Hi Graeme,
Some of these ideas would work, I am sure, and probably 'relieving' the shaft or the inside of the bushing would help to reduce excessive drag here.
Although I used to be very familiar with SU carbs (I spent many hours at the SU works, Wood Lane, Erdington, a long while ago), I dont recall now what the inside 'sleeve' or bore of the dashpot was like.
Does it have a pressed-in bushing (perhaps sintered metal) or does the piston rod move up and down in the bare alloy dashpot?
If the latter, I don't think the bearing (and its clearances) would last very well, as aluminium is relatively soft.
You could certainly machine up a bottom cap with a step in it (like a top-hat) so that it locates concentrically in the existing bore of the piston, as this bore is also concentric and well-finished, as is the outer surface of the piston, of course.
So long as you ensure the ball remains fixed to this cap, it wouldn't need to be made of hard metal, as there would be no relative movement or wear here. Brass would be quite easy to machine and it is easy to get a good finish when turning brass.
If you make a suitable depression in the underside, the fact that there is a much larger surface area of contact (as I said before), I would expect the ball to remain 'static' with the brass cap under normal circumstances. You could always use some Loctite, or even super-glue, just to make sure, and this would be close to ideal, I think.
The friction produced by the underneath portion of the ball rotating on the hard bottom plate, should be minimal, and this 'point-support' would be accurately centred with the axis of the shaft, which I consider to most desirable.
Here I depart from what Charles has said, and I can see no possible reason for the ball not to be centred, particularly from any engineering standpoint, unless one is simply unable to achieve this for whatever reason. It seems to me to be creating unnecessary friction, wear, possible 'noise' etc., but since Charles says it is deliberately done this way by someone, I don't doubt he is right, but perhaps he would kindly tell us who this is, and maybe suggest some reason for it, as it completely baffles me.
I haven't read the DIY TT thread, and, as I said before, I cannot comment on different ball materials, as I have not yet tried anything other than steel for myself, but I am sure they will make a difference both to the sound, and to the wear of the components. The best thing here is to try out various different types, which should be fairly easy with your suggested arrangement, to see what you think.
Being honest with my opinion, I still consider that the SU piston is rather larger in diameter than is ideal, but as previously mentioned, you will need to use what you can lay your hands on, and everything (unless purposely-designed for this job) will end up as some kind of compromise.
The accuracy, and surface finish of the SU piston was immaculate from my recollection (both plus points) and you have already suggested a good way to deal with the downthrust without too much difficulty, and the idea of damping the bore of the piston-rod cannot be a bad thing (try Blu-Tack, here).
However, for the other reasons I already explained, I would still consider Charles' inlet valve idea, as surface finish and accuracy are also good here, and the overall diameter is much better (3 plus points, in my view!).
The earlier concerns I explained in this regard were based on my experiences with valves/guides from some years ago, and mostly with cast-iron cylinder heads. It was common practice then to make the guides deliberately with oversize bores (with poorly machined bores, as well) so that when they were pressed into a cast-iron cyl-head under considerable pressure, they squashed down in diameter. Then one needed to ream the bores out to achieve correct clearances (with an expensive adjustable reamer) to suit the valve-stem diameters.
From what you said earlier, I guess with the valves and guides you already looked at before which had the silly 'clearances', these were of this type. However, if you can overcome this problem, and I don't doubt what Charles has said here, I guess that this would be a better way to go, provided you can do something about the thrust ball arrangement without too much trouble.
As I keep on saying, almost *anything* can be made to work after a fashion, it depends on how far you are prepared to go with costs and trouble etc., and as you say, you have plenty of time to consider this. However, I strongly believe that the centre bearing of any good-sounding TT is very important to get right, and I will do whatever I can to help in this regard.
Good luck, anyway.
Some of these ideas would work, I am sure, and probably 'relieving' the shaft or the inside of the bushing would help to reduce excessive drag here.
Although I used to be very familiar with SU carbs (I spent many hours at the SU works, Wood Lane, Erdington, a long while ago), I dont recall now what the inside 'sleeve' or bore of the dashpot was like.
Does it have a pressed-in bushing (perhaps sintered metal) or does the piston rod move up and down in the bare alloy dashpot?
If the latter, I don't think the bearing (and its clearances) would last very well, as aluminium is relatively soft.
You could certainly machine up a bottom cap with a step in it (like a top-hat) so that it locates concentrically in the existing bore of the piston, as this bore is also concentric and well-finished, as is the outer surface of the piston, of course.
So long as you ensure the ball remains fixed to this cap, it wouldn't need to be made of hard metal, as there would be no relative movement or wear here. Brass would be quite easy to machine and it is easy to get a good finish when turning brass.
If you make a suitable depression in the underside, the fact that there is a much larger surface area of contact (as I said before), I would expect the ball to remain 'static' with the brass cap under normal circumstances. You could always use some Loctite, or even super-glue, just to make sure, and this would be close to ideal, I think.
The friction produced by the underneath portion of the ball rotating on the hard bottom plate, should be minimal, and this 'point-support' would be accurately centred with the axis of the shaft, which I consider to most desirable.
Here I depart from what Charles has said, and I can see no possible reason for the ball not to be centred, particularly from any engineering standpoint, unless one is simply unable to achieve this for whatever reason. It seems to me to be creating unnecessary friction, wear, possible 'noise' etc., but since Charles says it is deliberately done this way by someone, I don't doubt he is right, but perhaps he would kindly tell us who this is, and maybe suggest some reason for it, as it completely baffles me.
I haven't read the DIY TT thread, and, as I said before, I cannot comment on different ball materials, as I have not yet tried anything other than steel for myself, but I am sure they will make a difference both to the sound, and to the wear of the components. The best thing here is to try out various different types, which should be fairly easy with your suggested arrangement, to see what you think.
