Good progress.
Hi Greame,
Yes, youv'e got it in one, exactly like the rifling in a gun barrel!
I'm sorry I didn't think of that description, but wouldn't have been sure you would have understood, anyway, as I would guess that relatively few people know about such matters.
Doing it this way is a 'double-whammy', as not only will you reduce the sliding surface area (which is good, as you will have rather more here than is ideal) but this also gives an excellent means of lubricating the entire bearing, as a bonus.
Otherwise, if you just attack the shaft and simply reduce its bearing *length* (all else being equal) you only gain part of the friction-reducing benefit because you still have this much increased circumference on the remaining part of the larger shaft (Pi x the increase in shaft dia.), and hence the substantially increased sliding speeds as well.
Of course, by removing material from the inner wall along the *length* of the sleeve, this helps to offset the greater 'circumferentially-derived' area, because you are removing some of the metal from this larger circumference here.
It may be more difficult, but extreme accuracy is not vital here, any groove cut in the inner wall need only be quite shallow, and if you can spiral it as suggested, this 'pumping' benefit is well worth while.
If you consider that the oil will try to 'follow' the direction of the shaft's rotation, and will be encouraged to lie in the grooves you cut, so long as you arrange the spiral 'screw' direction correctly, the oil will tend to rise up the gap made by the grooves, to be re-deposited back on to the shaft higher up.
In my case, I have (a bit like your proposed SU arrangement) a hole down the centre of the shaft, and by a bit of crafty drilling near the bottom at the side of the shaft for an 'outlet', I can see the oil circulating completely in a cycle. It appears at the top of the sleeve, having exited the grooves between the shaft and sleeve, and runs back down the hollow centre, ready to be pumped back up again.
In fact, it is hard (for me, at least!) to think of a better method of long-term lubrication, in my view.
Incidentally, Mobil 1 (fully synthetic, as I expect you will know) is the finest oil I have ever tried in TT bearings, and I have found no benefit in adding Moly, or STP., or Wynns, or whatever, when using this excellent oil. There are some specialist TT oils on the market, but they are very costly, and I somehow doubt they would be noticeably 'sonically' much better than Mobil 1. Different oils, and some additives, will affect the sound, though.
I thought there was a bush in these SU carbs., but it must be over 30 yrs. since I had one in my hands. I doubt that it would be *cast* in place as you suggest, though, and knowing the engineering 'likelihood' here, I would guess it is pressed in (or possibly heat-shrunk) during assembly, but I could be wrong.
I also rather doubt that it is steel, for what this is worth, as making a steel bush with such fine tolerances and high surface finish, would be fairly difficult (especially in those days!) and would add a lot to the cost. Try it with a magnet, anyway, and you should soon see, as stainless steel (most of which is non-magnetic, just to catch out the unwary doing this test!) was not readily available in those days, and is a pig to machine well and achieve the excellent surface finish as on these dashpot sleeves.
I guess it could well be sintered metal, as a lot of bushes are, and in case you are not familiar with this, the metal is initially 'powdered' and then moulded into shape under very high pressure and heat, until it forms a solid mass. The advantage is that the result is porous, and 'holds' lubrication in the pores, which would be very desirable in the carbs, themselves, and no bad thing in a TT spindle, either!
The reason I draw attention to this possibility, is that inherently such bushes can (all too readily) 'crush' and crumble away or completely collapse (particularly when old) if they are not supported by an outer shell, so tread warily if you remove one from the alloy outer die-casting it resides within. You might be able to identify this with a magnifying glass, as the ends of these bushes may look a bit porous, even though they have an overall surface 'shine' indicative of a good finish, and sometimes you can see tiny pits in the polished surface, together with a slight 'ring' where the moulding dies' halves come together
The best thing is if you have access to a scrap unit and see if you can knock the bush out, perhaps with some heat (dunk it in boiling water for a few mins. and the alloy should expand more than the bush) and then you can look at the metal of the bush better. Generally, as sintered bushes are subject to crumble, you can chip a bit of the end, or whatever, with a hard sharp tool, like a scriber, whereas with a 'solid' metal bush, you will only scratch it.
Regards,
Hi Greame,
Yes, youv'e got it in one, exactly like the rifling in a gun barrel!
