Head temperature

[wildcat]

What temperature is the head of your mill running at? My mill head is running at around 145 degree F and the motor (the stock motor) is at 165 degree F after approximately 2hrs of run time. At one point a little smoke even came out of the motor connection box after stopping. I have a new motor waiting on the correct VFD (received 1/4HP VFD after ordering a 3HP VFD). Anyway, I am most concerned about the head. Bob posted a picture of a guy that installed a radiator through which the head oil circulates - looked like a nice setup. I currently have Mobil Medium Heavy in the head. Should I be concerned about the head temperature?

Today I had the head pop out of gear (High 3) a couple of times and if I would not have been there to quick pop it back it could have been bad. Thought I might make something to positively lock the levers in place.

[NC Cams]

I"m not familiar with Mobil Med Heavy but I am familiar with automotive lubes which have to endure far worse operating extremes.

Depending on the lubricant being used, 145 to 165 F is not appreciably hot for most auto gear lubes - especially those fortifed with anti-friction or anti-wear additive packages.

Your temp is probably at the low range of a suitable continuous duty temp for APG90 gear oil and low to moderate temp range for Dexron III. It is probably too cool for APG140. A multi vis APG 90-140 would be at low end of temp range.

You DO want the oil to reach a bit of an elevated temp to "burn off" any condensate (moisture) that may have become entrapped. Also, the machine, if properly designed should be at the optimum temp for the desired/designed clearances to be at their optimum - 140-160 is not appreciably hot (actually probably on the normal side) for the machine tool bearings that I worked with.

If the temp climbs at at a reasonable rate and then stabilizes, that is pretty much to be expected. If it should SKYROCKET, that is usually not good.

In light of the fact that Dexron III is now used in a lot of manual trans automotive gearboxes, it is well suited to lube similar devices. Not saying to switch from what you're using but, with a bit of investigation into the MFR's lube specs, you just might find that automotive lubes you can get from the local NAPA or autoparts big box store might outperform the industrial lubes at a fraction of the cost with much easier availability.

[wildcat]

NC Cams - thanks the reassurance that the head temp is fine. As a matter of fact as soon as I can get the new faster motor on the head I had planned to switch to Dexron III given your previous suggestion. The viscosity ratings of Dexron III and Mobil Light (what Aaron recommends for running at 3600 RPM) are pretty similar.

[One of Many]

It has been my experience that no high quality bearinged running assembly that uses standard seals should get above 140F. Seal life is reduced by distortion. I would check the current draw, fan cooling etc.

Especially when using a VFD. An external fan should be added to TEFC type motors to protect them when the motor RPM is so low that its fan cannot produce enough air flow to cool it properly. Most of the heat in the head may be from thermal transfer of the motor. That does sound suspicous, but I have seen many import motors that do run HOT.

DC

[wildcat]

There is indeed a lot of heat transfer from the motor. Using a handheld IR thermometer it is pretty easy to map out the heat transfer from the motor into the head and then across the slide into the column. Perhaps the head temperature will be lower with the new motor?

[NC Cams]

The prior posting discussed and was intended to address lube and gear box temp ONLY.

TEFC motors rely on the FC thus low rpm/high load running can cause heating issues - as far as the lube goes, 140 to 160 should not be a problem for the reasons already cited.

A supplemental fan to keep motor (IE:windings, et al) cool is only smart if you're using VFD. If the gearbox lube is serving as the heat sink, the lube should not be bothered with the listed temps - the motor windings are an entirely different issue which I am not in a position to discuss.

[Cruiser]

the temp for the oil is low, but the temp for the gear box seems high, mine ran in the 90 deg bracket if i recall and the alarm is popping out of gear, you may have issue inside gear box, may be worth while to check it out, are there any scary noises, did you open box before using and clear any left over iron ? get a speaker magnet and put it on side of box and run it a while before pulling top off, it will draw fine to inside of box. I found too much fine in mine, before I ran it at all ! I meant to put in magnetic plug, but spaced it off till later hense external speaker mag ! the gears will eat a lot of iron without complaining but the bearings will take a beating. might check it out before it be too late. I'm reusing stock oil at this time, figuring on dex at change time, and a magnetic plug ! probably just drill it for a cyl mag and replace.