Being honest with my opinion, I still consider that the SU piston is rather larger in diameter than is ideal, but as previously mentioned, you will need to use what you can lay your hands on, and everything (unless purposely-designed for this job) will end up as some kind of compromise.
The accuracy, and surface finish of the SU piston was immaculate from my recollection (both plus points) and you have already suggested a good way to deal with the downthrust without too much difficulty, and the idea of damping the bore of the piston-rod cannot be a bad thing (try Blu-Tack, here).
However, for the other reasons I already explained, I would still consider Charles' inlet valve idea, as surface finish and accuracy are also good here, and the overall diameter is much better (3 plus points, in my view!).
The earlier concerns I explained in this regard were based on my experiences with valves/guides from some years ago, and mostly with cast-iron cylinder heads. It was common practice then to make the guides deliberately with oversize bores (with poorly machined bores, as well) so that when they were pressed into a cast-iron cyl-head under considerable pressure, they squashed down in diameter. Then one needed to ream the bores out to achieve correct clearances (with an expensive adjustable reamer) to suit the valve-stem diameters.
From what you said earlier, I guess with the valves and guides you already looked at before which had the silly 'clearances', these were of this type. However, if you can overcome this problem, and I don't doubt what Charles has said here, I guess that this would be a better way to go, provided you can do something about the thrust ball arrangement without too much trouble.
As I keep on saying, almost *anything* can be made to work after a fashion, it depends on how far you are prepared to go with costs and trouble etc., and as you say, you have plenty of time to consider this. However, I strongly believe that the centre bearing of any good-sounding TT is very important to get right, and I will do whatever I can to help in this regard.
Good luck, anyway.
offset ball bearing
Hi,
this is the turntable bearing that I found by chance which has an offset ball location by design:
http://www.welltemperedlab.com/designtech.html
In my turntable the ball should be in the center (by design) but may be a bit off center because when you glue in the valve-guide you may not be able to avoid a very small misalignment. Also the valve stem is longer than the valve guide, so any less than perfect installation will naturally lead to less than perfect centering.
I also thought about a bearing design with open "bottom" where the valve stem exits the main base at the bottom, and you can place the ball manually, but I doubt that this leads to a better centering...
Also, as any non-centered motordrive exerts some lateral force on the platter and bearing-shaft, and there always is some amount of bearing clearance, the shaft will assume a non-centered position in the guide, causing the ball position to be off center too, at least to a negligible degree. With a little luck the misalignment in valve-guide position and the lateral force by the motor will set the ball right back to the center, just joking ;-)
My perfomance test was as follows: After installation and lubrication of the bearing, I turned the platter and pressed my ear on the main base and tried to hear, feel, perceive 'something', but apart from blood running through my veins, I could hear nothing. The second test is putting the needle on the main base, turning the amplifier fully up and then turning the platter -> no difference. So I thought, this bearing to be good enough for me...
Charles
Hi,
this is the turntable bearing that I found by chance which has an offset ball location by design:
http://www.welltemperedlab.com/designtech.html
In my turntable the ball should be in the center (by design) but may be a bit off center because when you glue in the valve-guide you may not be able to avoid a very small misalignment. Also the valve stem is longer than the valve guide, so any less than perfect installation will naturally lead to less than perfect centering.
I also thought about a bearing design with open "bottom" where the valve stem exits the main base at the bottom, and you can place the ball manually, but I doubt that this leads to a better centering...
Also, as any non-centered motordrive exerts some lateral force on the platter and bearing-shaft, and there always is some amount of bearing clearance, the shaft will assume a non-centered position in the guide, causing the ball position to be off center too, at least to a negligible degree. With a little luck the misalignment in valve-guide position and the lateral force by the motor will set the ball right back to the center, just joking ;-)
My perfomance test was as follows: After installation and lubrication of the bearing, I turned the platter and pressed my ear on the main base and tried to hear, feel, perceive 'something', but apart from blood running through my veins, I could hear nothing. The second test is putting the needle on the main base, turning the amplifier fully up and then turning the platter -> no difference. So I thought, this bearing to be good enough for me...
Charles
valve guide materials
I forgot to say, there are different valve-guide materials available. I use the AMPCO45 material valve-guide (by Rowe, CA). This is a very suited material and the guide was very well reamed with a very nice finish.
I also have some OEM valve guides laying around, made from cast iron.
Don't - do not - use them for a platter bearing, they really will not perform well.
Charles
I forgot to say, there are different valve-guide materials available. I use the AMPCO45 material valve-guide (by Rowe, CA). This is a very suited material and the guide was very well reamed with a very nice finish.
I also have some OEM valve guides laying around, made from cast iron.
Don't - do not - use them for a platter bearing, they really will not perform well.
Charles
If I did not already own a Well Tempered record player I would put the platter bearing high on a list of DIY alternatives - it could be easily built with a drill press, a tap and a little creative sourcing of bits - the machining would not have to be very precise and the end result works very well. The link provided previously describes the bearing pretty well better than I could briefly. The WT players are quite creative and would be much easier for a DIY to emulate or use as a starting point than many other designs.
Bill
Bill
Hi Graeme, Charles etc.,
I see now , but I still guess this WT set-up is rather more a 'one-off' design, which is quite different in engineering concepts from the sleeve and ball idea which Graeme is talking about.
This WT spindle is supported in *both planes* by 'fixed' teflon pads, which don't rotate and are, or course, more 'slippery' than say a steel or ceramic ball would be. I am sure it works well, though, if Graeme is considering other alternatives.
For what it is worth, I also tried Charles' ideas to test the set-ups in use, and used a medical stethoscope which is very helpful too.
