John
The vertical resistance increases as the bearing has to slide over a greater distance on the rod/tube to effect the same pivot angle. The increase in bearing mass is small compared to the mass of the whole carriage. My alarms just gone off. Got to run, will try to add more later.
Niffy
Niffy, Bill,
On the 4 bearing the spacing of the bearings was important for the lateral tracking, not the vertical. Vertical tracking, footing in the groove and on warps was and is superior over the 2 bearing two tube design. Can't have both though, and a longer arm is even worse regardless of implementation. What ive discovered is that in a linear arm its better to have a stiffer vertical pivot (sory tracking force gauge worshippers), and free lateral movement with enough load on the bearings to quell any potential chatter. Another addition has been some precarious filling with some 3m memory foam in the drilled out cavities in the carriage T. But at the end of the day, its just my take
Colin
My reply to John seems to follow nicely to your post.
The single tube 4 bearing design will certainly exhibit higher vertical friction than the double tube 2 bearing design especially if a large diameter tube is used. With the single tube I would expect vertical friction to increase as the bearings are moved further apart as the contact pressure will increase as the contact angle increases. This may be difficult to detect as the lateral friction will also be increasing and will probably dominate any change in sound quality.
Why does higher vertical pivot friction work better?
My thinking so far is that the friction acts like an additional damped effective mass. The effective mass of an arm resists movement of the cartridge, the higher the mass the more it resists. Friction also resists movement. There is more to it than this such as the damping effect that is responsible for the tracking force gauge inconsistency.
When moving to the two tube design from the single tube the overall vertical effective mass decreased with the decrease in pivot friction. This was largely overcome by your splendid new headshell that increased the effective mass once more. What also decreased with the change was the damping. It was this extra damping that helped control the tracking of warps.
These are just my initial thoughts so far and have probably got a couple of holes in them.
Niffy
Hi all participants in this interesting discussion.
We seem to have forgotten all about the merits or demerits of radial free play in the bearings. This is the condition found in the Cantus arm and which we have gone back to in the 2 tube 2 bearing design. For normal play of records having warp which does not cause the radial play of the inner race to be exceeded I think that the whole subject of vertical friction of the bearings against the tubes is moot. We still have vertical friction to contend with within the bearing(s) itself(s). My observations would indicate that this is the case with the most of my records. In setting up my arm I try to adjust the wand so it is level and the inner race is not biased to either side. Adjusting the arm height to vary the VTA will upset this neutral bias. Under ideal conditions VTA should be adjusted by tilting the cartridge without changing the equal free play of the bearing inner race. I would like to try such a VTA adjustment. This may cause difficulties by adding an extra joint. Adjusting VTA by shimming the cartridge should eliminate the extra joint problem and one could make a series or tapered shims of various front to back slopes. I've done this successfully in the past. I've not covered all the factors here, but it is a good start. Have at it guys.
BillG
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Hi Bill,
Without a doubt the bearing will have free play that adds to the vertical pivot without rocking in the groove for a limited time depending on the severity of warp. Since the 4 bearing was loaded differently there was no fre play and it would slide across the tube back and forth. This definately did help damp the vertical motion and create in effect higher vertical effective mass than free play knife edge, etc. my original 4 bearing could track a warp so severe you would never have thought it would be playable, a pivoted would have gone into fits trying to find equilibrium in between the speed bumps.
This is a crude, torturous yet fine example of just how well it would track a pristine lp, if it can track the torturous test it will sail with flying colours through the mint vinyl. This bearing free play is just another enemy to contend with, hence why I've lowered the counterweight mass low, and increased the headshell mass to increase vertical effective mass, and get some of that damping back that made the four bearing work so well in the vertical plane.
