DIY linear tonearm

obstacles

Such a structure may not be desirable because of the combined weight of the cartridge and headshell is amplified by the arm tube. Therefore, the pressure of v groove bearings on the knife-edge rail will increase. In other words, the friction will increase.

A short arm may be a good option, however, there will be a structure over the LP.

You're right, Jim. I think shortening the horizontal tube is probably the only option to reduce friction. I have to look at the sum of cartridge + tube + carriage + rollers + blade as one GIANT headshell that contributes too much vertical mass.

If I have to hover over the platter, I'm thinking using a diagonal bar to hold the blade and make sure the vertical bearings have offset angle to parallel with the blade. And then add a swiveling mounting base. I'm just spitballing right now. Thanks for chiming in.


Vertical articulation: here it must be taken into account that the cantilevered tube + asymmetric double blade introduce a variable load on the 2 sides of this articulation

The variable load is a headache. I wonder if a hanging structure with spring(s) might work... It probably would be worse! I always wanted a pistonic type of vertical bearing so we don't have to deal with VTA once and for all! We can dream!

I had thought of a 5" diagonal wand with offset headshell and offset bearing at the base which consists of a rotating blade (pivot at platter level) as vertical pivot. That can lessen the vertical mass significantly. Since there's no counterweight on this diagonal tube, horizontal mass shouldn't be that great. That also probably, alas, created some undesirable twisting forces. It certainly can look cool (my eternal desire to retain that classic turntable look) and easy to use!

Again, spitballing...

No platter hovering was the starting point, isn't it?

Yes, that's what started the insanity! Audiophiles can be stubborn and I might be a masochist! But obstacles provide challenges to overcome and they're part of the fun of any hobby!

otherwise why not buying a Cle@r Audio ?...

Speaking of that brand, they have some well made items but not an ounce of originality. And when it comes to making certain white elephant product, it's down right stupid.

my compliments for your new graphic skills

It's really embarrassing compare to yours. Apologies to reusing and butchering your drawings!
 
Apologies to reusing and butchering your drawings!

...that are made just for that, Dd. Some new food for thoughts: a slimming diet for vertical mass...
(non recirculating balls - rail can be shorter, since the balls travel just half length; with a radial rail there no need to shorten too much the shaft (no torque from the side force): as for the aligned articulations i like also least possible VTA variations.

carlo
but that long lever still doesn't convince me - may you post the diagonal one? i cant' imagine how it works
 

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Hi all,

I don't check in on this thread for a couple of days and there's suddenly 3 whole pages to catch up on.

The main advantage of going linear tracking is not the reduction in lateral tracking error, although this is a bonus.
The main advantage is that it allows you to utilise a much shorter armtube, or even no armtube at all. If you reduce the length of a tube by 20% you double its rigidity. A more rigid arm will have less colouration. Reducing the armtube down to 2 or 3 inches can increase rigidity by over 1000% compared to a more conventionally dimensioned arm.
This does require that the rail has to be positioned above the platter and be retractable in order to change records. This does require an extra couple of steps to change the record so ease of use is compromised.
There is no such thing as a no compromise design. When manufacturers say they have a no compromise design it means they haven't cut corners for cost reasons which ironically means they have compromised affordability. The job of the designer is to find the best balance of compromise.
With my arm the rail slides to the rear of the deck to allow record changing. I decided to compromise a little bit of ease of use for reduced colouration. As I have been using this arm for many years I now find it much easier to use than a conventional arm. It what you're used to.

Short arms do have their downsides. Funnily enough increased VTA error due to warps isn't that much of a problem. The vast majority of VTA error is due to the slope of the surface of the record and not the pivoting of the arm about its vertical axis. VTA error with my 55mm arm isn't that much worse than that of a 9" arm. (The use of a parallelogram does not eliminate VTA error, it just reduces it a little bit). The main area that can be a problem is warp-wow. This can be largely mitigated by making the vertical pivot as close to the surface of the record as possible. The use of a record clamp designed to reduce warps obviously helps to reduce both VTA error and warp-wow.