However, I also found this did not tell the entire story, and whilst my remarks have always been that anything can be made to work, the differences which can be heard when *listening to records* are far from subtle.
I am of age-group who grew up with records (long before digital) and I have been playing about with TTs for over 40 yrs. I have made many DIY versions or modifications to different makes of TT, and have always been surprised just how 'sensitive' small changes can make to the sonic results.
Just take the differences due to an alternative make of the same grade of oil, for example, and I see the designer of this WT TT, went to great lengths over the choice of belt material in his development, which again, I know has a considerable influence on the sound.
I like Charles' idea of the valve and a *suitable* guide, which I also said I didn't know anything about before, but as he has found a good way of overcoming the problems I had originally referred to (and which Graeme discovered with VW valves/guides), my choice would be to consider this arrangement.
If that was done, I would grind a depression in the bottom of the valve stem, as suggested earlier, to take a ball of the chosen diameter. Then, the higher friction between the valve-stem and the ball (because of this greater contact area compared with the minimal contact made between the ball and the bottom plate) should effectively 'stick' the ball to the valve stem (or use some cyanoacrylate or Loctite to be certain) and then the ideal concentric ball arrangement would result.
If this was used, together with a bottom-plate (perhaps one of the OHC valve shims I suggested to Graeme before, when he asked about this plate) this would give a very smooth and quiet, low friction, long-lasting bearing, very similar to several commercial ones I have been involved with.
It is really up to Graeme to decide on the overall concept he wishes to adopt, together with whether he will purchase the Harley D. parts (which I would now recommend, incidentally) or whether he wishes merely to use the (almost?) free parts he can get hold of. Then he can take it from there, and maybe we can give some more specific suggestions regarding the finer details.
I see now , but I still guess this WT set-up is rather more a 'one-off' design, which is quite different in engineering concepts from the sleeve and ball idea which Graeme is talking about.
This WT spindle is supported in *both planes* by 'fixed' teflon pads, which don't rotate and are, or course, more 'slippery' than say a steel or ceramic ball would be. I am sure it works well, though, if Graeme is considering other alternatives.
For what it is worth, I also tried Charles' ideas to test the set-ups in use, and used a medical stethoscope which is very helpful too.
However, I also found this did not tell the entire story, and whilst my remarks have always been that anything can be made to work, the differences which can be heard when *listening to records* are far from subtle.
I am of age-group who grew up with records (long before digital) and I have been playing about with TTs for over 40 yrs. I have made many DIY versions or modifications to different makes of TT, and have always been surprised just how 'sensitive' small changes can make to the sonic results.
Just take the differences due to an alternative make of the same grade of oil, for example, and I see the designer of this WT TT, went to great lengths over the choice of belt material in his development, which again, I know has a considerable influence on the sound.
I like Charles' idea of the valve and a *suitable* guide, which I also said I didn't know anything about before, but as he has found a good way of overcoming the problems I had originally referred to (and which Graeme discovered with VW valves/guides), my choice would be to consider this arrangement.
If that was done, I would grind a depression in the bottom of the valve stem, as suggested earlier, to take a ball of the chosen diameter. Then, the higher friction between the valve-stem and the ball (because of this greater contact area compared with the minimal contact made between the ball and the bottom plate) should effectively 'stick' the ball to the valve stem (or use some cyanoacrylate or Loctite to be certain) and then the ideal concentric ball arrangement would result.
If this was used, together with a bottom-plate (perhaps one of the OHC valve shims I suggested to Graeme before, when he asked about this plate) this would give a very smooth and quiet, low friction, long-lasting bearing, very similar to several commercial ones I have been involved with.
It is really up to Graeme to decide on the overall concept he wishes to adopt, together with whether he will purchase the Harley D. parts (which I would now recommend, incidentally) or whether he wishes merely to use the (almost?) free parts he can get hold of. Then he can take it from there, and maybe we can give some more specific suggestions regarding the finer details.
Though not really on the topic of bearings, when we set up WT turntables we would give the belt a half turn going on to the motor pulley, the designer (I believe it was Firebaugh's (spelling?) idea) said it helped the belt leave the platter smoothly. Thought I would mention it while I was thinking of it. Can't say I ever tried to hear a differance, maybe some day.
As Bobken says small differences in turntables can make noticeable changes in the sound, I remember reading somewhere a long time ago a quote from a well known turntable designer that rung true for me, it basically said to design as technically correct as possible, and then make comprimises to make it sound good. That is not as well stated as I would like but hopefully the idea comes across.
Have fun designing and building, I always enjoyed designing record players, have done a couple, then I put together a WT based turntable (worked at a store, used a trade in base, a few new arm bits from WT, a machined arm bearing cup sold by the store, and ...) Someday I'll build the parallel tracking air bearing tt that been knocking around my head for 20 years or so! Hope your design sees the light of day sooner!!!
Bill
As Bobken says small differences in turntables can make noticeable changes in the sound, I remember reading somewhere a long time ago a quote from a well known turntable designer that rung true for me, it basically said to design as technically correct as possible, and then make comprimises to make it sound good. That is not as well stated as I would like but hopefully the idea comes across.
Have fun designing and building, I always enjoyed designing record players, have done a couple, then I put together a WT based turntable (worked at a store, used a trade in base, a few new arm bits from WT, a machined arm bearing cup sold by the store, and ...) Someday I'll build the parallel tracking air bearing tt that been knocking around my head for 20 years or so! Hope your design sees the light of day sooner!!!
