Cooling down a mini-mill motor

[jcrous]

 I have a mini-mill with the classic motor (smooth, un-ribbed sides).

When I mill a big cut it eventually get hot. I have to stop perodically to let the motor cool down. Same with my lathe.

I have been thinking to add a fast running (computer type) fan on top to force suck air through the motor at high speed. This may assist the motor to take more time before I have to take a break.

The ordinary 100mm (4 inch) fan is too big as the fans blades are extruding to past the holes in the top and the dead, solid area of the fan blocking the motor's holes. A 75/80mm (3 inch) will have a smaller inner area, causing the blades to be exactly over the breathing holes of the motor.

I have read an article on Andyf's Warco WM180 lathe page about adding a computer fan to the motor to cool it down and this inspired me in this direction of thinking.

Any ideas or references?

[Lew_Merrick_PE]

Johan,

Back in the dark ages (when I was still house training my dinosaur) I had a similar problem with a small but powerful motor that ran one of my grinding set-ups.  My solution was to wrap the motor with small diameter copper tubing that I soldered to the case and pump water through it with an aquarium pump.  It added about 1/2 inch (12 mm) to the motor's diameter and did not provide a chip ingress that blowing air sometimes allows.  My sump was a scavenged 5 gallon paint bucket (they were metal in those days).  ???

[Stilldrillin]

Johan.

I can thoroughly recommend a cooling fan, on mini machine motors!

Here's my lathe mod....   http://madmodder.net/index.php/topic,7560.msg81126.html#msg81126

Heavy, low revolution work, now leaves the motor aired, only.......   

David D

[jcrous]

Stilldrillin,

I have no idea at what power I am running the current job (I don't want to remove the job item I am working on before I am not done).

I am cautious (naturally). The motor is not getting as hot that I cannot touch it. It is still low enough that I can touch it without burning or without pulling away your hand when you touch it by accident. I guess still lower as bathing or shower water temperature.

I must also mention that the ambient temperature here in the summer is between 28 and 36 degrees of C (82 - 97 degrees of F). My swimming pool pump is equiped with cooling fins and it get very hot. Too hot to touch.

I just don't want to burn the motor of the mill. I have no previous experience with induction motors. At the low speeds I could not find the direction of air flow. I am now thinking of adding a plastic agricultural water pipe reducer over the motor that I can attach to the motor with a hose clamp. On the other side it is a little bigger, where I would like to add a small extracter fan that can deliver 90 cfm air. I think this should delay the getting hot some time. I can even keep the fan running when the mill motor is swithed off. I guess it will assist a bit. This setup will be approximately the same as yours. I guess you fitted a 100mm / 4inch fan. Is is delivering enough air/ Is it delaying the getting warm of the motor or preventing the getting too hot completely?

But again, I may be over cautious, but I have no experience of these type of motors.

[jcrous]

I have also found this article that gives an idea on how to make a shrowd from a soda bottle:
http://bbs.homeshopmachinist.net/threads/47611-Cooling-off-a-hot-treadmill-motor?highlight=PETG

I have now some ideas that I can adapt around available materials.

[Stilldrillin]

Johan.

The most important temperature, is that of the rotor. Not the temperature of the outside, where you can touch.

I blew my first lathe motor, on a heavy boring job. But the case was only warm during machining....... 

The 70mm square fan, runs all the time the machine is live.
For some time after machining is finished, there is a gentle, slightly warm stream of air around the chip tray.

David D

[jcrous]

I have done the mod because I was itching. The result can be seen here:
http://www.model-engineer.co.uk/forums/postings.asp?th=78440&p=2#1349152
It is working like a dream.

[ParCan]

Having just killed a Mill Motor, I plan to add a fan to my AMA16.
http://madmodder.net/index.php/topic,7982.0.html

The motor when it went was to hot to touch. It also took the board with it.
I have several from old PC's, it's just a pain that there is not a 12 Volt supply available on any of the electronics.

I'll document what I do when I do it in that thread. I have to say I like the Coke Bottle idea. Very Tidy.

[Stilldrillin]

I have done the mod because I was itching. The result can be seen here:
http://www.model-engineer.co.uk/forums/postings.asp?th=78440&p=2#1349152
It is working like a dream.

Very nicely/ tidily done, Johan! 

The motor's fan is (should be), at the drive end.
Run the motor at high revs, and check with smoke which way the air is blowing. Then mount your fan to assist it in the correct direction.......

David D

[Stilldrillin]

Looking forward to seeing your version, Alex! 

David D

[andyf]

  A very nice improvised solution, Johan, and 76 m³ per hour should keep that motor nice and cool. Yours is far better looking than the tin can contraption on my lathe and David D's syrup tin, as I'm sure he will agree. Still, David, we have no reason to be ashamed unless someone looks round the back.

Andy.

[Stilldrillin]

A very nice improvised solution, Johan, and 76 m³ per hour should keep that motor nice and cool. Yours is far better looking than the tin can contraption on my lathe and David D's syrup tin, as I'm sure he will agree. Still, David, we have no reason to be ashamed unless someone looks round the back.

Andy.

Andy.
I hope no one looks too closely at what I do...... Apart from several hundred Modders! 

Incidentally. I can't believe what a difference this mod has made! Out of all proportion to what I expected. 

Thanks for the original idea...... 

David D

[picclock]

That's a very good looking mod. I did my WM14 with a plastic pipe adapter from wickes and a mains fan motor from Maplin. Direction of airflow on these is normally from the front with a small fan on the shaft just before the armature - so the fan on top should be sucking to assist the fan and the natural flow convection - although I'm not sure it matters much as the armature fans are pretty ineffective.

I fitted mine after an extended run at 'high' speed when the motor got hot. The motor was fine but after I had stopped it to cool down and have a cuppa it wouldn't run. Investigation showed that the heat from the armature had traveled down the shaft and melted the teeth of a plastic gear where it was in contact with the metal pinion. Just the section of the gear in contact with the pinion was melted - I suspect that if I had kept it running at no load and reduced speed I would have got away with it.

Best Regards

picclock

[rdhem2]

Very fine fix on your mill motor.  Very creative.
However since this seems to be an on going problem with your lathe also may I suggest a couple checks.  Your being from S. Africa I do not know your hertz of your supplied power.  A 50Hz motor running on 60Hz gets hot.  Place an amprobe on the motor leads and see if the load is just too great for the motor supplied.  Suppliers are known to install minimal gear on a product just to save money.  Also check the insulation rating on the motor.  This will be given in form of a code letter.  Google up NEMA motor manufacturers and see what the temperature rating is.  Some ratings go 100C to 115C and we both know you do not want to touch that but the motor is fine.  Exceding these temperatures leads to insulation breakdown which leads to motor failure.  Check your incoming line voltage at the motor when running.  Low volts equal high amperage equals heat.  Power companies here in the states say 3% variation is ideal and 10% is acceptable.  National Code for electricians says 3% to 5% maximum.  The first is for supplied power and the second is for power in building wiring.  I could go deeper but only more confusing to the untrained.
Good chatting.  Hope this helps.