Batwing,
Having the wand on the same plane error wise would be ideal, but to do so the arm would have to be at least 6 inches to clear the platter or arm designed to fold away for record changing. I thought about this but then realized that can open another can of worms by needing super fine tolerances so that once set tracking wouldn't be off. Mechanically I like the fixed position mounting with the raised bar above the platter, it's solid and allows the arm to be short while allowing easy record changing.
Colin
Having the wand on the same plane error wise would be ideal, but to do so the arm would have to be at least 6 inches to clear the platter or arm designed to fold away for record changing. I thought about this but then realized that can open another can of worms by needing super fine tolerances so that once set tracking wouldn't be off. Mechanically I like the fixed position mounting with the raised bar above the platter, it's solid and allows the arm to be short while allowing easy record changing.
Colin
. Pic enclosed.
Hello vynuhl.addict
As you know, the total weight of your tonearm and its effective mass in the horizontal plane are identical. Isn't the effective mass in the vertical plane much less, considering that it pivots in the vertical plane?
Sincerely,
Ralf
As you know, the total weight of your tonearm and its effective mass in the horizontal plane are identical. Isn't the effective mass in the vertical plane much less, considering that it pivots in the vertical plane?
Sincerely,
Ralf
Last edited:
If I understand this correctly there is no theoretical difference in mass in between the horizontal and vertical plane. The reality in difference relates to the bearing rolling resistance in the horizontal plane vs. the sliding resitance of the bearings on the glass tube as the arm moves up and down. In the case of this arm those forces needed to overcome the resistances are pretty small and probably close to being the same in magnitude.
Not sure how to quantify this with my current equipment, but I will try when I finish up my test build. May have to wait a couple of weeks as I am leaving for Floyd Fest tomorrow.!!!
Not sure how to quantify this with my current equipment, but I will try when I finish up my test build. May have to wait a couple of weeks as I am leaving for Floyd Fest tomorrow.!!!
You guys have wetted my appetite with your enthusiastic posts so I've started ordering stuff.I've managed to get hold of some perspex sheet;alloy and carbon fibre tube and have some ceramic bearings winging it over from Acerracing and some 200mm long test tubes from fleabay.Trying to cut the groove down the side should prove interesting.If that doesn't work I'll go with the four bearings riding on top of the tube.Should prove interesting.
Thanks Colin I'll buy some the local sign maker stocks a variety of types and thicknesses so it shouldn't be a problem.I hadn't realised you had used such thin polycarb;guess my 10mm far too thick although perfect for the headshell.I was thinking more about having a reasonable gluing surface for the tubes than the weight but some drilling and cutting should reduce the weight without weakening hopefully.
Audiostar,
Just in the process right now of finishing a turntable. The motor is isolated on a lower portion, it uses easy to work with mdf in constrained layer, but uses very acoustically inert floor tile as the sandwich.!the upper plinth which contains the platter bearing and arm is isolated with rubber grommets from the lower half, results so far are no less than superb thus far. No acrylic platter happening here, as I have been using a superb cork/foam hybrid mat which I've used religiously for the last two years.
Colin
Just in the process right now of finishing a turntable. The motor is isolated on a lower portion, it uses easy to work with mdf in constrained layer, but uses very acoustically inert floor tile as the sandwich.!the upper plinth which contains the platter bearing and arm is isolated with rubber grommets from the lower half, results so far are no less than superb thus far. No acrylic platter happening here, as I have been using a superb cork/foam hybrid mat which I've used religiously for the last two years.
Colin
Never thought about the SME offset counter weight was a means to equalize inertia in the x,y axis. Rather I thought it was to compensate for balance due to the use of a bent tone arm on radial 2 axis pivot. That was my assumption at least, in reality I have little experience with the SME arms.
None of my other arms including my Triplanar have offset counter weight, but they also have straight tone arms.
If someone has a 3D modeling package like solid works, perhaps they could calculate the center of inertia for the two axis of the linear tracker and help com up with the ideal counter weight geometry. My former company had it but I have since retired and don't have access anymore. Would be an interesting thought exercise.
None of my other arms including my Triplanar have offset counter weight, but they also have straight tone arms.
If someone has a 3D modeling package like solid works, perhaps they could calculate the center of inertia for the two axis of the linear tracker and help com up with the ideal counter weight geometry. My former company had it but I have since retired and don't have access anymore. Would be an interesting thought exercise.
Last edited:
Have secured some length of 16mm borosilicate glass tubing for bearing race. It seems to be bigger than your design but I don't think it will be a problem as it is not a moving mass. Correct me if I am wrong though.
