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So I got a little itch to try making some roller blocks. Fortunately, I've got access to a full metal shop, including a SuperMax 3-axis CNC vertical mill running Mastercam V8 numerical control and Vellum Solids Cobalt on my laptop to create the model.Materials used:
2" dia. solid 4140 (normalized) chrome-moly steel round stock.
7/16" dia. Tungsten Carbide ball bearings (+.0000, -.0004).
On a lathe, I faced some 2" dia. x .500" tall cylinders as blanks, then chucked the blanks to the mill. The concave geometry is essentially a 5" diameter sphere, plunged .1875" into the top face of the cylinder. It was finish cut to .001" (could have gone to .0001, but there wasn't really a need, and it would have meant roughly 4 more hours in mill time). After milling, each cup, or race, if you will, was chucked back into a lathe and sanded, then polished. The final finish isn't perfect, but i couldn't feel any ridges with my finger nail. It's nearly a mirror finish.
I can easily say it was worth the 8 hours in the shop!!! Soundstaging improved dramatically over the set of Vibracones I used prior under my Rega Apollo. Tonally, my rig sounds even more fleshed out, with a midrange immediacy and palpability that's really quite pleasing. For roughly $50 in materials (and access to some really cool toys...) I'm a happy camper!
I'll try to snap some pictures once I get my camera back from a friend.
Follow Ups:
You might want to try some acoustic damping around the edges of your cups.I made some crude ones recently from stainless steel spoon bowls fitted in to ebony bases with steel-bearing epoxy. The friend I made them for is quite pleased with them. The ebony has good acoustic damping properties without adding too much vertical compliance.
I had thought about adding some damping material, but as it stands, the CDP sits on the roller bearings, which are on a maple platform, which sits on a set of 'sad' balls cut into hemispheres. I think i've got both the vertical and horizontal axes isolated from one another pretty well, but i'm still trying to think of a little more 'integrated' solution than what is effectively 3 layers of absorption/isolation. But, it sounds pretty damn nice right now!
Seems as though most of us experimenters AND many of the highest end manufacturers are stuck with multiple functional devices for each component's isolation/coupling.Take a look at the Grand Prix Monaco rack and see how many devices they've included, or the Pagoda rack or any of the others. If you look at some of the more elaborate constructions of footers, you'll find severl with multiple layers (balls, composite layers, isolators, couplers, etc.). So even in a compact state you end up using several devices.
Anyway, I'm using dead balls too, constrained layers, roller bearings, etc. in all my constructions, though each is done somewhat differently depending upon the weight and type of component. All DIY mind you, and I don't have access of skillset to use such a shop as yours.
When you look at how manufacturers with facilities (and the ability to sell their products at... high prices) have not come up with one simple combined solution, you might agree with me that it is probably beyond the abilities of the DIY-er.
It's always good to have something to think about though...
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