[Advil]

I know I've seen videos and pics of putting a PC fan on the top of the motor on 1100s and removing the crappy plastic air mover inside which improves balance, temps and reduces the load on the motor.

So, what about the 770? Looks like the same type of "fan" in the 1hp motor. Taking some measurements it looks like a quick fabbed bracket would hold two 140mm fans above the top of the unit quite nicely.

Is it adequate to have a couple of 120cfm fans just blowing down on everything in the enclosure? Or am I going to need to focus a specific blast of air down into the motor housing?

Looking for guidance and results from anyone who has already done this.

[CountrySmith]

The 770 fan expels air through the top of the cabinet. I replaced the OEM fan when it failed with a higher flow (50 CFM) fan with ball bearings instead of the bushings in the OEM fan. The replacement fan is an Orion OA938AP-11-1 from Mouser Electronics. After more than three years, I have never had a problem with overheating although my shop is between 64 and 72ºF year around. I believe that the OEM fan was around 35 CFM. At 50 CFM, I am replacing the cabinet air every two seconds.

I doubt that you would see much additional benefit from 240 CFM. If you do go that route, you would most likely want to increase the vent size in the bottom of the cabinet.

RJ

[kstrauss]

I'm confused. There is a muffin fan in the control cabinet but the motor on my 770 appears to have an integral fan. Which fan did you replace?

[Advil]

Yeah I think CountrySmith thought I was talking about the control cabinet. I mean the motor fan. Here's a Youtube video showing someone who replaced the fan on the 1100. I'm looking at doing something similar to the 770. Go to 8:33 to see the fan mod.
https://youtu.be/4YOtbSDSXNA?t=514

[CountrySmith]

I'm confused. There is a muffin fan in the control cabinet but the motor on my 770 appears to have an integral fan. Which fan did you replace?

I hadn't even thought about the spindle motor fan. I replaced the cabinet fan. It had failed fairly soon after I bought the 770. I have not had a problem with the spindle motor overheating although I have not pushed the motor to its limits.

I took a look at the setup for the spindle motor ventilation on the 770 and can see the possibility of overheating at low speed and high torque requirements. The integral fan pushes air through the fan shroud and past the cooling fins on the motor. I would be concerned that an external fan might alter the air flow. The 770 spindle housing has an open top and a relatively small opening in the bottom. If the top opening is completely covered by fans, all air would have to exit through the bottom opening. I would think that a a better strategy would be to place a single fan above the motor with a baffle in front of the motor forcing air past the cooling fins.

I watched the video that Advil posted and have one comment on the integral fan. It is a centrifugal fan and actually can move quite a bit of air. The air enters more or less at the center and the vanes trow it to the outside where it is pushed through the shroud and past the cooling fins. That type of fan was found on hand cranked blowers on rivet forges

RJ

[popspipes]

Yeah I think CountrySmith thought I was talking about the control cabinet. I mean the motor fan. Here's a Youtube video showing someone who replaced the fan on the 1100. I'm looking at doing something similar to the 770. Go to 8:33 to see the fan mod.
https://youtu.be/4YOtbSDSXNA?t=514

I guess they took your link out of the post, I cant find it anyway......

I had the same problem with my fan on my 1100 back in 2012, I drilled the bolt side of it to get it to static balance, there is a thread on the whole process "I love my Tormach but".
I had severe vibration problems with mine at 5K rpm is the reason I wanted it balanced.

We put secondary fan kits on some of the inverter drives we installed on Glenn mixers, we doubled the HP to 15 and added the fan kit as they ran mostly in the low rpm range and the motor fan didnt cool it properly, no over temp problems after that.

[tmarks11]

If you look at some expensive variable speed mills, like the Sharp TMV50DVS, the motor is built with 2 80mm muffin fans in the fan cowling like Advil is talking about, to avoid overheating at low commanded speeds.

Leeson or Baldor sells cowlings with a separate electric fan mounted in them.... but that cowling is as expensive as the motor itself, so probably not the way to go.

Somebody here on cnczone 3dprinted a new cowling for their 3 phase motor that had the correct mounting for a 140mm 120V muffin fan on. Looked very professional. Good excuse to buy a 3d printer...

To the OP, I recommend you purchase a good 120V fan, something like a Comair Rotran Major 170mm fan that puts out 235 cfm. Noisy, but it will keep your motor cool.

[Advil]

Thanks. Good ideas on the baffle, and for the Comair fans. Those move a ton of air... at 60db.

I went back through the "I love my Tormach But..." thread that was mentioned. A lot of those issues seem to center around the 1100 parts not being ideally balanced for high RPM. To keep the topic on the motor fan, they mentioned early fans having one screw on the side, whereas they now use two screws (one on each side) to better balance the fan. I'm still thinking as easy as it is to remove the thing it would be better off gone. Why use any of the available 1hp to turn a fan when electric fans couldn't be any more commonplace?

[tmarks11]

Thanks. Good ideas on the baffle, and for the Comair fans. Those move a ton of air... at 60db.

Yeah, maybe a variable speed switch would be nice to slow it down a bit, or a relay so it is running only when the spindle is turning (which is easy to accomplish as one of the logic outputs from the VFD is 12V whenever the spindle stops)

[MichaelHenry]

Yeah, maybe a variable speed switch would be nice to slow it down a bit, or a relay so it is running only when the spindle is turning (which is easy to accomplish as one of the logic outputs from the VFD is 12V whenever the spindle stops)

Sounds like a good application for an Arduino. Maybe John Saunders would be interested in that now that he is getting back to Arduino projects.

[pickled]

Sounds like a good application for an Arduino. Maybe John Saunders would be interested in that now that he is getting back to Arduino projects.

Agreed. An arduino would do well in such a simple application. You could pull the entire project off for <$20 in electronics. Hmmm now you got me thinking because I have a few arduino Unos sitting around here that were meant for a project that fell through. I might have to knock out a purposeful design for both my 1100 and my 770 here. Does anyone know if the motors changed at all since the Series II 1100? The fan on the 1100 is a one bolt design and the cowl on the motor itself is held on with 3 bolts. I'll take apart my older 770 (bought a month before they launched them as Series III) head tonight and see what that looks like too. It has milled a LOT of carbon fiber and wood so I'm sure that it is caked with itchy and disgusting particles.