Resin concrete tips? TT plinth/base.

[jeanvigo]

Love the renovated & optimized Empire 208 but now I scheme to take the nuts and bolts to new heights.

I'm thinking of scrapping the wood box in favor of a resin concrete plinth, ala the various Garrard 301/401 and TD124 implementations. I'd form two drop-in armboard slots, one in the usual spot, another in the left rear corner.

I'm competent and cofident enough to build a form but my experience with concrete is limited to pouring deck and porch footings with bags of Quikrete. I've used same kind of concrete material with latex in various outdoor applications, so I think I get the general drift of "resin concrete."

Soooo.....

Anyone done this? Do I mix from scratch? Sand, cement, and latex (without larger stone)? Seems like the concrete countertop guys have some tricks. Would that be a place to start? Also, the art store has a lot of options but art supplies are expensive. I'd prefer industrial suppliers.

One more thing. I was thinking that I'd embed stainless nuts in the armboard area(s), to facilitate armboard attachment and swapping. Wha'd'ya think? Is there a better way?

[ebrewste]

I don't know about resin concrete (sounds interesting), but I've made concrete countertops, so I'll say what I learned doing that.

With countertops, I get picky on finish, so the details are key. I decided to get expensive countertop concrete so I could concentrate on the process, not the mix. I used Buddy Rhodes. I don't think it is what you are looking for, but it worked great for my application. This stuff was really expensive ($40 / bag), but it was worth it to eliminate an unknown.

I also did lots of wet diamond pad polishing to get a nice finish. It might be an interesting idea for you to make things pretty.

Just an idea -- you might think of using no-shrink grout and latex water substitute. It makes a nice looking, uniform, easy to pour, strong substrate. You could use all sorts of stuff as an aggregate (rubber balls, bolts, glass chips, ...).

It wouldn't really be much different to use a resin like epoxy or urethane. Just be sure to not pour too thick with something that exotherms too much, or it can catch on fire. It's hard to do, but I've managed before.

[jeanvigo]

Nice note, ebrew!

I'd no idea about the Buddy What's-'is-name. Very interesting. I'll definitely look into that.

In my original post, I mentioned the plinths for classic Garrard and Thorens renovations. I was really referring to the shape. Namely, the "box" but instead of the hollow resonance chamber (beautiful though the Empire's is) a resonance-draining plinth ala the Slatedecks.

Kenwood/Trio used a resin concrete to attack the problem from a similar--and cheaper--angle. Not only does this seem sensible--the slate plinths are a small fortune--but I really dig the poured concrete, aesthetically. Love the countertops, sinks, tubs, etc. Also, I like the material's flexibility. I want to mess with color and texture. Slate's nice but in addition to the cost, it's always, well, slate. What if I'm not in a gray mood?

Thanks again. Keep 'em comin,' ya'll!

[SaSi]

OK, the purist approach is mix the ingredients and pour them in your own mold.

But, for the sake of appearence, I would recommend a different approach.

The latest fashion in kitchens nowdays is using a "quartzite" type of material which is 95% quartz dust and 5% resin. This is molded in slabs and then cut into 2mm, 4mm or 6mm, 8mm, ... , plinths. Used as countertop in kitchen benches.

It is heavy and it is hard, practically like marble or granite, but it doesn't break easily and you can process it like wood or mdf.

I was thinking of using a plinth, carve the inside appropriately, round the edges and give it an extra polish. That would make a really nice looking plinth.

For the diy die hards, there is another option.

The cheaper fashion in kitchen is another product called corian. It is manufactured by Dupont. See www.corian.com

This is moldable and can take any shape you want. You can also glue pieces together and then attach layers of corian sheets (something like veneering?) so that it gets a seamless finish.

Again, this material can be a quartzite / granite lookalike, so it doesn't look like plastic.

Perhaps these materials are better suited for a high-end finish and look.

[Aengus]

The Canadian National Research Council has this:

To produce PC [polymer concrete], a monomer or a prepolymer (i.e., a product resulting from the partial polymerization of a monomer), a hardener (cross-linking agent) and a catalyst are mixed with the filler. Other ingredients added to the mix include plasticizers and fire retardants. Sometimes, silane coupling agents are used to increase the bond strength between the polymer matrix and the filler. To achieve the full potential of polymer concrete products for certain applications, various fibre reinforcements are used. These include glass fibre, glass fibre-based mats, fabrics and metal fibres. Setting times and times for development of maximum strength can be readily varied from a few minutes to several hours by adjusting the temperature and the catalyst system. The amount of polymer binder used is generally small and is usually determined by the size of the filler. Normally the polymer content will range from 5 to 15 percent of the total weight, but if the filler is fine, up to 30 percent may be required.

.

Cement concrete will take on the finish of the mold material - I've had good luck with a table top by finishing the mold with Formica and pouring it upside down (so the bottom of the mold became the top of the table). Don't know whether this would work with the resin concrete but if it's epoxy or polyester resin it should work - might want to experiment with mold-release materials, though, since I suppose these could texture it (I haven't tried molding epoxy, though I've used it as a glue and GRP reinforcement.

Regards.

Aengus

[AuroraB]

I wonder how resonant this stuff might be...??

A company in my home area made headstones in this way, but went bankrupt a while ago. I've been trying to track down the guy responsible, to get some info, but no luck so far.

The first "Platine Verdier", as published in l'Audiophile, was made this way, with some terazzo-like molded concrete.

[jlsem]

Corian is an excellent choice for a turntable base because it uses barium sulfate as the filler material. Barium sulfate damps vibration very well, much better than rocks in concrete aggregate or quartz used as filler in similar materials. Barium sulfate (as well as barium titanate) is also the filler used in "loaded vinyl" sound damping panels.

John

[seventenths]

I've had very nice results with 5000 psi quickcrete w/plasticizer poured into melamine molds. Contrary to my initial thought process, the stuff polishes up very well with diamond wheels.


7/10

[jeanvigo]

Originally posted by jlsem
Corian is an excellent choice for a turntable base because it uses barium sulfate as the filler material. Barium sulfate damps vibration very well, much better than rocks in concrete aggregate or quartz used as filler in similar materials. Barium sulfate (as well as barium titanate) is also the filler used in "loaded vinyl" sound damping panels.

John

Now THAT is some useful information, Mr. J.

May cause me to rethink the whole corian thing. I'd wanted to avoid the stuff because it's, well, I'm not crazy about the bathroom sink look. But...

Maybe I stack up layers of corian and the ol' "constrained layer damping" material. Perhaps a lossy cement. Perhaps, too, use walnut veneer on the finish sides and edges, mimic the color, grain, and even shape of the original wood base. It could look just like the stock base but upon closer examination function as a serious base instead of a square banjo box.

Keep 'em coming. Nice work. And thanks again.

[jrevillug]

Originally posted by seventenths
I've had very nice results with 5000 psi quickcrete w/plasticizer poured into melamine molds. Contrary to my initial thought process, the stuff polishes up very well with diamond wheels.


7/10

Have you any photos of the polished quikrete?

Thanks,
James