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Old 15th November 2005, 06:41 AM   #11
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My fire is lit too!

Someone mensioned using an easton aluminium arrow tube as a tone arm, and being an archer (of sorts) I know there are many different types of arrow shaft available from cedar, fibreglass, alloy of varying grades, through to alloy/carbon composites and pure carbon. Easton probably has all the data on their website, and they aren't too expensive either (for one shaft).

I'm thinking 5mm or 5.5mm dia. carbon, or composite.

A question though....

On a uni pivot system, how is the lateral rotation controlled?
Is it simply balanced with a low C of G or is there more to it?
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Old 15th November 2005, 07:14 AM   #12
maxro is offline maxro  Canada
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Quote:
Originally posted by bobhayes
On a uni pivot system, how is the lateral rotation controlled?
Is it simply balanced with a low C of G or is there more to it?
Yes, usually low slung counterwieght.

The problem with a low weight is the effect it has on stylus pressure when warp riding.

I'm working on a design for a unipivot, with two small magnets to handle azimuth, so I can use a counter weight that is level with the pivot. The pivot point will be attached to the arm as will two magnets, either side of the arm, facing each other. The centre (both side-side and up-down) of the magnets will coincide with the point of the pivot. The pivot will ride in a punch mark in the centre of a steel disk. The disk will be twice as thick as the punch mark will be deep, so the magnets will ride around the disk's equator. The arm will be free to rotate up and down over warps, side to side across the record, but not able to yaw. I suppose the magnets will also provide some damping to the arm, hopefully not too much.

I've got the design mostly worked out. I just have to plan the easiest way to machine it. All aluminum with 3/8"x .035" arm wand

Oh, and it will have a pivoting headshell, like the 47 labs tonearm.

Max
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Old 16th November 2005, 06:01 AM   #13
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The magnets sound promising, but may not be easy to execute in practice. I assume (from thinking similar thoughts with magnets) that the steel disc will have a sharpened edge to concentrate the majority of the flux on the correct axis, and that the magnets will be thin cylindrical shapes, polarised along their axis?

I was thinking of experimenting with neodymium ring magnets and small cylindrical magnets (repelling) to see if I could successfully 'levitate' a tone arm!!!

The rings (dia 12.5mm, hole 6mm x 3mm thick) would be top and bottom of carbon rod arm (polarity aligned to concentrate flux and firmly trap arm). The cylinders or rods (dia 4mm x 10mm) would be planted in a surrounding frame, above and below the rings (both reverse polarity repelling the rings) and adjusted with grub screws to a position where the tone arm 'levitated')

Perhaps a little optimistic!

Can you post a diagram of your idea?
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Old 16th November 2005, 07:58 AM   #14
maxro is offline maxro  Canada
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Yes, 0.125" diameter neodym magnets with their axes in line. I figure that like poles facing each other will be vital so as to not polarise the disk. I was thinking a rounded edge on the disk.

I don't know how much success you will have with your mag-lev idea. Magnets repel each other in a rather chaotic fashion.

Have you seen the Schroeder tonearm? It uses attracting neodym magnets to control a tonearm suspended by a string. Sort of the gravitational opposite of what you are thinking. Here's a long thread about a DIY version, its inventor even chimes in:

DIY Schroeder Tonearm???

Here's a crude sketch of my design. Sort of an underside perspective.

Max
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Old 16th November 2005, 04:44 PM   #15
Nanook is offline Nanook  Canada
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Default to bobhayes... and a rant

I suggested the use of an Easton arrow shaft, a 9mm one in my tone arm found in "Nanook's $2.19 tonearm"

I think that it is a little reprehensible, and that merely knocking off an existing design is not completely DIY and should not be encouraged. Where is the creativity in that?

Now having said that, almost anything we come up with has been infact been tried or developed elsewhere by manufacturers or hobbyists . How do we justify simply copying an existing commercial product, and how can we justify it it as a original DIY piece?

Reproducing an existing product just means that you accept the design premise of those who did all the R&D and may have had to overcome financial barriers to produce the object that so many are willing to copy.

Perhaps some here should consider the relatively recent death of Thomas Scheu, and question the impact that knock offs and negative financial impact that may have contributed to his death. Hobbyists often become manufacturers because they believe in what they have accomplished , and through creativity and experiment have designed and refined their "thing" to the point that others have asked for it.

So go ahead and copy and implement completely original ideas all you want (and I'm not talking about the use of squash balls as isolation devices, etc but rather truely inspired and creative ideas), I'm sure we can continue on in this hobby with one less creative person (as in Mr. Scheu) walking the planet to feed the need for knowledge until they feel drained emotionally and financially and feel that perhaps there is no upside to continued life.
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Old 17th November 2005, 03:14 AM   #16
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Default Re: to bobhayes... and a rant

Quote:
Originally posted by Nanook
I think that it is a little reprehensible, and that merely knocking off an existing design is not completely DIY and should not be encouraged. Where is the creativity in that?

Now having said that, almost anything we come up with has been infact been tried or developed elsewhere by manufacturers or hobbyists . How do we justify simply copying an existing commercial product, and how can we justify it it as a original DIY piece?

