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  • jjgoertz
    replied
    Originally posted by mattsk8 View Post
    I know you mentioned making a bearing assembly; seeing how your platter must be fairly heavy, what bearing are you using for the platter to ride on? My only fear with a solid hardwood plinth would be expansion and contraction of the hardwood; depending on how you engineer the tonearm assembly, that could be a potential issue over time for azimuth and cartridge alignment.

    Also... this will be a belt drive; right?

    Yep it will be belt drive. Planning on an 1/8" o-ring and cutting a groove in the edge of the platter.

    Vertically the bearing will be opposed magnets. I have a pair of steel cased neodymium ring magnets that can hold what feels to be about 50 pounds. To counteract the force of the belt I have two solid teflon bushings that will be riding on a 16mm steel shaft.

    It will be interesting to see how much this thing changes size, but the adjustments will be pretty easy. This tonearm assembly will basically just sit on the plinth on height adjustable rubber feet so I'll be able to slide it around. The adjustable feet will give me level adjustment for the gantry as well as VTA.



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  • mattsk8
    replied
    I know you mentioned making a bearing assembly; seeing how your platter must be fairly heavy, what bearing are you using for the platter to ride on? My only fear with a solid hardwood plinth would be expansion and contraction of the hardwood; depending on how you engineer the tonearm assembly, that could be a potential issue over time for azimuth and cartridge alignment.

    Also... this will be a belt drive; right?

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  • replied
    Pics of my modest DIY turntable attempt. Click image for larger version

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    Click image for larger version

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  • jjgoertz
    replied
    I have to say, you take very nice photographs. What camera-lens are you using?

    These have actually all been with my phone camera, a Oneplus 2. I have a ton of lighting in the garage which really helps with pictures.

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  • replied
    I have to say, you take very nice photographs. What camera-lens are you using?

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  • jjgoertz
    replied
    I finished the finish with a wipe on coat after sanding everything down with 320 grit, and laid down a layer of cork on the bottom layer of the plinth. This is mainly to keep the two polyurethaned surfaces from gluing themselves together so the maple can expand and contract as needed.



    The two halves of the plinth get screwed together with 1/4" screws through 1/2" holes with thick fender washers to cover the holes. This is again to allow for movement.



    The feet are screwed into threaded brass inserts in the plywood.


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  • jjgoertz
    replied
    Originally posted by Brian Steele View Post

    ​Hopefully that lead shot ended up being smoothly distributed in that groove, otherwise you've just made a rumble-machine...

    I said it would have to be balanced, didn't I?

    Basically I set up the same system we use for balancing propellers. A tight fitting steel rod through the platter riding on two pieces of aluminum. It's important to get the rails level both along their length and between the two rails. Set the platter between the rails, making sure it doesn't touch either side, and you have a very sensitive balancing system. The platter will rock back and forth, eventually settling with the lightest part TDC.



    Now it's just a matter of adding weight to the light side until eventually the platter will stay at rest in any position. This set up is sensitive enough to get the thing balanced within +- a single piece of lead shot (0.145g) at a 5" radius. Here are pictures of the platter resting in two positions after adding some weight. There is 1.4g where the single piece of tape is, and 28.2g under the double piece of tape.





    Then it's just a matter of getting the desired weight of glue and shot and putting it in the right spot. I did abrade the surface slightly to get a better bond.

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  • replied
    Originally posted by Millstonemike View Post
    The Plithe is looking nice. But the platter is going to require the LP industry to invent "clear" vinyl
    ​I have one clear LP and one clear tinted blue and also one clear tinted yellow. The blue one is ABBA and the yellow one is Yellow Magic Orchestra.

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  • Brian Steele
    replied
    Originally posted by jjgoertz View Post
    Then I worked on gluing in the lead shot. This ended up being much harder than anticipated. My plan was to pour the epoxy into a cup of lead shot, mix it up, then spoon it into the groove. As it turns out epoxy and lead is an extremely viscous mixture and that combined with the exothermic reaction kicking off the glue a little faster than I expected and it was a real pain in the tuckus to fill. My recommendation after doing it would be to put the lead in the groove first, then use a low viscosity casting resin and pour it over the shot and let it run down on its own.
    ​Hopefully that lead shot ended up being smoothly distributed in that groove, otherwise you've just made a rumble-machine...

