kevin: properly impregnated oilite bushings
Kevin, as I understand it the Oilite bushings (not normal sintered broze) can be gently heated to a warm temperature, as well as the oil. (or perhaps together?). Then allow the Oilite to draw the oil into itself. This is just my take on things, but it makes sense rather than using cold oil and a cold bearing. The idea is of course as friction (and temperature ) increases, oils is "liberated" from the bushing, and is drawn back as the bearing cools. I should check with the manufacturer, Beemer Precision.
Kevin, as I understand it the Oilite bushings (not normal sintered broze) can be gently heated to a warm temperature, as well as the oil. (or perhaps together?). Then allow the Oilite to draw the oil into itself. This is just my take on things, but it makes sense rather than using cold oil and a cold bearing. The idea is of course as friction (and temperature ) increases, oils is "liberated" from the bushing, and is drawn back as the bearing cools. I should check with the manufacturer, Beemer Precision.
Hi Jeroen,
I've used Mirko's bushings in a couple of other TD-124, just not mine which has Jec965's bushings in it. They all looked like the originals.
Please do post a picture or two showing the differences between the two.. I've never had problems with bushings from anyone so far, but we are talking a small number of tables so far..
Yes, that is my understanding too, and I have always heated bearing and oil together and then allowed to cool.. The adjoining felt must be soaked as well..
We tend to use "oilite" and "sintered bronze" interchangeably in my circle, I had always understood "Oilite" was a trademark on a brand of sintered bronze bearing.. This of course may not be quite correct..
The replacement bushings and the original OEM bushings are not "Oilite" brand, but to operate on the same principles.
First off I'll try to sum up this brief exchange to date.
TT mechanic tells customer that motor bushings from Mirko are too tight because the motor doesn't come up to speed....even after running in. Said mechanic states he wants to purchase bushings from Schopper and use those.
kevinkr replys astutely by stating "how has he made that determination?".
I echo that reply. I'll get back to that in a minute.
kevinkr also notes that the bushing/shaft clearance can easily be observed prior to motor assembly simply by slipping the new bushing over one end of a cleaned motor shaft and then take note if the bushing doesn't slide back/forth easily.
Then more suggestions are offered/discussed about which alloy of sintered bronze was used in the machining of the bushings. Was it genuine Oilite? etc.
I think that covers the highlights of this discussion so far.
My thoughts:
Exact alloy of bushing is not at question here because even if a non-porous bronze is used with an adequate supply of lubrication, the motor should function for months, even years, before going dry on lube. So I dismiss that idea as a potential cause.
I do suggest to go with kelvinkr's suggestion about testing to see if the bushings are or are not too tight on the motor shaft simply by slipping one over a cleaned motor shaft and observe if the bushings slides back/forth, rotates easily but doesn't rattle or exhibit any discernible slop in the fit between bushing and shaft.
Above photo: testing bushing clearance over a gage pin that is the same size as the motor shaft. I would suggest doing the same thing with the rotor shaft. If you don't have the dial indicator/and other inspection tools in the photo, simply observe that the bushing will spin easily and slide up/down the shaft by gravity alone.
If the bushings pass this simple test, they are not too tight!
I'm betting that this is the case. The bushings will fit the motor shaft correctly.
The one assembly procedure that has not so far been discussed is the alignment between bushing and motor shaft.
We should note that the bushings have a spherical end. This is to allow the bushings to -change attitude- slightly within a spherical cup in the motor caps at either end of the motor. By this facility, bushings are intended to self align to the motor shaft.
However. And this seems to be tripping up lots of folks attempting to refurbish their E50 motors. The bushings don't exactly self align to the shaft all that easily. Rather there needs to be some coercive measures taken to ensure that the bushings in fact do find a coaxial alignment with the motor shaft at either end of the motor assembly. This process has been explained several times around the web, but I don't think anyone has illustrated the process in a way that has achieved universal understanding.
My guess; bushing/shaft alignments are at the root cause of your motor speed issue. Unless bushing/shaft alignments are correctly carried out, you will have a problem of bushing to shaft clearance being too tight. Rather, the bushings will be in hard angular contact with the shaft in one specific area of the bushing where -- instead -- there should be a uniform amount of clearance all around.
I would further add that we tend to be too quick to blame a manufacturer for problems that are actually caused by incorrect assembly.
