DIY linear tonearm

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I will be using a 16mm x 2mm sidewall tube. That's what I have, not sure it is super critical.
Carbon fiber tubing just came in. Found some tubes like Vynuhl used and then some ultralight that is the same weight at double the diameter so MUCH stiffer. (P90 SkysharkII) guess it is time to start the serious drawings and layouts. Let the fun begin.
 
second option is no tube at all

Does anyone know?

if you wanted to build inside a tube as in the Cantus arm you could eliminate the tube all together and simply use two one cm wide strips of window glass spaced apart at each end and on a slight angle. Space the strips in a very slight "V" so the bearing cannot drop through the bottom opening. There you go done like dinner. The more vertical the walls of the glass strips the less forward and backward motion of the arm as it rides a warp. So you will have a glass "V" with an open bottom and an open top. That's about a simple as it gets for diy. Best regards Moray James.
 
Hi Bill,


The bearings are used as shipped, I've also seen mention of bearing weight, I'll be lucky if these bearings even weight a gram each :). One must remember too in this design the bearings don't need to entirely rely on the bearing races, the brass spacer/tube will take up any resistance encountered. I'm sure as it comes apart the beautiful simplicity of it will reveal itself. In essence it has a back up system for lateral movement.



Colin
Hi, Waiting for my shipment of bearings to arrive. I'm beginning to see what you are doing with the brass tube/shim. So if the inner races were to seize in the outer races the bearings would still continue rotating albeit requiring more force than if the were free to rotate. A sleeve bearing within a ball bearing. Is this sleeve bearing well enough finished to permit the arm to continue following the grooves on its own?

I am surprised that the ball bearings when used in the as shipped condition work at all in this application.

Needless to say your video shows it working splendidly!

Now for a suggestion I may well try. Ball bearings with well finished corners make great wheels rolling in or on a track, glass or something else. Bo Hansson's ideas with the 2 bearings rolling on their corners make a superb sounding arm. As I see it the bearings and their lubrication or lack thereof with attendant cleanliness issues constitute some real issues to be dealt with. So let's build a carriage with a solid arbors tapered to a points and running in a tapered cups (jeweled or otherwise) like an alarm clock balance wheel. Jewels with endstones could be substituted to limit end shake. The arbors would be mounted in the bore of the ball bearings. Now we have a bearing that suffers from none of the problems of ball bearings. We can use the ball bearing parts with their radial free play to deal with small warps or we can lock the inner races to the outer races and allow the vertical motion to be supplied by sliding/slipping/rolling-sliding motion between the bearing wheels and the glass. This design copyright 8/8/13 for what ever that is worth.

Go at it guys. Tell me what I'm overlooking.

BillG
 
I don't know if it is an illusion but in the video mentioned above posted by woodturnerfran the stylus appears to be moving around a lot more than in the videos vynuhl addict shows of his arm. Is window glass flat enough for the carriage or wood strips of mirror or thin plate glass be smoother? It would seem to be easier to mount the strips on an aluminium v than using the glass tube. I do think vynuhl addicts slotion is quite elegant and very effective.
jamikl
 
Jamikl,

Many thanks, looking at the video again i see what you mean, the cantilever is wandering which will create some interesting effects on playback.

In regards to the brass spacer, it's not polished at all, just cut, the edges filed to scale and fit!. I'd have to add, the tube size is important to a degree, larger than 10mm and you will have to revise the bearing spacing, as to how this will work, I don't know. This bearing arrangement is a case where the tube , bearings, spacer and gravity all work together as a whole.

Colin
 
Watching in awe...

Hello to everybody,
I'm watching this thread with interest as I always dream to build a linear tracking tonearm to pair with my Lenco.
I was discourage by the air bearing ones because of their complexity and the high cost of a good air pump, but this design seems to be more easy to build.

Please Colin, post a bom as soon as possible and a building manual! I'm looking forward to start building mine!

Lots of compliment for your implementation!

Ciao!
 
Bonzo,

I think anyone can build the arm via inspection and variances based on locally available materials. All the information is in this thread and the previous one, referenced earlier in this thread.

Find some glass tubing, a set of bearings, then make the rest to hold it up in the air! :D

_-_-

Well, I red somewhere in the thread that a BOM and an instructions set were about to be published.
Anyway, can you tell me which bearings to use and the diameter of glass tube?
Do you think I could make all the rest of the arm parts with perspex?
Thank you for your help!
 
oh, well perhaps a BOM for Colin's version is forthcoming.

There are two main builds: bearings on top of a glass cylinder, and bearings inside a cut glass cylinder.

I haven't built this sort of arm myself, but it looks like an interesting design, even though there are some areas of "uncertainty" for the design principle. So, everything I am saying comes from reading the threads and other knowledge I've picked up along the way...

The diameters of the glass are discussed back in the threads.

There is a function up top under THREAD TOOLS that permits you to print the entire thread - you might want to print it out and make notes in the margin, and highlight key things.
 
Slowmotion,


The pivot point should be closer to the record height, this is to reduce warp induced error. If you look closely at my design on top of the tube it works as the pivot is lower if you think about it, even though it slides the top of the tube it pivots as if the center of the tube is the pivot axis. This is why I placed the counterweight tube at this axis, this will provide best tracking in this design.



Colin
 
I agree that there is probably enough information in the thread to build this arm or a derivitive of it, however, I think that one thing some of us are struggling to understand is the use of the brass shim inside the inner bearing race. Perhaps a diagram of how this part is arranged would help quite a few of us. Looking forward to any help you can give on this vynuhl addict. As they say : "A picture is worth a thousand words!".
jamikl
 
Diagram

Here is the bearing diagram
Colin
 

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Colin, if I could please. What is the dimension between bearing centers of your design?
I notice what appears to be a much farther spread than the Cantus.
Moray, any comments you know of this? I would assume from photos the Cantus to be around 30mm. Could a smaller positioning have much effect on drive or damping?