Bruhn:
I see we think alike -- using good measurement techniques.
After hand spinning my 3 sample tubes in a 5c collet in combination with a dial indicator the results were bad even buy eye.
I was going to make a pair of tight fitting brass plugs,put 60 degree centers in them and hand spin them in a hardidge dead center fixture but after making one plug I noticed it would fit in only one other end of the three tubes --it would be a waste of time. I took a tubing micrometer and measures .002 to .004 inches in wall variance. Lets face it, they were designed to view the water level in a boiler and perfection is not needed for that task.
What makes the extruded glass tubing so problematic is the variances are different at different parts of the tube !! Perhaps you can get lucky and get a passable lot of tubing but why take the chance. Most folks here do have the measuring capability.
You need a factory ground and polished glass/ceramic tube/solid rod for best results or you can choose a factory ground and polished carbide rod---which ever is easier to obtain.
Joe
I see we think alike -- using good measurement techniques.
After hand spinning my 3 sample tubes in a 5c collet in combination with a dial indicator the results were bad even buy eye.
I was going to make a pair of tight fitting brass plugs,put 60 degree centers in them and hand spin them in a hardidge dead center fixture but after making one plug I noticed it would fit in only one other end of the three tubes --it would be a waste of time. I took a tubing micrometer and measures .002 to .004 inches in wall variance. Lets face it, they were designed to view the water level in a boiler and perfection is not needed for that task.
What makes the extruded glass tubing so problematic is the variances are different at different parts of the tube !! Perhaps you can get lucky and get a passable lot of tubing but why take the chance. Most folks here do have the measuring capability.
You need a factory ground and polished glass/ceramic tube/solid rod for best results or you can choose a factory ground and polished carbide rod---which ever is easier to obtain.
Joe
Zene:
I personally like the tungsten carbide rod better as it is much harder then glass, not fragile, dimensionally " perfect "and solid.
However a factory ground and polished glass or ceramic tube /solid rod would also work perfectly well. I strongly recommend keeping an eye on ebay under " carbide blank". A little patience goes a long way. There is a company called Innovative Carbide ( Google it )that will grind and polish a tungsten carbide rod any size and length you want, however be prepared to pay dearly for it ( around $100-$200 I would guess ). I bought a highly polished 5/8" diameter x 6" long carbide rod for $85 that I used for a turntable bearing spindle and it worked out perfectly.
If this is within your budget I say go for it. A ground and polished glass/ceramic tube will also be expensive since there is machine time involved and usually a large minimum order.
Good luck
Joe
I personally like the tungsten carbide rod better as it is much harder then glass, not fragile, dimensionally " perfect "and solid.
However a factory ground and polished glass or ceramic tube /solid rod would also work perfectly well. I strongly recommend keeping an eye on ebay under " carbide blank". A little patience goes a long way. There is a company called Innovative Carbide ( Google it )that will grind and polish a tungsten carbide rod any size and length you want, however be prepared to pay dearly for it ( around $100-$200 I would guess ). I bought a highly polished 5/8" diameter x 6" long carbide rod for $85 that I used for a turntable bearing spindle and it worked out perfectly.
If this is within your budget I say go for it. A ground and polished glass/ceramic tube will also be expensive since there is machine time involved and usually a large minimum order.
Good luck
Joe
Joe, thx for supply tips. Although the steel rod might be excellent comparing straightness and surface to surface the overall gain might be zillch or even negative even though I understand everything you say is probably true. Be nearly impossible to tell, unless using laboratory conditions (including listening tests). Hell, polished wood may actually sound better. There is little or nothing to be learned by just one guy sitting down and listening. There are hundreds/thousands of factors in such a test as you know. It's just one empirical data point on an infinite (ideally) bell curve to look at. A double blind test is not anywhere near my friends' bag. Mainly I'm going by the risk/reward factor. Neither rod is worth the gamble to me. At that price I might as well explore "air bearings". Not that I'm even contemplating one, but how does one explain the huge laterally mass moving of the damn things? We're getting down to grams and the Terminator looks like a tank.
I don't want this to sound like the cheap DIY way of thinking. Building something of a totally less quality copy of the real thing is not my idea if making any sort of gains. DIY means most of us cannot afford an engineering staff and the equipment to build things, not just, "I want to make a copy as cheap as possible".
All that said I'm pretty chicken with the bucks and am not going to use either rod. Polished Brass is my next look. Not as hard, but may grip just right with less bounce. Insert with a non-polished carbide steel rod to help keep straight or dampen the inside with something. I can buy dozens to try for one spendy rod.
Ball bearings, not balls (I looked at my ceramics a bit) would be the optimum choice for lateral movement.
I slid them along everything I could find (the cat was the best) and no surface was smooth feeling. Ball to ball is great.
