How do I glue Vinyls LP togenter?

[YAKI]

Hi,
I want to tray and build a turntable platter using LPs. I will need to glue about 20-30 LP together. I have access to an industrial press (about 10 tones...), so I about to put a 6 mm bar in the hols, and glue it all together in press. The edges of an LP are higher then the groves levels themselves. Hence, I will need a glue which:
1. has a volume
2. drays slow (it will take me some time to put the LP's on on another, put into the press and press it...

I thought about epoxy but I don't know which. Alternatively, I thought about car-kit which is used to fix body problems with cars.

Can anyone help me with a recommendation?
Thanks!

[Scott594]

They're PVC, PVC pipe cement should do well, but use the slow drying type designed for large diameter pipe, or it won't have enough open time. It's available in varying thicknesses and colors, you'll want "heavy bodied"
You could also make your own by dissolving PVC (vinyl) chips in acetone or MEK until you get the desired viscosity.
I'd sand the outer edge lip off to make them as flat as possible before glueing, and add one at a time to giving the solvent time to migrate out (a day or so I'd guess.
I sure hope the LPs being used are trashed already, if not, please don't tell me.

[planet10]

When i considered this, i figured you'd have to heat the vinyl up until you could mosh it all together.

dave

[YAKI]

Hi,
Thanks. I think it could be a problem to send the outer ring, since I measured and see that the inner 10 cm of the LP is higher then the grove itself. Hence, it could be a problem to send it as well. But, I will try.
In addition two questions:
1. is the acetone based home made glue really strong? can it bent my LP's?
2. is epoxy is an option? it is the most easier to work with.

Thanks for your kind help!

[Scott594]

Originally Posted by YAKI

Hi,

In addition two questions:
1. is the acetone based home made glue really strong? can it bent my LP's?
2. is epoxy is an option? it is the most easier to work with.

Thanks for your kind help!

1. Commercial PVC cement is simply PVC dissolved in a MEK/acetone mix - the ratio controls drying speed - Acetone is fast evaporating, MEK slower. Sometimes some toulene is in the mix to make it more aggresive and tolerant of dirty pipe. The way these cements work is by actually dissolving the substrate, thus welding the 2 parts together. (similar to model cement for polystyrene). The PVC included in the mix acts a filler for small voids, and slows down the evaporation enough so the solvents have time to work on the objects being glued.

2. Epoxy probably would work, especially if you use a slow cure version like West Systems or even PC-7 or JB weld if those are available. My concern there would be after time the different expansion characteristics of the 2 dissimilar materials may cause cracking or warping.

All that being said, I'd glue up some test samples, stress test them, and see what you think. My instincts say PVC cement will win, but I've been mistaken before.

One other option is to cut a disk from commercially available PVC sheet, and avoid the glueing completely (probably the most practical, but doesn't have the same sense of style).

Hope you post the results/pictures.

[jloveys]

Hello Yaki,
For a platter I would use shellac records instead of vinyl. They are made of 15% shellac, a natural compound from an insect in India mixed with 40% slate powder and 40 % limestone powder, a chemical mix more suitable for a platter material.Each record is very heavy and very flat, no thick edge here.
Gluing the records together with shellac pellets ( a superglue ) is ideal because it has the same resonant signature than the records.
For info: Stacked platters...with shellac records ! (page 1) - The Lab - Lenco Heaven Turntable Forum

Good luck with your project !

[Mark Kelly]

I love the Shellac idea.

If you do go with vinyl, do not use solvent based glue (plumbing cement or the DIY version). These work by evaporating the solvent out so they fill space badly and shrink when curing.

Be very careful if you try heat and press methods - thermal degradation of PVC sets in at close to the melt temperature and releases hydrochloric acid gas. This is not pleasant.

Epoxy bonds PVC very well (vinylcell PVC foam is commonly used in the core of laminated structures) and is very dimensionally stable during cure.

The coefficient of thermal expansion of PVC is about 70 x 10^-6 / K, most unfilled epoxy glues are around 100. If you thicken the epoxy with about 30% of a silica based filler you should get a very close match. There's a lot of research focussed on finding low CTE epoxies to reduce the difference between the epoxy and carbon fibres in CFRP composites, if you search you may find a match that needs less or even no filler.

The problem I foresee is in balance and centreing - if you rely on the centre hole you'll be all over the place.

[planet10]

How about grinding the records into a powder, then setting it together with epoxy. We made a very good Linn outer platter using copper powder & epoxy. Sent the Linn distrib away shaking his head and was a lead0in to selling (the then new) Oracle tables. It would need to be machined after, but you could probably get away with a router and some jigs.

dave

[jloveys]

Originally Posted by Mark Kelly

I love the Shellac idea.

The problem I foresee is in balance and centreing - if you rely on the centre hole you'll be all over the place.

Do you have an idea how to balance the shellac platter once glued ?

Jean.

[Mark Kelly]

Static balance is really easy, mount it on the bearing, tilt to one side, observe the low point and add weight diametrically opposite until balanced (I'd use Tungsten powder in a hole drilled in the bottom disc.)

Dynamic balance is another story. Any good machine shop can perform dynamic balance but that's not really DIY.

It isn't particularly difficult to design a dynamic balancer, it's just a vibration analyser combined with a rotary encoder but that's a lot of effort for a one-off.