Colin
Without a doubt the bearing will have free play that adds to the vertical pivot without rocking in the groove for a limited time depending on the severity of warp. Since the 4 bearing was loaded differently there was no fre play and it would slide across the tube back and forth. This definately did help damp the vertical motion and create in effect higher vertical effective mass than free play knife edge, etc. my original 4 bearing could track a warp so severe you would never have thought it would be playable, a pivoted would have gone into fits trying to find equilibrium in between the speed bumps.
This is a crude, torturous yet fine example of just how well it would track a pristine lp, if it can track the torturous test it will sail with flying colours through the mint vinyl. This bearing free play is just another enemy to contend with, hence why I've lowered the counterweight mass low, and increased the headshell mass to increase vertical effective mass, and get some of that damping back that made the four bearing work so well in the vertical plane.
Colin
Hi all.
Another factor in the preloading of the bearings will be stylus drag. Depending on tracking force and groove modulation this will vary in the 0.4-1.5g range. A 1.4g tracking force will cause an average drag of about 0.7g. With the two bearing design, to balance the bearing so that it sits in the centre of its range of free play the bearing would need to be tilted by about 1.3degrees (for a 30g carriage) ldeally the glass rods would need to be tilted so the line through their centres was at the same angle. Neutrality biasing the bearings in this manner should give the lowest lateral friction. Unfortunately this will also give the lowest vertical friction.
Niffy
Another factor in the preloading of the bearings will be stylus drag. Depending on tracking force and groove modulation this will vary in the 0.4-1.5g range. A 1.4g tracking force will cause an average drag of about 0.7g. With the two bearing design, to balance the bearing so that it sits in the centre of its range of free play the bearing would need to be tilted by about 1.3degrees (for a 30g carriage) ldeally the glass rods would need to be tilted so the line through their centres was at the same angle. Neutrality biasing the bearings in this manner should give the lowest lateral friction. Unfortunately this will also give the lowest vertical friction.
Niffy
Niffy,
It's curious you mention this 1.3 degree bias. However this is so damn small its negligible. I run the cart with a slight downward tilt which biases the bearing away from flat for best sound Vta wise, gotta listen to those mids as they will tell all. There need to be a margin of error, even a small warp will change this bias drastically. Stylus drag is the main argument I've issued against the pure sideforce idea that some have on these arms. It's a resistive balance between too high, or low lateral movement against too low a vertical resistive force.
This last year of hands on has allowed me to seperate the BS from fact, and there is a lot of misleading still in audio, one must remember that at the end of the day I have no financial holdings in audio. There is a hell of a lot more precision in cutting music to acetate than there is is playback. Only the laquer is and cutting lathe are ever near close to perfect.
Colin
It's curious you mention this 1.3 degree bias. However this is so damn small its negligible. I run the cart with a slight downward tilt which biases the bearing away from flat for best sound Vta wise, gotta listen to those mids as they will tell all. There need to be a margin of error, even a small warp will change this bias drastically. Stylus drag is the main argument I've issued against the pure sideforce idea that some have on these arms. It's a resistive balance between too high, or low lateral movement against too low a vertical resistive force.
This last year of hands on has allowed me to seperate the BS from fact, and there is a lot of misleading still in audio, one must remember that at the end of the day I have no financial holdings in audio
. There is a hell of a lot more precision in cutting music to acetate than there is is playback. Only the laquer is and cutting lathe are ever near close to perfect.Colin
Colin
I totally agree 1.3degrees is tiny, it's still double the angle the arm will pivot on a severe warp.(one of the things I did as part of my investigation into arm design was measure the actual warp of a random selection of my collection. It was a long painstaking exercise but gave invaluable information). I am keeping my bearing axis horizontal to bias the loading slightly in order to minimize chatter. I only mentioned it for completeness sake.
I believe the best place to deal with record warps is at the record not the arm. My screw down reflex clamp virtually eliminates warps (the reason I measured all those records) and I'm seriously considering a ring clamp. If you have no warps you can have no warp wow, no warp induced tracking force problems and vta will remain constant. No arm can deal with warp induced vta variations as the majority of vta error is due to the surface angle of the record, the arms pivot angle make only a small contribution even with short arms. With flat unwarpped records the location of the pivot relative to the surface of the record and the arms centre of mass becomes much less critical. A descent clamp is as much a part of a tonearm as it is a part of the deck.