If all else fails, I'd ask Mirko himself to refurbish the motor for you. He'll get it right.
-Steve
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Essentially you need to slide the top and bottom covers around a bit to get good bearing alignment even before you put the screws back in.. Power up the motor and with the screws loose move the covers around until the least noise is achieved and with the power removed the shaft should turn freely with very moderate drag, give the shaft a spin and it should continue to spin for approximately a couple of seconds or longer.
One thing I did not mention is to make sure that the little ball bearing is present on the lower end of the shaft and that a thrust plate is also installed in the bottom bearing housing, missing either will create some interesting issues.
To be complete, it is a somewhat involved explanation That is why I alluded to other sources around the web that attempt to do so.
To put it briefly, and as kevinkr notes, the housing caps that hold the bushings can slide sideways a little bit within their mounting. The coaxial alignment is achieved by doing this. In conjunction with the sideways adjustments to the housing caps a mechanics' stethoscope is used to listen to the running motor for changes in noise output after each adjustment. Lower noise = better adjustment.
Any E50 refurbish project that does not pay attention to this very important process will fail.
-Steve
I got an email from another buyer of the mirko bushings on ebay and he has the same problems as me :
Beste jerovan123,
Hi Jeroen, your difficulties prompted me to start the motor rebuild using the kit from Sq38s. You are right the bushings are tight (but they fit) and the motor would turn only very slowly. Also the oil retaining felt rings are too thick. But I was able to overcome both those problems. For the bushings, I used a 3/16 drill and bore out the hole and they feel fine now. For the felt, I used a sharp blade and cut them in half and it was OK. I will also contact the seller to let him know of the difficulties, he is very experienced with the Thorens and the kit should fit properly without any adjustments. Hope this helps you. Regards, Montréal, Canada
- goldorak2
Beste jerovan123,
Hi Jeroen, your difficulties prompted me to start the motor rebuild using the kit from Sq38s. You are right the bushings are tight (but they fit) and the motor would turn only very slowly. Also the oil retaining felt rings are too thick. But I was able to overcome both those problems. For the bushings, I used a 3/16 drill and bore out the hole and they feel fine now. For the felt, I used a sharp blade and cut them in half and it was OK. I will also contact the seller to let him know of the difficulties, he is very experienced with the Thorens and the kit should fit properly without any adjustments. Hope this helps you. Regards, Montréal, Canada
- goldorak2
He doesn't describe the condition with any detail other than to say that "they are tight (but they fit)...."
That is not enough information to confirm whether the bushings were in fact incorrectly sized or not. In a previous post I did outline a common sense and simple method to determine if the bushings fit a motor shaft too tightly. I hope I don't need to repeat myself, because I won't.
Then he says: "For the bushings, I used a 3/16 drill and bore out the hole and they feel fine now."
As it turns out, a 3/16 inch drill is not that different in size from the motor shaft. However the drill is not designed to produce the straightness, roundness nor the surface finish necessary to ensure a proper bushing to shaft clearance and proper operation.
For myself, if my choice were to modify a new bushing by using a drill to 'open up the size a bit to improve clearance, or to clean and re-oil the original bushings, I take the latter path. The former path is just too ignorant.
Frankly, neither of you has offered enough information to actually confirm that the bushings were ever too tight.
Let me write down the name of that fellow, just to remind me not to buy a TD124 from him. Certainly not after he's re-sized the motor bushings using a drill bit.
-Steve
bushings and ignorance
Steve, et al:
Perhaps the key is to do good measurements of the motor shaft and the bushing itself (although this may be beyond what most can do, measuring an interior of bushing may take more than a digital caliper).
Just a thought: rather than "hogging out" a bushing is there a chrocus cloth attachment for a Dremel or similar, or some other polishing system that could be empolyed? (like a tiny buffer attachment and some lapping or polishing compound). What about using a precision ream of the appropriate size?
If the bushings are a little sloppy, what about the use of some good grease rather than oil? This is what Garrard has used, as well as Dual in the past.
Just some ideas, that's all. I am in no way a "refurb" expert.
Steve, et al:
Perhaps the key is to do good measurements of the motor shaft and the bushing itself (although this may be beyond what most can do, measuring an interior of bushing may take more than a digital caliper).