Now to the hobby store to get some bearings and the hardware store for the rest of the pieces. ;-) If I am lucky can have one built before I head to FloydFest this week.
Now to the hobby store to get some bearings and the hardware store for the rest of the pieces. ;-) If I am lucky can have one built before I head to FloydFest this week.
Just read through this interesting thread.
To recap and see if I am following this, the vertical bearing consists of the 4 ball bearing outer races sliding on the glass rod?? Also the mass of the entire assembly moves and rotates on the glass rod when it moves in the vertical axis?
Also, I am unclear on what was said about tracking warped records?
Pretty sure I read that it does well on off center records, but have you looked at the stylus carefully for horizontal offset under these conditions?
I was unable to look at the posted videos. And, I'm not putting Zoom player on my computer (had trouble with them before). Any chance of posting up to youtoobe??
Interesting project, seems like a simple path to a pretty high performing linear tonearm.
_-_-bear
PS a light smear of silicone or a suitable oil on the glass rod might further reduce the sliding friction of the vertical axis - if this is how it is operating.
If you consider how this "bearing" operates - or any bearing for that matter - initially any vertical force will be generated via pressure on the stylus. So, the stylus will deflect first, until it overcomes both the moving mass plus the friction inherent in the bearing. The additional friction in the bearing adds to the effective mass, and increases the force required to move the assembly. Then the assembly may well overshoot... the other half of this is depending on the stiffness/compliance of the particular cartridge, so the cantilever could well get "buried" before the arm assembly overcomes the threshold required for vertical motion. For stiffer higher tracking force cartridges, it might not be an obvious issue (A Denon DL-103 might be an example), but for lighter tracking, high compliance cartridges it could be a critical problem. Just thinking out loud.
EDIT: also occurred to me that most ball bearing assemblies have some slop between the inner race and the outer, meaning that if you place a shaft in the center and hold the outer solidly, the shaft can be made to wiggle a bit. So, to some degree you get more or less a point contact bearing in that axis of rotation. Of course that is limited, maybe even a degree or less, but sent out the length of the arm, that *might* be sufficient to provide enough motion in the vertical axis to track a flat LP. IF this is taking place then you end up with a bearing that has essentially two thresholds, one that is essentially nil friction, and then another after a teeny bit of motion that is much higher in friction... another random thought. Fwiw.
To recap and see if I am following this, the vertical bearing consists of the 4 ball bearing outer races sliding on the glass rod?? Also the mass of the entire assembly moves and rotates on the glass rod when it moves in the vertical axis?
Also, I am unclear on what was said about tracking warped records?
Pretty sure I read that it does well on off center records, but have you looked at the stylus carefully for horizontal offset under these conditions?
I was unable to look at the posted videos. And, I'm not putting Zoom player on my computer (had trouble with them before). Any chance of posting up to youtoobe??
Interesting project, seems like a simple path to a pretty high performing linear tonearm.
_-_-bear
PS a light smear of silicone or a suitable oil on the glass rod might further reduce the sliding friction of the vertical axis - if this is how it is operating.
If you consider how this "bearing" operates - or any bearing for that matter - initially any vertical force will be generated via pressure on the stylus. So, the stylus will deflect first, until it overcomes both the moving mass plus the friction inherent in the bearing. The additional friction in the bearing adds to the effective mass, and increases the force required to move the assembly. Then the assembly may well overshoot... the other half of this is depending on the stiffness/compliance of the particular cartridge, so the cantilever could well get "buried" before the arm assembly overcomes the threshold required for vertical motion. For stiffer higher tracking force cartridges, it might not be an obvious issue (A Denon DL-103 might be an example), but for lighter tracking, high compliance cartridges it could be a critical problem. Just thinking out loud.
EDIT: also occurred to me that most ball bearing assemblies have some slop between the inner race and the outer, meaning that if you place a shaft in the center and hold the outer solidly, the shaft can be made to wiggle a bit. So, to some degree you get more or less a point contact bearing in that axis of rotation. Of course that is limited, maybe even a degree or less, but sent out the length of the arm, that *might* be sufficient to provide enough motion in the vertical axis to track a flat LP. IF this is taking place then you end up with a bearing that has essentially two thresholds, one that is essentially nil friction, and then another after a teeny bit of motion that is much higher in friction... another random thought. Fwiw.
Last edited:
http://www.continuo.se/webb/glasror.JPG This is a good Shot of Bo's design showing the horizontal bearings. Bearing slack covers most small warps then if greater displacement is required the carriage is simply pushed up the wall of the glass tube and falls back after. You will find that dry clean surfaced will work best any contaminant even dust can bother the bearings lubricants are not a good idea. Best regards Moray James.
