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Poul Ladegaard's Air Bearing Tangential Tonearm - has anyone here built one?

Discussion in 'd.i.y.' started by Rosewind, Jan 12, 2019.

  1. Rosewind

    Rosewind Lost in Translation

    Hi.
    Just idling about the interweb I came across a mention of Poul Ladegaard's Air Bearing Tangential Tonearm that is a DIY-job away. It is this one - first on a fully built DIY TT (I actualy own one the same squeeze-on record clamp with box and all that you see in the photo) - the second version is on a modified Thorens TD 150:

    [​IMG]

    [​IMG]

    I have always liked tangential arms, and my first turntable was a Sansui Tangential tt - I do not recall which version it was. I sometimes wonder why I did not buy a B&O turntable, but they were probably too expensive for me, or too "pretty.". Instead I sold my Sansui and bought a Thorens TD 160 mk. ii that had been modified to Super status. It came fitted with a Poly Push suction system, a Morch UP 4 and an Ortofon MC200 cart.

    Now I have a Thorens TD 147 Jubilee with a Thorens TP 16 arm on it. I do not have a lot of money left so the Poul Ladegaard Air Tangential Arm would be a fun project.

    Has anyone here tried to build one?
     
  2. Rosewind

    Rosewind Lost in Translation

    This arm is not suitable for a bouncy TT, so my Thorens 147 is not really suited. Too bad as I think it would have been fun to build this fairly straightforward arm.

    This arm is a predecessor of the Trans Fi Terminator.
     
  3. h.g.

    h.g. pfm Member

    Is the problem a difficulty attaching it to the sub-chassis, a problem with very low frequency motions of the sub-chassis, or something else?
     
  4. Rosewind

    Rosewind Lost in Translation

    I think that the arm has difficulty following the movements of a subchassis resting on springs. My Thorens is on a shelf so it is well protected and may work well.

    Anyway, I will see how hard it is to build the arm in the summer. I have several ideas for an arm wand - one is to use a part from an IKEA kitchen utensil. Poul Ladegaard suggested a carbon wand from a badminton racket.
     
  5. h.g.

    h.g. pfm Member

    Are you proposing to attach the arm to the main housing instead of the subchassis?
     
  6. Rosewind

    Rosewind Lost in Translation

    Yes. I think that is the only way if you look at the mounted arms above.
     
  7. Rosewind

    Rosewind Lost in Translation

    Arm wand materials - dampened metal (IKEA):

    [​IMG]

    Solid carbon wand, round, 8 mm:
    [​IMG]

    Solid aluminium. round, 8 mm:
    [​IMG]
     
  8. h.g.

    h.g. pfm Member

    The arm and platter are mounted to the subchassis so that they can be isolated from the vibration of the main chassis at audio frequencies. If you attach the arm to the main chassis it will experience this vibration. The vibration from the motor may need checking since it will have been chosen and the mounts designed knowing the arm is not attached to main chassis.

    Is the dampening those 4 rubber blocks?

    Why solid? I would have thought a hollow tube was preferable since it is likely to be lighter, almost as stiff and you can run the cable through it rather than wrapping it around the outside in an ugly manner. Carbon fibre will have better damping than aluminium from the resin.

    Perhaps I should declare an interest in your progress since I have had an item on my to-do list for several years to add a DIY arm like this to either a TD160 or TD280. It is low down on the list though and likely to remain so for a few years possibly even until retirement.
     
  9. Rosewind

    Rosewind Lost in Translation

    Couldn't you isolate the armbase by using a rubber seal between the base and the chassis instead of screwing it on?

    Or place it outside the chassis? Like in photo one?

    I hoped the IKEA tubes had been stuffed with foam. I will investigate. They may also just be hollow tubes of aluminum or steel.

    Poul Ladegaard suggested a wand scavenged from carbon fiber badminton racket. Carbon fiber arrows, carbon fiber fishing rods ... etc may also be used.
    Hardwood wands are also used - although they may have been treated withe dampening glue of some sort.

    Re: Hollow tube - I read somewhere that a hollow tube would be preferable - even a plastic wand dampened with artificial clay.

    I am someone who saddles many horses without riding them ... just look up my FirstWatt F4 project. So I am with you all the way to back of the project list.
     
  10. Rosewind

    Rosewind Lost in Translation

    The wand: would it make sense to use a 9mm hollow aluminum wand with a 7mm hollow carbon fiber wand inserted inside it, which in turn is to be filled with silver litz wire and some type of foam. Or is this just a bad idea?

    I am afraid that the carbon fiber wand on its own will be brittle.

    EDIT: I have no qualms about having the wires run outside the wand - except that they will then be unscreened.
     