Just a thought: rather than "hogging out" a bushing is there a chrocus cloth attachment for a Dremel or similar, or some other polishing system that could be empolyed? (like a tiny buffer attachment and some lapping or polishing compound). What about using a precision ream of the appropriate size?
If the bushings are a little sloppy, what about the use of some good grease rather than oil? This is what Garrard has used, as well as Dual in the past.
Just some ideas, that's all. I am in no way a "refurb" expert.
Good replacement bushings specifically for the Thorens E50 motor are available from a number of sources, so probably not a very good investment in time and effort to work around bad/defective/worn out ones - just replace them.
They can probably be machined on a milling machine with some care, but a standard drill bit is not the way to go.. I wouldn't even attempt it on my mini-mill..
They can probably be machined on a milling machine with some care, but a standard drill bit is not the way to go.. I wouldn't even attempt it on my mini-mill..
One of the main problems associated with resizing the inside diameter of a porous bronze bushing is the tendency of the abrasive cutting to "smear" the surface in a way that tends to seal up the pores, effectively turning the bushing into a normal bushing that does not retain lube, then release it slowly over an extended period of time as Oilite bushings are designed to do. You polish it, you ruin it.
To do the job right on Oilite or any alloy of porous bronze, one has to take special care not to 'smear' the surface. Generally, a boring bar with single point cutting edge is the traditional means of boring out the inside diameter of these bushings. A lathe job. It could also be done on a milling machine, but the lathe is a natural tool for it. Secondary operations to adjust that last little bit of size using sand paper, or hone stones are not allowed. Reamers also tend to smear porous bronze.
So anything done in the home garage to alter size of one of these bushings is likely to ruin it.
-Steve
Here's a copy paste of the image from post #439.
In the photo you can see the porous nature of the bushing material in the two parts on the left. Those that are identified as being purchased from Mirko. It looks like the right material to me. The material from Schopper isn't as porous, obviously. Do they state what alloy they use? There are several alloys of porous bronze currently available. The Schopper bushings (on the right) appear to have been made with greater attention to detail. For instance, I can see a sharp edge in Mirko's bushings at the bore openings. That's not a good thing. The Schopper bushings show edge breaks which should exist on a properly turned bushing. Apart from that, you can't tell whether or not the bushings are sized correctly.
I will note that porous bronze, if it is the correct alloy, will not produce a beautifully smooth surface. You see the porous structure of the material on the surface. It's not a poxy disease.
It is per design. What is also important is whether or not the bushings are sized correctly, that the internal surface of each bore be straight and round and to size within the operating tolerance.
I know when I contracted to have the two lots of bushings that I supplied I allowed a .0008 to .0013 (inches) amount of running clearance between bushing and shaft. That's pretty close tolerance work for a machinist using a lathe to single-point cut the bushings. CNC or manual, the machine has to be in good condition to be able to hold that tolerance. And the machinist needs to stay awake..
-Steve
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Bearing Porosity and Alignment
Further to the discussion, Oilite or porous bronze bushings self lubricate by creating heat at the bearing surface. The temperature differential causes the lubricant to wick to the bearing surface. It is important to make sure that when sizing the bushing that one does not close the pores in the material. This has been discussed at length here. It is also important that the motor shaft is clean and smooth. Perhaps the tightness being referred to is caused by the condition of the shaft.
As to alignment, the motor is self aligning, so it is important that the bearing be able to move where it is captured in the spring washer. If the felt is too thick, for example, it may inhibit the free movement of the bearing and thus cause alignment problems. Best to slide the end covers around with the screws loose to get the proper alignment as well. The Garrards are similar, but the casings do not have any real play, as in the Thorens E50.
Just some comments from the peanut gallery.
Further to the discussion, Oilite or porous bronze bushings self lubricate by creating heat at the bearing surface. The temperature differential causes the lubricant to wick to the bearing surface. It is important to make sure that when sizing the bushing that one does not close the pores in the material. This has been discussed at length here. It is also important that the motor shaft is clean and smooth. Perhaps the tightness being referred to is caused by the condition of the shaft.
As to alignment, the motor is self aligning, so it is important that the bearing be able to move where it is captured in the spring washer. If the felt is too thick, for example, it may inhibit the free movement of the bearing and thus cause alignment problems. Best to slide the end covers around with the screws loose to get the proper alignment as well. The Garrards are similar, but the casings do not have any real play, as in the Thorens E50.