Niffy
I totally agree 1.3degrees is tiny, it's still double the angle the arm will pivot on a severe warp.(one of the things I did as part of my investigation into arm design was measure the actual warp of a random selection of my collection. It was a long painstaking exercise but gave invaluable information). I am keeping my bearing axis horizontal to bias the loading slightly in order to minimize chatter. I only mentioned it for completeness sake.
I believe the best place to deal with record warps is at the record not the arm. My screw down reflex clamp virtually eliminates warps (the reason I measured all those records) and I'm seriously considering a ring clamp. If you have no warps you can have no warp wow, no warp induced tracking force problems and vta will remain constant. No arm can deal with warp induced vta variations as the majority of vta error is due to the surface angle of the record, the arms pivot angle make only a small contribution even with short arms. With flat unwarpped records the location of the pivot relative to the surface of the record and the arms centre of mass becomes much less critical. A descent clamp is as much a part of a tonearm as it is a part of the deck.
Niffy
The thing we are trying to compensate with the dual rod rail is called "bearing shatter" , something we would never ever allow to happen with conventional tonearms something we don't find in a platter bearing for example , due to the oil film filling the fractional amount of play between spindle and bushing .
A little hard to implement in the LT arm I suppose . however , we might be able to put a small amount of load to the bearing , soft spring load or some other smart *** trick .
THX
Paul
something we don't find in a platter bearing for example , due to the oil film filling the fractional amount of play between spindle and bushing . A little hard to implement in the LT arm I suppose . however , we might be able to put a small amount of load to the bearing , soft spring load or some other smart *** trick .
THX
Paul
Paul
Did you mean "bearing chatter"? Bearing shatter is a phenomenon caused by excessive loading or speed, neither of which are likely to occur in this design.
My original design did not use conventional ball bearing but instead used pin bearings similar to those used in clocks and watches. I have double yokes each supporting a vee cup bearing with a wheel on an axil, with pins at the ends, between them. A pin bearing can give much lower friction than a ball race with less play, which is why they are used in watches. Conventional pin bearings use ruby for the vee cups. This is not suitable for tonearm design as ruby bearings need "end shake", a small clearance to prevent binding. This clearance combined with the hard materials would be a source of chatter. I manufactured my vee cups from Teflon. These give almost as little friction as ruby but with no end shake and a soft contact, eliminating chatter. Unfortunately the wheels I made were eccentric causing tracking problems. I purchased a lathe to make better wheels but the lathe was faulty. My current plan is to use conventional ball race bearings and a double rod track. This will give me three options.
1. Run a solid axil between the yokes with the ball race bearing in the middle and dispensed with the pin bearings.
2. Place the new bearing on my existing pin bearing axle but use oversized mountings so to lock the bearing and use the outer race as a wheel, using just the pin bearings for rotation.
3. Mount the ball race bearings on my existing axil and have both bearings free to rotate. You never know it might work the best.
I now have all the materials needed and hope to make the modifications over the next couple of weeks and will post any findings.
Niffy
Did you mean "bearing chatter"? Bearing shatter is a phenomenon caused by excessive loading or speed, neither of which are likely to occur in this design.
My original design did not use conventional ball bearing but instead used pin bearings similar to those used in clocks and watches. I have double yokes each supporting a vee cup bearing with a wheel on an axil, with pins at the ends, between them. A pin bearing can give much lower friction than a ball race with less play, which is why they are used in watches. Conventional pin bearings use ruby for the vee cups. This is not suitable for tonearm design as ruby bearings need "end shake", a small clearance to prevent binding. This clearance combined with the hard materials would be a source of chatter. I manufactured my vee cups from Teflon. These give almost as little friction as ruby but with no end shake and a soft contact, eliminating chatter. Unfortunately the wheels I made were eccentric causing tracking problems. I purchased a lathe to make better wheels but the lathe was faulty. My current plan is to use conventional ball race bearings and a double rod track. This will give me three options.