  11. h.g.

    h.g. pfm Member

    Carbon fibre tubes are the opposite of brittle if you consider how much they bend in things like badminton racquets and fishing rods. Even if they were brittle why would it matter since there is pretty much zero applied force. They need to be stiff and damped with a mass likely guided by the stiffness of the cartridge to be used. I haven't done the sums but expect others will have over the decades.
     
  12. Rosewind

    Rosewind Lost in Translation

    I will have to handle a hollow carbon fibre tube to see how it feels in my hands. If it is strong enough, I think I could just use that with a filler of sorts.
     
  13. h.g.

    h.g. pfm Member

    What is the function of the filler?
     
  14. JensenHealey

    JensenHealey pfm Member

    Hollow carbon fibre is OK for Golf Shafts. Strong enough for that, then clearly strong enough to be an arm. As to resonance properties - I am less sure
     
  15. Rosewind

    Rosewind Lost in Translation

  16. Rosewind

    Rosewind Lost in Translation

  17. Rosewind

    Rosewind Lost in Translation

    I have ordered 4 x 5/16'' wood dowels in 4 variations of wood: sapete, tuliptree, iroko and walnut. So for now it will be wood for the arm wand and external wiring. That is if I don't cut a channel for the wires and seal them in there with as light a material as possible.
    I have also ordered anodised aluminim angles 20x20x2 mm. Here is a photo of Paul Ladegaar's drawing for one of his prototypes:
    [​IMG]
     
  18. Rosewind

    Rosewind Lost in Translation

    EDITED with a bit more thoughts + YET ANOTHER EDIT to reflec the purchase of Litz wire and cart tags:

    I will need ...
    - to make an arm wand choice: should it be wood or is a combination of carbon fiber / aluminum a better choice? Should I taper the arm wand towards the headshell (if I can)?
    - to buy fairly long silver litz wire (screened?) with connectors at both ends (cart connectors to RCA. How long? I would think at least 3 feet or 75 centimeters so I can trace it the best way. I have now ordered copper Litz wire and Cartridge tags from Trans-Fi Audio. Will need some good RCA connectors at the end of that.
    - to find a way to fix the arm to the stanley knife blade bearing: to be fixed as described with a flange or with parts from my other DIY project...? I have seen alternative mounting methods.
    - to device a counterweight - I may simply reuse spares I have from my Thorens TP16 arm. They will have to be modified a little. I saw a build where the counterweight was hanging from the arm in a string like a pendulum. That could be done. I will investigate.
    - to make or buy a headshell and find a way to mount it on the chosen arm. Wood? Aluminum?
    - make or buy an arm rest. If I make it, I could use aluminum or wood: the aluminum one in the second photo looks like it would do the job well.
    - to consider if a harder bearing than anodised aluminium is needed. An added layer in the floating angle may may also be used to adjust arm height.
    - to cut the lengths of the aluminum angles to 30 cm / 30 cm / 18 cm
    - to drill - very carefully - air vent holes in one of the 30 cm angles and one 5mm air intake hole in the other 30 cm aluminun angle.
    - cover the air vent holes with tape and make small syringe holes where the air vents are.
    - to buy a good double sided adhesive tape to make an airtight seal between the two bottom aluminum angles.
    - buy a 5 mm nipple + 5 mm tube for the air supply + an air supply system for a fish tank (as silent as possible). Will I need a surge tank to even out air pressure?
    - make a support block for the air bearing arm "slider" - to be fixed with double sided foam tape. The foam tape may also act as decoupling. Precision cut wood seems the easiest solution.

    This will take time to get hold of and make.
     
    Last edited: Jan 17, 2019
  19. Rosewind

    Rosewind Lost in Translation

    Found yet another resource for great ideas for a cheap tone arm and what comes with it: arm wands, head shells, Litz wire, ball bearings (from biro pens) and so on. Great resource thread - my latest iteration of "Nanook's 219 tonearm":

    https://www.diyaudio.com/forums/analogue-source/173861-iteration-nanooks-219-tonearm-9.html

    As for a head shell: file the front end of the wood wand level, drill a small hole through the wand (don't break it), attach a flat piece of aluminum or wood with holes for easy mounting of the cart. Not unlike this, although mine will not be with the fancy head:

    [​IMG]
     
  20. Paul R

    Paul R pfm Member

    I think these things are cheap enough to play with, and you don't need to make all the decisions on detail up front.

    I'd stick with the Ladegaard until it works in some form, and then try the unipivot.

    Perhaps it would be worth finding a research turntable to play with, a Lenco or something that can sit on a baseboard and give you experimental flexibility.

    I have an SP10, and some years ago I got as far as looking at aquarium pumps.... A pile of Quads to do first.
     

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