sorbathane
excellent arms, really appeals to me to team one of these with a scheu.
just a thought about the resonance and "air hiss" transmission;
why not use cartridgemans' isolation "thingy" between the cartridge and the armhead, i think its most likely made from sorbathane, great stuff which disipates and absorbs energy (more effectivily than anything else i know of). it could also be used between the floating runner and the isolated upper floating runner. you can buy sheets of it, (there used to be ads for it in the back section of hi-fi world magazine).
excellent arms, really appeals to me to team one of these with a scheu.
just a thought about the resonance and "air hiss" transmission;
why not use cartridgemans' isolation "thingy" between the cartridge and the armhead, i think its most likely made from sorbathane, great stuff which disipates and absorbs energy (more effectivily than anything else i know of). it could also be used between the floating runner and the isolated upper floating runner. you can buy sheets of it, (there used to be ads for it in the back section of hi-fi world magazine).
From my limited experience, you better keep any compliant/soft material as far as possible from your arm. It absorb vibration in highly eneven manner: kills high frequencies, doing about nothing with the low's. As a result, it sucks life from the music and all low fq vibrations are bounced back to stylus from the boundary between soft and hard materials, screwing up the sound. Nothing can be worse. I tried to decouple counterweight by means of rubber bushings and washers of all sorts, from thick to very thin.
The resulting sound was consistenly horrible.
decoupling the counterweight is a black art and involves trial and error... but ur right rubber (or sorbothane ) will not work there.... whatever methods and materials u use will have a sonic effect... its just a question of tuning the arrangement to satisfy your own ears
i was really suggesting the cartridgeman isolating cartridge isolator for k9vap, as he already uses a musicmaker cartridge. also hes using rubber between his two floating runners already, sorbothane may be a better bet there for him.
and also k9vap should check out http://www.william-reed.net/audio/newpics/ (jeff) could have a better answer for bearings and counterweight.
i'm working on designs for an arm myself;
one is floating a solid balsawood cylinder on a semi- circular concave track... the ebony armtube passing through its central axis (i feel having the arms centre of gravity in line with the axis will lead to a more stable arrangment and negate the need for an underslung counterweight).
i was really suggesting the cartridgeman isolating cartridge isolator for k9vap, as he already uses a musicmaker cartridge. also hes using rubber between his two floating runners already, sorbothane may be a better bet there for him.
and also k9vap should check out http://www.william-reed.net/audio/newpics/ (jeff) could have a better answer for bearings and counterweight.
i'm working on designs for an arm myself;
one is floating a solid balsawood cylinder on a semi- circular concave track... the ebony armtube passing through its central axis (i feel having the arms centre of gravity in line with the axis will lead to a more stable arrangment and negate the need for an underslung counterweight).
the air supply is another interesting area.
how about using a giant suringe with a large weight on top to regulate pressure (no pump).... similar to the old coal gas storage cylinders ... silent and constant pressure... to refill with air; just open a valve and pull the cylinder up by hand , sucking in air.
how about using a giant suringe with a large weight on top to regulate pressure (no pump).... similar to the old coal gas storage cylinders ... silent and constant pressure... to refill with air; just open a valve and pull the cylinder up by hand , sucking in air.
hi, dragging this thread back up, hope you dont mind
Im half way through building one of these myself but am having air issues.
I built it using 1.5x20x20 angle, but may rebuild with 1 inch profile as it seems this is better.
I cant get the carrier to float properly. It does, but only un laden. Add the arm and it binds.
Im using a different air pump, not a rena 400, but it should pump more air than the rena. Can anyone who is using one of these arms tell me the specs of their airpump?
Also, its a twin outlet pump, feeding into a smoother tank, but the air line from the tank to the arm is the same size as the line from the pump to the tank. Will this restrict the air flow? I realised the outlet from the tank probably needs to be bigger, am i right?
Im half way through building one of these myself but am having air issues.