Bill
Hello, I am new here. I was taking pleasure in reading the ideas about using automotive parts as a basis for bearing assemblies. One of the users questioned the use of auto related parts due to the loose tolerances. This had me thinking of a component that woul put a turntable bearing to shame. The component that I am thinking of is The Roosamaster fuel injection pump. This pump was used old John Deere farm tractors and in some American diesel engined car and pickup trucks. The pump is a rotary pump. The central shaft rotates in the center of a ported block and distributes fuel to the injectors like an ingnition distributor. The fit between the shaft and block is so tight that water will not pass between the parts. Finger prints will not allow the parts to fit together. If my memory serves me right, this shaft is about 1 inch in diameter and the block is about 4 inches in diameter. This would make a massive and very precise bearing assembly. Don Nebel
Hi Don,
This is an interesting one, but I am not familiar with the part you describe, regrettably.
How would you be able to lubricate the set-up, though, if even a finger-print prevents assembly of the parts? The clearances must be minute here, and normally there would need to be a suitable clearance so that capillary action will keep the lubricating oil between the 'sliding' surfaces of the rotating bearing.
Also, I am sorry to say that for TTs, as I have already said several times, I believe that 1" (approx. 25mm) is really too large in diameter to be ideal for this application.
Ideally, a much slimmer shaft with a suitable clearance between it and its sleeve, so that this annular gap between the two parts is fully taken up by the thickness of a film of the chosen oil, would be my goal.
Theoretically, there would be no friction due to this (as there should be no direct metal-to-metal contact) and no 'play', whatsoever, in this arrangement. The entire assembly needs to sit in a well of oil, and with a slow spiral groove (helix) cut into the sleeve wall, this will 'pump' oil upwards to maintain this film of oil around the shaft-to-sleeve gap right to the top, and with a drilling down the shaft's centre, the excess oil will drain back down again.
This gives a constant circulation of oil and helps to maintain the integrity of the (very important) oil film to eliminate any metal-to-metal friction/noise/wear, and whatever.
Then one merely needs to take care of the axial thrust, of course, and if this done equally carefully, a very good-sounding bearing will result, as I know.
There must be many possibilities of achieving quite good bearings (using already machined parts intended for alternative applications) but the shaft length, diameter and surface finish, together with that of the sleeve in which the shaft runs and the critical clearance between the parts (and the kind of metals used) are the important things to get right.
This is an interesting one, but I am not familiar with the part you describe, regrettably.
How would you be able to lubricate the set-up, though, if even a finger-print prevents assembly of the parts? The clearances must be minute here, and normally there would need to be a suitable clearance so that capillary action will keep the lubricating oil between the 'sliding' surfaces of the rotating bearing.
Also, I am sorry to say that for TTs, as I have already said several times, I believe that 1" (approx. 25mm) is really too large in diameter to be ideal for this application.
Ideally, a much slimmer shaft with a suitable clearance between it and its sleeve, so that this annular gap between the two parts is fully taken up by the thickness of a film of the chosen oil, would be my goal.
Theoretically, there would be no friction due to this (as there should be no direct metal-to-metal contact) and no 'play', whatsoever, in this arrangement. The entire assembly needs to sit in a well of oil, and with a slow spiral groove (helix) cut into the sleeve wall, this will 'pump' oil upwards to maintain this film of oil around the shaft-to-sleeve gap right to the top, and with a drilling down the shaft's centre, the excess oil will drain back down again.
This gives a constant circulation of oil and helps to maintain the integrity of the (very important) oil film to eliminate any metal-to-metal friction/noise/wear, and whatever.
Then one merely needs to take care of the axial thrust, of course, and if this done equally carefully, a very good-sounding bearing will result, as I know.
There must be many possibilities of achieving quite good bearings (using already machined parts intended for alternative applications) but the shaft length, diameter and surface finish, together with that of the sleeve in which the shaft runs and the critical clearance between the parts (and the kind of metals used) are the important things to get right.
Hi Don,
I didn't realise that this looks to be your first post here, until after my reply.
Welcome to the Forum, anyway, and please don't be deterred by my comments. I am sure Graeme who started this thread will be glad of all (sensible, as yours clearly was) ideas or suggestions relating to TT bearings etc.
I don't post much here, myself, but this topic I do have some experience of, so I am trying to assist Graeme and avoid him taking too many blind alleys.
I am sure some of the other members will welcome you in due course.
Kind regards,
Edit. Probably this post is not seen by very many members, so why not introduce yourself to the others with a "Hello, I am new" etc., perhaps?
I didn't realise that this looks to be your first post here, until after my reply.
Welcome to the Forum, anyway, and please don't be deterred by my comments. I am sure Graeme who started this thread will be glad of all (sensible, as yours clearly was) ideas or suggestions relating to TT bearings etc.
I don't post much here, myself, but this topic I do have some experience of, so I am trying to assist Graeme and avoid him taking too many blind alleys.
I am sure some of the other members will welcome you in due course.
Kind regards,
Edit. Probably this post is not seen by very many members, so why not introduce yourself to the others with a "Hello, I am new" etc., perhaps?
Hello Bobken, The injection pump that I mentioned is lubricated by the Diesel fuel that it pumps. I found it very interesting that water would not pass between the shaft and block yet fuel oil would pass through it. Can you imagine turntable bearings with this kind of precision. What would the cost be to make a bearing assembly with this kind of precision? I know that using the before mentioned parts is inpractible, but when I saw the posts discussing automotive parts, I thought I would throw this out there. If you are not familiar with what this injector pump looks like, do a Google search for: Roosamaster injection pump. Don Nebel
Fuel-injection pump TT bearings
Hi Don,
I agree wholeheartedly about the precisison in manufacture of pumps like these, and I have stripped and repaired a few (mainly Bosch) over the years, although, as I said, I haven't seen a Roosamaster (yet!).
Turbocharger parts are also extremely well made too, as they need to be with their speeds often running at anything between 50 -100 thousand RPM.
