DIY Schroeder Tonearm???

[konstantin]

And..........Another one

[mgreene]

WOW! That is beautiful work.

I think many here will be interested in the actual machining plans in terms of how the magnets are connected to the base and arm

As a side note to Hartmut, I recieved my magents yesterday - although very strong, they dont seem to have 10KGs of attraction. One set, about 8mm wide and 6mm tall could lift about 2KG. Ones about 12 X 10 mm - I could not seperate with hand strength.

Konstantin, any comments or advice about the magnets you used?

Regards

Mike

[konstantin]

Sure. The magnets i used are Neodymium rare earth magnets.
They are actually Grade N40, and they are 6mm X 6mm size rod.
The N40 Grade are powerfull. You can't seperate them easilly



Regards

[mgreene]

Thanks K,

I just got a few generic neodymium samples off eBay to experiment on. I assumed that there would be different grades but hadn't gotten that far yet.

Did you drill through your arm magnet to mount it?
It has been suggested here that drilling in these magnets is quite challenging.

Mike

[konstantin]

Mike,

There is absolutely no way to drill these magnets without destroy them. Neodymium is Very hard but is also very corrosive and even if you drill them you will take of some of the hard Chromium they have on the surface to prevent corrosion. What you can do is to order predrilled magnets as i did. 6mm X 6mm rod with a 1.5mm hole in the middle.


Regards

[AuroraB]

I can get varius predrilled Neoymium magnets here in Scandinavia, from 10x3mm to 16-20-35 mm dia and 3.5 to 5.5 mm thickness, holding strengts are listed from appx. 0.8 to 3o kg for the largest..

Has anyone made some seriuos thoughts on what strength would be the optimum...??

What kind of wire, in terms of stiffness..??
Antiskating would be a combination of wire stiffness and magnet, or just by the magnet pull vs. distance..??

[mgreene]

Mr B.,

Note that Hartmut said that his original model Schroeder's magnets have 10KG of holding force. The newest Schroeder Reference arm apparently has more powerful magnets. Konstantin's magnets are grade N40 - the grades go up to N50.

I have not been able to figure out yet if the holding strength is the same number quoted by magnet manufacturers as the "coercive force", i.e., KOe. If so this would seem to be a generic holding force for the grade of magnet as opposed to the actual holding force for a magnet sized for our work here.

Can someone with a physics or other suitable background, help us here?

Mike

[fdegrove]

Hi,

Can someone with a physics or other suitable background, help us here?

Could do but it would take me several pages.

Try to use a search engine such as Google and type in magnet strength.
You'll find numerous sites giving you all the theory.

Cheers,

[mgreene]

Hi Frank,

I generally try to get the info on the web, as you suggest, before making an open inquiry. Even looked in a couple of physics textbooks. I did not find an answer to the question asked above in either venue.

What manufacturers of neodyium magnets generally do not list is a "lifting strength" number analogous to the number quoted by Hartmut.

Of course, the easy answer is simply to follow Konstantin and get reasonably sized magnets in grades at or above N40.

BTW: Schroeder's patent can be accessed here:
http://l2.espacenet.com/espacenet/bn...+02095736A1+I+

Perhaps those speaking german can give us the gist of enabling design parameters.

Mike

[fdegrove]

Hi Mike,

I did not find an answer to the question asked above in either venue

You mean what the N# stands for?

Well, it's just a guess, I heard from a cartridge manufacturer that the N stands for North type of magnet and the number the ckass off lifting strenght.

Also, he said that there's more than one standard of classification...seems to make it easier on us.

INTERESTING READ

Cheers,