[S Clark]

The amount of heat is proportional to the amount of catalyst.  Basically, the slower it catalyses the easier for the heat to escape.  I've had some cast that were hot to the touch, but never anything that came close to boiling.  One way to avoid heat build up would be to pour the resin in several applications.  If it's only an inch thick at a time, it's easier for heat to escape.  There are lots of reasons to look at other options, but I would think that heat build up is one that's easily overcome. 

[ACHiPo]

The amount of heat is proportional to the amount of catalyst.  Basically, the slower it catalyses the easier for the heat to escape.  I've had some cast that were hot to the touch, but never anything that came close to boiling.  One way to avoid heat build up would be to pour the resin in several applications.  If it's only an inch thick at a time, it's easier for heat to escape.  There are lots of reasons to look at other options, but I would think that heat build up is one that's easily overcome.

Is there any issue with the subsequent pours sticking to each other?  Doing thinner slabs would simplify a few things.

[neobop]

Casting epoxy will need a lot of experimenting, when epoxy cures it produces a lot of heat because the two chemicals react in an exothermic reaction. Too much heat and the epoxy will boil and foam.

I use a lot of epoxy and buy it in 5 gallon containers from West System http://www.westsystem.com/ss/ Check their Where to Buy list for a local distributor.
The company does extensive testing and could advise you how to cast epoxy, I have called tech support many times and they are friendly and helpful.

West also sells epoxy additives and thickening agents. Mixing in colloidal silica can make the epoxy as thick as peanut butter if you want and as hard as quartz.
http://www.westsystem.com/ss/406-colloidal-silica/

Thanks for the info.  I saw a series of posts on a boat building site where he was mixing epoxy with limestone.  Seemed pretty straightforward when used in thin pieces, although will have to experiment with the mix.

My original plan was to use polyester resin mixed with the limestone.  This is the composition of Kenwood's  anti-resonance material.  In layers, it might be easier to use something like Corian and join the layers with epoxy.  Can't envision problems with layers sticking together using epoxy or polyester resin (auto body putty).
neo

 

[S Clark]

Is there any issue with the subsequent pours sticking to each other?  Doing thinner slabs would simplify a few things.

We have had a few cast that needed repair, either some where we didn't get the resin evenly distributed in the mold, or, in a couple of cases, where we had dropped them.  I never had an issue with the resin sticking to itself. 

[WGH]

Each epoxy pour will chemically bond to the last as long as it is not completely cured, after curing the only bond will be physical. The cured epoxy will have to be roughed up with course sandpaper. I would never try to cast a turntable base, even with 35 years experience making custom furniture and doors it would be very hard to make a dead flat slab similar to a Corian or granite. Using a milling machine or wide belt sander on the cast slab would insure the top and bottom are perfectly parallel and flat.

The best method to laminate layers is to use a vacuum bag veneer press. Clamps and cauls can never equal the perfection of the vacuum bag. Below are custom door panels with handmade 1/8" fir veneer laminated to 9-ply plywood with epoxy using a vacuum veneer bag press, each panel was perfect.

[ACHiPo]

We have had a few cast that needed repair, either some where we didn't get the resin evenly distributed in the mold, or, in a couple of cases, where we had dropped them.  I never had an issue with the resin sticking to itself.

That's great info.  Thanks!

[ACHiPo]

I would never try to cast a turntable base, even with 35 years experience making custom furniture and doors it would be very hard to make a dead flat slab similar to a Corian or granite. Using a milling machine or wide belt sander on the cast slab would insure the top and bottom are perfectly parallel and flat.

WGH,
The people that have cast plinths have used gravity to ensure a flat surface--they level the mold, then the top surface will be parallel to the bottom.

Nice looking laminations!

[WGH]

A Google image search for "cast turntable plinth" has a lot of interesting ideas. Has anyone come across a how to guide to casting one?

The guys at Plinth-Design really know what they are doing
http://www.plinth-design.com/






Here is a Lenco mold, you will have to make one of these before casting.
http://www.lencoheaven.net/forum/index.php?topic=4448.0

[WGH]

How to make a mold
http://www.miwis-bastelbu.de/Galerien/Lenco2/index.html

thread
http://www.lencoheaven.net/forum/index.php?topic=15441.15

[ACHiPo]

A Google image search for "cast turntable plinth" has a lot of interesting ideas. Has anyone come across a how to guide to casting one?

