Meet my Maggie - the last incarnation of my homebrewed TT, based on magnet repulsion.
The platter is a massive sandwitch made of hardwood, bronze, sorbotane and aluminum stuffed with leadshot. Only 3 kg out of total 33 is taken by vertical bearing (ceramic ball running on HSS instrumantal steel thrust plate); the rest is supported by a couple of neodimium magnet rings. The lateral bearing (journal) comprises of bronze-steel matched pair, lubricated with Van den Hul TT oil. It's a wonderfull stuff: very low viscosity combined with high resistance against breaking of lubrication film, which gives me the lowest possible viscous friction for substantional total bearing surface area.
The base is made of aluminum and birch plywood, also stuffed with leadshot. The legs are solid bronze cylinders resting on ceramic balls. Two arms are mounted: dedicated mono and ladegaard clone, which was shown on this forum earlier.
The Teres motor/controlled is incased into plywood/lead housing, adding mass and allowing precise levelling. VHS tape is used for belt.
All this stuff is resting on the sandbox, made of birch plywood with the marble upper plate. The sandbox is supported in turn by another three pairs of neodimium super-magnets, bearing the total mass of about 70 kg.
My greatest fear was if a magnetic field can affect delicate MC carts. Good news: no influence whatsoever, if the magnets are kept far enough from cart, under thick platter.
I live for a week with my new TT and I feel much closer to analog heaven.
The platter is a massive sandwitch made of hardwood, bronze, sorbotane and aluminum stuffed with leadshot. Only 3 kg out of total 33 is taken by vertical bearing (ceramic ball running on HSS instrumantal steel thrust plate); the rest is supported by a couple of neodimium magnet rings. The lateral bearing (journal) comprises of bronze-steel matched pair, lubricated with Van den Hul TT oil. It's a wonderfull stuff: very low viscosity combined with high resistance against breaking of lubrication film, which gives me the lowest possible viscous friction for substantional total bearing surface area.
The base is made of aluminum and birch plywood, also stuffed with leadshot. The legs are solid bronze cylinders resting on ceramic balls. Two arms are mounted: dedicated mono and ladegaard clone, which was shown on this forum earlier.
The Teres motor/controlled is incased into plywood/lead housing, adding mass and allowing precise levelling. VHS tape is used for belt.
All this stuff is resting on the sandbox, made of birch plywood with the marble upper plate. The sandbox is supported in turn by another three pairs of neodimium super-magnets, bearing the total mass of about 70 kg.
My greatest fear was if a magnetic field can affect delicate MC carts. Good news: no influence whatsoever, if the magnets are kept far enough from cart, under thick platter.
I live for a week with my new TT and I feel much closer to analog heaven.
Fantastic!! ... I especially like the generous use of wood structural parts.
Nice looking as well as obvious attention to engineering detail.
Curious: what do you sit the TT on?? (I saw a high end TT sitting on a marble slab ... on top of a water filled wheel barrow inner tube ... on top of a marble pedistal .. and that sure took care of any passing truck traffic as far as rumble, etc.)
Nice looking as well as obvious attention to engineering detail.
Curious: what do you sit the TT on?? (I saw a high end TT sitting on a marble slab ... on top of a water filled wheel barrow inner tube ... on top of a marble pedistal .. and that sure took care of any passing truck traffic as far as rumble, etc.)
What FastEddy said 
Couple of Q's for you. First how does this compare with your earlier glass topped constrained layer effort? I meant to ask about the mag repulsion when you posted the draft of your stand base in another thread. After reading the write up on the Continuim table, I thought this approach was pretty slick. Are you using n40 or n50 mags? What is the surface area of the mags vs. weight? I assume you are using "donut" mags for the stand and platter, is this correct?
Thanx,
Casey
Couple of Q's for you. First how does this compare with your earlier glass topped constrained layer effort? I meant to ask about the mag repulsion when you posted the draft of your stand base in another thread. After reading the write up on the Continuim table, I thought this approach was pretty slick. Are you using n40 or n50 mags? What is the surface area of the mags vs. weight? I assume you are using "donut" mags for the stand and platter, is this correct?
Thanx,
Casey
Magnetically suspended sandbox is sitting on the custom build stand (nothing special really, but I don't care - I have sufficient isolation from outside world).
