DIY Schroeder Tonearm???

[mgreene]

Thanks Frank,

Interesting read.

I've had a brain storm however, I will simply harrass a manufacturer for this information

Mike

[Paul Ebert]

Originally posted by mgreene
Thanks Frank,

Interesting read.

I've had a brain storm however, I will simply harrass a manufacturer for this information

Mike

You might want to check out:

http://www.fieldlines.com/section/magnets

as well. I've had a few discussions with the guy who runs wondermagnet.com and he seems fairly knowledgable.

Paul Ebert

[krishu]

;ktin

How did you fix the string? Knot? Screw?

How much is the distance between the neodyms?

@everybody
since i am german i could read the patent paper of the schröder arm. In this document nearly the whole construction of the bearing is described. It is written in a very scientific language so that i am too lazy/stupid to translate the whole. The drawings show nothing less than the text tells about the basic construction.

It is told that neodym magnets are the best and that the string must be not elastic. Also something about oil dampening is told there, but i think this is not interestning at the moment.
It is described, how the aluminium around the magnets influence the magnetic field to force the arm to good behaviour.

cheers
christian.

[fdegrove]

Hi,

I didn't spot it at first but from the drawing alone you can actually accurately copy the whole design.

If anyone needs help translating the German text, I may be able to help out.

Tchues,

[mgreene]

Christian and Frank,

In regard to the patent, I was just curious to know if there was anything in the claims that wasn't obvious from the drawings.

For instance, some magnet companies make steel holders for disk shaped magnets like these and I wondered if this was a good solution. Now, Christian mentions something in the patent about alumium enhancing the magnetic field. That is the kind of info I am interested in.

BTW: altavista and other translation programs do not do much with long, multisyllable germanic words - so, no help there.

In regard to the distance between the two magnets, this info is in the arm setup instructions on Schroeders website. He writes that the thickness of a business card is the starting point - if the magnets get too close or touch the cartridge will start to skip - anybody planning to use their $7K Clearaudio to test with? I assume that the string is something like 50 pound test, leader - i.e., fishing line. Leader material is usually much tougher (non-stretch) than regular line.


Regards

Mike

[AuroraB]

Just read the patent script briefly. Must study it more carefully tonight,-
aluminium cannot enhance the magnetic field...??
However,- he does mention eddy currents being induced in the bottom alu holder - as a damping mechanism.

People has questioned the possibillity of drilling the Nd Magnets, but the patent script also sketches the use of a drilled upper pole piece on the opposite side of the air gap. This can be drilled to hold the thread...the drawings in the patent script really speaks for themselves..

Fly line backing is indeed a good idea for the string/thread. There is also multifilament fishing lines on the market with incredible strength vs. the line thickness. One brand here in Scandinavia is called "Fire Line", but there shure is alot of others.

[berlinta]

Hi everyone,
Yup, it's me(Frank Schröder), the guy who's work by now enjoys the privilege to be copied. No need to worry, I have nothing against DIY enthusiasts, enjoying a few nights in the basement workshop, but, - you guys could have made it alot easier on yourselves if you had contacted me directly. My email and my phonenumber can be found on my "webpage".
One word of caution though. If you think that by mere "copying" the drawings in the patent you will end up with an arm that sounds just like one of my own making is optimistic, putting it mildly. Chances are though, that you will end up with an arm that betters anything commercially available for up to 1000$+. BUT, - the inherent superiority of the bearing design is only one of several aspects that "make" my arms.
Let me remark on some of the points raised in previous posts.
Carbon fibre is a decent material to be used as an armwand but exibit a fairly strong resonant behaviour if used "naked".
Yes, neodym magnets can be drilled(heck, anything can be..)
Very little energy is "drained" via the bearing, you'll have to deal with it differently.
Nah, I won't give away too many of my trade secrets(it would spoil your fun, wouldn't it?;-)
And if anyone decides to turn this into a commercial undertaking it will make my lawyer even more rich and you poorer than you'd believe was possible - sorry, I had to add that(no offense meant).
Enjoy the tinkering but more importantly, enjoy the music once you've succeeded.

Cheers,

Frank

[krishu]

Hello to everybody,

underneath the lower magnet and above the upper one there shall be discs of high permeability (like frank schroeder wrote in his patent) to increase magnetic field. Therefore those steel cups to hold the magnets one of you mentioned wouldn't be a bad idea. The aluminium's influence to the magnetic field ist more an influence of the magnetic field to the aluminium to force it into its right position/to dampen movement.
So the aluminium won't enhance the magnetic field.

Thank you for the information concerning the distance between the magnets.

For the string, a guitar string may also be used, but must be dampened then. Schroeder wrote that where the string is attached to the arm there should be a cup that will carry some dampening oil.

What advantages/disadvantaghes do you see in using One string or two strings (schroeder did both)...

@Frank Schroeder
I think it is better for us to figure out everything by ourselves. First, to learn. Second, we might (but probably will not) solve problems in a new way, which you can use for your arms. But this is worlds away, now.
If anybody would be interested in producing your design commercially, it would be no good idea anyway. I cannot imagine that it is possible to build those arms really cheaper than you do in good quality. So why should anyone buy them? That means: alles im grünen Bereich.

I attach a scetch that shows just ONE possible way to build it as described in the patent paper and I did construe it.

Cheers
Christian.

[mgreene]

Hi all,

I sent Frank a friendly email, offline through DIY, as soon as I saw his post. It is possible he didn't get it. Frank are you really willing to correspond with us or did you sign on mainly to inform us of your patent rights?

BTW: It should be apparent that very few of those who can really afford such equipment would waste their time trying to build it.

Nice drawing Christian - and thanks everybody for pointing out my poorly chosen word - "enhance". Even I know that Al is non-magnetic.

regards

Mike

[berlinta]

Hello Mike,
I did get your mail, please see my private response for an explanation why I didn't respond any sooner, sorry again..
BTW, informing you guys of the patent wasn't neccessary, someone had already posted the proper link. Previous (negative) experiences led me to this remark, I won't mention it again.
The drawing is very good indeed, leaves out some important details though. And the shape of the upper polepiece is not quite correct. Build it and tell me if you managed to achieve equal VTF and azimuth from beginning till the end of the record...

Gotta run, pick up some groceries...
Have a great weekend.
I'll be back,

Frank