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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

    Edited

    I can get hold of angles that are 1.5 mm thick and 20 x 20.

    If I use my existing unsymmetrical angles as the 2 bases (the one with the air intake hole in it + the one with the air cushion holes for the floater) and then use a completely Symmetrical 1.5 mm thick floater with a Symmetrical 1 mm x 15mm x 15 mm bearing angle glued to it so the floater has a thickness of 2.5 mm, perhaps then I am not so far up shit creek that I can't paddle down and out again.

    Again: air intake hole - dead centre or not?

    Surge tank? - will do.

    Level bearing? Yessir! that is what I aim to do. I have two old carts that I can use when setting up. Just so I don't rip anything expensive apart.
     
  2. Rosewind

    Rosewind Lost in Translation

    Ah ha ha. The wood arm wands (8mm duwels), ordered in the UK, were due to be delivered by UPS at the end of the day on Monday 21, but one week later they still haven't been delivered. The UPS website lists the last scan as having been done on Friday 17, so no listing of what I was shown last week.

    With this and the unsymmetrical 20 x 20 x 2 mm aluminium angles, I am beginning to believe that I live somewhere in Africa or China, not in Denmark which is supposed to be part of Western Europe. In this part of the world, things are supposed to work, to be delivered on time and to have been manufactured within small margins of tolerance. 2 out of 2 purchases gone wrong.

    Buy locally and go handle the goods yourself before you carry them home yourself.
     
  3. booja30

    booja30 pfm Member

    Don't feel bad. I'm in Spain and have the same experience all the time! ;)
     
    Rosewind likes this.
  4. Paul R

    Paul R pfm Member

  5. Rosewind

    Rosewind Lost in Translation

    Yes, but their delivery / handling prices are meant for businesses that buy in bulk. However I think I have found a good source locally in a store for local plumbers / craftsmen.

    Today I am down with a mild version of the flu whereas my wife has been away from work for two weeks now with the real deal.
     
  6. Rosewind

    Rosewind Lost in Translation

    I just received a partial refund from the aluminium angle debacle. Will buy some symmetrical aluminum L-angles locally - I may have to settle for 25 mm x 25 mm x 2mm if that is alright?

    I also found a viable inexpensive pump for the project, an adjustable Sera Air 275 R (or its bigger sibling the 550) which willl give an adjustable air flow of up to 275 liters per hour (or up to 550 liters). The cost is £17 (£35).
     
  7. h.g.

    h.g. pfm Member

    Good to see progress. Interest is growing at this end in building a numerical model to answer some of the questions raised about how well parallel tracking arms might work compared to conventional ones but it won't be until the summer at the earliest given a bunch of pressing non-hifi projects.

    Given you didn't trim your angles to size do you intend to do something like lapping the surfaces of your bearing or do you intend to see what happens with a relatively rough surface finish and blowing a bit harder?
     
  8. Rosewind

    Rosewind Lost in Translation

    h.g.
    Trimming? I mean to make the angles symmetrical - either I will find a local craftsman who can cut off the extra 1.2 mm on one side, or I will buy new angles that are even. The pieces will be cut to (2 x) 30 cm and (1 x) 18 cm exactly.

    EDIT: it is going to be new profiles, at least for the hovering angle. I talked to a local craftsman who said it would be very difficult to shave off just 1.2mm of one side of the angles. I think I have found a supplier of 20 x 20 x 2mm aluminium angles. I will order some tomorrow.

    Lapping: I am not sure if I need to treat or sand the surface of the bearing in any way. I suppose I will see what happens when I get that far. The insides of the aluminum angles are fairly smooth apart from a tiny ridge at the bottom. The outsides are smooth as they have been anodised.

    It will be great fun to see if it works in the end. I have read about people's surprise when the sleigh/arm floats as I should for the first time. Of course there will be a lot of agonising over how to balance and weighing the arm down correctly as well as setting up the air pump and adjusting that.
     
    Last edited: Jan 29, 2019
  9. Rosewind

    Rosewind Lost in Translation

    I think I will try to use the "duff" aluminium angles to build the first two levels of the air bearing arm - the air intake level and the level with the air bearing holes in them. Here you can see the support for the first level that will be glued together with epoxy glue (or could I just use strong double-sided foam tape that would have a dampening effect also? Or would the foam tape be prone to wobbling ...?):
    [​IMG]

    Below this I will glue wood with two grooves for the support to "slot into". At the base of the wood, that will be wider than the slider for the arm, I would be able to have adjustable legs ... Hmm.

    Well now I just used the strong adhesive foram tape and will see how it goes. Pictures on Thursday. Thursday and Friday I am off from work and will drill some holes and buy the pump. Perhaps then I will be able make a piece of angle aluminium float (with weight on it) ...
     
