Here is a list of all the postings Andy Carlson has made in our forums. Click on a thread name to jump to the thread.
|Thread: GEC Motor Bearings for Lathe Motor|
I had initially thought that the previous owner must have rotated the ends through 180 degrees but this theory was an attempt to explain why the noises stop when the belt is tight. Now I think that the noise is down to vibration of the shaft in the bearing. This theory explains why the noise goes away with no need to assume any other changes... and it also means that rotating the ends wont help with the noise.
I'm not shying away but having taken the thing apart and discussed it here I do now think that the problem is less severe than I had first thought. 'Leave well alone' is definitely still an option in the short term but I plan to keep this lathe and don't really want to put up with the noises indefinitely. Replacing the whole motor is an option but not my first preference.
At the moment cautious, reversible steps towards replacing the plain bearings 'like for like' (or very close to) is my preferred option.
Some progress to report... I found that the outer end cap on the non-pulley end came off with some very light taps with an 8mm rod through the bearing. Taking out a wick 'washer' revealed the view in the photo below.
So this does seem to be a thin walled bush. As far as I could measure by poking around with the calipers it seems to be roughly 10.8mm OD (and an 8mm shaft). The bush is inside a bore in the main casting but this part of the casting is surrounded by several slots for more wick material.
I've also had an unsuccessful attempt to get the inner cap off using a few quick and dirty options. My anchor bolt does not expand enough to grip the cap so I'm planning to make something with a step to engage positively inside the rim. Not sure if that will happen today because I have some errands to run.
Thanks again for your suggestions so far.
Thanks. Yes, heat is an option but the dilemma that I have is where to apply any force, be it using a punch, puller or whatever. The construction of the bearing assembly is not easy to decipher from the outside and there are definitely bits like the tufnol piece and the wicking that would be damaged if I do the wrong thing.
At the moment it seems like the inner cap needs to come off first. A puller seems like the best option for this, especially on the non-pulley end where the outer cap is completely blank.
Thanks for the photos Ian. I do have a faceplate for the Cowells but clearly I can't be turning bits from the Cowells motor on the Cowells.
I now have my thinking cap on to see what could be repurposed to make the 'expanding puller' that Clive suggested.
Having measured both 'indoor' and 'outdoor' caps the 'indoor' ones are slightly bigger so clearly they must have been pushed in from the inside end... so pulling them out from that side seems like a logical step. Then hopefully I might get a better clue how the bearing itself is held in because at the moment all except the inside of the bore is hidden by fuzzy felt.
I've just been having another look at the motor following tonight's discussion.
I put it back together to take another look at the bearing wear. Having done this I found that I could not get the rotor to touch the stator in any position so things are probably not quite as bad as I had initially thought.
As originally noted, there *IS* bearing wear. There is play in the shaft in the direction of the belt load but not in the direction perpendiclar to this. The motor definitely does make some nasty noises. I now suspect that the noise is caused by vibration of the shaft in the sloppy bearing rather than by the rotor contacting the stator. This noise would, of course, stop when there is enough tension in the belt.
A few more posts while I was writing mine. Thanks again. I will give the 'expanding puller' thing some thought and will have a rummage through some more civil engineering type bolts to see if anything can be pressed into service. This seems like the type of approach where I could bug out and just tap the cover back on if I wasn't happy with the way things were going.
The photo below is a bit more of a close up of the 'indoor' end but the flash still tends to flatten everything so it's not as good as actually looking at the real thing. The brown thing is the bit that I think is Tufnol. The bearing itself is behind this.
So it sounds like trying to take the 'indoor' caps off may be the way to go... although the taper on the cap and the similar taper on the alloy casting did make me wonder if the whole assembly had been inserted from the 'outdoor' end... but then looking at that end it seemed unlikely.
Thanks for the posts so far. The PDF is interesting but I suspect a lot more modern than my motor. Interesting that they are still trying to flog plain bearings for similar sized motors though.
My other lathe is a Unimat DB/SL so it would not be able to swing the alloy ends of the GEC motor.
I didn't notice any sign of thermal damage to the windings when poking around with a lamp in there. The photo was done with flash which can make things loook a bit odd. Certainly the motor does not upset the RCD on our ring main... which plenty of other domestic appliances (mostly steam irons) have managed to do.
I'm reluctant to try anything too risky or irreversible because the motor does actually work and the lathe has already done plenty of good work. Having had a look inside now I'm also less worried that it might chew through something carrying 240V.
I was rather hoping that, being an old design, there would be a straightforward way to replace the bearings 'like for like' (after all the label does seem to suggest that spare parts were obtainable back in the day).
This single phase AC motor (see photos) was supplied with Cowells lathes in the late 1970s (and perhaps later).
The motor is GEC 'type BS 1508-C, 1425 rpm, for spares quote D44568' if anyone wants the blurb from the sticker.
The bearings appear to be worn sufficiently for the rotor to rub on the stator when the drive belt to the lathe is not tight.
