andyr Posted June 21, 2015 Posted June 21, 2015 @Tasebass: in my last thread about my SkeletaLinn (sorry, can't find it), when I posted I was going to try out 2 motors - you suggested that if the 'normal' motor position is 10:30 or 11 o'clock, if the 2nd motor was to be located 180 deg opposite, it would have to be positioned very near the arc of the cartridge ... and the motor's electrical/magnetic field would generate noise in the cartridge. That's certainly a reasonable theory ... but I'm happy to report that my experiment just now has shown it to be false! Duc had made up a 2nd pulley for me, I bought a 2nd 24v Rega motor from Steve last week and this afternoon: connected up the 2nd motor - including earthing the case, rested the stylus of my LOMC on the platter, about 20mm in from the outer edge put the pulley directly under the cart (no belt) and switched on the motor. No noise! I have sourced silicon O-ring belts in 3 slightly different lengths: Linn size (7" diam), 7 1/4" diam and 7 1/2" diam - so now I can set out the locations of the 2 motors on the TT base, in order to find the positions that: are 180 deg apart yet don't foul the outer rim of the outer platter and fit one of the 3 belt sizes. Regards, Andy
andyr Posted June 21, 2015 Author Posted June 21, 2015 (edited) Without pics none of it never happened. No celebrity publishes pics of themselves, the day they have plastic surgery, mate ... they wait until the swelling has gone down. Pics will be provided: when I have positioned the motors in the right place - and have cut another 80mm diam hole in the base board have had a 2nd brass motor pod machined by Duc plus a 2nd motor plate (which bolts to the motor pod and supports the motor) made up ... so the 2 motors look nice and have belts attached! My post was basically just an alert to Tony, to let him know that AC motors do not cause noise in LOMCs. Regards, Andy Edited June 21, 2015 by andyr
Luc Posted June 21, 2015 Posted June 21, 2015 Ah, i c , prognostication then. I await the pics with eager anticipation.
Tasebass Posted June 21, 2015 Posted June 21, 2015 Andy. I'm in hospital with some complications. Hopefully out soon. Cheers Tony
andyr Posted June 21, 2015 Author Posted June 21, 2015 Andy. I'm in hospital with some complications. Hopefully out soon. Cheers Tony That's no good - hope you are better, soon. Andy 1
Addicted to music Posted June 21, 2015 Posted June 21, 2015 Andy. I'm in hospital with some complications. Hopefully out soon. Cheers Tony Hope you get well soon @Tassbass and make a full recovery..........love your dedication, even though you dragged yourself to hospital and just about go into surgery you still post on SNA......now that's real dedication! 1
Tasebass Posted June 21, 2015 Posted June 21, 2015 This is my second visit in less than a week after major rectal surgery due to the big C. I'll probably start a post regarding my experiences over the last 6 months
Luc Posted June 21, 2015 Posted June 21, 2015 Thinking of you TB and hoping your going to get better. @@andyr Andy, what is the reasoning for having two motors? I'm not quite sure I understand what your trying to achieve there. Will two be better than one because....? Is it more reliable or a more steady drive under load or something?
andyr Posted June 21, 2015 Author Posted June 21, 2015 This is my second visit in less than a week after major rectal surgery due to the big C. I'll probably start a post regarding my experiences over the last 6 months Hope you're on the upward curve now, Tony. Andy
andyr Posted June 21, 2015 Author Posted June 21, 2015 (edited) Andy, what is the reasoning for having two motors? I'm not quite sure I understand what your trying to achieve there. Will two be better than one because....? Is it more reliable or a more steady drive under load or something? There are 2 reasons Luc - which, luckily, as I've been able to show that motor position is not an (noise) issue, I can achieve: 1. The torque or 'drive' applied to the Linn inner platter. When we did the experiments last year with increasing the voltage applied to the motor, we found that as we upped the voltage, the sound became better in many ways. More voltage means more torque from the motor - although the downsides are: a. it gets hotter, and b. it vibrates more. With my SkeletaLinn design, a. is solved - as the motor is in free air, not under a top-plate, inside a plinth. So it remains cool - even when feeding +1/3rd more voltage to the motor (32v instead of 24v). Steve's motor controller solves b. as you can adjust phase (between the 2 pairs of motor wires) to minimise motor vibration (you hold the motor in your hand while altering the phase value with your computer). It also was designed to drive 2 motors (you need to be able to adjust phase between them). So a 2nd motor (also driven at 32v) will deliver twice the torque I get now. 2. With 1 motor/belt, the chassis is pulled towards the motors (this even happens - to a smaller degree - with an LP12). By putting a 2nd motor on the other side of the platter, I can neutralise this side-ways pull. Regards, Andy PS: Shouldn't you be out fishing? Edited June 22, 2015 by andyr
Luc Posted June 22, 2015 Posted June 22, 2015 Ah,I see. So you have neutralised the pull towards the motors this way. Umm you'll probably shoot me but, of you did away with the motor belt idea and did a direct drive would you achieve the same thing? Fishing, yes I would be but work has intervened or will when I finally get moving and go and do some..