Why aren't linear bearing given a good look? I rem only one comment (forgot) here that they were too heavy. It's very difficult to ask the bearing manufacturers about their use even though there are a few companies making tonearms with them. Seems as if removing many of the balls could get us closer to what we need? Maybe they only work with longer arms? Enough babbling Zene, go to work.
Thanks guys
I don't want this to sound like the cheap DIY way of thinking. Building something of a totally less quality copy of the real thing is not my idea if making any sort of gains. DIY means most of us cannot afford an engineering staff and the equipment to build things, not just, "I want to make a copy as cheap as possible".
All that said I'm pretty chicken with the bucks and am not going to use either rod. Polished Brass is my next look. Not as hard, but may grip just right with less bounce. Insert with a non-polished carbide steel rod to help keep straight or dampen the inside with something. I can buy dozens to try for one spendy rod.
Ball bearings, not balls (I looked at my ceramics a bit) would be the optimum choice for lateral movement.
I slid them along everything I could find (the cat was the best) and no surface was smooth feeling. Ball to ball is great.
Why aren't linear bearing given a good look? I rem only one comment (forgot) here that they were too heavy. It's very difficult to ask the bearing manufacturers about their use even though there are a few companies making tonearms with them. Seems as if removing many of the balls could get us closer to what we need? Maybe they only work with longer arms? Enough babbling Zene, go to work.
Thanks guys
Wilfried ... Looked at similar before, but did not follow up. Prob is getting a good rod to work with it. Spendy again. However, the rod could be smaller than bearing ID and just let it hang. Less balls, less friction. Or, two smaller parallel rods inside? Even less friction and the bottom side of the rods could be dampened or use a third rod for stiffness. Endless possibilities, thanks.
Zene
Zene
A little help here guys. I need to know what length to make the counterweight arm so I can plan on the queuing proximity to the main tube. I can't go farther with the main support until I know. Read that high compliance carts need the weight close to pivot point and low compliant carts need it farther away. I know it has to do with inertia and not just balance. No comprendo.
Thanks, Zene
Thanks, Zene
Hello staggerlee
I think that this is an excellent idea. During a warp the entire support rail would rotate thus eliminating the sliding friction between the carriage bearings and the support rail. The bearings must not be greased or otherwise lubricated.
Sincerely,
Ralf
I think that this is an excellent idea. During a warp the entire support rail would rotate thus eliminating the sliding friction between the carriage bearings and the support rail. The bearings must not be greased or otherwise lubricated.
Sincerely,
Ralf
Hello Zene
Linear bearings sound good on the surface. The reason I would not use them is as follows: The balls in a linear bearing are not sealed and isolated from the support shaft. Any dust particles and other debris deposited on the support shaft will be picked up by the balls and transported into the recirculating path of the bearing. In addition, the diameter of the support shaft determines the diameter of the linear bearing and thus its weight. For a 10mm shaft that bearing would simply be too heavy.
Ball bearings on the other hand may be sealed such that dust particles will not enter the bearing races. The diameter of the carriage bearings is not dependent on the diameter of the support shaft. Ball bearings for a tone arm application must not be lubricated in any way. They simply don't spin fast enough .
Please don't be impressed by tone arms using linear bearings on U-Tube. You don't know how much tracking force is being used to make that work. However, my hat is off to the maker for the obvious quality of the workmanship of that arm.
Sincerely,
Ralf
Linear bearings sound good on the surface. The reason I would not use them is as follows: The balls in a linear bearing are not sealed and isolated from the support shaft. Any dust particles and other debris deposited on the support shaft will be picked up by the balls and transported into the recirculating path of the bearing. In addition, the diameter of the support shaft determines the diameter of the linear bearing and thus its weight. For a 10mm shaft that bearing would simply be too heavy.
Ball bearings on the other hand may be sealed such that dust particles will not enter the bearing races. The diameter of the carriage bearings is not dependent on the diameter of the support shaft. Ball bearings for a tone arm application must not be lubricated in any way. They simply don't spin fast enough .
Please don't be impressed by tone arms using linear bearings on U-Tube. You don't know how much tracking force is being used to make that work. However, my hat is off to the maker for the obvious quality of the workmanship of that arm.
Sincerely,
Ralf
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To All
There has been much discussion about the material that the support shaft should be made of. McMaster-Carr (and maybe others) sells 6061 aluminum, hard anodized shafts in diameters ranging from 1/4" to 1 1/4". The are straight to .004"/foot and have a hardness of 70 Rockwell on the C scale. That is at least as hard as glass or carbide. Here is a link: McMaster-Carr. A 1/2" diameter, shaft 12" long costs $16.40.