I built it using 1.5x20x20 angle, but may rebuild with 1 inch profile as it seems this is better.
I cant get the carrier to float properly. It does, but only un laden. Add the arm and it binds.
Im using a different air pump, not a rena 400, but it should pump more air than the rena. Can anyone who is using one of these arms tell me the specs of their airpump?
Also, its a twin outlet pump, feeding into a smoother tank, but the air line from the tank to the arm is the same size as the line from the pump to the tank. Will this restrict the air flow? I realised the outlet from the tank probably needs to be bigger, am i right?
Sorry to bring up questions regarding such a brilliant design, but I was wondering if anyone had considered making the inner, static section using a piece of anodised aluminium tube, and having the slider as a semicircular section of tube that's a very good fit on the inner section (possibly polished against a spare piece of the inner section)
It would seem to me that this would remove the need for a vertical bearing, as the outer section could 'rotate' around the inner section.
Another alternative might be to make the slider hollow and blow the air through it, thus not wasting so much air that's currently blown through the holes that are not covered. Very thin silicone tube would probably suffice, and has very little stiffness.
Any comments?
It would seem to me that this would remove the need for a vertical bearing, as the outer section could 'rotate' around the inner section.
Another alternative might be to make the slider hollow and blow the air through it, thus not wasting so much air that's currently blown through the holes that are not covered. Very thin silicone tube would probably suffice, and has very little stiffness.
Any comments?
The strong side of Ladegaard is you do not have to worry about perfect match of the slider/rail surfaces. You simply cut one profile to pieces and here you are. It costs you virtually nothing.
With the tube-like rail, the ideal match between tube and semi-circular or circular slider is mandatory, otherwise your slider will never become airborne. And this is whole another story implementation-wise.
As for air pressure supplied to the slider, it is another challenge.
The air supply tube shall be super thin and flexible. I had to dismiss my favorite silver wire and replace it with regular Cardas, since it was too stiff and applied variable side force to the slider.
With the tube-like rail, the ideal match between tube and semi-circular or circular slider is mandatory, otherwise your slider will never become airborne. And this is whole another story implementation-wise.
As for air pressure supplied to the slider, it is another challenge.
The air supply tube shall be super thin and flexible. I had to dismiss my favorite silver wire and replace it with regular Cardas, since it was too stiff and applied variable side force to the slider.
I have been involved in developing the Ladegaard over the years, & have also built a number of these arms for other enthusiasts. There is alot of work involved in its construction, & altho parts & materials are cheap, the labour is intensive.....typically 24hrs.
One of my problems has been to make one design fit all turntables, the limiting factor being the minimum platter height required......the higher the better. Platter heights of 1cm are difficult to accomodate, if not impossible.
It was my idea to work on a design where the tonearm could be suspended from below. I knew this would be easier by inverting the bearing. At the same time, I wanted to see if I could shorten the arm carrier. With this design, the arm can be suspended over the platter, so the distance from the spindle on different decks doesnt matter........adjusting the length of the arm accomodates this. The sideways positioning is done by a slot, & vertical by moving nuts on a threaded 22mm brass bar which sits in the plinth hole.
One of the other problems I felt with the design was the waste of air escaping from the holes not covered by the slider. To this end, the slider now is active.
I have read threads on the 'backlash' present in these arms due to the cushion of air. I am weary of increasing the air pressure & mass of the slider in an attempt to harden the cushion of air. Too much airflow is audible in the speakers as it gets amplified thru the armwand & stylus. I found that by doubling the depth of the slider (35mm) & halving the width (9cm) I could get the slider to float efficiently with less air pressure than I have ever used. I have my Sera 275lph pump on minimum with air valve 1/4 off! With the increase in slider depth, the backlash is also reduced.
I now have this incarnation of the arm working reliably on my test bed. The airline is too stiff, but i have ordered some superflex material & am hoping will sort it. I must stress I have not mounted this yet on my main turntable, so have no idea what it sounds like to my conventional design, but I have high hopes!