I'm sorry I didn't think of that description, but wouldn't have been sure you would have understood, anyway, as I would guess that relatively few people know about such matters.
Doing it this way is a 'double-whammy', as not only will you reduce the sliding surface area (which is good, as you will have rather more here than is ideal) but this also gives an excellent means of lubricating the entire bearing, as a bonus.
Otherwise, if you just attack the shaft and simply reduce its bearing *length* (all else being equal) you only gain part of the friction-reducing benefit because you still have this much increased circumference on the remaining part of the larger shaft (Pi x the increase in shaft dia.), and hence the substantially increased sliding speeds as well.
Of course, by removing material from the inner wall along the *length* of the sleeve, this helps to offset the greater 'circumferentially-derived' area, because you are removing some of the metal from this larger circumference here.
It may be more difficult, but extreme accuracy is not vital here, any groove cut in the inner wall need only be quite shallow, and if you can spiral it as suggested, this 'pumping' benefit is well worth while.
If you consider that the oil will try to 'follow' the direction of the shaft's rotation, and will be encouraged to lie in the grooves you cut, so long as you arrange the spiral 'screw' direction correctly, the oil will tend to rise up the gap made by the grooves, to be re-deposited back on to the shaft higher up.
In my case, I have (a bit like your proposed SU arrangement) a hole down the centre of the shaft, and by a bit of crafty drilling near the bottom at the side of the shaft for an 'outlet', I can see the oil circulating completely in a cycle. It appears at the top of the sleeve, having exited the grooves between the shaft and sleeve, and runs back down the hollow centre, ready to be pumped back up again.
In fact, it is hard (for me, at least!) to think of a better method of long-term lubrication, in my view.
Incidentally, Mobil 1 (fully synthetic, as I expect you will know) is the finest oil I have ever tried in TT bearings, and I have found no benefit in adding Moly, or STP., or Wynns, or whatever, when using this excellent oil. There are some specialist TT oils on the market, but they are very costly, and I somehow doubt they would be noticeably 'sonically' much better than Mobil 1. Different oils, and some additives, will affect the sound, though.
I thought there was a bush in these SU carbs., but it must be over 30 yrs. since I had one in my hands. I doubt that it would be *cast* in place as you suggest, though, and knowing the engineering 'likelihood' here, I would guess it is pressed in (or possibly heat-shrunk) during assembly, but I could be wrong.
I also rather doubt that it is steel, for what this is worth, as making a steel bush with such fine tolerances and high surface finish, would be fairly difficult (especially in those days!) and would add a lot to the cost. Try it with a magnet, anyway, and you should soon see, as stainless steel (most of which is non-magnetic, just to catch out the unwary doing this test!) was not readily available in those days, and is a pig to machine well and achieve the excellent surface finish as on these dashpot sleeves.
I guess it could well be sintered metal, as a lot of bushes are, and in case you are not familiar with this, the metal is initially 'powdered' and then moulded into shape under very high pressure and heat, until it forms a solid mass. The advantage is that the result is porous, and 'holds' lubrication in the pores, which would be very desirable in the carbs, themselves, and no bad thing in a TT spindle, either!
The reason I draw attention to this possibility, is that inherently such bushes can (all too readily) 'crush' and crumble away or completely collapse (particularly when old) if they are not supported by an outer shell, so tread warily if you remove one from the alloy outer die-casting it resides within. You might be able to identify this with a magnifying glass, as the ends of these bushes may look a bit porous, even though they have an overall surface 'shine' indicative of a good finish, and sometimes you can see tiny pits in the polished surface, together with a slight 'ring' where the moulding dies' halves come together
The best thing is if you have access to a scrap unit and see if you can knock the bush out, perhaps with some heat (dunk it in boiling water for a few mins. and the alloy should expand more than the bush) and then you can look at the metal of the bush better. Generally, as sintered bushes are subject to crumble, you can chip a bit of the end, or whatever, with a hard sharp tool, like a scriber, whereas with a 'solid' metal bush, you will only scratch it.
Regards,
yeah, this is as i figured.
Without one in front of me though i cant explain details.
The bush is white metal, and not cast, thats why i thought steel.
The surface is polished which is why i thought it could be plated.
