DIY Schroeder Tonearm???

[mgreene]

With all the recent talk about unipivots and such, has no one ever considered knocking off a magnet stabilized string pivot like the Schroeder? I have been considering a DIY arm just to add a mono cartridge to my TT. This implementation "looks" fairly simple Assuming you have a source of wood and carbon fibre, the only things slightly out of the ordinary are the neodium magnets, which are fairly ubiquitous on the web.

See pics and a review of the Schroeder's stuff at his website: http://www.schroeder-tonarme.de/

Mike

 

[Brett]

With all the recent talk about unipivots and such, has no one ever considered knocking off a magnet stabilized string pivot like the Schroeder? I have been considering a DIY arm just to add a mono cartridge to my TT. This implementation "looks" fairly simple Assuming you have a source of wood and carbon fibre, the only things slightly out of the ordinary are the neodium magnets, which are fairly ubiquitous on the web.

I've thought about this too. It does look straightforward, and I have a spare tonearm mount on one of my TT's....
I'd try a carbonfibre arrowshaft as the tube.

I have a couple of other projects to finish first, but I'm very interested in doing a 12" version.

 

[CV]

Hi fellas,

It might *look* straightforward, but if you read the hifi+ interview with him (it may be available on his website), you'll see it's not quite simple; takes hours + hours to drill the tiny hole through the Nd magnet for instance. I wonder if drilling un- or demagnetised Nd and then charging the magnet would be easier.

Anyway, makes very interesting reading.

cheers

 

[mgreene]

Schroeder arms

Brett, CV,

I went to the archery store this weekend. A nice, good sized, carbon fiber shaft costs a wopping $5.

As to drilling the magnet, etc., - the interview is not on line where I can find it. CV - can you give us the technical gist of the interview?

Had a few more thoughts over the weekend. Might be possible to simplify construction and get a better result using misc parts such as various aftermarket upgrade parts (arm weights and VTA devices) for Rega and other arms.

Regards

Mike

 

[fdegrove]

SCHROEDER.

Hi,

You guys think it's simple?

No way.

Keeping magnets in place around a pivot is not simple at all.

Moreover, all the energy from the catridge has to be drained by the shaft, you see it ain't all that simple since there is no other way to drain of spurious energy.

Not that I want to discourage anyone of course,

 

[CV]

Hi

...the interview in hifi+...

The Nd magnet is an extremely hard material; trying to drill a tiny hole in it and get rid of the swarf material (which is strongly attracted back to the block) is a nightmare. Took him about 8 hours to go a few mm IIRC...

Will try and dig out the magazine and see exactly what he had to say.

Why not try drilling a tiny hole in a cheap ferrite magnet and see how you get on with that?

cheers
cv

 

[fdegrove]

HI-FI +

Hi,

CV,

No need to dig it up.
There's a scan of the article on Frank Schroeder's tonearm on his website.
See the link in the first post.

Thought I'd save you the trouble,

 

[mgreene]

Schroeder arm article

Thanks CV. Something comes to mind - Schroeder is building with long term quality control in mind - I may be able to epoxy - if it eventually comes loose w/o destroying the cartridge it won't be a big deal.

Frank - Schroeder's interview is not included in the material on his website.

Mike

 

[mgreene]

Magnets and pivot point

So Frank,

What's the secret? It hadn't occured to me that the magnets could be unstable in this configuration - only a few thousandths apart.

Mike

 

[fdegrove]

REPELLING MAGNETS.

Hi Mike,

What's the secret?

The problem as I see it is that the N/S relationship of two magnets is easlily disturbed when one is moved and the other held stable.
Surely you recall the force it takes to keep them in repelling position when held by hand?

This is a problem another German designer (it may even have been the same designer, I can't recall) faced with a similar offering about 15 years ago.

I really haven't got a clue how this one works, admittedly I only took a quick look at the pix on his site.
It seems to work well enough but untill I fully understand the design I'd better zip it.

Cheers,

 

[mgreene]

Repelling?

Ummm...

