Resin & Bentonite clay plinth build.

awty

Member
Hi all
Thought I would share my latest plinth build using polyester resin and bentonite clay.
First of all I have to acknowledge that this mix was developed by Hrappur Magnusson (goes by the forum name "The Rap") and I got a bit of information from the audio qualia forum and I used a template from lenco heaven, which I altered a bit to suite.
The mix has very good dampening properties, but that could depend on the mix and materials. In the small sample range a Isophthalic polyester resin gave a better result. I just used the basic Orthophthalic polyester resin you can buy easily and cheaply.
The mix is roughly 60/40-65/35 bentonite/resin, 1% catalyst. Will depend a bit on weather. Mix the resin and catalyst first (I do it in 2 kg lots) and then add the bentonite, then pour into the mould. if you start with 60/40 you can add more Bentonite into the mould until you only have a paper thin layer of resin on top. The bentonite will sink. Takes about an hour to go off (obviously depending on weather). Allow for a little shrinkage. (mine shrunk about 1mm over all).
Oh and Bentonite clay is used for kitty litter.

Enough with technickle dribble, now to my progect. I originally made a 1" thick table top plinth for my old Orpheus turntable, that worked really well (well the second time around, first one was a failure, the resin stuck to the mould). This time I bought a Lenco L78 deck only and decided to make something a little more challenging than a basic table top with a hole for a tt.

The L78 arrived and it was in such good order that I decided not to cut it up, also purchased a original tonearm I'm in the process of restoring. The deck will be all original with auto stop function.

Im going to counter sink the deck, add a bevel face and sides, try and hide the wiring, add a on light, use squash balls in the feet, use a coloured epxy top coat and try not to muck it up.

For the mould I made the sides from pine and base and plug from MDF, cutting using a template, then redoing a bit of it to suite mine. Not a good idea using MDF for the plug as you will find out later, but it was cheap and plentiful. Need to remember to do everything in mirror reverse....oops. Painted everything with PVA mould release that put a thin pv layer on every thing to stop sticking.

more to come......
 

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Thanks Paul!

I will be following your post as I'm getting ready to do something similar.

Looks great BTW>

KC
 
I too will be interested in how this goes. I'm not so much planning a plinth entirely made of those materials, but perhaps as a part pf the build. Never worked with them, so how you do it and what the pitfalls might be will be very instructive.
 
:lurk::lurk::beer:

Oh thats right its my thread.:lmao:
Wish there was one for me when I did my first build, then I wouldn't of made so many mistakes. Well there was a thread, but it was in French and the admin from audio qualia gave me some tips, but I still mucked up the first one.
I dont have much in the way of wood working skills and tools and I know even less about fibreglassing.
The first build I used a 50/50 mix (too much resin), 1.5% catalyst (too much) and I used MDF without any mould release. So it went off quickly, stuck to the MDF and cracked (see photo). Second attempt was a rush job, wrapped everything in PVC duct tape to prevent sticking and added some fibreglass to the corners for strength. This time it didnt crack, still shrunk by about 2-3mms and the pvc tape melted a bit leaving a ripply effect in the finish. Nothing I couldnt fix and its all finished and working well. There was a noticeable affect on the turntable from the old heavy wood plinth before. It was a lot more musical than the wood. Amazing what a better plinth material can do.
heres some photos of my Orpheus build.

Will post up some more of the current Lenco build shortly.
 

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Tested the PVA mould release by painting the end of a piece of MDF and dipping it into a cap of resin, waited till it went of and was able to remove the MDF without any sticking. You can also use mould release wax or both. Wax first then PVA.
Anyhow I calculated the mould to hold around 14ltrs minus the plug I guesstimated at about 5-6ltrs, so with only 4 kgs of resin I was going to be short. I made a couple of inserts in some thick areas to try and use up a bit of space. Mixed up 2ltr batch mixed in the bento added 1% coloured paste and poured, went in well, stirred in a bit more bento clay added some nylon matting (not sure if its necessary) for extra strength. Mixed up the rest of the resin/bento, was obvious I was going to be short. Crammed in as much bentonite I could (had plenty of time as it takes about 40mins-1 hour to go off). Added the inserts, positioned the bottoms of some beer cans (perfect shape for squash balls), tried to get it as level as possible, still was about 7mm short and wasnt encasing the wire as I wanted. By this time it was starting to go off and I had to leave well enough alone.