However, for this application, I can see some practical disadvantages, which would deter me from using them, myself, and this was what I was commenting on for Graeme's sake.
Firstly, unless one has 'unusual' access to these (or turbocharger)parts, they will be very costly to obtain new, and if they are worn-out (and have been scrapped) their performance will be unlikely to be very good due to the wear etc.
Secondly, they are (IMHO) simply unnecessarily large, generally speaking, which creates other headaches. With your engineering background, I am sure you appreciate that with an increase in shaft dia., not only will this increase the area of contact between the sliding surfaces by a factor of Pi, but also the 'moment' is increased as the 'area of interest' is further from the axis of the shaft (giving higher surface speeds).
When one considers that (usually) an elastic band will be driving the TT, and there is a relatively weak motor providing the motion as well, unless one takes care to avoid any variables, the overall speed stability will tend to suffer.
Unfortunately, in a normal domestic environment there will be temp. variations and with a relatively large contact area between shaft and sleeve and a higher moment as well, any change in viscosity in lubricating oil (and changes in high-tolerance clearances) due to temp changes, will have a much greater adverse effect on this speed stability.
Of course, there are ways of overcoming this, but for Graeme, I think it would be better to keep this potential to a minimum (at this early stage of his experiments) and, therefore, keeping the shaft diameter as small as practical is a distinct advantage in minimising such variations.
However, if Graeme happened to have some pump (or turbo) parts to hand for free, I would certainly try them out to see what he can make of them.
Otherwise, I would go for something more like Charles' idea, as the diameter of the shaft is more suitable (again IMHO) as I think it will result in an easier, but still very good, result.
Hi Don,
I agree wholeheartedly about the precisison in manufacture of pumps like these, and I have stripped and repaired a few (mainly Bosch) over the years, although, as I said, I haven't seen a Roosamaster (yet!).
Turbocharger parts are also extremely well made too, as they need to be with their speeds often running at anything between 50 -100 thousand RPM.
However, for this application, I can see some practical disadvantages, which would deter me from using them, myself, and this was what I was commenting on for Graeme's sake.
Firstly, unless one has 'unusual' access to these (or turbocharger)parts, they will be very costly to obtain new, and if they are worn-out (and have been scrapped) their performance will be unlikely to be very good due to the wear etc.
Secondly, they are (IMHO) simply unnecessarily large, generally speaking, which creates other headaches. With your engineering background, I am sure you appreciate that with an increase in shaft dia., not only will this increase the area of contact between the sliding surfaces by a factor of Pi, but also the 'moment' is increased as the 'area of interest' is further from the axis of the shaft (giving higher surface speeds).
When one considers that (usually) an elastic band will be driving the TT, and there is a relatively weak motor providing the motion as well, unless one takes care to avoid any variables, the overall speed stability will tend to suffer.
Unfortunately, in a normal domestic environment there will be temp. variations and with a relatively large contact area between shaft and sleeve and a higher moment as well, any change in viscosity in lubricating oil (and changes in high-tolerance clearances) due to temp changes, will have a much greater adverse effect on this speed stability.
Of course, there are ways of overcoming this, but for Graeme, I think it would be better to keep this potential to a minimum (at this early stage of his experiments) and, therefore, keeping the shaft diameter as small as practical is a distinct advantage in minimising such variations.
However, if Graeme happened to have some pump (or turbo) parts to hand for free, I would certainly try them out to see what he can make of them.
Otherwise, I would go for something more like Charles' idea, as the diameter of the shaft is more suitable (again IMHO) as I think it will result in an easier, but still very good, result.
concentricity
perhaps another way to get bearing concentricity with the spindle:
assume a flat bottom hole for the spindle. Drop in 3 bearings that will fit in the bottom, but won't be tight. Drop a 4th bearing on top of the first 3. Presto, instant alignment when the top bearing is pressed down.
And I guess you could tack a cup to the bottom of spindle with a slow drying adhesive and drop that in and get that presto aligned too.
perhaps another way to get bearing concentricity with the spindle:
assume a flat bottom hole for the spindle. Drop in 3 bearings that will fit in the bottom, but won't be tight. Drop a 4th bearing on top of the first 3. Presto, instant alignment when the top bearing is pressed down.
And I guess you could tack a cup to the bottom of spindle with a slow drying adhesive and drop that in and get that presto aligned too.
smaller shaft diameter
Hi Bob, Graeme,
if you think that an even smaller shaft diameter would be useful -> I lately took a look into a friend's Royal Enfield cylinder-head which he took off for tuning. This is of the famous Bullet 500 model, still manufactured in India, which is a great motorcycle by the way, if not the greatest
This engine has a smaller diameter valve-shaft, and the valve guide also looks like a quality piece made of brass or similar material (in any case, not cast iron).
The intake-valve-head is still of a large diameter (not as large as that of the Shovelhead, though), so that a platter is easily attached. The valve is also machined from all sides (including the head) so that an aligned platter installation will result.
The parts cost are EUR 20,- for the intake valve and EUR 8,- for the valve guide (taken from the german distributor ZMT parts list), which is also a bit cheaper than the HD valve setup by Rowe.
Charles
Hi Bob, Graeme,
if you think that an even smaller shaft diameter would be useful -> I lately took a look into a friend's Royal Enfield cylinder-head which he took off for tuning. This is of the famous Bullet 500 model, still manufactured in India, which is a great motorcycle by the way, if not the greatest
This engine has a smaller diameter valve-shaft, and the valve guide also looks like a quality piece made of brass or similar material (in any case, not cast iron).
The intake-valve-head is still of a large diameter (not as large as that of the Shovelhead, though), so that a platter is easily attached. The valve is also machined from all sides (including the head) so that an aligned platter installation will result.