The magnets are attracting eachother in the Schroeder - or I'm far dumber than I thought I was

My understanding is that the pivot is the "string" that the arm is hanging on and the mobile magnet (in the arm) attracting the stationary magnet (on the base) keeps the pivot stable.

Mike

 

[fdegrove]

SCHROEDER.

Hi Mike,

As I said, I didn't really look into the design.
Only problem I see is the drainage of vibrations emanating from the cartridge which is probably why the designer uses all kinds of woods.

The attracting magnets are an interesting idea though, I guess I'll have to to my homework on this.

 

[Paul Ebert]

Re: SCHROEDER.

Only problem I see is the drainage of vibrations emanating from the cartridge which is probably why the designer uses all kinds of woods.

I thought about this (a Schroeder clone) prior to settling on my air bearing arm. Wouldn't the vibrations simply drain via the magnetic field (i.e. heat)?

One thought that occurred to me was using rare earth magnets to stabilize a unipivot. But, that's another thing all together.

Anyway, similarly to the Ladegaard air-bearing design, this approach has the benefit of quite low cost. You don't have to commit a lot of funds to experiment.

Someday, I may give it a try.

Paul Ebert

 

[mgreene]

Schroeder vibration

Why can't the built up vibrations escape via the pivot string to the arm pillar?

I agree that it looks cheap to try. I've started to line up some parts.

Mike

 

[fdegrove]

RE:RE:Schroeder

Hi,

Why can't the built up vibrations escape via the pivot string to the arm pillar?

That's about the only path there is that would provide a little drainage.

Paul,

The magnetic field won't couple vibrational energy throgh the air.
With an airbearing the pressure field of the air provides a coupling path.
I used to know all the theory behind all that stuff but it's getting rustier by the day.

I agree that it looks cheap to try. I've started to line up some parts.

Good on you Mike.
Keep us posted please.

Cheers,

 

[Paul Ebert]

Re: RE:RE:Schroeder

The magnetic field won't couple vibrational energy throgh the air.

I used to know all the theory behind all that stuff but it's getting rustier by the day.

Hmm, (dusting off my antiquated physics...)

The magnetic field creates forces that act to damp the components of any vibrations that are perpendicular to the field. It does this by inducing currents, in the magnetic material - not the air, which are then converted to heat in that material (unless they are drained in an electric circuit of some sort).

So, there is an energy coupling, but it's independent of the air.

Am I missing something?

Paul Ebert

 

[Paul Ebert]

RE:Schroeder

The magnetic field creates forces that act to damp the components of any vibrations that are perpendicular to the field. It does this by inducing currents, in the magnetic material - not the air, which are then converted to heat in that material (unless they are drained in an electric circuit of some sort).

Thinking about this further, I'm not saying that the magnetic field drains all, or even a majority, of the vibration. I do think that the 'string' would drain quite a bit. Perhaps the way to think about this is that the magnetic field preloads the string 'bearing', by increasing the tension on it and thereby making it a more effective energy drain. But, I do think that some energy would be converted to heat.

The main point is, however, that this may not be any less effective at draining energy away from the cartridge than a typical physical bearing. It all depends on the strength of the magnetic field and the elasticity of the string. At least that's how I see it (which could very well be wrong...).

Paul Ebert

 

[fdegrove]

RE:RE:RE:SCHROEDER.

Hi,

The magnetic field creates forces that act to damp the components of any vibrations that are perpendicular to the field. It does this by inducing currents, in the magnetic material - not the air, which are then converted to heat in that material (unless they are drained in an electric circuit of some sort).

Interesting.
Are you sure about this?
If so, any idea on how to find more technical info on the net?

Cheers,

 

[fdegrove]

PHYSICS.

Hi,

In case we're both in need of a refreshment course:

ERIC WEISSTEIN

Cheers,

 

[Paul Ebert]

Re: PHYSICS.

Interesting.
Are you sure about this?

Yes, this is interesting stuff. I feel fairly confident about it, but it has been over 20 years since I studied it in college.

In case we're both in need of a refreshment course:

ERIC WEISSTEIN

What an amazing resource. Thanks!

Paul