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  • Face
    replied
    Originally posted by Millstonemike
    The Plithe is looking nice. But the platter is going to require the LP industry to invent "clear" vinyl
    I don't recall which ones they are, but I have a few clear records in my collection. But due to the grooves, they're not exactly transparent. ;)

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  • Millstonemike
    replied
    The Plithe is looking nice. But the platter is going to require the LP industry to invent "clear" vinyl

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  • replied
    Originally posted by jjgoertz View Post
    Then I worked on gluing in the lead shot. This ended up being much harder than anticipated. My plan was to pour the epoxy into a cup of lead shot, mix it up, then spoon it into the groove. As it turns out epoxy and lead is an extremely viscous mixture and that combined with the exothermic reaction kicking off the glue a little faster than I expected and it was a real pain in the tuckus to fill. My recommendation after doing it would be to put the lead in the groove first, then use a low viscosity casting resin and pour it over the shot and let it run down on its own.
    Next time, pour all the lead shot and all the necessary epoxy into a disposable mixing container, but don't stir it yet. Then place the whole darn unstirred mess into a refrigerator and let it cool down. When finally cooled, start mixing, when mixed pour. You'll get more working time, less exothermic if you cool down the epoxy before stirring.
    Last edited by ; 09-18-2016, 05:05 PM.

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  • replied
    The exothermic properties of epoxy are indeed problematic to work with. I mixed up a big batch once and it got so hot that not only was it was too hot to handle, but it even melted the plastic mixing container I was using. I found several ways to deal with the exothermic problem, either only mix up small batches or mix up a larger batch in a very shallow pan. Then I figured out that cooling the epoxy before dispensing and or stirring would be the most effective method of dealing with the problem. Yes, I cool Part A and Part B in the refrigerator. You can also dispense your required amount of Part A and Part B into a mixing container but do not stir it until after you have cooled it. The cooled epoxy mixture is slightly more difficult to stir because it is thicker, but the working time is improved considerably.
    Last edited by ; 09-18-2016, 05:04 PM.

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  • jjgoertz
    replied
    Made some pretty good progress in the last two days. Started by getting the live edge plinth cut to length and flattened.



    Put a 1/2" radius on the straight edges then I played with the layout a bit.





    This morning I started with a coat of a 2lb cut of de-waxed amber shellac. This is the first time I've used shellac and I am super happy with how it brought out the chatoyance.



    And then it got the first coat of poly. Really excited for how this board will look once the finish is completely smooth.



    Then I worked on gluing in the lead shot. This ended up being much harder than anticipated. My plan was to pour the epoxy into a cup of lead shot, mix it up, then spoon it into the groove. As it turns out epoxy and lead is an extremely viscous mixture and that combined with the exothermic reaction kicking off the glue a little faster than I expected and it was a real pain in the tuckus to fill. My recommendation after doing it would be to put the lead in the groove first, then use a low viscosity casting resin and pour it over the shot and let it run down on its own.



    Finally I got to work on the tonearm carriage. It's 3mm carbon plate with a 10mm OD carbon tube.





    Attached the bearings and got to playing around with the carriage. It's riding on a hard anodized aluminum shaft that's meant for linear bearings. Friction is nice and low, you only need a couple degrees of slant to the rod for the carriage to roll either way. I will probably swap out the shoulder bolts for nylon ones to save some weight once I find some of the right length. Current weight is 48 grams.

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  • jjgoertz
    replied

    ​Almost seems a shame to make the platter so attractive, since it will be unseen whenever you are playing a record. If you decide to use a platter mat that will also cover up the beauty. Had you thought about recessing the center of the platter just a tiny bit to accommodate the label thickness of a typical LP?

    Had not thought of cutting a recess. I'm going to use a felt mat, so that would probably make the recess unnecessary, right?

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