Niffy
 
I have , with great interest , been following the suggestion’s from nocdplz and directdrive on how to make an arm that is not hoovering over the record and now I cannot resist bringing my favorite solution to this .
I know that there will be some yelling KISS!! to this suggestion, but given the complexity of the latest suggestions, I find this point rather mute .
My suggestion is to make a very short horizontal bearing , where the cartridge can only move ,say, 10mm and this bearing could be air bearing or a Lil Casey type or glass rods with two steel balls or similar.
This bearing is seated in a structure that can travel laterally across the record surface. The vertical bearing could be the normal pivoting type with a very short arm or some sort of a Lil Casey bearing ( could probably be made simpler and lighter as there will be no displacement of the weight ).
Two proximity sensors determine the relative position of the cartridge inside the horizontal bearing and the output from them is routed to an Amanero (or a custom made circuit) and the output controls a steppermotor that moves the supporting structure across the record. This structure can be made very rigid and heavy and still there will be very little force needed to make the lateral movement , as the velocity is very small. I suggest using a spindle as the ones used in a CNC machine or 3D printer.
If the horizontal bearing has no (air) or very little friction, the cartridge will not notice the movement of the supporting structure, as far as I can see.
I think this will overcome the problems pointed out by nocdplz and at the same time eliminate the drag from the wires ( and improve the aesthetics from long wires hanging in the air) and it would be pretty easy to make such an arm completely automatic.
I must say , I adore the visual simplicity an aesthetics of Lil Casey and my suggestion will probably be a more bombastic looking arm.
Why do I not build such an arm? Well I probably will , eventually, but I would like to have suggestions from some of the clever members in this forum, if anybody should find my suggestion valid and interesting.
 
...I would like to have suggestions from some of the clever members in this forum, if anybody should find my suggestion valid and interesting.

At the risk of being presumptuous by associating myself with the category of being a 'clever member' on the forum, your idea seems to combine the disadvantages of mechanical linear trackers and servo linear trackers. Even though the cartridge moves a small distance, it still has to overcome friction/stiction issues which have already been thoroughly addressed earlier in the thread. Now add to this the complexity of a servo control system. A very slick implementation of mechanical linear tracking plus servo control has already been done on another diyaudio thread:

A Revolutionary Pivoting Tangential Tone Arm

Ralf's design is a shining standout in the 'clever' category. If you dig into it more deeply, you will also see that it involves a lot of precision machining which is not so easy to DIY. A better implementation of your idea would be to design a good conventional arm using a bearing type of your preference, and design a servo control to move the pivot so as to maintain tangency. But now that would be a 'traditional' servo controlled linear tracker arm, of which there are many existing design concepts to choose from to DIY.

While I have a bias towards servo controlled linear trackers, I think the spirit of this thread was to implement a linear tracker design that does not use servo control. If you do intend to use servo control in the design, I think that would merit starting a new thread. Best of luck with your efforts.

Ray K
 
I have, with great interest, been following the suggestions from nocdplz and directdriver on how to make an arm that is not hoovering over the record and now I cannot resist bringing my favorite solution to this.

Thanks for joining in the crusade of hover-less tonearms!

Ray just beat me to it about Ralf's invention and his thread.

So here are some videos of that arm you can check out:
Video#1 Over-head view
Video#2 Close-up view
Video#3 @12:15 for 5 minutes

I agree with Ray's view that this thread is more about mechanical parallel trackers with no servo. I, however, would love to see a new thread that explores the wonders of servo tonearms and servo drive systems.
 
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may you post the diagonal one? i cant' imagine how it works

This is just a rough drawing. Obviously the vertical bearing angle needs to be offset to match the horizontal blade. And the counterweight also needs to be arranged accordingly. None of that is shown in the drawing. Obviously the structure will be hovering over the platter and a swiveling base is needed for changing records. Now the carriage can be as short as possible.

parallel-tonearm-rev9.jpg
 
Ok.
Apparently the reaction to my idea is that it is OT in this thread, so I will stop posting more about it in this thread, although I do not feel it is OT.
IMHO it does not introduce the weaknesses of the traditional servo arms, as these are error correction systems, where a tracking angel error is detected and corrected by the servo system, and this can be heard as a popping in and out of focus. This is not the case in my suggestion.
 