The parts cost are EUR 20,- for the intake valve and EUR 8,- for the valve guide (taken from the german distributor ZMT parts list), which is also a bit cheaper than the HD valve setup by Rowe.
Charles
Balls!
Hi kjunom,
That is an excellent idea, with easy to obtain (and cheap) parts, and will be entirely self-centering, as you suggest.
Whichever way you look at it from the overall friction viewpoint, all of the TT supporting contact surfaces will be very small, too, so it wouldn't matter much where any rotating 'slippage' between the shaft and bottom plate takes place with this multiple ball idea.
By this I mean there would be no need to ensure that the previously-discussed single ball remained 'static' with the shaft, or whatever, so I don't think any cup arrangement would even be necessary. Although I earlier suggested that a concentric depression in the bottom of the shaft would be ideal (IMHO, when using a single ball), as I well know, this machining is not so easy to achieve without specialised equipment, especially if the shaft is already hardened.
I had heard of such an arrangement somewhere before, possibly in a different environment than TTs, but it has not been tried by me, and I had completely forgotten about this possibility.
This is exactly the kind of help I reckon Graeme would be glad of, in his present position, where he is still getting his thoughts together.
Hi kjunom,
That is an excellent idea, with easy to obtain (and cheap) parts, and will be entirely self-centering, as you suggest.
Whichever way you look at it from the overall friction viewpoint, all of the TT supporting contact surfaces will be very small, too, so it wouldn't matter much where any rotating 'slippage' between the shaft and bottom plate takes place with this multiple ball idea.
By this I mean there would be no need to ensure that the previously-discussed single ball remained 'static' with the shaft, or whatever, so I don't think any cup arrangement would even be necessary. Although I earlier suggested that a concentric depression in the bottom of the shaft would be ideal (IMHO, when using a single ball), as I well know, this machining is not so easy to achieve without specialised equipment, especially if the shaft is already hardened.
I had heard of such an arrangement somewhere before, possibly in a different environment than TTs, but it has not been tried by me, and I had completely forgotten about this possibility.
This is exactly the kind of help I reckon Graeme would be glad of, in his present position, where he is still getting his thoughts together.
Getting shafted!
Hi Charles,
More useful info for Graeme, I hope.
Most of the shafts I have seen, and made myself, have been in the 10mm. dia. range, so I guess that quite a lot of automotive valves would be quite suitable for this purpose. A few mm. either way would not be any big deal, but going much larger will tend to make the speed stability issues harder, as I have explained, and this is not needed for strength as 10mm. would be plenty strong enough.
In my youth (!) I used to modify BMC 'A' Series engines (amongst others) for racing and rallying purposes. For top results, we used to install sodium-filled valves (for better cooling) and Hidural-Bronze valve guides. I guess these guides you refer to will probably be of a similar material, as brass alone wouldn't be so good here, although it is probably tough enough for TTs.
This Hidural Bronze was an alloy of hiduminium & dural (hence HI- DURAL) and probably some other metals (copper & tin etc. for bronze) if I recall correctly, and would be excellent as the sleeve for a TT, I reckon.
You are also quite right to comment on the 'finish' of the valve head, of course, unless Graeme can machine this for himself, as this does need to be flat and true for his purposes. I think a lot of valves are left unmachined on their tops, and although reasonably accurate from the forging process in manufacture, this would not be good enough for Graeme's purposes.
When we used 'pressed in' valve-guides which then needed subsequent reaming before use, it was normal practice to allow slightly higher valve-stem - to- guide 'clearances' with exhaust valves, to account for their greater expansion due to the higher temps. exhaust valves run at.
I mention this because if one uses guides which are already 'finished' (like you have used) and don't require any reaming, it may be that these clearances are also deliberately marginally different, and this could give an alternative choice of clearances, perhaps, but this is just a guess and would need to be looked into.
Actually, I am in the very fortunate position of having full workshop facilities of my own, including a small Austro-Swiss model-makers/ clockmakers lathe, which enables me to make all my own bearings, nowadays.
However, I have not forgotten how difficult it is when you need to source these parts from 'ready-made' components, as Graeme is now doing, and some very good ideas are already evolving in this thread.
Hi Charles,
More useful info for Graeme, I hope.
Most of the shafts I have seen, and made myself, have been in the 10mm. dia. range, so I guess that quite a lot of automotive valves would be quite suitable for this purpose. A few mm. either way would not be any big deal, but going much larger will tend to make the speed stability issues harder, as I have explained, and this is not needed for strength as 10mm. would be plenty strong enough.
In my youth (!) I used to modify BMC 'A' Series engines (amongst others) for racing and rallying purposes. For top results, we used to install sodium-filled valves (for better cooling) and Hidural-Bronze valve guides. I guess these guides you refer to will probably be of a similar material, as brass alone wouldn't be so good here, although it is probably tough enough for TTs.
This Hidural Bronze was an alloy of hiduminium & dural (hence HI- DURAL) and probably some other metals (copper & tin etc. for bronze) if I recall correctly, and would be excellent as the sleeve for a TT, I reckon.
You are also quite right to comment on the 'finish' of the valve head, of course, unless Graeme can machine this for himself, as this does need to be flat and true for his purposes. I think a lot of valves are left unmachined on their tops, and although reasonably accurate from the forging process in manufacture, this would not be good enough for Graeme's purposes.
When we used 'pressed in' valve-guides which then needed subsequent reaming before use, it was normal practice to allow slightly higher valve-stem - to- guide 'clearances' with exhaust valves, to account for their greater expansion due to the higher temps. exhaust valves run at.
