To quote the Reynolds Rockett adverts, "On butter coated paper under water"
billG
skf has these miniature ball transfer units with 360 degree movement:
http://www.skf.com/us/products/othe...nits/miniature-ball-transfer-units/index.html
I have feeling of us suffering from highenditis as these and tungsten rods and whatnot are all more difficult to get your hands on than the original solution in all its simplicity (at least here they are).
No compromises usually means unneccesarily complicated design and unobtainium in materials. Though I'm all ears and eyes if someone can make the original design more simple and better.
http://www.skf.com/us/products/othe...nits/miniature-ball-transfer-units/index.html
I have feeling of us suffering from highenditis as these and tungsten rods and whatnot are all more difficult to get your hands on than the original solution in all its simplicity (at least here they are).
No compromises usually means unneccesarily complicated design and unobtainium in materials. Though I'm all ears and eyes if someone can make the original design more simple and better.
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realy so so intereresting subject 
gravity , weight sliding across a rod , a diamond tip tracing a pattern in a record groove . how we suppose to manage things givin the parameters that's realy an interesting thing .
For a short moment ... some time ago , I was thinking about a completely different approach too . nothing bearing but fluid and floating properties of an air filled compartiment , movement controlled by magnetic force etc. sure .. i'm working on it right now but will only throw it into the group as soon as
things are working in practice .
Paul
gravity , weight sliding across a rod , a diamond tip tracing a pattern in a record groove . how we suppose to manage things givin the parameters that's realy an interesting thing .For a short moment ... some time ago , I was thinking about a completely different approach too . nothing bearing but fluid and floating properties of an air filled compartiment , movement controlled by magnetic force etc. sure .. i'm working on it right now
but will only throw it into the group as soon as things are working in practice .
Paul
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I admit I'm not happy with using ball bearings to slide sideway, too. I'm also not really happy with having the pivot so far above the record surface.
I'm working on an alternate design that separates the lateral motion from the vertical motion, damps the vertial motion, and has the vertical pivot near the record surface. I'll show pictures/design as it formulates. That's likely not to be immediate, as I need a turntable to mount it on first, the one I have just isn't good enough...
I'm working on an alternate design that separates the lateral motion from the vertical motion, damps the vertial motion, and has the vertical pivot near the record surface. I'll show pictures/design as it formulates. That's likely not to be immediate, as I need a turntable to mount it on first, the one I have just isn't good enough...
trail and error , play your wands and learn ( also from mistakes ) ! that's how good things are coming alive .
I'm still amazed about the performance of the arm as is , but trying to make things better is what our hobby is all about . meanwhile ... enjoy my first homebrew linear tonearm , spinning at least 5 albums a day
Paul
I'm still amazed about the performance of the arm as is , but trying to make things better is what our hobby is all about . meanwhile ... enjoy my first homebrew linear tonearm , spinning at least 5 albums a day
Paul
if that were true, I'm sure the Wright brothers, if still alive, would still not get anything to fly!
Designs that work are arrived at through knowledge of what is being designed, it's not (often) trial and error, or learnt from mistakes. The SME factory is not knee deep in failed tone arms!!!
if that were true, I'm sure the Wright brothers, if still alive, would still not get anything to fly!
Designs that work are arrived at through knowledge of what is being designed, it's not (often) trial and error, or learnt from mistakes. The SME factory is not knee deep in failed tone arms!!!
if that were true .. the Wright brothers would have been more stupid than anything else in the world
think again Paul
so how many times would they have had to crash before they learnt from their mistakes?
Most people who have produced innovative design have done so through scholarship, not bull ship.
thinking about the ball point pen idea, getting back OT, the ball point design was not meant to carry much weight (or force), and needs a lubricant (the ink) to work effectively. I like the idea, but I would have thought a beefier version was necessary, Zene. One also has to think stiction as well as friction.
Most people who have produced innovative design have done so through scholarship, not bull ship.
thinking about the ball point pen idea, getting back OT, the ball point design was not meant to carry much weight (or force), and needs a lubricant (the ink) to work effectively. I like the idea, but I would have thought a beefier version was necessary, Zene.
One also has to think stiction as well as friction.
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so how many times would they have had to crash before they learnt from their mistakes?
Most people who have produced innovative design have done so through scholarship, not bull ship.
thinking about the ball point pen idea, getting back OT, the ball point design was not meant to carry much weight (or force), and needs a lubricant (the ink) to work effectively. I like the idea, but I would have thought a beefier version was necessary, Zene.