Im not sure, but ill pull a used one about, and when ive sussed it ill make the final version with new parts.
I thought the bush was cast into the alloy housing as you cant see the ends, the alloy sort of wraps over the ends of the bush, so i dont see how it could be pressed in. May be wrong though, i wish i had one here as i type!
Ill have one soon, so ill be able to describe it.
The idea has potential though so ill make a rough platter and try it out.
It really helps the thought process to be able to talk about ideas, makes me see things better.
Thanx.
Without one in front of me though i cant explain details.
The bush is white metal, and not cast, thats why i thought steel.
The surface is polished which is why i thought it could be plated.
Im not sure, but ill pull a used one about, and when ive sussed it ill make the final version with new parts.
I thought the bush was cast into the alloy housing as you cant see the ends, the alloy sort of wraps over the ends of the bush, so i dont see how it could be pressed in. May be wrong though, i wish i had one here as i type!
Ill have one soon, so ill be able to describe it.
The idea has potential though so ill make a rough platter and try it out.
It really helps the thought process to be able to talk about ideas, makes me see things better.
Thanx.
Hi Graeme,
In view of what you now say, you must be right in that the alloy must be cast around the bush, but this does surprise me. I wish my memory was better, as I have stripped and serviced dozens of these carbs years ago.
There is no other way to do this that I can conceive of, if both ends of the bush are not showing, as you now suggest.
Also, I now doubt that they would cast around a sintered bush, so my earlier comments about this may not apply.
As you say, you do really need to look at a scrap unit and see for yourself, just how the whole assembly has been put together.
The second car I owned was a 1933 MG six cylinder 'K' Type Magnette, and this had 3 X 1.25" SUs on it, so these carbs are a very old design, although their method of manufacture could have changed over the intervening years.
I've had several cars since then also with SUs on them (mainly BMC A Series, like very rapid Minis etc.) but I didn't really notice how these dashpot assemblies were constructed.
Good luck, anyway, and I'm sure you will get there in the end.
In view of what you now say, you must be right in that the alloy must be cast around the bush, but this does surprise me. I wish my memory was better, as I have stripped and serviced dozens of these carbs years ago.
There is no other way to do this that I can conceive of, if both ends of the bush are not showing, as you now suggest.
Also, I now doubt that they would cast around a sintered bush, so my earlier comments about this may not apply.
As you say, you do really need to look at a scrap unit and see for yourself, just how the whole assembly has been put together.
The second car I owned was a 1933 MG six cylinder 'K' Type Magnette, and this had 3 X 1.25" SUs on it, so these carbs are a very old design, although their method of manufacture could have changed over the intervening years.
I've had several cars since then also with SUs on them (mainly BMC A Series, like very rapid Minis etc.) but I didn't really notice how these dashpot assemblies were constructed.
Good luck, anyway, and I'm sure you will get there in the end.
Now I'm wondering why the conversation hasn't moved onto magnetic bearings... Should easily be do-able with the SU parts - a pair of opposing NDFeB magnets epoxied in place, and a suitably hefty platter (MDF and Pb) and your in superleague territory - there'll be no 'ball' noise on that 
Owen
Owen
could well work, but its things i dont fully understand.
I want to keep the whole project cheap and simple. I thought about all sorts of different ideas, mostly involving floating platters and oil baths.
Then i found the TT thread on here and read the parts about oil supported unipivot designs and got put off. I was going to use the su shaft and bush and float the platter instead of a ball, but its over complicated and probably wont work well anyhow.
Simplicity is best at first, this is my first attemp at a tt, so lots of learning will be had.
I want to keep the whole project cheap and simple. I thought about all sorts of different ideas, mostly involving floating platters and oil baths.
Then i found the TT thread on here and read the parts about oil supported unipivot designs and got put off. I was going to use the su shaft and bush and float the platter instead of a ball, but its over complicated and probably wont work well anyhow.
Simplicity is best at first, this is my first attemp at a tt, so lots of learning will be had.
This has been done, in the "Platine Verdier", about 20 years ago.
But you need a very large ring magnet to make it work, - something like 10-15 cm. in dia, and preferrably (most likely a must) a polepiece of soft iron , to get enough lift to float the platter..........
Very, very far from being a simple project.