I'd like to replace them but how to get them out is not clear to me. I'm hoping that someone here has successfully done something similar.
The motor seems to be a pretty simple affair with no slip rings or commutator involved. The alloy ends house the bearings and are secured by two (2BA?) threaded rods that go right through the casing. With the nuts undone it is easy to take off the ends and pull out the rotor.
The bearings seem to be plain (bronze I guess) but they are enclosed by what look like pressed steel caps both on the outside and inside ends. There seems to be some wicking material surrounding them and a wick in contact with the motor shaft. The shaft has a spiral groove presumably to persuade the oil into the bearings. A (tufnol?) part surrounds the shaft inside the end caps on the 'indoors' end.
Can anyone advise on how to get the bearing housings apart without causing damage please?
I suspect that a previous owner has turned one of the ends through 180 degrees such that the unworn side of the bearing takes the load of the drive belt. This does stop the rotor from rubbing on the stator as long as the belt is tight but it can still make grating noises when starting and I'm not happy with it as a long term answer.
|Thread: Lathe bearing oiler wicks/felt|
The orange belt that came with my lathe looks like it has seen a fair bit of oil in its time. Not sure if they are intended to cope with such an oily environment but I guess they must be.
I've ordered a new belt from Cowells (among other things) and will keep the other one as a spare, I suspect the new one will get oily too.
The motor belt is a rubber vee belt but from the spray marks inside the wooden base it looks like this has seen some oil too... which reminds me I still need to source one of these because the old one, while intact, has definitely developed a 'memory' of being left in one position probably for years.
Yes, the lathe will need to be house trained. It will certainly be stored indoors when not being used. I will use it outdoors or in the shed when possible but I'd like to have the option of using it indoors when the job is small and the weather is inclement.
I anticipate arranging some splash guards but just now the focus is on getting the thing fettled and hopefully soon putting it back together.
Tanya at Hardy and Hanson was very helpful. The 5mm diameter s44 stuff is on sale just now on their web site but they make other things. They don't do cord in less than s44 grade (which is harder than F-1) though but I think they do other shapes/sheets in the softer felt. She was keen to quote me for a custom job to do the exact size I wanted... but 5mm was probably my best guess anyway... assuming I even need any felt now!
As far as I could gather from various sites, F-1 and F-3 are the usual choices with F-1 being preferable.
Gosh, many replies. Thank you all.
I don't think there is any question of 'misleading' - my original question was based on an assumption that turned out to be wrong so no worries there.
The more general question is whether the 'open bottom' cup arrangement on my lathe will cause too much oil flow and general spraying of oil from the spindle pulleys etc onto the lathe's surroundings. Time will tell. If so then I wil be looking for ways to get enough oil flow without getting too much.
Any info on what arrangement Cowells now use for the oilers would be useful - like I said there appears to be a 'thing' in between the oiler and the top of the headstock casting in the photos of a more recent machine on the Cowells site.
I've managed to dig up some more info since my original posting.
First off I managed to order some almost correct felt as 5mm diameter cord from Hardy and Hanson. It's the right material but the grade is harder (s44) than would be perfect - s36 seems to be a match for the American F-1 grade.
Secondly I think that my oil cups are still available from Adams Lube in Coventry. Judging by the size I think they are 'BS1512 shoulder drive oil cup 3/16 inch hole' but without taking mine out I can't be 100% sure of the size. I contacted Adams and was advised that they are recommended to be used with nothing in the oil flow.
So I think that the oilers probably left the factory without any felt in them.
It remains to be seen whether this will produce a reasonable oil flow on my lathe. It's in bits just now. If it proves excessive then I will experiment with the felt and also consider fitting different lubricators altogether.
Looking at the photos on Cowells site they still use very similar cups but there is an extra 'thing' between the cup and the top of the bearing casting. Does anyone know what this 'thing' is? I can guess but does anyone know? My cups are fitted straight into holes in the bearing casting.
Thanks Michael. Yes, oil lamp wicks could be an option
Were you able to find something of the right shape and size in a fabrics shop?
If so, any idea what I should be looking/asking for?
I've also seen discussion about cutting up felt sheet but I'm not too confident that I could cut such a small cylindrical shape from such a spongy material. If possible I'd lilke to find something that is sold in cord form so that I just need to cut a suitable length.
This is a US example...
I've recently acquired a Cowells lathe.which I'm currently giving a darned good strip down and clean before I start using it. Colin Childs of Cowells estimates that mine was made in the mid-1970s
Mt micrometer indicates that wear on the bearing faces of the spindle seems commendably low and I'd like to keep it like that.
I've seen discussion on US forums about replacing the wicks in the oilers of plain bearing lathes. I've also found US sites selling the felt wick material in various grades and diameters...
... but I've found no UK suppliers
I've asked Cowells but they don't sell anything like this.
Has anyone found any UK suppliers for wick material for plain bearing oilers?
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
Sign up to our newsletter and get a free digital issue.
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.