[wildcat]

Is it much of a process to pop the top of the head off? Can it be done without ruining seals? The head is certainly load compared to my Grizzly gearhead lathe but still tolerable without earplugs.

[Cruiser]

WC, Its not much of an ordeal to do. the motor needs to be unhooked and pulled first. then you can pull the whole head or just the top off of gear box. I would say just the top for now. take out bolts and there are one or two square head bolts that when run in will lift the cap enough to get in with a screw driver wedging cap till it is loose then just lift it off. the plug to drain it is in cavity from underside and should be drained into something clear so you can see any solids in oil, the oil can be reused if you save it. you can fish the inside with a magnet and look things over, select the gear it was popping out of and inspect the shift forks and gear mesh, make note that the tops of the shafts are not supported, they also can be pulled out for a closer look. I'll leave the rest of it up to you .... do yourself a favor and drill the drain plug for a magnet or put one on side of gearbox, drain plug prefered ! Now I must go out and rewire some silly resistors. OH yea, when reinstalling the cap onto the shafts, be cautious with the reallignment, if it don't go, take a closer look ! once aligned it drops on fairly easy. Now to the resistors !

[wildcat]

Got the correct VFD today and switched out the motor for a Leeson (couldn't believe Leeson motors are made in China?!?!?). While at I popped the top off the head to see what might be wrong with the gears. I found nothing wrong with the gears thankfully. The circulating oil got replaced with Castrol Dexron III. The end result, after 1 hr of operation, was slightly higher head temperature of 165F (but remember the spindle speed has doubled), lower motor temp (~95F), less foaming, and surprisingly much quieter operation. Could the temperature still be a problem to the seals?

[NC Cams]

The results reported in post #10 are a classic reason why some automotive lubricants are far superior to "industrial" lubes.

The demands for fuel efficiency have necessitated the use of improved lubricants under higher demanding conditions. Dexron III is one such lubricant that has been developed to provide superior lubrication over longer periods and under much more severe operating conditions (higher high temp and lower low temp).

This is where the additive packages contained in the lubes comes into play.

Normally, one would think that higher temps would thin out the oil more and thus the lube films would likewise suffer. Actually, with modern chemistry, you can modify the "shear viscosity" wherein the viscosity at the load point remains stable/high even though the thermal viscosity is dropping.

We too noticed that Dexron would run a bit warmer in our grinding head spindle fitted with precision bored sleeve bearing. HOWEVER, the grinding finishe noticeably improved. Duh???

The thicker oil added a bit more viscous drag ergo the higher temp due to friction. BUT the slightly higher viscosity of Dexron (compared to the prescribed spindle oil) provided for superiour oil film thickness within the sleeve bearing clearance where load was actually carried. The improved "shear viscosity" (ability of the film to support load and remain in place as the load tries to shear it) of the fortified additive package made a noticeable difference in grinding finish.

These "magic features" of Dexron probably explain why the other positive results as noted in post 10 were encountered.

NOTE: Dexron III is an industry standardized rating qualification method. Thus brand "A" Dexron can be formulated differently than brand "B". As is often the case, your individual results could vary from brand to brand as as result of the differences in the base stock formulation.

Although "generic" Dexron will test out the same on the cert trials as a brand name product, a given brand may offer noticeably better or worse performance in "off label" use (IE: machine tool spindle gearbox) than the same product offered by a different supplier.

You may want to experiment a bit if you're contemplating the use of Dexron in your gearbox - the first brand you choose may not be the best one for your needs.

[philbur]

It could also be due to its lower viscosity.

Regards
Phil

Originally Posted by NC Cams . These "magic features" of Dexron probably explain why the other positive results as noted in post 10 were encountered.