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Simple wood tonearm with magnetic bearing
Simple wood tonearm with magnetic bearing
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Old 1st January 2018, 09:02 AM   #1
pixworld is offline pixworld  Sweden
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Default Simple wood tonearm with magnetic bearing

I have built this 13" all wood tonearm using a very simple magnetic bearing.
Seems to work just fine.
Complete built shown here:
HiFiForum.nu - Pix - Projekt Pukor & Trumpeter. Dagboken

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.
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Old 1st January 2018, 10:24 AM   #2
basreflex is offline basreflex  Spain
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great job, actually I expected juniper wood, the famous swedish butterknife wood.
I once built a tonearm using juniper to replace it on a pioneer PL12. the sound was stunningly open and clear.
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Old 1st January 2018, 06:48 PM   #3
pixworld is offline pixworld  Sweden
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Thanks,
Yes I have planed to try different types of wood
Juniper, and also slow fir doesn´nt sound that exotix, but it´s two very resilient type of wood.
The next arm, I will also glue the wood in sheets using the annual rings for stbility, and also leave a open chanel for the cartridge wires

Here is a closeup on the magnetic bearing
Click the image to open in full size.
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Old 1st January 2018, 06:56 PM   #4
basreflex is offline basreflex  Spain
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did you now that one of the secrets of the old pritchard tonearm was the slit to run the wires through. it was filled afterwards with some resin that expanded, and that made the arm stiffer.
I made my wire using a center wire of 0.05mm and having 5 wires of 0.03 wrapped around it. I cut a circle of single well carton with 5 side cuts and did hang the carton on the 5 0.03 wires. the 0.05 coaxial core was hung by a small weight through a hole in the center of the carton circle. simply by blowing to the side of the carton the 5 outer wires wrapped around the center.
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Old 1st January 2018, 06:58 PM   #5
basreflex is offline basreflex  Spain
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use copper saturated solder to reduce dissolving the wire into the solder. solder quickly. the copper dissolves at 10um per second into the solder.
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Old 2nd January 2018, 05:54 PM   #6
pixworld is offline pixworld  Sweden
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Yes, I have previously used that method when making twisted speaker cables.
Since my background in military design, I have some 0,4 mm kevlar string with three 0,05 mm internal twisted copper wires. Since most cartridges has four pinns, I guess I need to use two strings.
Perhaps I could glue these two strings on the arm-downside using super-glue, just the way ones glue strain gauges.
Here is another picture with the arm base
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Old 11th January 2018, 07:10 AM   #7
Cold Beer is offline Cold Beer  Croatia
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Looks very nice
Antiskating ?
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Old 11th January 2018, 07:40 AM   #8
Rodeodave is offline Rodeodave  Austria
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Simple wood tonearm with magnetic bearing
The Well Tempered Lab tonearms have antiskating implemented by twisting the suspension thread, maybe pixworld has done the same.

Very nice build!
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Old 11th January 2018, 06:14 PM   #9
Bare is offline Bare  Canada
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Very nice craftsmanship in that project.
Bit confused re the Magnetics though.
Seems like the mags simply centralize the arm while the Y (?) shaped wires (?) fitted into those inset brass tubes act as the actual bearing/ pivots.
Can't see what keeps the Two mags from eagerly sliding away / repelling/ / escaping each others magnetic field as fast as possible .
Or am I missreading ?

Last edited by Bare; 11th January 2018 at 06:16 PM.
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Old 12th January 2018, 10:51 PM   #10
rickmcinnis is offline rickmcinnis  United States
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Quote:
Originally Posted by Bare View Post
Very nice craftsmanship in that project.
Bit confused re the Magnetics though.
Seems like the mags simply centralize the arm while the Y (?) shaped wires (?) fitted into those inset brass tubes act as the actual bearing/ pivots.
Can't see what keeps the Two mags from eagerly sliding away / repelling/ / escaping each others magnetic field as fast as possible .
Or am I missreading ?
With admiration for the quality of the build I, too, find calling this a magnetic bearing a little presumptuous.

My first thought would be for the builder to experiment with more than two strings for the bearing like Pete Riggle does. I am using his arm and know that very fine sound is available from this approach. His arm is fully suspended from the top with what might be considered a less elegant way to stabilize the arm than the magnets. Unless as stated above the magnets are not absolutely attracted to each other in a line and you end up having to add something to keep them in check. If that is not the case you end up having to do something like Pete did and if you have to stabilize the magnets then you might as well do without it.

The more I think about it it would seem a very long wand would be required to minimize the upper magnet's displacement when making vertical movements? And would the change in attraction have some kind of effect on the stiffness of the bearing? It would introduce a change. Of course, a purely suspended arm would have a comparatively always "loose" bearing. AS I think about it if the two magnets do stay reasonably in line with each other at all times this has to be something worth trying. For all I know it is a concept as old as tonearms!!!

As i argue with myself I keep in mind: Compromise is the one thing we can be sure of. All that matters is which approach produces a sound we can easily convince ourselves has something to do with music in our systems. Sure would be nice if there was the one perfect way.

Not feeling able to make a good arm i went with Pete's. I could afford it and had the adjustability I wanted. Wish I could make my own arm! With Pete I enjoyed doing business with an audio craftsman.

Great admiration for this project.
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