1. Run a solid axil between the yokes with the ball race bearing in the middle and dispensed with the pin bearings.
2. Place the new bearing on my existing pin bearing axle but use oversized mountings so to lock the bearing and use the outer race as a wheel, using just the pin bearings for rotation.
3. Mount the ball race bearings on my existing axil and have both bearings free to rotate. You never know it might work the best.
I now have all the materials needed and hope to make the modifications over the next couple of weeks and will post any findings.
Niffy
Hi Niffy ,
Perhaps "bearing play" would be a better phrase indeed !
However , it will make the bearing rattling freq. wise , which we must solve some way . I figure that we can minimize race bearing play by applying some sort of soft tension to either the inner or outer bearing race , and yep !! this of course adds some friction to the balls + race . but that's not a real issue because we can choose the amount of force applied to the bearing .
My guess is that option 2 you are mentioning in above post could be a very good one !! please keep us posted about your results / findings !!
Keep up the good works !
PS: wondering if it would be practical to apply a very little off-set to bearing positioning on the carriage ? sort of what happens in Colin's
first design ;-)
THX
Paul
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Paul
Thank you for your encouraging words.
I also think option 2 is most likely be the best. Not only are the pin bearings ridiculously low friction (give the wheel a gentle flick and they spin for ages) but this option has the no chatter. If I choose this option I'll pack the ball races with epoxy to prevent the balls from rattling inside what will then be solid wheels.
I will probably try option 3 first, the one with both bearing types free to rotate. If the axil rotates this will show that the pin bearings are the lowest friction. If the axil doesn't rotate the the ball races will be the lowest.
I will of course try all three options and the final arbiter will be my ears.
Niffy
Thank you for your encouraging words.
I also think option 2 is most likely be the best. Not only are the pin bearings ridiculously low friction (give the wheel a gentle flick and they spin for ages) but this option has the no chatter. If I choose this option I'll pack the ball races with epoxy to prevent the balls from rattling inside what will then be solid wheels.
I will probably try option 3 first, the one with both bearing types free to rotate. If the axil rotates this will show that the pin bearings are the lowest friction. If the axil doesn't rotate the the ball races will be the lowest.
I will of course try all three options and the final arbiter will be my ears.
Niffy
Hi Paul.
I didn't immediately reply to all the points in your last post as I knew I was missing something important.
Bearing chatter can be addressed in several ways. Peloading the bearing as previously mentioned, packing the races with grease or oil to damp any Internal movement or decoupling the bearings from the carriage. All of these options have negative effects, especially the last two.
What I had missed was that not once in this entire thread has anyone reported problems with bearing chatter. I don't think chatter is a problem that this design of arm suffers from. Are we trying to fix a problem that doesn't exist? If I'm not mistaken (Bill, please correct me if I'm wrong) in Bill's current set up he has achieved the best sound by biasing the bearing for minimum side load, is running his bearings dry and has a solid ccoupling of bearing to carriage. In other words doing the exact opposite to the solutions at the beginning of this post.
If it 'ain't broke don't fix it.
Niffy
Niffy,
Hi, you have remembered the details correctly. I think these bearings are going so slowly that they can't possibly chatter.
I'm very interested in your alternate bearing approach. Being a clock restoration guru, I have lots of experience with these bearings. In fact my engineering notebook has sketches of just such designs which I was contemplating prior to getting sidetracked onto Cantus style ball bearings. Perhaps I should pick up the clock bearings again and see how it goes.
Rgds,
BillG
Hi Bill.