I mention this because if one uses guides which are already 'finished' (like you have used) and don't require any reaming, it may be that these clearances are also deliberately marginally different, and this could give an alternative choice of clearances, perhaps, but this is just a guess and would need to be looked into.
Actually, I am in the very fortunate position of having full workshop facilities of my own, including a small Austro-Swiss model-makers/ clockmakers lathe, which enables me to make all my own bearings, nowadays.
However, I have not forgotten how difficult it is when you need to source these parts from 'ready-made' components, as Graeme is now doing, and some very good ideas are already evolving in this thread.
I think im going to use the su carb innards.
I like the idea for a few reasons,
firstly the top of the tube is threaded so i can easily fit a plug to rest on top of the ball (does that make sense?)
Also, the center rod is a tube so i can fill it with resin, or similar, to help reduce vibration into the plinth as it wont ring like a hardend steel rod.
Also, there is a natural oil reservoir so oil will be drawn up the shaft.
It all seems quite easy to adapt, although i dont have the parts in front of me to determin details.
The clearance is perfect, the surfaces are very smooth, maybe micro polished.
It all seems very good, exept the fact that the shaft is probably around 15-17mm.
This is why i think ill clearance the middle of the shaft to reduce drag, and go with a heavy platter.
It will also be easy to make the bearing sit 5 mm down inside the rod so it can sit in its own oil bath.
I will be able to turn small pieces so making the other pieces shouldnt be a problem.
I was thinking of making a MDF platter for cheapness, and adding weight with lead. As long as i can balance it well. Ill see if i can take it to an automotive engineer, they balance flywheels so may be able to help.
I was then going to add 3 spikes to the platter and sit an acrylic platter on top. This platter will have the center pin so any resonance from the bearing will have trouble getting to the record.
As i mentioned somewhere else, i want to keep it cheap, without much compromise, so i can spend the money on a decent arm and the motor.
I guess i can sink about 750-1000 GBP into the whole deck, including cartridge.
I may still look into valves and other options, just because the diameter of the shaft is better. However, if the clearencing of the shaft i mentioned works, then its not a problem.
Once i have the parts, ill let you know what seems to work.
One last thing, can i forget motors ect till i have the platter/bearing sorted?
Or do i need to make sure the platter in exactly a certain diameter? The belt will go around the platters diameter.
I know nothing about motors/power supplies/pully diameters yet. Can it always be made to work, no matter what the platter diameter?
I like the idea for a few reasons,
firstly the top of the tube is threaded so i can easily fit a plug to rest on top of the ball (does that make sense?)
Also, the center rod is a tube so i can fill it with resin, or similar, to help reduce vibration into the plinth as it wont ring like a hardend steel rod.
Also, there is a natural oil reservoir so oil will be drawn up the shaft.
It all seems quite easy to adapt, although i dont have the parts in front of me to determin details.
The clearance is perfect, the surfaces are very smooth, maybe micro polished.
It all seems very good, exept the fact that the shaft is probably around 15-17mm.
This is why i think ill clearance the middle of the shaft to reduce drag, and go with a heavy platter.
It will also be easy to make the bearing sit 5 mm down inside the rod so it can sit in its own oil bath.
I will be able to turn small pieces so making the other pieces shouldnt be a problem.
I was thinking of making a MDF platter for cheapness, and adding weight with lead. As long as i can balance it well. Ill see if i can take it to an automotive engineer, they balance flywheels so may be able to help.
I was then going to add 3 spikes to the platter and sit an acrylic platter on top. This platter will have the center pin so any resonance from the bearing will have trouble getting to the record.
As i mentioned somewhere else, i want to keep it cheap, without much compromise, so i can spend the money on a decent arm and the motor.
I guess i can sink about 750-1000 GBP into the whole deck, including cartridge.
I may still look into valves and other options, just because the diameter of the shaft is better. However, if the clearencing of the shaft i mentioned works, then its not a problem.
Once i have the parts, ill let you know what seems to work.
One last thing, can i forget motors ect till i have the platter/bearing sorted?
Or do i need to make sure the platter in exactly a certain diameter? The belt will go around the platters diameter.
I know nothing about motors/power supplies/pully diameters yet. Can it always be made to work, no matter what the platter diameter?
Hi Graeme,
I thought you might go for the SU parts, and in several ways, it could turn out to be good choice. At least if its (nearly?) free, you have little to lose but your time.
As I already said, I remember the shaft fit and finish is excellent with SU pistons, and reducing the 'rubbing area' is probably well worth doing.
You haven't mentioned the material of the sleeve (or bush) which I asked about before, but if this is a sintered insert (I still don't remember), this also should be good.
If it was possible, in order to reduce the 'rubbing area', I would try to machine the bore of the sleeve, either with axial grooves, or better still, the spiral helix I said about. I would even do this with a Dremel/Minicraft or similar miniature drill arrangement with a suitable mini-grinder/cutting tool, as this could be done by hand with a bit of care.
The disadvantage of your suggestion, if I understand you correctly, is that you will end up with a 'step' in the shaft and the tiny clearance between the two parts will not be maintained all the way to the top of the bearing. If this is the case, you will lose the benefit of capillary action maintaining the oil film as well as it would be with an 'un-modified' plain shaft.
Also, bearing in mind the greater 'moment' I mentioned earlier, it would be technically better to reduce this 'rubbing area' by removing a part of the *overal diameter* of the shaft/bush, rather than reducing the *length* of the rubbing parts, if this makes sense to you.
You will still have plenty of support remaining to 'centre' and support the shaft with such a largish diameter, anyway, and if you were even able to effect this in a quite crude way, the resulting helix (providing it is the right way around) will pump the oil up the shaft to the top, which I do in my bearings, and I consider ideal.