I need to thank Erik for his brief correspondence with me. His idea of using a square section in his design flipped a switch in my head!
Here is a brief overview I have prepared of this arm with some pics. Happy New Year to all!
Advantages
- Fits any deck, no matter how low the platter is.
- Single point fixing adjustable for height, tilt & horizontal alignment.
- Carrier overhangs record allowing easier positioning & shorter wand resulting in less vertical mass
- Slider now carries air supply instead of carrier so there are no holes open allowing inefficient escape of air. This means a lower pump setting can be used & less noise.
- Wider angle extrusion (35mm) used allowing shorter slider & carrier resulting in overall smaller dimensions. Larger area also reduces backlash present within air-cushion.
Disadvantages
- Extra tension from airline to interfere with slider movement
- Cosmetically challenged?
- Changing arm wand more difficult
One of my problems has been to make one design fit all turntables, the limiting factor being the minimum platter height required......the higher the better. Platter heights of 1cm are difficult to accomodate, if not impossible.
It was my idea to work on a design where the tonearm could be suspended from below. I knew this would be easier by inverting the bearing. At the same time, I wanted to see if I could shorten the arm carrier. With this design, the arm can be suspended over the platter, so the distance from the spindle on different decks doesnt matter........adjusting the length of the arm accomodates this. The sideways positioning is done by a slot, & vertical by moving nuts on a threaded 22mm brass bar which sits in the plinth hole.
One of the other problems I felt with the design was the waste of air escaping from the holes not covered by the slider. To this end, the slider now is active.
I have read threads on the 'backlash' present in these arms due to the cushion of air. I am weary of increasing the air pressure & mass of the slider in an attempt to harden the cushion of air. Too much airflow is audible in the speakers as it gets amplified thru the armwand & stylus. I found that by doubling the depth of the slider (35mm) & halving the width (9cm) I could get the slider to float efficiently with less air pressure than I have ever used. I have my Sera 275lph pump on minimum with air valve 1/4 off! With the increase in slider depth, the backlash is also reduced.
I now have this incarnation of the arm working reliably on my test bed. The airline is too stiff, but i have ordered some superflex material & am hoping will sort it. I must stress I have not mounted this yet on my main turntable, so have no idea what it sounds like to my conventional design, but I have high hopes!
I need to thank Erik for his brief correspondence with me. His idea of using a square section in his design flipped a switch in my head!
Here is a brief overview I have prepared of this arm with some pics. Happy New Year to all!
Advantages
- Fits any deck, no matter how low the platter is.
- Single point fixing adjustable for height, tilt & horizontal alignment.
- Carrier overhangs record allowing easier positioning & shorter wand resulting in less vertical mass
- Slider now carries air supply instead of carrier so there are no holes open allowing inefficient escape of air. This means a lower pump setting can be used & less noise.
- Wider angle extrusion (35mm) used allowing shorter slider & carrier resulting in overall smaller dimensions. Larger area also reduces backlash present within air-cushion.
Disadvantages
- Extra tension from airline to interfere with slider movement
- Cosmetically challenged?
- Changing arm wand more difficult
hello...I would like to comment on your pictures if you dont mind some comments from an Engineering view point....
Your execution is valid but your fabrication is wrong...the wood swells with humidity and the 6061 aluminum is not meant for that kind of application...its not even treated from any oxidation especially where the inter connects are.....its screaming for contamination because sheilding is of importance here...
After a brief look....I dont want you to take offence because I respect what you did with this and I think if you take a small part of my advice you will find a big difference.
The best to your project, JOE DIRT®
Your execution is valid but your fabrication is wrong...the wood swells with humidity and the 6061 aluminum is not meant for that kind of application...its not even treated from any oxidation especially where the inter connects are.....its screaming for contamination because sheilding is of importance here...
After a brief look....I dont want you to take offence because I respect what you did with this and I think if you take a small part of my advice you will find a big difference.
