the way it's set up. On my mill reusing the old motor pulley gives me plenty of wrap (the controller will overcurrent before the belt slips) and on my lathe I remade the motor and countershaft pulley to give me both a larger motor pulley and a larger step down ratio, so the motor spins faster for a given spindle speed.

Variable speed is pretty darn awesome though. Did some work on a piece of 5/8" stainless on the lathe yesterday - turning and chamfering with carbide at ~700rpm, then parting off with HSS at ~150rpm, all with a twist of the dial

 

[RJSakowski]

Variable speed with a single-phase AC motor isn't practical. But a variable frequency controller and a 3-phase motor will be much stifferthan the variable speed DC motor.

My Tormach mill has a 1 hp 3 phase motor with a VFD and it struggles with cutting a 1/4 countersink at 10% of the motor's rated rpm. On the other hand, I have a 2.5 hp d.c. motor running with a custom PWM controller which generates useful torque at 1% of the motor's rated speed. I use a home brewed encoder to provide feedback re. motor speed and the circuitry will increase pulse width when sensing a slowdown due to increased load. The encoder consists of a satellite of forty magnets embedded in the motor pulley and a Hall effect sensor. At very low speeds, the motor tends to cog as there is about .2 sec. between encoder updates. This limits the low end speed but even then, there is useful torque.

I am currently working on a dynomometer to plot rpm vs. torque curves so I can quantify the observations and optimize the controller but even wth preliminary settings, I have a 135:1 speed range (considering a 35% overspeed capability).