Reproducing an existing product just means that you accept the design premise of those who did all the R&D and may have had to overcome financial barriers to produce the object that so many are willing to copy.

Perhaps some here should consider the relatively recent death of Thomas Scheu, and question the impact that knock offs and negative financial impact that may have contributed to his death. Hobbyists often become manufacturers because they believe in what they have accomplished , and through creativity and experiment have designed and refined their "thing" to the point that others have asked for it.

So go ahead and copy and implement completely original ideas all you want (and I'm not talking about the use of squash balls as isolation devices, etc but rather truely inspired and creative ideas), I'm sure we can continue on in this hobby with one less creative person (as in Mr. Scheu) walking the planet to feed the need for knowledge until they feel drained emotionally and financially and feel that perhaps there is no upside to continued life.
Whoa, yikes! I hope that wasn't directed at me.

My suggestion of the Schroeder arm was because it seems like a similar design to what Bobhayes was thinking, only turned upside down.

If you read the Schoeder thread, it is basically just about trying to figure out how to do an exact copy of the Schroeder arm. I agree that this is not in the true spirit of DIY, and morally iffy. Despite this, Mr Schroeder himself offers his advice.

What I am proposing is a magnetic arrangement that I have not seen used in a tonearm pivot. I haven't done a patent search. But, why would I, unless I was looking to sell the design? Maybe it has been done before. I would not be surprised.

Now, the pivoting headshell, I will fully admit to copying that part from 47 Labs. It just seems like an interesting idea and one that I want to try out.

We must remember that many (most?) DIYers can't afford high end components and use duplication as a means to afford them. How many Gaincard sales has 47 labs lost from all these Gainclones being built? Probably not many. I wouldn't even consider spending that much on an amp. And, if I had that to spend, why DIY? That said, it is the DIYers who innovate and bring new ideas that keep this forum most interesting.

Max
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Old 17th November 2005, 03:38 AM   #17
Nanook is offline Nanook  Canada
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Default not a direct reference to anybody..per sey.

Although Mr. Schroeder did post some comments in another thread, I agree with his idea of intellectual property. This is not directed at any "you", perhaps a generalized "you" or "us". I think that we should respect the time, effort and financial commitment some hobbyists put into their items especially when they make the jump to manufacturing them as a commercial concern.

Having said that, Mr. Schroeder is not the originator of using magnets in the making of tonearms. Garrard, on their Zero series tables, used magnets to apply an anti-skating force (as well as a pivoting headshell).

I understand that many who knock off a product do so because they can't afford the "real thing". I don't begrudge any, just trying to point out that some who do have the means make a comment like ,"I can to that". Sure one can do it, but why hadn't they? Yes DIYs are a relatively rare breed. I am just trying to promote creative , individual thoughts and solutions to audio situations and problems. It ain't easy being green.

Copying a product constitutes intellectual theft. Thankfully most manufacturers could care less, as long as the fruits of the DIYer's efforts are not promoted for personal financial gain from selling the products.
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Old 17th November 2005, 05:22 AM   #18
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Maxro,

I like your idea a lot, it looks relatively easy to execute compared to mine.
Would you mind at all if I was to produce a one off, of your 'intellectual property' for my own use only?

Here's a drawing of what I had in mind.
The repelling fields should (mmm) keep the arm centred, with a little play to ride the warps.

BTW, I have never seen any tonearm using magnets, and have never heard of shroeder. I thought about suspending an arm in such a manner too, with no outside influence, so if I had have built one of these devices without knowing they already existed, would I still be an 'intellectual property' thief?

Come on....
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Old 17th November 2005, 06:52 AM   #19
maxro is offline maxro  Canada
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Quote:
Originally posted by bobhayes
I like your idea a lot...
Thanks.

Quote:
it looks relatively easy to execute compared to mine.
I agree, though you ought to do a mock up of your design as a test of the concept. I'm curious to see if it will behave predictibly.

Quote:
Would you mind at all if I was to produce a one off, of your 'intellectual property' for my own use only?
Go right ahead. Just let me know if you go into production and we can discuss royalties.('')

Quote:
BTW, I have never seen any tonearm using magnets, and have never heard of shroeder.
Actually there are a bunch. Graham, Decca, Morsiani. But these all use magnets for anti-skate. The Schroeder is the only one I've seen that uses magnets to control unwanted arm movements, but its control is not directional.

If you build one like mine, just remember to place the axis of the magnets paralell to the headshell, so that the azimuth doesn't change when warp riding. Look at an S shaped (or ,properly designed, straight, gimball pivot) tonearm from above to see what I mean.

Quote:
I thought about suspending an arm in such a manner too, with no outside influence, so if I had have built one of these devices without knowing they already existed, would I still be an 'intellectual property' thief?
Legally, maybe, but only if you start selling them.

Max
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Old 17th November 2005, 07:17 AM   #20
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I understand about keeping the axis of rotation aligned with the headshell to maintain azimuth.

I reckon the trickiest part is guesstimating the correct size for the magnets so as to hold the arm in place, but not drag it from its mount towards one side?

Did you estimate, or calculate? (The maths must be mind boggling!!)
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