You can see it here more clearly:
http://img253.imageshack.us/my.php?image=img0196kd1.jpg
Some more pictures for those who cares:
http://img266.imageshack.us/my.php?image=img0216hh2.jpg
http://img253.imageshack.us/my.php?image=img0194ph8.jpg
http://img329.imageshack.us/my.php?image=img0149ee5.jpg
http://img444.imageshack.us/my.php?image=img0215ov5.jpg
The black belt is hardly seen on background of middle portion of the lower platter, painted black. Yes, static builds up on the belt, but it somehow discharges during play (may be through the bearing housing, which is grounded). If I start TT after break, the belt seems to stick to the platter and makes crackling noise during first turn or two (but it is not audible through speakers). No noise/sticking between records though.
FastEddy said:... consider a Bismuth /Magnesium & Zinc layered platter next time = a superconductor at about 120 degrees K when activated with a small electrostatic charge (according to Los Alamos Nat. labs).
Then it would be really cool ...
Talk to a TEM specialist about unwanted vibrations from boiling Nitrogen. It's about the last thing I'd want on my tt.
Bye-bye Maggie!
I quit the magnetic bearing route eventually.
I struggled to minimize magnetic flux on the platter surface, especially in vicinity of the bearing axle (inner grooves). In spite of the fact that magnetic field seems to have no audible effect on the cart, I was still a bit worried about long term consequences.
The stanless steel shaft which appeared to be ferromagnetic, was replaced to non-magnetic SS alloy with little effect. The only thing left to try was Mu-metal magnetic shielding, means major re-design of the bearing and platter, not to mention money/time expence.
The main driver behind the mag bearing was the scaring weight of my platter: 35 kg total! I though it is impossible to bear such weight with conventional ball-thrust plate design. I was wrong!
Now I end up with 1/2 inch steel ball running on the delrin thrust plate. Large ball increases the contact area and reduces stess. Another essentinal component is the low viscosity Van-den-Hul bearing oil; any other oil I've tried slowed down the platter too much. Following three weeks of spinning, I disassembled the bering. There was a dimple 1 mm deep in the delrin - not a big deal! The most important, sonically I did not noticed any deterioration, comparing to both fully suspended and partially supported by magnets platter. Quite the opposite - with a fully suspended platter I could not get rid of feeling somehow "springy" bass, quick but lack of authority and proper decay. Subjectively, conventional bearing has more relaxed, full-bodied sound, I was always after. So, why bother with magnets?
I want to say my TT in its recent state leaves very little to desire for me, especially after I switched to wonderfull Sumiko Celebration cart, which appeared to be very good match to my linear tracker.
I quit the magnetic bearing route eventually.
I struggled to minimize magnetic flux on the platter surface, especially in vicinity of the bearing axle (inner grooves). In spite of the fact that magnetic field seems to have no audible effect on the cart, I was still a bit worried about long term consequences.
The stanless steel shaft which appeared to be ferromagnetic, was replaced to non-magnetic SS alloy with little effect. The only thing left to try was Mu-metal magnetic shielding, means major re-design of the bearing and platter, not to mention money/time expence.
The main driver behind the mag bearing was the scaring weight of my platter: 35 kg total! I though it is impossible to bear such weight with conventional ball-thrust plate design. I was wrong!
Now I end up with 1/2 inch steel ball running on the delrin thrust plate. Large ball increases the contact area and reduces stess. Another essentinal component is the low viscosity Van-den-Hul bearing oil; any other oil I've tried slowed down the platter too much. Following three weeks of spinning, I disassembled the bering. There was a dimple 1 mm deep in the delrin - not a big deal! The most important, sonically I did not noticed any deterioration, comparing to both fully suspended and partially supported by magnets platter. Quite the opposite - with a fully suspended platter I could not get rid of feeling somehow "springy" bass, quick but lack of authority and proper decay. Subjectively, conventional bearing has more relaxed, full-bodied sound, I was always after. So, why bother with magnets?
I want to say my TT in its recent state leaves very little to desire for me, especially after I switched to wonderfull Sumiko Celebration cart, which appeared to be very good match to my linear tracker.
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