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Old 6th November 2013, 05:37 PM   #1051
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Quote:
Originally Posted by lexx21 View Post
Spinning Wheel... are you using a glass rod and is it completely clean? Also are you using the same sized bearings that Colin used? How much of a deviation are you seeing?
Hi , a duran 10MM O.D. glass tube , bearings ( open type ) UL 610X-L 23 Switzerland . SMR106 RVS (Inox) minilagers van RMB (Zwitserland)

d=6mm

D=10mm

B=2,5mm

6x10x2,5mm


Aprox. 0,4 Gram deviation !

THX ,
Paul




5MM gap between them .. polished brass shim
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Old 6th November 2013, 05:40 PM   #1052
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Originally Posted by bgruhn View Post
Hi Paul and others trying to sort out the running of these magnificent linear mechanical tone arms.

Here is what I've come up with so far. For starters, go back and reread everything Bo Hansson has written on the subject. IIRC he suggests letting ones ears tell you when the tracking force is correct. For his arms (CANTUS) he never mentions a suggested tracking force. A ball park figure is what I wanted and tried all the tricks in the book to make my LT arm work at some reasonable figure. NO luck, I couldn't measure it. there was always the arm doing what it wanted and not what I thought I was asking it to do. Better results from ignoring the scales and just listening. Then the penny dropped. Never with existing scales and balances will it be possible to measure the vertical tracking force under the dynamic condition of playing a record, especially with the mechanical bearings rolling on the glass tube or rod. But will it be possible to set the counter weight so that when dropping the cartridge from a height that just allows the stylus to graze the recorded track repeatably. I tried it and yes one can achieve this degree of balance. Now take that digital scale you almost threw out and make some little lumps of putty or plasticine that weigh what you are trying to achieve for tracking force. Place a most likely candidate right above the stylus and listen. Once you have seen and heard the results I think you will be amazed at how well your arm tracks with a much lighter weight than you were expecting.

BillG
Thanks for the suggestions ..
THX
Paul
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Old 6th November 2013, 09:41 PM   #1053
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Location: Long Beach, California
I've been trying to upload some photos relevant to the issue of edge-polished bearings on vertical friction, along with explanatory text - and also detailing an alternate construction method for low-weight of the carriage/wand/headshell. The "failure to upload from computer" error has been consistent for many hours now. Previously I'd uploaded photos to this thread - and the current photos are well within parameters for size and resolution.

Anybody got a clue as to what the problem might be? I rebooted my computer several times.

John

p.s. Polished bearing edges seem to have little or no influence on vertical friction with either a polished SS rod or borosilicate glass tubing. Dry Teflon applied to the SS rod seems a very minor help. In both cases friction is very great.
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Old 6th November 2013, 11:11 PM   #1054
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Same problem at other thread to- so is not your computer.
Gabor
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Old 7th November 2013, 12:29 AM   #1055
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just a reminder that from Bo's point of view you want to have very low resistance in the horizontal plane and a high resistance in the vertical so that the arm is stiff in that plane. This is the preferred arrangement over the previous rolling knife edge design which allowed for resonance in the vertical plane. Best regards Moray James.
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Old 7th November 2013, 12:50 AM   #1056
bgruhn is offline bgruhn  United States
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John,
Sorry, I have no clue as to why you can't upload pics. Perhaps it will resolve.

This friction/stiction business is getting out of hand. I think we need to look at what we are trying to do, and what role friction plays in doing or not doing what needs to be done. For one thing, if an impulse comes along which kicks the arm upward, we don't want the arm to fly up to the limits of its travel. So friction can be a mechanical shock absorber (aka damper). By the same token, we don't want the arm to stay stuck at the top of its travel because the friction won't let it come down. So some friction will help us track a record. The value must allow unimpeded vertical motion of the cartridge to rise and fall with a warp. Intimate contact with the groove must be preserved. Right now I can't follow through on this line of analysis in real time. What I am requesting is that we all think this through to the best of our abilities to determine what is required and how any given parameter will allow our cartridge to meet the requirements. The shotgun in the dark approach may hit the target but we won't know it because we don't know what we are shooting at.