The drawings were published in the french mag. "L'Audiophile" some time late 80s or early 90s.......
But you need a very large ring magnet to make it work, - something like 10-15 cm. in dia, and preferrably (most likely a must) a polepiece of soft iron , to get enough lift to float the platter..........
Very, very far from being a simple project.
The drawings were published in the french mag. "L'Audiophile" some time late 80s or early 90s.......
I think the suggestion was to replace the axial bearing with magnets to float the platter. It's been discussed before and the consensus is that it will not be stiff enough, ie it will bounce.
If I'm not mistaken Platine Verdier uses the ring magnets to take up a fraction (half?) of the axial load from the platter.
If I'm not mistaken Platine Verdier uses the ring magnets to take up a fraction (half?) of the axial load from the platter.
The primary eason for the pole piece is to generate enough 'lift' from the ceramic ring to float the massive platter.
My son has some 'geomag' toys he was bought for Christmas - they created some 3Kgs of repulsive force (tested using strainguage kitchen scales) - plenty for an initial DIY platter when I tested them last night.
They can easily be bought bigger and stronger from www.wondermagnet.com to cope with heavier platters, and there is no worrying about centralisation of the ball and so on... so they cost in money, but less in time.
Owen
My son has some 'geomag' toys he was bought for Christmas - they created some 3Kgs of repulsive force (tested using strainguage kitchen scales) - plenty for an initial DIY platter when I tested them last night.
They can easily be bought bigger and stronger from www.wondermagnet.com to cope with heavier platters, and there is no worrying about centralisation of the ball and so on... so they cost in money, but less in time.
Owen
I originally posted this elsewhere but it is more relevant here I think.
Hi guys I know this isnt a class piece of gear but I think the bearing
I made for my home built TT may be of use and its dead simple-
When you make the spindle support bush it will probably have the drill
angle left at the bottom of the tube, 118 degree vee for a normal twist drill. Drop a suitable ball bearing into the bush about 1/4 or 5/16 depending on the spindle size .Drill the end of the spindle so that a
1/8 or 3/16 ball bearing fits in to just over half its depth and peen it in with a dot punch. eh voila hardened steel point contact. fill with oil to taste.
_
Hi guys I know this isnt a class piece of gear but I think the bearing
I made for my home built TT may be of use and its dead simple-
When you make the spindle support bush it will probably have the drill
angle left at the bottom of the tube, 118 degree vee for a normal twist drill. Drop a suitable ball bearing into the bush about 1/4 or 5/16 depending on the spindle size .Drill the end of the spindle so that a
1/8 or 3/16 ball bearing fits in to just over half its depth and peen it in with a dot punch. eh voila hardened steel point contact. fill with oil to taste.
_
If you Know someone with a model lathe you can still use this simple thrust bearing by turning a top hat bush to fit in the end, to carry the small bearing .It does, though , mean that the the support bush in the deck has also to be inverted TOP HAT in section, as in the original post I forgot to mention this " MINOR " point. ha ha
Incidently always drill and ream bushings first then turn and polish shafts to fit ITS A LOT EASIER to achieve the tolerances required
cos you can emery the final stage to within 0.0001"
Incidently always drill and ream bushings first then turn and polish shafts to fit ITS A LOT EASIER to achieve the tolerances required
cos you can emery the final stage to within 0.0001"
Attempt at well tempered bearing
Hi There,
I've tried to fit a well tempered look-a-like bearing to my scrapyard turntable . To be honest I've used some Thorens donated parts.
This is how I've proceeded: The bearing bushing of the turntable is of a thorens with 10 mm spindle. In this I fitted a teflon sleeve with 6 contact points as in a well tempered bearing. The sleeve has a bottom shaped by the end of the drill bit. In this, a Thorens spindle with a diameter of 7 mm was fitted.
Results: a very silently running but mightily wobbling platter! The tension of the belt is way to low to keep the platter straight up. So, I've to look for a shorter belt and a heavier motor housing because the motor (which is in a separate housing) is pulled towards the platter.
Does anybody have any ideas of the belt tension of a Well tempered turntable (or other good suggestions to better my approach)?
MArco
Hi There,
I've tried to fit a well tempered look-a-like bearing to my scrapyard turntable . To be honest I've used some Thorens donated parts.