Sincerely,
Ralf
There has been much discussion about the material that the support shaft should be made of. McMaster-Carr (and maybe others) sells 6061 aluminum, hard anodized shafts in diameters ranging from 1/4" to 1 1/4". The are straight to .004"/foot and have a hardness of 70 Rockwell on the C scale. That is at least as hard as glass or carbide. Here is a link: McMaster-Carr. A 1/2" diameter, shaft 12" long costs $16.40.
Sincerely,
Ralf
Ralf ... I'll take that as a, "not worth trying" and I agree.
BTW "no lube" is correct. I finally remembered all the different gyro bearings had no lube and my vile of them says that also. Good enough for the Navy, good enough for me. Also worked on the moon lander gyro, same thing. But one thing to remember, lateral damping is one of the criteria for better movement control if needed and that could possibly include lube. Wonder if we'll get to point of dragging a paddle thru a tough of STP under the sled? Hope not!
Zene
BTW "no lube" is correct. I finally remembered all the different gyro bearings had no lube and my vile of them says that also. Good enough for the Navy, good enough for me. Also worked on the moon lander gyro, same thing. But one thing to remember, lateral damping is one of the criteria for better movement control if needed and that could possibly include lube. Wonder if we'll get to point of dragging a paddle thru a tough of STP under the sled? Hope not!
Zene
The problem is that the tube is to heavy so you will still get sliding instead of rolling...
But if the carriage could be fixed and only be allowed to move sideways one could move the vertical movement down under the carriage hanging in a needle bearing (suppose thats the name for it
). But the accuracy will of course be dependent of the play atleast forward since the vinyl will drag the needle forward. I don't see the necessity to have any backside support - and wouldn't drag take care of any variations at macroscale? It will have a force upon it as long the needle is in contact with vinyl keeping the whole structure firmly set. The variations will be at macroscale keeping the variations in vta very low and this depending of the distance between the bearings in the carriage. So we need a extra stabilizer for the carriage - a dual vertical tube arrangement maybe?Use whatever rods you like but please report prefereably with a comparison report!
I will as a first step try out the original idea of V.A. to be able to compare. Then experiment with different rods, arrangements and so forth...
Brgds
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All,
Honestly, this has turned into an interesting thread, but I'm thinking we need to put an emphasis on concentrating the ideas into a working form, it would be very nice to see this turn into a hands on thread of which was started here. We would make the best progress this way I believe.
It needs to be assessed how much of a real world difference it would make first of all the impact that "imperfection" of the tube would realistically make on horizontal/vertical movement. We must keep physics in mind realizing that a slightly skewed under 1cm long cantilever is greater than a slightly warped tube whether it be glass or NASA material. Also, is vinyl pressed so perfect that this will make a difference beyond a altering of resonances. My results have been a healthy mix of empirical and subjective, it's amazing what the eyes and ears can do, never doubt those given tools.
Colin
Honestly, this has turned into an interesting thread, but I'm thinking we need to put an emphasis on concentrating the ideas into a working form, it would be very nice to see this turn into a hands on thread of which was started here. We would make the best progress this way I believe.
It needs to be assessed how much of a real world difference it would make first of all the impact that "imperfection" of the tube would realistically make on horizontal/vertical movement. We must keep physics in mind realizing that a slightly skewed under 1cm long cantilever is greater than a slightly warped tube whether it be glass or NASA material. Also, is vinyl pressed so perfect that this will make a difference beyond a altering of resonances. My results have been a healthy mix of empirical and subjective, it's amazing what the eyes and ears can do, never doubt those given tools.
Colin
Quite right Colin. At the speeds these imperfections are entered - I don't believe that they are audible. But then we have the psycological part knowing that my rod might not be as perfect as my neighbours ;-) .
Then again I welcome the different ideas of perfecting it but that will mostly take care of the psycology. It will also give new technical solutions of which a few might really improve your design. It's marvellous! But we are not against you but there might be ideas that will take us further - let us play and discuss even if it is your thread. We could start anotherone of course but it is a lot more fun if you choose to let us play on your ground were you hopefully would participate with an open mind.
Maybe I have missunderstood how you see us alter your design - sorry if thats the case. But there are admitably some technical flaws in the design that seeks their solution.
Brgds
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Ralf ... I used to play Robin Hood and always have arrows around for hobbies. I'll be using my one and only alloy carbon for my long (19") arm. Not even sure if you can buy a half dozen to get one.
Easton's top alum arrow is the Eclipse 7178-T9 (?) with .001 straightness full length. Max dia is 10.7mm. No idea of hardness. These you can buy one at a time.
Zene
Easton's top alum arrow is the Eclipse 7178-T9 (?) with .001 straightness full length. Max dia is 10.7mm. No idea of hardness. These you can buy one at a time.
Zene