I'm anxious to see your pics.

Rgds,

BillG

Thanks Moray. That in part is one of the things I was driving at.

BG

Last edited by bgruhn; 7th November 2013 at 12:55 AM. Reason: more
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Old 7th November 2013, 01:23 AM   #1057
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BillG & Moray James,

Given what you've both written, then the polished-edge bearings and polished SS rod meet the criteria in spades. As to whether they might provide any added sonic benefit is unclear. I've got 7 photos of an alternate 'low mass' fabrication method, an a whole lot of text explaining the photos. Quite frustrating to get the whole thing written up, and the photos processed, and then no go loading to this thread. Maybe tomorrow - as Gaborbela has written above the problem is in other threads also.

There is a very clear rolling 'sound' difference (at high speed) between the bearings on glass and on polished SS. Much, much nicer on SS than on glass. Probably irrelevant.

Here's the alternate fabrication method teaser, or not as the case may be. My carriage (without cartridge, cartridge clips, wire, or counterweight, etc.) weighs in at 16.7 grams, with a total length of the wand/headshell at 8 3/8" (hence 6" for the counterweight end). I'm thinking, possibly wrongly, that that is pretty low mass - using balsa composite, magnesium, and a section of an Easton aluminum/carbon competition arrow. The bearing axles are 1/8" diameter aluminum tubing. Mostly all glued together. I've followed Colin's 'last testament' as closely as possible for the carriage dimensions.

If ChrisG is reading, do you have another nut underneath the top washer in your mount fixing the threaded rod securely to the washer along with the top nut - or is there only the top nut as seen in your latest photos? The photos don't show the underside of the top washer. Are the 3 leveling screws 'free' on the bottom washer? Thanks in advance if you can answer.

Polishing my (SS) rod [still],
John
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Old 7th November 2013, 04:53 AM   #1058
Bob690 is offline Bob690  Australia
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Quote:
Originally Posted by vynuhl.addict View Post
New developments!,


One thing im noting, as the glass tube gets smaller the lower the friction and the better the vertical pivot. This explains why I have no issues setting tracking with the 10 mm tube. I've since tried 4 fixed bearings and 5mm tube and the horizontal friction is lower along with a vertical pivot that is almost like having a wand pivot f its own!. More to follow, oh and this.comes with even better stability too.


Colin
Hi Colin,

Wondering what ever happened to the experiments with a smaller diameter tube (smaller than 10mm)??
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Old 7th November 2013, 07:47 AM   #1059
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Bob,


Was a no go, 10mm proved best overall and as has been correctly stated, we want horizontal friction low and vertical higher.


To all, on the bearing issues, I've inspected my 9mm bearings and realize they have very little edge to them, almost no bevel which explains alot of why I have had flawless success with them, maybe go for 8mm bearings as they are more common and work almost as well as 9mm. Also, my bearings are 3mm wide, maybe just maybe parts choice is mor important than I thought, as 12mm bearings did not work near as well. As the bearing gets larger I can see a need for degreasing, but not apparently necceassary for the smaller sizes it seems.


Colin
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Old 7th November 2013, 09:53 AM   #1060
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Another point which hasn't been addressed which I'm sure those who have built the arm can also point out. Any noise contributed by the bearings is dominate by any vinyl noise and to an even larger extent in some cases the noise of the record cutting lathe advancing between tracks. If we were to get very technical we could say potentially bearing noise would be higher with louder cuts with fewer lines per inch engraved but from my findings it's lower than the noise floor of vinyl in which I can't audibly hear with an lp playing. Worst case scenario it would be truly more audible on a runout groove, but, this noise is usually dominated by the rapid advancement of the cutting lathe. One thing that is astounding is just how noisy some lathes are and how easily that gets picked up by the cutterhead.


Colin
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