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Thread: Tonearm vertical axis position?

  1. #11
    Join Date: Jan 2013

    Location: Carlisle - UK

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    I'm Ken.

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    hi John - you pretty much enforced the point I was trying to make, that there are a huge number of constraints and variables at play and that Tonearm design is a very complicated business.

    I tried to make the point that, what is an ideal state of conditions for the cartridge to perform at its best may not be best for the bearings to do same. I wasn't proposing lowering the axis, just making the point there are good reasons not to. Its not as straight forward as manufacturers cutting corners, being lazzy or trying to maximise profits. Lowering the horizontal axis will solve some issues and is easily achieved, trouble is it raises a whole lot more, so you end up chasing your tail. Pretty much in your corner again.

    This is why all tonearms are a compromise and different designers have different views on where the emphasis should lie. Leads to some very contrasting and interesting soloutions to tracking that groove.

  2. #12
    Join Date: Apr 2012

    Location: N E Kent

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    I'm Geoff.

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    Quote Originally Posted by John Gordon View Post
    If the bearing is not at stylus level then any force which has a resultant acting to pull against the arm horizontally - groove friction, groove modulation, dust particles, warps - will also have a vector acting to rotate the arm upwards.
    This is precisely what I'm getting at. I don't need lectures on general arm design, I just want an answer to that point! Never mind any design implications or cost, why are arms not made with the stylus and arm bearing in the same plane (allowing for variations in cartridge depth)? That was what I asked. All I really wanted to know was if there is a specific reason why having both in the same plane seems to be avoided. Am I missing something?
    It is impossible for anything digital to sound analogue, because it isn't analogue!

  3. #13
    Join Date: Jan 2013

    Location: Carlisle - UK

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    I'm Ken.

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    Sorry if I was lecturing, the thing is you seem to be over simplifying and looking at one item in isolation. Your specific question has been answered.
    You keep repeating why arn't there arms that have the bearing axis on the record plane, there are several that do. Also extremes in the oposite camp 6" above the record. I've given my reason why I don't think it is practical, so nuff said.

  4. #14
    Join Date: Apr 2012

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    I'm Geoff.

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    Quote Originally Posted by Qwin View Post
    you seem to be over simplifying and looking at one item in isolation. Your specific question has been answered.
    Precisely, I was "looking at one item in isolation" and the question has not been answered.

    The issue has been skated around, but no direct answer has been put forth. I'll assume that there is no reason why the stylus and pivot should not be in the same plane.

    I've asked this specifically as I'm intending to build a pickup arm (correct name really, tonearms belong on gramophones). I've had a design in mind for some time and it's very different to the run of the mill. My design includes bearing axis and stylus in the same plane. I merely wanted to know if there were good engineering reasons why this is not universally used. I cannot think of one.
    It is impossible for anything digital to sound analogue, because it isn't analogue!

  5. #15
    Join Date: Jan 2013

    Location: Carlisle - UK

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    I'm Ken.

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    Good luck with the project, wouldn't mind seeing the result.

    Like I said its been done many times before.


  6. #16
    Join Date: Apr 2012

    Location: Co. Durham

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    I'm Stephen.

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    Isn't it simply a question of following convention and the convention being to have the horizontal bearing axis in-line with the armtube? Which means you're never going to get the bearing and stylus point in the same plane. Every arm I have ever seen - apart from the odd one or two - has been made this way. I don't really think manufacturers generally give it much thought.

  7. #17
    Join Date: Apr 2012

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    I'm Geoff.

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    Quote Originally Posted by Mr Kipling View Post
    Isn't it simply a question of following convention and the convention being to have the horizontal bearing axis in-line with the armtube?
    That seems to be the case.

    My thinking often goes against convention.
    It is impossible for anything digital to sound analogue, because it isn't analogue!

  8. #18
    Join Date: Apr 2012

    Location: Co. Durham

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    I'm Stephen.

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    Will it be a uni-pivot? Ever since I got my first Hadcock I've been intrigued by uni-pivots.
    I have one or two ideas of my own to help with stability that I've never seen on commercial designs.

  9. #19
    Join Date: Feb 2008

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    The Kuzma Stogi S is a great example of how to get great stability with the pivot point on the same plane as the stylus. Not only does it use counter weights at or below the pivot point theres substantial mass in the shape of a bell type housing below the pivot point ensuring stability.
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  10. #20
    Join Date: Apr 2012

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    I'm Geoff.

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    Quote Originally Posted by Mr Kipling View Post
    Will it be a uni-pivot? Ever since I got my first Hadcock I've been intrigued by uni-pivots.
    I have one or two ideas of my own to help with stability that I've never seen on commercial designs.
    Yes!

    The bearing will be different to anything I've seen tried elsewhere (if it works). I have some evaluation to do yet.

    I'm aiming to keep the bearing axis approximately in plane with the stylus tip. Which was why I'd been asking my question. The arm will be of low to medium mass and stabilised by keeping as much weight as possible underslung. I'm hoping to use little or no metal in the construction. The bearing will be directly fluid damped. Not saying too much, as I don't want to give the game away.

    I already have all the materials and need to 'soak test' my design thoughts. I seldom go wrong when building something, because I think it all out, over and over and visualise things in 3D in my head. Works for me.
    It is impossible for anything digital to sound analogue, because it isn't analogue!

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