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  • #16
    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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    • #17
      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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      • #18
        The Plithe is looking nice. But the platter is going to require the LP industry to invent "clear" vinyl

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        • #19
          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. ;)
          "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche

          http://www.diy-ny.com/

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          • #20
            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...
            Brian Steele
            www.diysubwoofers.org

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            • #21
              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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              • #22
                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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                • #23
                  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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                  • #24
                    I have to say, you take very nice photographs. What camera-lens are you using?

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                    • #25
                      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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                      • #26
                        Pics of my modest DIY turntable attempt. Click image for larger version

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                        • #27
                          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?
                          "The ability of any system to produce exceptional sound will be limited mainly by the capability of the speakers" Jim Salk
                          "Audio is surely a journey full of revelations as you go" JasonP

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                          • #28
                            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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                            • #29
                              Originally posted by Face View Post
                              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. ;)

                              Oh Brother Where Art Thou OST and I have some SoA OST clear vinyl, too.

                              रेतुर्न तो थे स्रोत
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                              in war, victory . . . in peace, vigilance . . . in death, sacrifice.

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                              • #30
                                Interesting stylus
                                It is estimated that one percent of the general population are psychopaths - New Criminologist: Understanding Psychopaths

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