Just some comments from the peanut gallery.
510, a response, and good suggestions
my comments were in response to:
So I agree. As far as machining Oilite bushings, I have to believe you. And it makes some sense. As far as I understand things, one specifies the bushings to Beemer, and they provide the bushings, They have several grades of bushings available. Specifically, Oilite bushings are the only that are to be "oil impregnated", thus "oil impregnated sintered broze bushings":= (defined as being equal to) Oilite. Perhaps semantics, but everything else is a copy otherwise. Some precision needs to be exercised in the use of language.
If using the original (as in old, dirty, etc) bushings, I'd use crocus cloth and some good grease. Dumb simple, easy to do. If not, check the bushings or alter the motor shaft (or rather polish it with crocus cloth), and clean the bushings.
my comments were in response to:
So I agree. As far as machining Oilite bushings, I have to believe you. And it makes some sense. As far as I understand things, one specifies the bushings to Beemer, and they provide the bushings, They have several grades of bushings available. Specifically, Oilite bushings are the only that are to be "oil impregnated", thus "oil impregnated sintered broze bushings":= (defined as being equal to) Oilite. Perhaps semantics, but everything else is a copy otherwise. Some precision needs to be exercised in the use of language.
If using the original (as in old, dirty, etc) bushings, I'd use crocus cloth and some good grease. Dumb simple, easy to do. If not, check the bushings or alter the motor shaft (or rather polish it with crocus cloth), and clean the bushings.
Cleaning and relubricating old bushings
I do not think it would be advisable to use grease, especially in such a location that is difficult to access and relube. The best thing to do with old bushings is to heat them up and sweat out the oil and then clean in solvent. Do this several times until no dirty oil oozes out. Then, put the cleaned bushings in heated oil and let them sit for a day. The bearing will absorb the oil. Better yet, if you have access to a small vacuum chamber, put the oil and bearing in vacuum and draw the oil in that way. This is the way that the original bearing material is impregnated. The saturated felts in contact with the bushing act as oil reservoirs to keep the bearings lubricated. Using grease will block this lubrication. If the bearing fit is too sloppy, then the oil will not draw, but then again, the bearings would not really be serviceable.
The fit of the bearing to shaft needs to be fairly tight. The shaft does not run in an oil bath but is boundry lubricated. The bearing is supplied oil from the friction and heat generated with the motor shaft in partial contact with the bearing. The Garrard motors work the same way, but the Garrard motor is far better built than the E50, which was originally used as a fan motor. The difference is larger and beefier castings, larger armature with built in cooling fan and more fasteners at the bearing plates. The E50 works more than adequately on the Thorens turntable, but I think extra care and adjustment is needed with the E50 to get the most out of it.
I do not think it would be advisable to use grease, especially in such a location that is difficult to access and relube. The best thing to do with old bushings is to heat them up and sweat out the oil and then clean in solvent. Do this several times until no dirty oil oozes out. Then, put the cleaned bushings in heated oil and let them sit for a day. The bearing will absorb the oil. Better yet, if you have access to a small vacuum chamber, put the oil and bearing in vacuum and draw the oil in that way. This is the way that the original bearing material is impregnated. The saturated felts in contact with the bushing act as oil reservoirs to keep the bearings lubricated. Using grease will block this lubrication. If the bearing fit is too sloppy, then the oil will not draw, but then again, the bearings would not really be serviceable.
The fit of the bearing to shaft needs to be fairly tight. The shaft does not run in an oil bath but is boundry lubricated. The bearing is supplied oil from the friction and heat generated with the motor shaft in partial contact with the bearing. The Garrard motors work the same way, but the Garrard motor is far better built than the E50, which was originally used as a fan motor. The difference is larger and beefier castings, larger armature with built in cooling fan and more fasteners at the bearing plates. The E50 works more than adequately on the Thorens turntable, but I think extra care and adjustment is needed with the E50 to get the most out of it.
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While I understand your concern and I understand that "oilite" is the trademarked brand for a bushing made by Beemer, Inc., it has become as generic a term as "Kleenex" or "Jeep" and is widely understood to specify a specific type of oil impregnated sintered bronze bearing. One word versus five...