The chatter I was referring to is not caused by rotation. Within the bearings the radial load is supported by only the balls at the bottom of the race. If axial load is low the rest of the components in the bearing will only be in light contact with each other. During record replay vibration from the stylus passes via the carriage to the bearings causing the loose components to rattle against each other producing further vibration which in turn is passed back to the cartridge. The effect occurs at discrete frequencies where the components resonate against each other. The effect is audible as a harshness associated with certain notes.
This is probably a moot point as cantus, clearaudio and the contributors to this thread all use unlubricated ball races and don't seem to suffer chatter. I have heard an old sme with shot bearings that suffered chatter.
Pin bearings are definitely worth investigation. They're relatively easy to make and cost a lot less than premium ball races.
Niffy
Hi Niffy ,
I couldn't give a better description of what happens when using unloaded ball bearings at almost zero speed . these gems needs SPEED to do their trick
That doesn't mean they can't be used in a tonearm , but we must be aware of their weaknesses in this particular design .
Are you willing to share the details of your bearing design .. as soon as you worked out something ?
Frank Schoeder was using an outer ball bearing race , and a smaller bearing inside of this one ! something simular could be done with your pinn/ball bearing proposal .
THX
Paul
Hi Paul,
"Frank Schoeder was using an outer ball bearing race , and a smaller bearing inside of this one ! something simular could be done with your pinn/ball bearing proposal . "
It's an inner ball bearing race that's on the outside... and the smaller ball bearing inside is offset to provide a preload on said bearing.
Niffy explained the effects of a "loose" bearing rather well.... all contact zones(bearings, press-fit or glued connections, etc...) in an arm require a constant, purpose-defined contact pressure. Any energy transfer change, chance of contact loss, etc... will lead to resonances/reflected energy: "harsh" sound in really bad cases, still very common are compromised detail retrieval and/or colorations.
Cheers,
Frank Schröder
"Frank Schoeder was using an outer ball bearing race , and a smaller bearing inside of this one ! something simular could be done with your pinn/ball bearing proposal . "
It's an inner ball bearing race that's on the outside... and the smaller ball bearing inside is offset to provide a preload on said bearing.
Niffy explained the effects of a "loose" bearing rather well.... all contact zones(bearings, press-fit or glued connections, etc...) in an arm require a constant, purpose-defined contact pressure. Any energy transfer change, chance of contact loss, etc... will lead to resonances/reflected energy: "harsh" sound in really bad cases, still very common are compromised detail retrieval and/or colorations.
Cheers,
Frank Schröder
Here are a couple of pics of my pin bearings. I hope the pictures are clear enough. I've shown them attached to the yokes of the carriage and separated for clarity. The attached wheel is 21mm diameter to give a bit of scale. The wheel is a little eccentric and is to be discarded.
The vee cup is just visible in the end of its mounting. The mounting is made from 3mm aluminium and is 13mm long. It's threaded for mounting and adjustment. The vee cup is fitted into a 1.6mm diameter hole in one end. The vee was made by inserting a short piece of 1.6mm teflon into the hole. The teflon was formed by pressing a heated former, a 40degree cone with a 0.65mm domed end, into it using a drill press keeping everything nice and square.
The axil is threaded 3mm aluminium again. The thread has been removed on the exposed section. The pins are 1mm diameter stainless steel with a 20degree cone with a 0.5mm domed end. They are press fit, with a bit of superglue for safe measures, into 1mm holes in the ends of the axils.
The wheel as shown is held in place by threaded hubs made of acrylic. I am hoping that these hubs, at 7.5mm diameter, will be large enough to lock the outer race of 3x10x4mm bearings allowing them to be used as wheels.
The overall length of the axil, from pin tip to pin tip, is 25mm. There is virtualy no play and this keeps the axil very stable with no wobble. The axils are also 60mm apart giving the carriage a very stable footing.
If you need any more details let me know. Unfortunatly I couldn't get the drawings to upload.
niffy