New WM-DD center gear prototype is here (EDIT - final version is here)

Okay..more questions... more experienced people will gave advice like you

 

The center gears that I make are perfectly round. The problem is not in the new center gear design, it is pretty concentric. When the center gear was produced originally, the metal disc was inserted into the mold and then it was filled with POM plastic. Sometimes it happened that the metal disc was not inserted exactly into the middle. Normally, it was not a problem, because the plastic center and outer gear were always concentric. Only the metal disc was shifted a bit. But the new center gear design relies on this metal disc concentricity. Approximately, 1 of 5 gears have this problem.
It means that none new center gear design can be used successfully in such a case.

You can compensate for this original metal disc eccentricity by making the new gear a little eccentric, too. I used to grind it from the inner side using the Dremel tool and then place it in such a way that the eccentricity of the final assembly is removed. If you position it correctly, then the eccentricity of the final assembly will be eliminated.

The advantage of my design is that the gear ring is pushed to the metal disc by six screws. The metal disc is perfectly flat, which means that the result gear will be also flat. Producer of the new center gear design sent me this gear for testing. At the time when I was testing it, the gear was little small and it didn't fit well. It was very difficult to install and after I succeeded, it was wavy. I sent my feedback to the producer and I think hey fixed it. So I believe this design is very good, now, based on your feedback.

 

Thank you for the explanation, @mihokm !
I always wondered how those gears were made at the factory, because the original plastic one seemed to be molded directly onto the metal disc (now you confirmed that is indeed the case), as both lips are very large, making a manual installation impossible.

The fact that the metal disc was not inserted exactly in the middle sometimes also explains the variation between devices, as on some walkmans the new gear has very low eccentricity and on others it's higher.

Given these details, it is clear that your gear is the only one that can grinded to be made eccentric to compensate for the eccentric disc, so it's the one that should be used. The other type cannot be sanded inside the lip.

 

Yes, exactly. And I also have CNC-made version. It is extremely accurate and smooth design.. but the hole was made a little eccentric. That's why I do not sell them.
But they're perfect for this original center gear eccentricity compensation. When someone mentiones that he has such troubles, I always send him such gear, or other gear for experiments. So there is no problem when you damage the gear by experimenting - just let me know and I will send you another one for free.

 

So..has anyone tried to communicate with Sony as manufacturer about the plastic gear?
Аs a large company there should be an option to produce it as it is the original. I ask you because my friend managed with many nerves to order a front panel for his cassette deck tc-ka6es in 2006... and he succeeded.....Sony produced 3 pieces for him..so who will try this thing?

 

Probably no because of 3 simple reasons:
1. The original gear was molded onto the metal disc, meaning you will only be able to buy the complete assembly. Even if they would make that, it will be signficantly more expensive than just the gear.
2. The original gear is prone to breaking exactly becasue it was molded onto the disc, meaning it shrinked after cooling, so it was in high tension to begin with.
3. We already have a better replacement from @mihokm. Why would we want the original if that has a design flaw ?

I personally prefer to replace a part that has a design flaw with a better one that doesn't have that problem.

 

I've read this three times and did not get it. Does eccentricity in the gear "compensate" for eccentricity somewhere else, so it should be placed at the exact position for the cumulative angular speed to remain constant?

Or the old plastic and metal gear was a "sandwich", and the plastic gear was properly circular with a hole in the middle, but the metal disk was shifted, this having the hole not in the middle? I thought that this gear has a plastic ring around metal disc, but maybe I am mistaken. Hard to understand without a picture

 

@CDV I put 2 pictures explaining what is happening.
The idea is the middle plastic bushing (with the center hole on which the gear rotates on) and the outer gear were molded onto the metal disc.
So in this scenario, even if the disc itself is not put perfectly in the middle of the mold, it doesn't matter, because the assembly will be perfectly centered.
However, the problem is the disc will be eccentric on that middle plastic bushing.

Of course the eccentricity marked in red is exxagerated, in reality it's very small, like 0.1mm.

EDIT: In the second picture description, by "opposite to the eccentricity of the disc" I mean as far as outer part is concerned.
The inner part of the gear should be matched on the same side, meaning the grided part of the gear should go where the disc is eccentric.

 

Welcome to 2023

 

Congratulations Marian, near to 1000 pcs

 

That's only from ebay, he sells from his website too

 

Units sold on https://www.fixyouraudio.com are the following:
- WM-DD has 681 units old;
- WM-DDII 120 units sold;
- WM-DDIII 97 units sold;
- WM-DD100 35 units sold;
- WM-DC2 137 units sold;
- WM-DD30 104 units sold;
- WM-DD33 313 units sold;
- WM-D3 272 units sold;

This would give a total of 1759 units sold on FYA + 719 on ebay = 2478. Very good !