This is how I've proceeded: The bearing bushing of the turntable is of a thorens with 10 mm spindle. In this I fitted a teflon sleeve with 6 contact points as in a well tempered bearing. The sleeve has a bottom shaped by the end of the drill bit. In this, a Thorens spindle with a diameter of 7 mm was fitted.
Results: a very silently running but mightily wobbling platter! The tension of the belt is way to low to keep the platter straight up. So, I've to look for a shorter belt and a heavier motor housing because the motor (which is in a separate housing) is pulled towards the platter.
Does anybody have any ideas of the belt tension of a Well tempered turntable (or other good suggestions to better my approach)?
MArco
baggins said:
In the "real world of machining" the exact opposite applies. You would "hone" the bushings to fit the shaft which ideally would be O.D. ground for size, straightness, and proper surface finish.
If you're a garage machinist then Baggins way will work but taking emery cloth to a shaft will not deliver exacting tolerances.
Well-tempered TT bushing
I see that one can actually buy the WTT bushing for $215. Does anyone know what the spindle diameter is, and does it vary with the TT model (and if it doesn't, why you have to specify the TT it's for when you buy the bushing)?
I must say that on paper this looks a very elegant solution to the bearing noise problem. I'd be glad to hear comments from those with mechanical engineering knowledge.
Regards.
Aengus
I see that one can actually buy the WTT bushing for $215. Does anyone know what the spindle diameter is, and does it vary with the TT model (and if it doesn't, why you have to specify the TT it's for when you buy the bushing)?
I must say that on paper this looks a very elegant solution to the bearing noise problem. I'd be glad to hear comments from those with mechanical engineering knowledge.
Regards.
Aengus
Vinyl-Addict said:
Isn’t that why this is “diyAudio”?
Even the best-equipped home workshop is unlikely to have precision grinding facilities and honing a bore of about 15mm is equally unlikely. Given that, traditional methods of the kind that were taught for a very long time do achieve high precision results (Check out a good ship’s chronometer or any engine by Napier) but skill, practice and a lot of time is needed,
I think for a home workshop (or even a toolroom) one-off, shaft-to-bore is the way to go. It’s also being done in production millions of times a day wherever a ball bearing is being used….
jeff spall said:
I was responding to Baggins mention of this:
ITS A LOT EASIER to achieve the tolerances required
cos you can emery the final stage to within 0.0001"
I'd like to see the process for obtaining this level of tolerance in your garage and how you inspect it to prove 0.0001 tolerance.
BTW, I'm not saying you can't build a good bearing in your garage.
Well, for inspection a mixture of 19th century and modern methods.
internal: go/no-go plugs
external: good modern Mitutoyo digital micrometers.
Don't forget you only need one and the fit of shaft to bore is the critical factor, not adherence to drawings. That's how watchmakers achieved great precision without any way of measuring their work.
The arms I build do need to achieve that kind of precision in the bearing carriers and bearing shafts and i really inspect them by trial fit and test. they are designed around the available machining facilities.
To achieve the precision, again a mixture:
- In my "garage' a good modern lathe with 2-axis DRO (I'm in awe of the glass slides that have a test certificate that shows a few microns deviation over 600mm)
- A good knowledge of of the kind of workshop practice that's available to most amateurs
- Intelligent design for the tools
- Patience and no commercial restraints
- 40 year's experience
in me "garage" (i work metric nowdays!):
internal: go/no-go plugs
external: good modern Mitutoyo digital micrometers.
Don't forget you only need one and the fit of shaft to bore is the critical factor, not adherence to drawings. That's how watchmakers achieved great precision without any way of measuring their work.
The arms I build do need to achieve that kind of precision in the bearing carriers and bearing shafts and i really inspect them by trial fit and test. they are designed around the available machining facilities.
To achieve the precision, again a mixture:
- In my "garage' a good modern lathe with 2-axis DRO (I'm in awe of the glass slides that have a test certificate that shows a few microns deviation over 600mm)
- A good knowledge of of the kind of workshop practice that's available to most amateurs
- Intelligent design for the tools
- Patience and no commercial restraints
- 40 year's experience
in me "garage" (i work metric nowdays!):
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