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Old 4th February 2005, 02:32 PM   #1
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Location: Portland, Or
Default Intro from newbie TT builder

Hi All,
I just wanted to introduce myself- Colby from Portland Or. I've been working on design for a few weeks now, and am starting to build the table as we speak. I'd like to give you a brief description and get any comments that anyone here might have.

The base will be a 20" X 24" vibraplane. I may modify it to take up less space. I'll bolt down the components to it's top surface.

The bearing will be inverted. The center shaft will be 7/8 dia. Thomson Shaft, press fitted into a base flange 1/2" thick. Thomson Shaft is some sort of steel (sorry) case hardened .06 deep to Rc 60 and ground to an 8 finish. The shaft will be approx 3.5 inches long. It will have a piece of nylatron pressed into the top end to support the ball bearing (5/16 dia).

The bearing outer race: silicon bronze with 1.00 dia. bore. The O.D. is tapered 10 deg. approx. 2" dia. at top, 2.5" dia. at bottom. All but the top and bottom half inch or so on the O.D. is undercut. It will fit into a tapered bore in the 3.5 inch thick acrylic platter. In the bore of the outer bearing race will be two bearings, top and bottom, made of sintered bronze. Clearance will be .0003 to .0005 on diameter.

Above the shaft and bearing is a piece machined from silicon bronze that has the ball bearing pressed into the bottom. It is 1/2 " thick. The outer dia. is tapered 60 degrees, large end up, approx. 2" dia. at bottom. It has 3 countersunk holes that match 3 threaded 1/4-20 holes in the top of the outer race. It has a .281 dia. extending up for the record hole. It has a matchiing tapered bore in the top of the platter. So when the whole thing is assembled the pieces tighten into their respective tapered holes.

I think I'm going to drill a hole through the top "plug" for adding oil. I plan to just let the oil run out the bottom. I think if it is the right viscosity, it will run through very slowly, and will actually form a vacuum up above as it leaks out. That should slow it down. The oil fill hole will have a plug.

This is all I have time for now- look for part 2 coming soon!
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Old 4th February 2005, 02:54 PM   #2
phn is offline phn  Sweden
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If you want to impress people on this forum, a DIY TT is the way to go.

Good luck. I'm looking forward to see the finished result.
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Old 6th February 2005, 01:39 AM   #3
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Hi InDa,

Any drawing of the spinde bearing ?
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Old 6th February 2005, 03:17 AM   #4
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Oh, you might find it in a nearby thread
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Old 11th February 2005, 01:30 PM   #5
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Default Bearing is finished

Yesterday I finished the bearing. I lucked out and found two oilite bearings (sintered bronze) that required very little machining. I bored the bearings/bushings and turned the outside 10 degree taper of the outer race in one operation. I ended up with .0006" diametrical crearance- a little more than I wanted.

I filled the clearance area above the lower bushing with light oil, then added oil above the upper bearing as I assembled it. It felt a bit stiff, turning it by hand, so I chucked on the record spindle with a drill press and let it run for awhile at 100 rpm. Then it turned much easier by hand- I assume the oil had worked down through the lower bushing. I coontinued to run it with the drill press for awhile and saw no sign of oil leaking out the bottom. Time will tell.

Then I put an indicator against the outer race with everything clamped down rigid. I could only get .00015" play by pushing back and forth, and when I just turned it with no side force, I got no runout, so everything is peachy I think.

The acrylic is supposed to be in today....
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Old 15th February 2005, 09:59 PM   #6
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hi guys

indagrove you are so right about acrylic being in at the moment
have you any pictures of your work?

best wishes
j7
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Old 16th February 2005, 01:22 AM   #7
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Ummm...I meant it was in at the plastics supplier. In the last few days, I turned the acrylic and faced it flat- it doesn't come very parallel sometimes when it's that thick. I'm thinking about layering another material between the 2" and the 1.5" acrylic, and making a teflon top piece like the redpoint. I found a source for carbon fiber mat material, and I might try that as well, making it interchangeable with the teflon.

I got most of the work done on the arm wand today. I took a piece of solid carbon fiber rod (3/8" dia.) and machined 4 grooves down the side lengthwise, just big enough for wires. Then I stuffed it into the piece of African Blackwood, and got that turned on the lathe. I'm making it tapered, but not a straight taper- a curved taper if you know what I mean. I'll machine the shell at a 15 or so degree angle horizontally.

I don't have a digital camera at the moment, but will soon, and I'll post some pics then.
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Old 16th February 2005, 01:24 AM   #8
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Quote:
Originally posted by InDaGroove
I don't have a digital camera at the moment, but will soon, and I'll post some pics then.
Looking forward to it!
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Old 31st March 2005, 01:24 PM   #9
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Default Pictures coming soon

I've been trying to post some pictures with no success. The file I'm trying to attach is under the size limit, but I get "This page cannot be displayed" when I try to submit.
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Old 31st March 2005, 01:29 PM   #10
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Default Pictures!

Finally, after many hours spent working through breaks at work, I have something to show. Some comments on the various components:

Platter: Two layers of acrylic...2" at bottom, then 1", then a piece of clear PVC (vinyl) on the top. The two pieces of acrylic have a circular, half round groove milled into the surfaces that join, to form a 20 mm dia. chamber that connects to the 8 bores. Lead shot is filled from the bottom. The top of the upper acrylic piece drops .06" going toward the center, and the PVC is restrained down to it. Right now the only thing holding the PVC down is the upper spindle piece that contains the thrust bearing. I have to add bolts. Weight= 26 lbs. I posted a the original bearing/platter sketch in another thread- I should re-post it here.

Shroder clone: Drilling the magnet was not a problem- I used a .025" Carbide end mill, then counterbored with a 1/16 end mill to provide space for the knot. The holes in the armwand tube were not centered good enough, so I have to do that over- the magnets won't stay parallel. I used .025" dia. Kevlar thread, but it seems too stiff- I'm going to try heavy nylon thread.

That interesting piece holding up the Shroder is a hollow stainless reduction fitting from an exhaust system- just the right height. I will probably fill it with lead shot and modify the top.

Armwand: Two woods used- the outer piece is African Blackwood with a 3/8 dia. hole through it. A 3/8 dowel of Black Palm is inserted (press fitted) into it, and the BP has two tiny grooves running down the side for wires. It was soaked in Teak oil for 3 weeks. Right now it will make an effective lenth of 12", but I think I want to cut down the length to 9-10", and also reduce the diameter and remove the sides on the headshell to allow a cart to be mounted at an offset angle.

Still to be made are the clamp and tonearm lift, and a means of adjusting VTA.

Enjoy!
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