Anyone "Handy" interested in a DIY Turntable Project?

Oops
sorry about the vast drawing, I forgot I was working on the PC

 

Hi Granville,

Good stuff.

The arm at rest doesn't need to be over the plinth no. The deck I use every day is a NAS Spacedeck - and that has the arm hanging in mid air at rest - no small children or small animals chez Unc.

Nice idea, but I've never been overly convinced about the need for a 12 inch arm argument. Current setup has a 210mm arm and a 222mm arm and doesn't seem to suffer from misalignment nasties at the end of side.

The downside to the above design is size - my "slot" for the deck is 48 cm wide by about 38cm deep but I can live with mebbe 2 or 3cm overhang, back and front. If my quick calculations are right, the Granville Mk1 (we'll give it a formal name is about 60cm wide and about 45cm deep. Lots of mass I'll grant you and not unattractive either, but it won't fit. If I had a two foot wide slot and really needed a 12" arm, it might just be goer

The Uncle Ants Mk2 (if I count the first drawing as Mk1 then its Mk2 ) won't take a 12" arm (though a thought did occur which might work at a pinch without changing the design too badly and might still fit, need to sleep on that), but its pretty economical space wise.

I like the sunken platter. The more I think about it, the more I like it. It'd make it look a bit more svelte. My initial thought was that we couldn't sink it as far as you have it here - the belt would have to ride quite high and you would run a risk of accidentally knocking it down the gap when you changed from 33 to 45, but I had a thought - I could use a Speedbox - that would give push button speed change from 33 to 45 all running on the 33 pulley (it ups the "mains" frequency to 67.5 and thus runs the motor faster for 45). Voila, little need to touch the belt and we could probably bury the platter half way.

I like acrylic I must admit

Oh yes - and the subplinth and sorbothane sheet thing - makes sense.

 

12 inch armboard:



Not got the curve quite right (I had to give Auntie her draughtsman's curves back - she's worried I'd lose them ). The bottom of the arm's mounting column would be in free air outside the plinth ... but its round the back so you wouldn't see it. Only adds 2cm to the depth I think. If the armboard material were stiff enough, it should work, I'd have thought

 

More thoughts

Hi Tony, Are there any issues with the cartridge if we use steel to add mass to the deck ? or do we need to use a non magnetic material. I was going to suggest we used 10mm mild steel.

What are your thoughts with regards to feet, I was thinking about 3 stainless steel discs sunk into the underside with a csk dink in the bottom. you could then use any number of points, balls etc. or even rubber pads. What do you use as the support for the deck ?

Any drawings re the bearing yet.

I understand what you getting at re the longer arm, we could make a special arm board to suit,
providing it doesn't compromise the design, I supose you could fit any arm you wanted to.

regards Ian

 

In theory yes as its likely going to be an MC cart, but I don't think in reality it would be a problem - the platter is 4cm thick acrylic, so any cart is going to be a fair distance from any steel. Might be wise to use it in the lower part of the plinth rather than the top half maybe.

No specific thoughts other than a rubbery lump of some sort, some foculpods or some such

Not yet, no. This post has triggered me to chase though.

That's the aim

I'll try and post a new sketch later with the changes need to "sink" the platter a bit and if I get any info back re the bearing will post that too.

Cheers

Tony

 

Hi Tony
I await your post with interest, once you have a more detailed sketch I will draw it up on the PC and run off some S/S plots and send them over for you to ponder. Much easier to sort out potential cock ups, than on a scale drawing.

 

Hi Granville,

Sorry for the delay. Should be able to post some more sketches this evening or tomorrow. Been a busy weekend.

Sounds like a good idea.

Cheers

Tony

 

Hi Granville,

Okay a bit of spare time this afternoon - got to have me tea now and then go watch The Wicker Man, which the Grauniad kindly gave a way for free yesterday

top and front view piccy's 1 large sq=1cm, scale of 1:2. Bearing piccy's not to scale.

New top down sketch for the slightly sunk plinth version:



PS. the platter has a 15 cm radius (the hole it sits in has a 15.2 (or so radius).

The curve along the back is a part of a 52cm radius circle with its centre point 30 centimetres to the front of the platter spindle (if that makes sense). The side curves I did with a set of curves.

front view:



I haven't got any accurate measurements on the bearing and won't have until I/you can get our mitts on one (probably a couple of weeks. But I have drawn some sketches to show you what it looks like in principle - proportions and sizes will be pretty inaccurate, but it paints the picture so to speak.

A sketch of the lower part of the bearing including the mounting plate:



And how it attaches to the plinth (To an extent guesswork, but roughly how I remember the one I saw - think I got the bolts a bit too close together and maybe a bit short though - in fact its possible the top of them were in fact a countersunk phillips heads level with the top of the plinth), but anyway it gives a rough idea:



Thoughts appreciated.

Cheers

Gonna go and watch Britt Ekland (or her body double) prancing in the nude and Edward Woodward getting barbecued now. Later

Tony

EDIT: Looking at my diagram of the bearing, one thing I've definitely got wrong is how far it extends into the platter - it goes up to half way I think. so that the contact point is just about level with where the belt sits on the edge of the platter. The bolts are definitely too close together tooo I think. But its for illustrative purposes to give an idea of how it might be attched to the plnth.

 

Why not support the bearing from beneath ie a rod and spike to the base plate. A number of speakers use a similar set up to tune out vibration, by bearing down on the back of the driver.

 

the bearing doesnt look to stable to me, to much weight above it, try making it so the bearing body continues further into the platter.

 

Hi penance. I understand, but the diagram is in no way to scale the proportions are going to be verty inaccurate - I've only ever seen one of these bolted into a deck - which worked fine - it was really to show how it roughly attaches to the plinth. In fact I'm pretty sure it does extend a lot further into the platter. at least half way, maybe more - problem is its from memory.

 

I'm not sure I understand exactly - can you draw a diagram?

 

If were still on for tomorrow 11.00 ish ...multimeter and cables I'll do a diagram .!

 

Yes, definitely on for tomorrow, so that will be good yes.

 

By the power of the mighty photoshop, more like so:

 

yer that looks better

 

Thought so - gotta bear in mind as well, that there isn't really a bloody great gap between the shaft and the bearing housing either

 

Sorry for the delay replying and thanks for the link. I got hold of a NOS Garrard SP25 motor but the trouble is all the idler drive motors run to fast so I am going to have to dig deep and buy a new Premotec. I can get high torque 250 rpm synchronous motor from the UK distributor in either 24 or 220 volt. Just got to decide which one to go for.

Paul.

 

How come they run too fast? .... actually I think I know .... you are planing to run the idler onto a subplatter yes .... these were designed to run agin the platter rim.

My first proper TT was an SP25 - it was rubbish

 

Well. if the "quality" of the motor is anything to go by, then i'm not suprised it was rubbish!


Paul.