The best to your project, JOE DIRT®
I have no experience here, so take my suggestion as just this: a spurt of imagination. I see the work you have done as an advancement of this art.
2 things, taken together...What if the arm carrier, that thing to which the air line is attached above, were longer? Also, what if the air line were routed differently...passed through the wood and injected through the bottom angle? This would require the air holes to be located within the limits of travel of the arm carrier.
Would this work? Could the underside (mating face...bearing surface) of the arm carrier be shaped to form a plenum and better distribute the air pressure....in effect to localize the bearing surfaces at the perimeter of the arm carrier?
2 things, taken together...What if the arm carrier, that thing to which the air line is attached above, were longer? Also, what if the air line were routed differently...passed through the wood and injected through the bottom angle? This would require the air holes to be located within the limits of travel of the arm carrier.
Would this work? Could the underside (mating face...bearing surface) of the arm carrier be shaped to form a plenum and better distribute the air pressure....in effect to localize the bearing surfaces at the perimeter of the arm carrier?
hey...I like where your taking this and your concern about the bearing is essential...I have to read up on this thread because I havent had the time to be truthful....modulating air is what I do for actuators and robotics...so maybe I can give some advice...thanks for the positive reply....ego`s can fly on these forums...hahaha...but I`m JOE DIRT the extremist
Regards, JOE DIRT®
Regards, JOE DIRT®
Hi Joe
Thanks for the reply!
You certainly can help me with regards to finding some siutable flexible tubing. Also, I have halved the diameter of the airline supply from 4mm ID to 2mmID with this design. What effect does this have on airflow? At the moment, I have used the same inlet adaptor barbs as i used for the 4mm tubing, but inserted the tubing inside the adaptor as it wont fit from the outside. I am afraid using the proper 2mm adaptor will futher restrict the airflow.
Any advice, suggestions?
Thanks
Vic
Thanks for the reply!
You certainly can help me with regards to finding some siutable flexible tubing. Also, I have halved the diameter of the airline supply from 4mm ID to 2mmID with this design. What effect does this have on airflow? At the moment, I have used the same inlet adaptor barbs as i used for the 4mm tubing, but inserted the tubing inside the adaptor as it wont fit from the outside. I am afraid using the proper 2mm adaptor will futher restrict the airflow.
Any advice, suggestions?
Thanks
Vic
Tubing
Nice try, Vic!
I wish you eventually find suitable tubing, being flexible/thin enough and not blocking the airflow at the same time. I believe the main advantage of such design is lower lateral mass due to shorter arm. I would put lighter counterweight further from the pivot to keep the vertical effective mass closer to the optimum. Also try to avoid additional connections within your wireing.
Keep us updated as you project progressing.
Happy new year,
Michael
Nice try, Vic!
I wish you eventually find suitable tubing, being flexible/thin enough and not blocking the airflow at the same time. I believe the main advantage of such design is lower lateral mass due to shorter arm. I would put lighter counterweight further from the pivot to keep the vertical effective mass closer to the optimum. Also try to avoid additional connections within your wireing.
Keep us updated as you project progressing.
Happy new year,
Michael
havent you gone back to the Dennesen?
since you are hanging the cradel for the arm why not go to a captive air bearing with a certre tube with holes in it that has a short tube that slips over it that provides you horizontal slide which your arm attaches to. That way your air line supply tube can simply fit into one of the closed ends of the centre air tube. This way you could even get your vertical arm motion like the Dennesin did (though it was non captive) along with easy VTA adjustment.
since you are hanging the cradel for the arm why not go to a captive air bearing with a certre tube with holes in it that has a short tube that slips over it that provides you horizontal slide which your arm attaches to. That way your air line supply tube can simply fit into one of the closed ends of the centre air tube. This way you could even get your vertical arm motion like the Dennesin did (though it was non captive) along with easy VTA adjustment.
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