I think that sounds like a good idea too .I,m finding difficulty in
trying to design contact points out of the system I can only envisage a minimum of three to enable the arm to resist the forces generated by the cartridge . The lower roller could perhaps have a clearance off the wire by thous' and act as "keeper" when initially loading a disc, thereby reducing the friction to 2 anulus rings of PTFE on steel shafts,
assuming low rolling resistance?
trying to design contact points out of the system I can only envisage a minimum of three to enable the arm to resist the forces generated by the cartridge . The lower roller could perhaps have a clearance off the wire by thous' and act as "keeper" when initially loading a disc, thereby reducing the friction to 2 anulus rings of PTFE on steel shafts,
assuming low rolling resistance?
I dont think teflon on the rails will be an improvement resistance wise. I think that the majority of the resistance will occur from within the bearing itself. i think the best property that the bearing should have is the ability to leak vibrational enery away from the bearing and arm as well as to resist chatter. The compliance doesnt have to be infinitely tight, all we have to do is make a more linear arm than a pivoted arm... The main worry will be any bearing noise which should be negligible given the small force and slow speed. Especially if the record is not terribly out of round.
Its easy.
Use a flanged bearing housing to provide a near knife edge bearing to handle the vertical deflection...
Something like the right hand bearing in this piccy
From
http://www.nationalprecision.com/m55.htm
If you wanted to machine the flange so that it came closer to a knife edge, then thats possible too
Owen
Use a flanged bearing housing to provide a near knife edge bearing to handle the vertical deflection...
Something like the right hand bearing in this piccy
An externally hosted image should be here but it was not working when we last tested it.
From
http://www.nationalprecision.com/m55.htm
If you wanted to machine the flange so that it came closer to a knife edge, then thats possible too
Owen
I've been lucky enough to have a good look at both a souther and clearaudio liner trackers, one with glass rails and the other with wires. Just to let you know that while the carriage that holds the cartridge runs freely on the wire/glass, is not nearly as free as you might think... I was really surprised that it wasn't even silkier in its movement.
I'd say you'd get away with quite a bit in making one of these. I think the souther just has metal rollers that run on the glass. They aren't even bearings (I think) in the proper sense of the word. They seemed to be just metal sleeves running on a plasttic shaft.
If anyone is going making one, it would be well worth your while getting to hold one of these in your hand to get a feel for it.
It seems to me though that the air bearing one is the easiest way to go
Fran
I'd say you'd get away with quite a bit in making one of these. I think the souther just has metal rollers that run on the glass. They aren't even bearings (I think) in the proper sense of the word. They seemed to be just metal sleeves running on a plasttic shaft.
If anyone is going making one, it would be well worth your while getting to hold one of these in your hand to get a feel for it.
It seems to me though that the air bearing one is the easiest way to go
Fran
Hi all,
Ive just got back on line --- Dont you just love I.S.P,s ? Anyway
In a similar vein I was going to suggest that ball bearings as supllied would be unsuitable due to the radius that they grind (turn) to facilitate ease of pressing into seats. I was going to suggest turning some thin wall sleeves with a lip shaped to give a rolling knife edge action action. Incidentely , going back to a question I posed earlier in this thread .If one achieved the ultimate theoretical nil mass ,nil friction
parallel tracker would the masses required to enable the correct resonances to pertain ,be best :-
a. at the cartridge
b. at the centre of the carriage
c. uniformly distibuted in the arm.
Ive just got back on line --- Dont you just love I.S.P,s ? Anyway
In a similar vein I was going to suggest that ball bearings as supllied would be unsuitable due to the radius that they grind (turn) to facilitate ease of pressing into seats. I was going to suggest turning some thin wall sleeves with a lip shaped to give a rolling knife edge action action. Incidentely , going back to a question I posed earlier in this thread .If one achieved the ultimate theoretical nil mass ,nil friction
parallel tracker would the masses required to enable the correct resonances to pertain ,be best :-
a. at the cartridge
b. at the centre of the carriage
c. uniformly distibuted in the arm.
Wanted to post a reply yesterday, but could not get on this diyaudio-site.
I like the Opus design, nice small and compact, no large protruding tubes which can pick up resonances more easy. If i can manage, will build one for myself.
Have thought also of grinding an edge on outer race of bearing to create a knife-pivot, but i think its not neccesary. The ball bearing itself has some play, this should be enough for a normal (flat) record. Uneven records or bumps are not a good thing for this linear arm(and not for high-quality replay either)
When the arm lift is used, the 2 point contacts from outer race of each bearing will easily glide over the hard glass.
I like the Opus design, nice small and compact, no large protruding tubes which can pick up resonances more easy. If i can manage, will build one for myself.
Have thought also of grinding an edge on outer race of bearing to create a knife-pivot, but i think its not neccesary. The ball bearing itself has some play, this should be enough for a normal (flat) record. Uneven records or bumps are not a good thing for this linear arm(and not for high-quality replay either)
When the arm lift is used, the 2 point contacts from outer race of each bearing will easily glide over the hard glass.
Maybe something like this can be used to copy the opus principle?
An externally hosted image should be here but it was not working when we last tested it.
The soft suspended cartridge has to move the whole system, so a higher rolling-resistance will add tracking errors then, with softer wheels. (the cantilever first moves to a certain angle, before the bearings are moving) Thats why the rolling resistance has to be as low as possible. Otherwise you will get greater tracking errors then a regular pivoted arm imo.
Dampening can be done in an other way: wrapping the glass C-shaped tube in a C-shaped lead lining.
Also some experimenting with different grade of oils in the bearings are required i suppose for dampening, from very thin silicone oil to some thicker clock oil.
Eric ,
are they the bearings from a filing cabinet drawer?
Generally ,
I still wonder why, if the compliance of the stylus mounting is capable overcoming the resistance of the 4 contact points of the opus arm ( in the vertical plane ) why bearings are needed at all in the horizontal plane. surely polished rounded points should work in both planes?
are they the bearings from a filing cabinet drawer?
Generally ,
I still wonder why, if the compliance of the stylus mounting is capable overcoming the resistance of the 4 contact points of the opus arm ( in the vertical plane ) why bearings are needed at all in the horizontal plane. surely polished rounded points should work in both planes?
Afaik the Opus lineair arm does not combine very well with soft suspended carts (with a higher compliance-value), for this reason.
Sliding contact points for the horizontal movement is too stiff, the force to move the lineair arm has to get over a certain point before it will move, with a ball bearing the "starting" force before a movement is smaller.
(try it yourself: slide a heavy box along the floor, it will move at a certain force, and when it moves the force can be lower to keep it moving)
Then an air suspended horizontal movement is in advance.
But yesterday i thougt again about this arm at a meeting for my work in Germany, had dinner with collegues. Meanwhile rubbed 2 hardened glass ashtrays along eachother: felt allmost no resistance because of the hard glass & small indenting points, and imagined it was the outer race of bearing on the glass tube.
But still: these are my thoughts about it.
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