In spite of the problems, I was getting very decent sound from the arm. It is just that the arm works so much better now. Was listening for several hours last night with the vertical tracking force at 0.9 grams. Seemed to have less surface noise from my old records.
BillG
Bill,
You have discovered its other benefit, significantly reduced surface noise. I had tried a two bearing version using two 5mm glass tubes similar to a glass v, it worked pretty good but not as good as the four bearing, especially in the vertical plane, the easier the arm can pivot the less damping on imperfections. I know some seem to be set on copying the Cantus, but I would strongly recommend atleast just giving the four bearing a try, you might just be pleasently surprised.
Colin
You have discovered its other benefit, significantly reduced surface noise. I had tried a two bearing version using two 5mm glass tubes similar to a glass v, it worked pretty good but not as good as the four bearing, especially in the vertical plane, the easier the arm can pivot the less damping on imperfections. I know some seem to be set on copying the Cantus, but I would strongly recommend atleast just giving the four bearing a try, you might just be pleasently surprised.
Colin
Colin: please do not take this as an attack on the four bearing design you have built. I am delighted that you started your thread and immensely pleased with the response that your thread has generated.
You design with four bearings riding upon a glass tube does not pivot as did your first posted knife edge bearing did. You four bearing carriage slides on the glass tub perpendicular to the horizontal plane of travel. I cannot see how four bearings can slide more effectively on the outside of a tube than two do in the inside of a tube. I can see that the reverse is the case and that may be what is accounting for your performance as the less the arm move the better from an exchange of energy point of view. To say which is better is I think difficult to say as alignment and construction accuracy will come into play. If my theory is correct I would expect to see further improvements with your design if you were to use a smaller diametre glass tube to ride upon. I hope that this is of interest. Best regards Moray James.
You design with four bearings riding upon a glass tube does not pivot as did your first posted knife edge bearing did. You four bearing carriage slides on the glass tub perpendicular to the horizontal plane of travel. I cannot see how four bearings can slide more effectively on the outside of a tube than two do in the inside of a tube. I can see that the reverse is the case and that may be what is accounting for your performance as the less the arm move the better from an exchange of energy point of view. To say which is better is I think difficult to say as alignment and construction accuracy will come into play. If my theory is correct I would expect to see further improvements with your design if you were to use a smaller diametre glass tube to ride upon. I hope that this is of interest. Best regards Moray James.
Hi guys, This discussion is continually more interesting. My observation that when riding a warp of perhaps 1/8" total excursion the stylus was retracting a good way into the cartridge before the arm started up (even though in Bo's terminology it was going forward not up. I hope we've gotten over that one by now.) Will save it for another discussion. This retraction of the stylus said to me that the vertical motion required by the warp just wasn't being provided by the 4 bearings. They were not sliding easily on the glass surface. So I looked at the state of the bearing corners and found that they were not nicely radiused or smooth with essentially a mirror finish. The stylus was being driven into a probably non linear portion of the magnetic field and distortion would be present if not severe. So I radiused the corners and polished them to mirror brilliance. Now when playing the same warp the cantilever stays in its non deflected state, the arm rides up the warp and follows it down. There is no audible distortion throughout the warp. With the new found freedom of vertical motion I find it easier by far to set the counterweight to that just grazing the record before putting a measured weight on the head shell. Most amazing is that it is now possible to track the grooves in the record with sub gram tracking force. No the arm isn't a precision lab balance yet, but much closer. The Cantus gets around this by utilizing the radial play inherent in the bearing design. If the warp gets bad enough, the bearings will have to slide one way or the other. What I suspect is that in the Cantus when the warp gets beyond radial play correction the unloaded side of the bearing releases it grip and the arm actually does pivot on the loaded edge of the outer race. It turns into a rolling knife edge design. IMHO the secret to achieving superior performance of the 4 bearing design lies in achieving the lowest possible friction between the steel and the glass. Perhaps the bearings specified by Cantus have that degree of perfection. If not I believe it would help to achieve it.
BillG sorry for the long reply.
