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Old 10th May 2010, 11:46 PM   #21
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Quote:
Originally Posted by max426 View Post
The pivot at the red arrow is stationary and at the blue area follows the slot or linear bearing as the arm moves across the record?
Sorry for the confusing drawing. The arm in the picture is a side view and fail to convey the tricycle idea. Just imagine all three wheels are V-groove or U-groove bearings. I drew another crude drawing. Essentially we have a track with two paralleled rods and in front of it we have a curved rod that can guide the arm and for the cartridge to move inside the Thales semi-circle.

Idea #1 is the tricyle idea above.

Idea #2 is to dispense the third wheel and replace it with a attaction magnet to follow a curved track right below the parallel track without being touched.

Idea #3 is to dispense the third wheel and replaced it with a guiding arm that pivots, which is probably what you have in mind. But to be precise geometrically the pivot has to have a cam system as a circular pivot will not preserve tangency at the cartridge. To get this curve the right shape, you have to plot it out on paper depending on where you want the place the arm between the pivot-to-spindle distance. Unless a geometry genius can show me a way to do it pivotally. The Thales arm does the guiding at the headshell which is what we want to avoid.

Of course one can make the tricycle independent of the arm wand to have a stable platform and then add a twin spike pivot on the arm wand for vertical movement. Since we have two wheels already can give us vertical movement, I thought why not use them. The arm assembling with twin spikes on the tricycle resembles the Ladegaard arm idea.

The curved rail is a brute force way of preserving tangency but still simple enough.

Another note is that the longer the effective length, the shorter the linear motion needs to travel. For a 12" arm the linear motion bearing only need to travel about 2 inches. I think 10" is a good compromise.

I hope this makes sense. Thanks again for your interest and feel free to comment and add ideas.
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Old 11th May 2010, 02:17 AM   #22
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I think this Robert Van Eps designed tonearm would benefit from using unipivot bearing for each armwand. It begs for it as it will simplify the design without the disadvantage of unipivot as the dual armwands would take out the azimith rocking. Conceptually similar to Thales Simplicity arm. If the geometry is figured out I believe the Van Eps arm using unipivot bearings have the potential to sound the best of the lot.

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Old 11th May 2010, 07:08 PM   #23
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Another picture of the new Thales Simplicity arm in action in a three-arm turntable at the recent 2010 Munich Show. It certainly looks more practical than the two arms of the Original model. Simplicity is correct!

To be honest, I fail to understand why the Original model has to be done such way that's so awkward to install for most turntable. Surely, one can design a guiding arm without being position so low. I am sure there are other ways to handle that. Well, at least the Simplicity sounds like a self critique.

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Old 12th May 2010, 11:26 PM   #24
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This picture is not as out of focus as the earlier one.

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Old 13th May 2010, 11:32 PM   #25
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More interesting patents:

http://www.freepatentsonline.com/3476394.pdf by R. W. Birch 1969

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http://www.freepatentsonline.com/4580258.pdf by Dinsdale and Birks 1986

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Old 14th May 2010, 12:09 AM   #26
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Here are some Exel files for download from a Japanese fellow who is like a mad scientist of all things analog. Fascinating stuff as he analyzes and calculates tracking error on these novel ideas including the Thales tonearm.

http://www7a.biglobe.ne.jp/~yosh/sitemap.htm --- sitemap, some text in Japanese

http://www7a.biglobe.ne.jp/~yosh/auto-offsetting%20arms.xls ---- Download

http://www7a.biglobe.ne.jp/~yosh/moving%20pivots.xls --- Download
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Old 22nd May 2010, 11:53 PM   #27
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More interesting tonearms.

chukai.ne.jp/~stail/free.html

chukai.ne.jp/~stail/susan.html

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Old 23rd May 2010, 03:44 AM   #28
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More rotary headshell, diy style.

www.chukai.ne.jp/~stail/kaiten.html

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The above pictures suggested to me that the best and easiest tonearm for this kind of mod is the Clearaudio Satisfy tonearm:

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Old 23rd May 2010, 08:06 AM   #29
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Default That's not a tone arm - that's a steam engine!

Simplicity is best when it comes to arms, and has been pointed out, the real driver for parallel trackers is the elimination of bias force. Mind you, the cost of that elimination is high. I wondered about parallel trackers and air pumps then gave up when I discovered how noisy even the quiet ones were.

It's a very pretty steam engine, though.
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Old 24th May 2010, 02:07 AM   #30
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Quote:
EC8010: "Simplicity is best when it comes to arms, and has been pointed out, the real driver for parallel trackers is the elimination of bias force. Mind you, the cost of that elimination is high. I wondered about parallel trackers and air pumps then gave up when I discovered how noisy even the quiet ones were."

Yes, simplicity is the best but much engineering is to start with complex design and then pare it down to the essentials. I want to figure out a way that is hopefully clever and yet simple to deal with in a tonearm design. If by adding an extra pivot point(s) can minimize anti-skating force and lower tracking error it might not still be worth it and is still simpler than using air bearing. As stated in my opening post, I want to pick people's brain by not using air bearing or even mechanical parallel designs. The topic is to use a pivot design without resorting to linear motion designs like rails and air bearings. I believe much innovation hasn't been exhausted yet.

Of course, the above example is just an extreme case of doing too much but I still appreciate the designer trying new things. One wouldn't appreciate simplicity until a complex issue is thought through. Once again, this is purely an intellectual exercise and for fun. Apparently I haven't really generated much interest. But it's not going to stop me from trying and I will keep marching to my own beat.

It's still more fruitful than talking about cables.
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