The member known as "Rap" seems to have it pretty well sorted, plus he's an acoustical geologist, so knows a thing or three about vibration transmission and absorption in solids.

http://lenco.reference.clicforum.fr/t2198-Donc-je-recommence.htm?q=rap

[ACHiPo]

I received a box of samples from Richlite...



The box is quite heavy, which makes me think the product is pretty dense.  Very interesting laminations available...



The company gave me a list of local fabricators that use the product, so hopefully I'll be able to find some remnants to play with.  The product comes in 4' x 8' sheets and sells for $8/sf to >$30/sf, so in the range of Panzerholz.

[ACHiPo]

Well I dove in head first this weekend.  First task was to trim the top plate...



No turning back now!



With the top plate roughed out, it was on to the plinth layers. 



I ended up with an oopsie on one of the plinth layers, so decided to mock up the top layer.   Good thing I did, as the template I used was made to keep the top plate in tact, and thus the cut out for the pan was a bit too big.  It also gave me the chance to figure out a few other things on layout and construction.



Plinth will be 6 layers of Baltic Birch plywood with a couple MDF layers for flavor    The top two layers will both be plywood and glued with wood glue (no constrained layer damping, just a glulam).  The other 4 layers will alternate MDF and ply, with polyurethane construction adhesive (cured durometer ~60, so flexible and enabling a constrained layer sandwich).

Got the top two layers cut out and figured out the tone arm board locations and sizes.





That's all for this weekend.  Next weekend plan to get the other 4 layers cut, the arm board cut outs done, and everything glued and clamped.  I might even get the top plate stripped and prepped for paint.

[ACHiPo]

Quite a bit of progress this weekend.  Will post pics tomorrow.

Still a lot of work to do though.

[ACHiPo]

Just realized I forgot to update progress as promised.

Veneer ordered--I'm shooting for something like this:



I think the pictured table is curly Koa ($$$), although I bought curly Etimoe.



All layers have been cut out at this point, and the armboards are roughed out as well...

















Also ordered three of Herbie's feet...



http://herbiesaudiolab.net/studgl2.jpg

Family is visiting this weekend, so no progress, but hopefully I can get everything laminated next weekend with the polyurethane glue and maybe even get it sanded and prepped for veneer.  Also need to get the pan shaped, stripped, sanded, and prepped for paint.

[S Clark]

Wow.  That Koa is stunning, but Etimoe can be as well.  I've got a bunch of it that I ordered for a big project that never came to fruition.  I may try to use some of it on a plinth as well. 
Tell you family, that the visit was nice, but it's time to go home... you have people waiting on pics of your finished product!

[ACHiPo]

Wow.  That Koa is stunning, but Etimoe can be as well.  I've got a bunch of it that I ordered for a big project that never came to fruition.  I may try to use some of it on a plinth as well. 
Tell you family, that the visit was nice, but it's time to go home... you have people waiting on pics of your finished product!

Scott, it's my darling younger daughter and her boyfriend home for a brief visit from New York, so gotta make hay while the sun shines.  First time meeting the boyfriend and I have to say she seems to have done well--I like the kid much more than I wanted to!   Heading to the city for a Giants game shortly.

[JDUBS]

Also ordered three of Herbie's feet...



http://herbiesaudiolab.net/studgl2.jpg

Family is visiting this weekend, so no progress, but hopefully I can get everything laminated next weekend with the polyurethane glue and maybe even get it sanded and prepped for veneer.  Also need to get the pan shaped, stripped, sanded, and prepped for paint.

Have you used these feet w a turntable before?

Jim

[ACHiPo]

Have you used these feet w a turntable before?

Jim

This is my first turntable build, so no I haven't.  They were recommended, and seem like they'll work.  I couldn't find anything I liked better.

[Halcro]

Just caught up to this Thread and am impressed.
Have you selected the veneer?
Regards

[ACHiPo]

Just caught up to this Thread and am impressed.
Have you selected the veneer?
Regards

Halcro,
Thanks! I ordered Etimoe veneer and supplies (glue, tape, saw, etc.), but haven't received them yet.  Hopefully they'll arrive this week.
AC