Rough but correct, imho.
Rotating the vertical pivot axis instead, it will no longer be parallel to disc radius. On warps the point A will go higher than B. (attachment)
Simple mock up: take a rectangular cardboard and paste on it a stick, rotated. Now push up the stick and see what happens.

carlo
still not understanding...
 

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Carlo, sorry for the confusion in my wording. As I said the vertical pivot angle has to match the radius so, yes, they have to be parallel. What I meant was the counterweight and all the attachments have to be angled. Bottom line is that the two pivots have to have equal mass distribution. It's not that much different than conventional tonearm with offset angle headshell and offset angle bearing so the counterweight has to be angled accordingly. Again, the vertical bearings placement has to be in parallel with the radius.

(I am sticking to V-groove bearing or ball bearing. I can't see myself fiddling with rolling balls and their placements.)

Due to the high vertical mass and the need for swiveling base, I might scrap the whole idea. I would just build a parallel tracking with a diagonal tube, about 5 inches long, headshell on front end and back end (with no counterweight) is the carriage on two rods and they are attached to a pivot and counterweight. This is not that much different from most of the parallel arms here except the sliding area is next to the platter instead of hovering above it.
 
Now i got it, thanks!
Evidently I have few neurons left, although I prefer to think that English is not my language.
I believe (learned with the Syrinx mK2 attempt) that your hypothesis is really difficult to achieve passively. There seems to be a progressive convergence on the innovative work of Ray and Ralf (and now the ideas of Koldby) on a sort of completely rethought semi-active LT. Maybe someone should open a new thread: it is strange to find so many infos on all kinds of TAs, and so little on servos.
carlo
 
more or less...
not easy, but maybe feasible (acceptable vertical mass)
carlo
being based on weight and not on bearing's stiffness this vertical articulation need s to be corrected due carriage travel- eg offseting the CW, or with a magnet inside to increase the force on the 2 jewels
 

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CW - you're right; better an offset placement, without breaking the shafts, imho. Or instead, to reduce the vertical eff. mass, to use a spring CW, as once suggested by Walter for first Lil Casey.
The trickiest part to build is the carbon rail, to be milled or sawed carefully for the steel rods inserts. All the rest is diy machining (quite) as usual

c
but the hovering?
 

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The trickiest part to build is the carbon rail, to be milled or sawed carefully for the steel rods inserts. All the rest is diy machining (quite) as usual

I think two carbon fiber tubes stacked together (or even just a single carbon fiber rectangular rod that shaped like a ruler) and then glue two 1mm thin carbide rods or even ruby rods top and bottom are suffice.

but the hovering?

Yes, the hovering is still stuck in my craw. Although having a swiveling base is acceptable. But I might change course. We'll see...

I must say I really appreciate you indulging me. Thank you, Carlo!
 
one more -slow- step

Designing is almost funnier than building, and much more comfortable, at this age: so thank you for bringing the ideas to the party.
I fear that carbon does not have the necessary consistency for a long-lasting V blade. But for this, as for the carriage shape and bearings (difficult to imagine the best way to share the weight on the wheels) better to ask our friend Niffy, and his great experience
carlo
 

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I fear that carbon does not have the necessary consistency for a long-lasting V blade.

The carbon fiber horizontal bar can be lined with 1mm tungsten carbide rods or ruby rods for the top and bottom. So the V-groove bearings will be touching hard surfaces and not on the carbon fiber parts.


as for the carriage shape and bearings (difficult to imagine the best way to share the weight on the wheels)

The carriage you drew does not work because mass is on the right side of the top bearing and it will pivot to the left along with the right bearing. The idea of my arrangement is to use the least number of bearings, which is two, so three bearings are not necessary. In general, I try to use the least number of parts if possible. (It's like intellectual Jenga!) And that the top and right bearings are loaded provided the sum mass of headshell and cartridge is on the left side of the hanging bearing and heavier than the right side.

Since the design requires a swiveling base, why use vertical pivot at all? I'm thinking of a hanging structure with springs for vertical movement. Hmm....

parallel-tonearm-rev12.jpg