I am not sure about auto engineers when balancing is concerned, as their set-ups are usually quite specific, and they may have difficulty in 'mounting' the platter, but it is certainly worth a try.
Also, they normally deal with higher RPMs (circa 5K'ish, and above)
and they will look to balance both statically and dynamically. In case you don't know, dynamic imbalance is what you observe if you spin a cycle wheel, holding it by the spindle, and whilst it spins, the rim will try to wave up and down while you are holding it.
At merely 33.3 RPM, you dont need to worry quite so much about dynamic balance, and with a free-running bearing you should be able to balance a platter very well statically. By holding the arrangement so that one side of the platter is very low down compared with the opposite side (ideally the platter's diameter should be vertical, instead of horizontal, but this is usually almost impossible in practice as the bearing separates!), spin the platter and see where it finally comes to rest.
It is worth doing a few times for consistency, and then the lowest part of the platter needs some material removing (or weight adding to the diametrically opposite side as a counterbalance), as this lowest part is the heaviest. This will be a careful process of repetition, until (again ideally) the platter stops at different places each time, and then you know the balance is pretty good.
With motors, it will depend on whether you intend to use an AC motor, or a DC one, and there is another thread currently on this subject which I have commented on, and will be worth looking at.
If you choose to go DC, the speed (within reason) can be finally adjusted by varying the DC voltage, and this is relatively easy, and means the exact size of pulley and platter diameter are less critical.
However, with AC synchronous motors, the 'mains' frequency dictates the motor speed, so you will need to plan ahead if you go this route.
I hope this helps.
I thought you might go for the SU parts, and in several ways, it could turn out to be good choice. At least if its (nearly?) free, you have little to lose but your time.
As I already said, I remember the shaft fit and finish is excellent with SU pistons, and reducing the 'rubbing area' is probably well worth doing.
You haven't mentioned the material of the sleeve (or bush) which I asked about before, but if this is a sintered insert (I still don't remember), this also should be good.
If it was possible, in order to reduce the 'rubbing area', I would try to machine the bore of the sleeve, either with axial grooves, or better still, the spiral helix I said about. I would even do this with a Dremel/Minicraft or similar miniature drill arrangement with a suitable mini-grinder/cutting tool, as this could be done by hand with a bit of care.
The disadvantage of your suggestion, if I understand you correctly, is that you will end up with a 'step' in the shaft and the tiny clearance between the two parts will not be maintained all the way to the top of the bearing. If this is the case, you will lose the benefit of capillary action maintaining the oil film as well as it would be with an 'un-modified' plain shaft.
Also, bearing in mind the greater 'moment' I mentioned earlier, it would be technically better to reduce this 'rubbing area' by removing a part of the *overal diameter* of the shaft/bush, rather than reducing the *length* of the rubbing parts, if this makes sense to you.
You will still have plenty of support remaining to 'centre' and support the shaft with such a largish diameter, anyway, and if you were even able to effect this in a quite crude way, the resulting helix (providing it is the right way around) will pump the oil up the shaft to the top, which I do in my bearings, and I consider ideal.
I am not sure about auto engineers when balancing is concerned, as their set-ups are usually quite specific, and they may have difficulty in 'mounting' the platter, but it is certainly worth a try.
Also, they normally deal with higher RPMs (circa 5K'ish, and above)
and they will look to balance both statically and dynamically. In case you don't know, dynamic imbalance is what you observe if you spin a cycle wheel, holding it by the spindle, and whilst it spins, the rim will try to wave up and down while you are holding it.
At merely 33.3 RPM, you dont need to worry quite so much about dynamic balance, and with a free-running bearing you should be able to balance a platter very well statically. By holding the arrangement so that one side of the platter is very low down compared with the opposite side (ideally the platter's diameter should be vertical, instead of horizontal, but this is usually almost impossible in practice as the bearing separates!), spin the platter and see where it finally comes to rest.
It is worth doing a few times for consistency, and then the lowest part of the platter needs some material removing (or weight adding to the diametrically opposite side as a counterbalance), as this lowest part is the heaviest. This will be a careful process of repetition, until (again ideally) the platter stops at different places each time, and then you know the balance is pretty good.
With motors, it will depend on whether you intend to use an AC motor, or a DC one, and there is another thread currently on this subject which I have commented on, and will be worth looking at.
If you choose to go DC, the speed (within reason) can be finally adjusted by varying the DC voltage, and this is relatively easy, and means the exact size of pulley and platter diameter are less critical.
However, with AC synchronous motors, the 'mains' frequency dictates the motor speed, so you will need to plan ahead if you go this route.
I hope this helps.
it helps alot, thanks.
I like the helix idea, so basicaly i rifle the bush like a gun barrel?
I had already thought about the step, i was thinking of using the oil well for the ball to supply oil to the top section, but its easier to just do it your way.
Good news on the balancing, i can manage that myself then.
Ill read up on motors soon then before i start just to make sure.
As for the bush material, im not sure.
I think its hardened steel, the same as the shaft, i suppose it could be chromed brass, but i would have thought chrome wasnt very good to machine after to get the fit.
I think its steel, its cast into the dash pot.
I may use part of the dash pot, or i may cut the sleeve out, not sure yet.
I like the helix idea, so basicaly i rifle the bush like a gun barrel?
I had already thought about the step, i was thinking of using the oil well for the ball to supply oil to the top section, but its easier to just do it your way.
Good news on the balancing, i can manage that myself then.
Ill read up on motors soon then before i start just to make sure.
As for the bush material, im not sure.
I think its hardened steel, the same as the shaft, i suppose it could be chromed brass, but i would have thought chrome wasnt very good to machine after to get the fit.
I think its steel, its cast into the dash pot.
I may use part of the dash pot, or i may cut the sleeve out, not sure yet.
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