Cats squirrel,
I'm not asking or wanting the pen nib to do anything other than holding the ball(s) stationary resting/sliding on the glass surface. A point contact with minimal friction. You guys don't like ball bearings, I'm eliminating them. I do not know if or how well this idea will work, but it is worth a shot.
BillG
personally, I like the idea of ball bearings (I'm using them in my design, but in a grooved format), but they need friction to work properly. Else, they just skid, which tends to negate their purpose.
If using skids, then ptfe on ptfe is about equivalent to wet ice on wet ice. Ironically, that may be too low friction!
If using skids, then ptfe on ptfe is about equivalent to wet ice on wet ice. Ironically, that may be too low friction!
Zene, others,
Engineering principles mean a huge deal, this goes without saying. However I must admit that I haven't been too cozy with many engineers over the years due to the fact I have found much better subjective sound going against the grain of what is deemed "right" over the years. First example, open loop output stages in amplifiers, adaptive bias negating any use of global negative feedback, sounds better than any globally wrapped stage I've heard.
My goal here was to design a linear arm which avoids the problems that some others run into. A carriage that slides well horizontally without sticking, which applies in both directions for off center records, smooth travel along the tube and minimal mass to have to stop to traverse an opposing direction. Decently damped vertical movement, which is helped immensely by the short arm as there is less vertical inertia to stop since all records have some sort of imperfection this ulmately leads to better tracking keeping the stylus firmly locked in the grooved, eg, ever watch an undamped 9" arm travel over a warp and see the stylus act very much like a cars suspension going over a speed bump?.
There needs to be more applied theory and less pen and paper rhetoric to convince me of the merit of new ideas as more than just a theoretical concept. At the same time, I've been around doing this long enough that I'm well aware of the ego that gets involved in this game.
Colin
Engineering principles mean a huge deal, this goes without saying. However I must admit that I haven't been too cozy with many engineers over the years due to the fact I have found much better subjective sound going against the grain of what is deemed "right" over the years. First example, open loop output stages in amplifiers, adaptive bias negating any use of global negative feedback, sounds better than any globally wrapped stage I've heard.
My goal here was to design a linear arm which avoids the problems that some others run into. A carriage that slides well horizontally without sticking, which applies in both directions for off center records, smooth travel along the tube and minimal mass to have to stop to traverse an opposing direction. Decently damped vertical movement, which is helped immensely by the short arm as there is less vertical inertia to stop since all records have some sort of imperfection this ulmately leads to better tracking keeping the stylus firmly locked in the grooved, eg, ever watch an undamped 9" arm travel over a warp and see the stylus act very much like a cars suspension going over a speed bump?.
There needs to be more applied theory and less pen and paper rhetoric to convince me of the merit of new ideas as more than just a theoretical concept. At the same time, I've been around doing this long enough that I'm well aware of the ego that gets involved in this game
.Colin
it would be interesting to measure the resonance peak of the short arm, compared to a more normal length arm, with the same cartridge.
I have seen a cartridge suspension act as you mention (on a well respected Rega 250), and concluded the cartridge was not compatible with the arm. Will this happen with a short arm, I wonder?
BTW, my design has an arm length of about 200mm, but it is variable.
I have seen a cartridge suspension act as you mention (on a well respected Rega 250), and concluded the cartridge was not compatible with the arm. Will this happen with a short arm, I wonder?
BTW, my design has an arm length of about 200mm, but it is variable.
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Interesting to read these lively discussions, so I will also throw a little pepper into the soup.
A couple of weeks ago (I don't want to search that entry again) someone mentioned the carbide rod offered on Epay. Well this rod is now relaxing in my tonearm stuff drawer. But as it sometimes happens, I also discovered that I have a box full of glass tubes and they are - o wonder - around 10 mm diameter.
So my first concern: are they straight? I happen to own a granite surface plate, and rolling these tubes on the plate I can say: they are as straight as they can be...
Then the question if a carbide rod is 'better' than glass. Well I don't know, but due to the wonders (again) of the Internet it's easy to find friction coefficients for almost every material combination. And what do we see here:
Glass/steel (dry): 0.5-0.7
Tungsten carbide/steel (dry) 0.4-0.6
So from that point it would be just a tiny bit better - think of that what you want.
And to end: I guess that the smallest of these transfer units (from posting 883) are worthy for doing a test. Just have to find a supplier...
I hope it's not too much pepper in the soup now!
Greetings, Hansrudolf
A couple of weeks ago (I don't want to search that entry again) someone mentioned the carbide rod offered on Epay. Well this rod is now relaxing in my tonearm stuff drawer. But as it sometimes happens, I also discovered that I have a box full of glass tubes and they are - o wonder - around 10 mm diameter.