Moray,
Sorry, didn't take it as an attack, but would love to see this design being even further refined and riding on the tube leaves it open to anyone regardless of skill. However if someone wanted to do a group buy of pre made split glass tubes that. Would be great for those who want to do the cantus arm. I'm currently experimenting with 5 mm tube, have some new ideas
.
Colin
Sorry, didn't take it as an attack, but would love to see this design being even further refined and riding on the tube leaves it open to anyone regardless of skill. However if someone wanted to do a group buy of pre made split glass tubes that. Would be great for those who want to do the cantus arm. I'm currently experimenting with 5 mm tube, have some new ideas
.Colin
well yes that's obvious
the four bearing carriage weighs a lot more at the very least double the bearing weight and bearing mounting hardware and has double the friction in the bearings. What I am looking for here is what actually is accounting for the performance which is being heard. Best regards Moray James.
the four bearing carriage weighs a lot more at the very least double the bearing weight and bearing mounting hardware and has double the friction in the bearings. What I am looking for here is what actually is accounting for the performance which is being heard. Best regards Moray James.
I agree, and thought aloud about this earlier. Might I also add, it's hard enough to align two wheels to ride completely straight and true. Many planes of action to be accounted for. Let alone four. None of these I assume are milled, nor with any precision. There is also a relying of slip motion in the four bearing to align itself.
How do we know the level of peformance is being heard. Know pudding for the proof.
I m afraid the inherent ease of construction in Colin's design makes a big difference for DIY attempts.
By the way, I was talking today with a friend about racks and how 3 legs are way easier to adjust, and it hit me...
The 4 bearings can be easily made 3 with no significant change in the original design and perhaps no penalty in the vertical or horizontal axis motion or stability. We would just need a third spacer on the carriage top to accommodate for a middle bearing on one side, either front or back of the glass tube. The total weight should be more or less the same because we lose a bearing but we add a spacer, but the friction with the glass tube should be 3/4 of what it is in Colin's version
By the way, I was talking today with a friend about racks and how 3 legs are way easier to adjust, and it hit me...
The 4 bearings can be easily made 3 with no significant change in the original design and perhaps no penalty in the vertical or horizontal axis motion or stability. We would just need a third spacer on the carriage top to accommodate for a middle bearing on one side, either front or back of the glass tube. The total weight should be more or less the same because we lose a bearing but we add a spacer, but the friction with the glass tube should be 3/4 of what it is in Colin's version
Yes, of course there is an increase in rolling friction within the bearings, but if you don't *want* friction within the bearings, go air bearing. The idea alleged about Bo's design paradigm was to make the best, most solid connection between the moving carriage/arm and the "track". Less friction implies a less "solid" connection. The point of "balance" between these aspects is where the design issues lie, imo.
I agree, but when making bearings the focus is not the make the radius on the edge of the bearing smooth or in anyway perfect. this is contrary to the fit on the surface that is ground and perfect (as can be) in circularity. I believe angled bearings are worth a try. and a reduction to 3 as well
I tried a three-bearing tricycle carriage for this design because the idea of reducing rolling friction that way was tempting. It was inherently very unstable. Any horizontal force at the head shell pivoted the carriage around the center bearing regardless of which side of the support tube the bearings were on because the outer bearings are free to slide vertically on the tube. Colin's four-point arrangement eliminates that.
You hit it on the nose Doug. I did the same experiment with the same result. It was awful. Tried it once on a stool behind a cow. That was a disaster also!
BillG
New developments!,
One thing im noting, as the glass tube gets smaller the lower the friction and the better the vertical pivot. This explains why I have no issues setting tracking with the 10 mm tube. I've since tried 4 fixed bearings and 5mm tube and the horizontal friction is lower along with a vertical pivot that is almost like having a wand pivot f its own!. More to follow, oh and this.comes with even better stability too.
Colin
One thing im noting, as the glass tube gets smaller the lower the friction and the better the vertical pivot. This explains why I have no issues setting tracking with the 10 mm tube. I've since tried 4 fixed bearings and 5mm tube and the horizontal friction is lower along with a vertical pivot that is almost like having a wand pivot f its own!. More to follow, oh and this.comes with even better stability too.
Colin