  10. Rosewind

    Rosewind Lost in Translation

    So now I have everything for the prototype run of the arm in the house:

    1) A 1 meter long perfect 20x20x2mm aluminium angle - I will use 18 cm of this for the slider for my prototype (first go). The surplus aluminium will be kept for an improved version of the arm if need be.
    2) An aluminium tube (8mm) - enough for several arm wands if needed.
    3) A 5 meter length of 5 mm soft silicone air tube, a short length of which will just fit inside the aluminium wand to help dampen It while also protecting the litz wires that I will now run inside the wand
    4) A Sera fish pump (the 275 litre / hour version)
    5) 6 plastic air vent nipples (2 that will be glued onto the arm bearing and 2 onto the surge container (= a water bottle)
    6) 1 metal air vent for easy adjustment of the air flow for the prototype air bearing arm
    7) Super glue and epoxy filler to make the arm air tight
    8) Tiny 0.3 and 0.4 mm drill bits

    Pictures later today and tomorrow.
     
  11. booja30

    booja30 pfm Member

    Why does the arm need to be air tight? Just curious.
     
  12. Paul R

    Paul R pfm Member

    The cavity between the angles that form the base needs to be air tight so air only escapes through the holes into the bearing.

    Confused? You will be...

    Anyway looking forward to this, might even play along later...
     
    Rosewind likes this.
  13. Rosewind

    Rosewind Lost in Translation

    I will use the new angles all the way in order to ensure that they match up exactly. The cutting and drilling will be done later today in my workshop after I have walked the dog. I have a bench press drill that I will set up for the drilling. I will take my time so I get it right.
     
  14. Rosewind

    Rosewind Lost in Translation

    On my way. My drilling and cutting accuracy is not as good as I had hoped for. It would have been great to have somewhat better tools for holding, cutting and drilling more exactly than I was able to. We will see if the arm works as intended even with my limited skills. Otherwise I will ask a coupke of neighbours if I can borrow their machinery.

    Today, I finished cutting and drilling and I am slowly assembling the tangential air bearing arm using mostly double-sided foam tape that will also act to dampen the arm.

    I just finished fitting stands and a metal air vent to the bottom angle - again all secured with strong double-sided tape - if it works, it works - or the tape will be replaced / reinforced with strong glue. I haven't decided what to use as a base for the arm - most likely it will be a block of wood with adjustable legs.

    I have begun lining the first angle of the arm with a thin slice of doublesided tape on which I will place the second angle with the air holes in it. These holes still need to be covered with a layer of tape in order to make the 0.3mm holes in that.

    I have made up a small surge tank from a 1 liter Lidl juice bottle and glued plastic air vents onto it - again with double-sided tape and an extra sprinkle of glue to make a better seal. If it works it works.

    For the arm wand, I squeezed the front 1 cm of an 8mm aluminium tube flat - as was suggested above - and I drilled a mounting hole in it for a future headshell. I have also drilled a hole on the underside towards the front of the arm wand for the internal litz wires to come out near the cartridge.

    I have assembled the blade bearing - not the prettiest thing in this world because of my lack-lustre handy-man skills but it will do for now. I stand by my intention to line the inside of the wand with simple silicone air tubing - if I can make it go all the way through with the fragile litz wire. If not, I will find something else.

    I need a properly made headshell. The ones I tried to make are simply not precise enough to be any good. But there are other days ahead, and I will receive a cheap one soonish. If I am lucky, that headshell will fit straight on another length of aluminium tube.

    Pictures ... tomorrow.
     
    Last edited: Jan 31, 2019
  15. h.g.

    h.g. pfm Member

    Looking forward to them.

    Where do you intend to take the wire out of the wand?
     
  16. booja30

    booja30 pfm Member

    Sure, I understand that the angles that make up the sled would need to be airtight to distribute air from the hose to the holes.

    By 'arm' I assumed the arm that would go between the air bearing sled to the cartridge, and this would just mount atop the sled.

    So, is this a terminology problem, or does the arm need to be airtight for some reason? I thought maybe it had to do with keeping the wires fixed in the tube.
     
  17. Rosewind

    Rosewind Lost in Translation

    Here:
    [​IMG]

    This is where I am at:
    [​IMG]

    You can see a part of the tube with which I hope to line the inside of the arm wand.
    [​IMG]
     
  18. Rosewind

    Rosewind Lost in Translation

    I am not a native English writer, so my terminology is fluid at best when it comes to specialist language.

    The arm is the whole thing. The arm wand is the wand only.

    No. The arm wand rests on a Stanley knife bearing that itself rests on an air cushioned floater that floats on air coming from an air tight chamber fed by a Sera 275 air pump via a surge chamber and a long silicone air supply tube
     
  19. booja30

    booja30 pfm Member

    Ok, that sounds like what I was picturing, just a difference in terminology. Thanks!
     
  20. Rosewind

    Rosewind Lost in Translation

    4 wood duwels arrived at noon today. I will test these as arm wands with external wiring. They will need some kind of treatment before use.

    [​IMG]
    Otherwise I have struggled to create the airtight chamber using the tape I have, but I think that I have found a nice solution. It came to me while walking the dog.Yes! It takes time to get it right. This before I am able to test anything.

    I have trimmed the rounded screws used to hold the stanley knife edge so thay do not obstruct the arm.

    I have put together the air supply system with the surge tank. The fish air pump hums so it will be put in a closet inside a styrofoam box.

    I will need to get 5mm silicone tube if I want it to fit inside the aluminium wand.
     
    Last edited: Feb 1, 2019

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