After about another hour I started to remove the pine sides, hoping they didnt stick. They came away easy and the resin remained intacked, took out the inserts, as much of the plug I could, waited a bit longer, tipped it over and removed the MDF base. Couldnt get out any more of the MDF plug without cutting it out, so left it to get harder and stronger.

More to come....
 

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After leaving the plinth for a couple of hours I came back to find a crack near the tone arm. The plinth was hard and strong now but shrunk a little and cause I didnt remove the MDF plug it fractured. Had to quickly get the rest of the MDF out, so used a spade bit, jigsaw and chisel. The rest came out OK, but I made a big mess.
The crack pulled tight after I removed the plug. Next day I glued the crack with epoxy, had to drill holes in the crack, prise apart a little with a chisel and inject the epoxy glue using a syringe. Clamped it tight. Developed a bit of a warp to, cause I left it sitting on the legs before it was completely cured. Had to spend 40mins with a paint stripping heat gun to get enough heat into it, so I could clamp it down flat to a bench. All worked well and it was nice and flat and all in one piece.

Note! dont use MDF for a plug, you need something that is a little more flexible and/or comes out easy.

Had to drill holes for the deck and grind out some spots with a sand paper grinder attachment.

Oh and I used about 11kgs of indigence. Heavy for a small plinth.

Its all ready for the top coat, more to come.

 

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After leaving the plinth for a couple of hours I came back to find a crack near the tone arm. The plinth was hard and strong now but shrunk a little and cause I didnt remove the MDF plug it fractured. Had to quickly get the rest of the MDF out, so used a spade bit, jigsaw and chisel. The rest came out OK, but I made a big mess.
The crack pulled tight after I removed the plug. Next day I glued the crack with epoxy, had to drill holes in the crack, prise apart a little with a chisel and inject the epoxy glue using a syringe. Clamped it tight. Developed a bit of a warp to, cause I left it sitting on the legs before it was completely cured. Had to spend 40mins with a paint stripping heat gun to get enough heat into it, so I could clamp it down flat to a bench. All worked well and it was nice and flat and all in one piece.

Note! dont use MDF for a plug, you need something that is a little more flexible and/or comes out easy.

Had to drill holes for the deck and grind out some spots with a sand paper grinder attachment.

Oh and I used about 11kgs of indigence. Heavy for a small plinth.

Its all ready for the top coat, more to come.
Beautiful work, awty.

I'm not a fan of the Lenco sound but I sure wouldn't mind hearing one done up in that plinth!:yes:
 
Nice job! :thmbsp:

I really dig the design of the plinth, it flows nicely with the shape of the TT.

I'm really looking forward to seeing the results as you finish it up.

KC
 
Beautiful work, awty.

I'm not a fan of the Lenco sound but I sure wouldn't mind hearing one done up in that plinth!:yes:

Thanks
The top coat is proving to be a challenge, didnt stick well to the sides and part of the plug mould got stuck and caused a chip hopefully I can touch it up and it will buff out.

Havent heard a Lenco yet, so dont know the sound. With the other plinth (old suspended belt drive) going from heavy wood to bento/resin, definitely changed the sound to more neutral, less coloured sound with more wider detail.
 
All done.
Really heavy and sounds great.


The epoxy top coat was a challenge. Takes about 24 hours to touch dry and a week to go really hard. Didnt have the patients for that and had to do a second coat (probably do with a third coat). I used too much on the first coat and it went every where......looks like a really bad wedding cake.

The squash ball feet work well although hard to adjust in the right spot and get level.
 

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Cool! Thanks for posting this. I'm tempted to try this for a Rek-O-Kut table I have that needs a plinth.
 
Nice - but should not have painted it. It looks very good painted but the raw plinth looked more like a piece of art.
 
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