Angling for 90 - tangential pivot tonearms - Page 80 - diyAudio
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Old 2nd September 2014, 11:53 PM   #791
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Location: Prescott, Arizona
Default Hi David

I have to go into Town this minute, but I'll reply with more detail later tonight.

Sincerely,

Ralf
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Old 3rd September 2014, 06:40 AM   #792
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Default Hi David

Quote:
Originally Posted by AVWERK View Post
ST

Will you exhibit this year at CES?

Regards
David
I am not in the financial position to exhibit my tone arm. I made a transparent display case for my tone arm and carried it throughout the show to see if I could find someone interested to manufacture it. If I get the time tomorrow, I'll take a picture of the tone arm and post it.

Sincerely,

Ralf
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Old 3rd September 2014, 03:44 PM   #793
dtut is offline dtut  United States
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Straight Tracker,

Congratulations on completing your arm. I'm looking forward to photos.
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Old 30th September 2014, 08:11 PM   #794
2wice is offline 2wice  South Africa
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Default Pivot Arc Calcs

I'm trying to plot the pivot arcs for my own implementation.

Please don't laugh at my funky maths :P

I hope it looks OK.

200mm Plot
10.5" Plot
300mm Plot
Excel Calcs
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Old 15th October 2014, 11:55 PM   #795
dtut is offline dtut  United States
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I hate to see this thread go cold.

2wice: I hoped someone more numerate would respond to your post.

If you zoom into the pivot track in any of your plots, the dots form a figure shaped like a comma and don't follow the arc. I got that same shape, or something very much like it, tracing the track of a point behind the pivot and in line with the wand on a mock up I built. Forcing that point to follow an arc resulted in tracking error at the stylus.

Do you have a design for your arm? And will you be posting it?

Regardless, good luck with it.
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Last edited by dtut; 15th October 2014 at 11:57 PM. Reason: hope for clarity
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Old 16th October 2014, 06:03 AM   #796
2wice is offline 2wice  South Africa
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That also bugged me and I spent lots of time trying to find the equation of the path the dots trace. I did find it but only after learning a branch of maths unknown to me before. It is an arc from an ellipse so I had to abandon that model. I was able to plot another arc using an offset circle without a cam as needed by the ellipse. If viewed at scale now the arc traces the circumference perfectly, only when you zoom in very deep can you see a slight deviance.
The design is complete but I'm worried that it works very well and someone else gets to monetize it before me.
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Old 16th October 2014, 09:06 AM   #797
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Monetizing own invention is the most challenging part. Taking in account that independent inventor is the most discriminated category in modern society, not protected by government at all. Without huge resources to protect/ promote and manufacture his product, there are minimal chances to capitalize even most innovative and ingenious design... There are some exceptions, basically among people, who already invested many years to make a name and build some connections...

Last edited by walterwalter; 16th October 2014 at 09:09 AM.
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Old 16th October 2014, 10:21 AM   #798
2wice is offline 2wice  South Africa
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Here are the new calculation.

There is still an error but it is tiny.

https://www.desmos.com/calculator/7lgwjfzho1

The biggest deviation swings from 0.08452 Degrees smaller to 0.235883 degrees bigger than tangent.

Would anyone be able to hear this? I do not think so.
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Old 16th October 2014, 12:17 PM   #799
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Somehow your drawing differs from the original patent drawing in important points, i. e. in the point where the elongations of the tonearm intersect.

Click the image to open in full size.
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Old 16th October 2014, 01:10 PM   #800
2wice is offline 2wice  South Africa
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Quote:
Originally Posted by alighiszem View Post
Somehow your drawing differs from the original patent drawing in important points, i. e. in the point where the elongations of the tonearm intersect.
Hi alighiszem

That cat was skinned by another person with another method.

I started with a right angled triangle and then used matrices to rotate and translate that triangle so that the short side of every triangle goes through the spindle, in increments of 0.5 degrees.

Is there anything that you see that might cause the stylus not to be tangential to the spindle, so that I can fix it please?
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