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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

    I have assembled the air bearing but I need to seal it on all sides and around the air intake vent with heavy duty Epoxy "filler" once I am certain that the bearing is level and all.

    I made a preliminary test without the epoxy seal and I got the floater to float - just. There was a big leak at one of the ends that I could feel with my English lecturer's soft hands. Next time I make one of these, I know what to look out for: that the foam tape should extend all the way down to the bottom of the angle at both ends in order to seal the air tight chamber properly.

    Arm wand: the one I have now will be used as is - with just a little dampening inside - for testing and setting up the whole arm.

    Later I will first make a good aluminium wand stuffed with 5mm silicone tubing and then I will try to determine which of the four types of 8mm wood duwels that I have here will make the best arm wand (yes, with external wiring secured by thin rubber sealing rings around the wand to hold the wire in place). I have got these four types of wood dowels to choose from (provided that they are in fact straight and stay straight when they dry a bit):
    • Iroko
    • Sapele
    • Tulipwood
    • Walnut
    Any comments on the type of wood I should use?

    Pictures? Yessir!

    The metallic tape on the air bearing angle without punched 0.3 mm holes (I later used a tiny 0.3 mm drill bit that cost me £1.5).
    [​IMG]

    The assembled air bearing before I have applied the epoxy seal. And no, you are not imagining things - the air holes dance up and down in this first attempt at making Poul Ladegaard's tangential air bearing arm:
    [​IMG]
     
    Last edited: Feb 2, 2019
  2. Paul R

    Paul R pfm Member

    Great stuff.

    'duwel'

    On a sidetrack, because I'm logged in...
    IIUC, in English, a 'dowel' (dow -el, 'ow' as in hitting my thumb with a hammer) is a short piece of cylindrical wood used to pin a joint. Ikea supply a plasticky version in their flat packs. 'dowelling' is therefore long lengths of this that can be bought from any 'DIY' type shop for making kites or models. Is 'duwel' a Danish spelling of the same thing? How's it pronounced?
     
  3. Rosewind

    Rosewind Lost in Translation

    Danish = dybel/dyvel. I have no idea how the u got in there. That's what happens when you leave the English language in the hands and mouths of foreigners.
     
  4. booja30

    booja30 pfm Member

    Absolutely nothing to worry about! Native english speakers have it quite easy given that it's such a common 2nd language for non native English speakers. Quite a few native English speakers have never even given a second language a shot.

    I had a few years of French in school but I never really made good progress on another language until I moved to Spain. And after a year here with lots of classes, I'd say your English is miles (or kilometers) ahead of my Spanish. :)
     
  5. Paul R

    Paul R pfm Member

    According to my dictionary the word comes from Middle/Low German, which might explain why it is basically the same in Danish.
     
  6. Rosewind

    Rosewind Lost in Translation

    I have taken the angle with the air bearing off again as it was not level enough across the short part. The problem was at one of the ends where the foam tape had not been pushed all the way into the corner of the angle. This means that I will have to scrape off adhesive and foam from both angles and glue once again. I will put the foam tape on the upper part this time. I hope this will let me control the height of the barrier better.

    Yes, English and European languages are related, Brexit or not.
     
  7. booja30

    booja30 pfm Member

    I wonder if instead of tape you could do something more precise. I was thinking you could use two small pieces (~5mm wide) with the legs shortened to act as spacers. Glue the spacers to the bottom angle near the ends. Apply a thin bead of silicone around the perimeter of the bottom angle (where you're using tape now). Put the top half on and clamp while the silicone dries (e.g. with clothespins). This should create a perfectly even and air tight gap between the angles.
     
  8. Rosewind

    Rosewind Lost in Translation

    Edited:

    A general observation: Always have a spirit level around when you build this. I have just realigned the feet that I mounted with double-sided tape, and now the arm base is level. It wasn't really level before. I will have to check again when I mount the angles on its wood base and when I put the air bearing section back on it.

    Foam tape may not be such a good idea - other than for dampening purposes.
     
  9. Rosewind

    Rosewind Lost in Translation

    Took a look at the wood dowels. Three of them seem straight enough to be used for an arm wand. I bought some rubber rings with which I will dampen the wand and strap the wires to it.
    The angles have been cleaned and are ready to be put together again. In a week's time, I have three days off from work. Then the good work will go ahead.
     
  10. h.g.

    h.g. pfm Member

    Good to see things progressing. I doubt rubber rings will do anything much in terms of damping. To do something effective you will likely need the bending of the arm to put a material with high damping into shear. A composite material. An example would be carbon fibre where the fibres provide high stiffness and the resin high damping.

    BTW this sort of thing is likely worth pondering because the motion of the cartridge will vibrate the arm significantly. A few years ago I shone a laser doppler vibrometer on an arm tube around it's mounting and the signal from the record was very clear.
     
  11. Rosewind

    Rosewind Lost in Translation

    Two reasons why I am not doing any work on the air bearing arm:
    [​IMG] [​IMG]
     
  12. Rosewind

    Rosewind Lost in Translation

    Back home the headshell that I ordered some time ago had been delivered. As I hoped, it had a hole that I could expand using the little blue grinder head on my small drill. Now it fits over the various 8 mm arm wand dowels/tubes that I have, be they aluminium or wood. Here is the headshell and the blue grinder head.
    [​IMG]
    [​IMG]
    [​IMG]
     
  13. Rosewind

    Rosewind Lost in Translation

    I put the air-bearing angles back together - level this time - and applied the epoxy filler to both ends and along the edges of the air bearing section of the arm in order to seal it fully this time. So there is no going back with this first build. The epoxy filler makes it look decidedly home-made (by a five year old and his play-doh). I will see if I can "prettify" the build a little when it has settled, but if I sand the settled epoxy filler, I am afraid that the dust may enter into the air holes ...

    Next: is it air tight, or not ...? As stated above, I have assembled the Sera 275 air pump with air tubes and a surge chamber made from a Lidl juice bottle.
    Then: "prettify" or not to "prettify"?
    Then: conjure up a "plinth" for the air bearing arm with a clever way to height adjust it ... and put it next to the turntable
    Then: make two new prototype arm wands - first one from an 8 mm wood dowel with wires running down the length of the arm, then perhaps one from aluminium tube
    Then: balance the arm perfectly for a trial run with an Ortofon OM5 cart from a NAD 5120 TT
    Then: hold my breath ...

    OK - a photo:
    [​IMG]
     
  14. stevec67

    stevec67 pfm Member

    What have the Saxons ever done for us?
     
  15. Rosewind

    Rosewind Lost in Translation

    Ask not what the Saxons did for you, but what you can do for the Saxons. It seems to be pay-back time.
     
  16. Rosewind

    Rosewind Lost in Translation

    Well, the Epoxy filler is no good. It failed to solidify and I removed it after 2 days. It left some chalky residue along the edges that I will remove later on.

    So I will have to find something else with which to seal the air-bearing angles of the arm if they need it. Another lesson learned.
     

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