So my first concern: are they straight? I happen to own a granite surface plate, and rolling these tubes on the plate I can say: they are as straight as they can be...
Then the question if a carbide rod is 'better' than glass. Well I don't know, but due to the wonders (again) of the Internet it's easy to find friction coefficients for almost every material combination. And what do we see here:
Glass/steel (dry): 0.5-0.7
Tungsten carbide/steel (dry) 0.4-0.6
So from that point it would be just a tiny bit better - think of that what you want.
And to end: I guess that the smallest of these transfer units (from posting 883) are worthy for doing a test. Just have to find a supplier...
I hope it's not too much pepper in the soup now!
Greetings, Hansrudolf
Brumm:
Glad to see you took my suggestion about getting a tungsten carbide rod. You are probably the only one besides me. Most people have no idea how hard and dense that material is and more importantly how dimensionally accurate it is. I was lucky the first time I checked ebay and scored a 1/2" x 12" long polished piece.
If you have access to a lathe, put the glass tubes in a 10mm 5c collet and spin them. When I did this on the 3 samples I have the results were bad ( bent and out of round ).
Joe
Glad to see you took my suggestion about getting a tungsten carbide rod. You are probably the only one besides me. Most people have no idea how hard and dense that material is and more importantly how dimensionally accurate it is. I was lucky the first time I checked ebay and scored a 1/2" x 12" long polished piece.
If you have access to a lathe, put the glass tubes in a 10mm 5c collet and spin them. When I did this on the 3 samples I have the results were bad ( bent and out of round ).
Joe
Joe,
How about trying that on Brumm's tubes? Another test, turn accurately fitting end plugs with centers, put your samples between centers and see how your tubes stack up. Turn them by hand, don't use a faceplate and lathe dog to spin them. Depending on the condition of "your" tubes and holding only one end in a collet, you could easily see major runout at the end 8 to 10 inches away from the collet face. I would trust the surface plate test way over the lathe/collet test.
BillG
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All or not so all ... Breaking initial friction is a problem and although I've suggested sliding that may not be good enough even thou the coefficient of friction of the parts is low. Teflon on Teflon is a good example. Most know a rolling connection is best. Good example is the train wheel. Steel on Steel. If they could slide with something they would do it, not magnetically suspended systems which are beyond most of our capabilities for tonearms. Or are they?
One of the worst/best cases of stiction (thanks Cat for the reminder) is two lapped steel blocks fit so well you can't get them apart.
Even a super smooth steel ball sliding (not rolling) on a glass or polished tungsten carbide is still going to suffer from stiction. I don't like the wear a ball may have as it doesn't turn. Every time anything changes 180 deg direction it must come to an absolute dead stop, not a rolling stop. It just sits there until acted upon. Nit picking, not on your life?
That seems to contradict my static bearing approach, but not really. That was only a suggestion to see if we could cure the problems of vertical movement of a ball bearing as it slide along the outer race with usually terrible friction. The vertical element movement of a record groove is much more critical than the horizontal. The vertical resistance needs to as close to zero as possible.
If someone can design a rolling lightweight sled that does not need an arm for stabilization I can show how to do exactly that for vertical movement. So far I'm drawing blanks. Two parallel rods did not seem to be the answer as stabilization could suffer.
Zene
One of the worst/best cases of stiction (thanks Cat for the reminder) is two lapped steel blocks fit so well you can't get them apart.
Even a super smooth steel ball sliding (not rolling) on a glass or polished tungsten carbide is still going to suffer from stiction. I don't like the wear a ball may have as it doesn't turn. Every time anything changes 180 deg direction it must come to an absolute dead stop, not a rolling stop. It just sits there until acted upon. Nit picking, not on your life?
That seems to contradict my static bearing approach, but not really. That was only a suggestion to see if we could cure the problems of vertical movement of a ball bearing as it slide along the outer race with usually terrible friction. The vertical element movement of a record groove is much more critical than the horizontal. The vertical resistance needs to as close to zero as possible.
If someone can design a rolling lightweight sled that does not need an arm for stabilization I can show how to do exactly that for vertical movement. So far I'm drawing blanks. Two parallel rods did not seem to be the answer as stabilization could suffer.
Zene
Zene, It occurs to me that once a record is playing no matter that the carriage changes direction either up or down it will not come to a dead stop relative to the surface of the support rod. even though the horizontal direction may reverse there will be vertical motion taking place due to some slight warp or runout in the record or platter. So I don't see stiction rearing its ugly head during normal play conditions.
BillG