andyr Posted June 22, 2015 Author Posted June 22, 2015 Ah, I see. So you have neutralised the pull towards the motors this way. Umm you'll probably shoot me but, if you did away with the motor belt idea and did a direct drive would you achieve the same thing? But I like belt-driven TTs! Andy
Luc Posted June 22, 2015 Posted June 22, 2015 But you'd achieve the same thing maybe if you did have a DD?
andyr Posted June 22, 2015 Author Posted June 22, 2015 But you'd achieve the same thing maybe if you did have a DD? But I didn't set out to create a new TT from scratch, Luc - I set out to see if I could use a 12" Univector arm on my LP12. After it became obvious that that was never going to work - without butchering my beautiful LP12 - I moved down the path of using the core Linn parts (which I know work well and sound good) to create a platform for the 12" Univector. I have achieved that with my SkeletaLinn (FrankenLinn is probably a better name! ) - and it sounds better than my ever LP12 did! So now it's a matter of what I can to do to take its performance to the limit. But I couldn't have achieved these last couple of improvements if I hadn't found Steve Tuckett and his 'magic' speed controller. That was serendipity! Andy
andyr Posted June 22, 2015 Author Posted June 22, 2015 I await the pics with eager anticipation. Just for you, Luc - here's a pic of the set-out. Andy 1
Luc Posted June 22, 2015 Posted June 22, 2015 Must be hard to get those motors in synch is it or is it that they have the same rpm so that it's a matter of correct switching. What's the belts made out of?
andyr Posted June 22, 2015 Author Posted June 22, 2015 Must be hard to get those motors in synch is it or is it that they have the same rpm so that it's a matter of correct switching. What's the belts made out of? Belts are silicon. Yes, the motors are identical but, to get it working properly (as the diameters of the two pulley grooves may be marginally different), I will have to: adjust the speed (Hz) of the 2nd motor so that it - by itself - rotates the platter at exactly the same speed as the 1st motor. adjust the phase difference between the 2 motors (another unique feature of the 'Number9' speed controller! ) to get the smoothest operation. Regards, Andy
andyr Posted September 26, 2015 Author Posted September 26, 2015 (edited) OK, @@Tasebass - this afternoon, Steve Tuckett (the designer of the Number9 AC motor speed controller that I use) and I finally fired up my SkeletaLinn driven by 2 motors. So @@djb, here is something to save your pennies for, after you've recovered from the vast expense of getting your wonderful T-1Ds working to their full potential! I had got a second motor from Steve and a second pulley from @@lovetube, a while ago - and had a new perspex base made up (with 2 holes for the motor pods ... which took a deal of careful measurement to get the pulleys 180 deg aligned, relative to the platter spindle). Then I had to wait for Steve to get his engineers to program an extra adjustment parameter for the software in the chip which is at the heart of the speed controller. This was needed to allow the speed for each motor to be adjusted (by changing the Hz which is fed to the motor) so that each motor could be set independently to run at the correct speed (thus compensating for any slight difference in pulley diameters resulting from manually machined pulleys). I'm happy to report that the results are according to theory! We first listened to just 1 motor - then we connected the 2nd belt. We found that having 2 motors - rather than just 1 - delivers the following (this was using a couple of LPs that we were familiar with, having used them in previous tests of power supplies for the speed controller): you are seated towards the front of the concert hall instead of towards the back. the 'attack' is better. instrument separation is better. to use a motoring analogy ... in terms of 'delivery', it's like driving a 5l Ford V8 rather than a Fiat 'Bambino'. So it's a resounding success! And here's a pic of the 2-motor SkeletaLinn: Regards, Andy Edited September 26, 2015 by andyr 5
djb Posted September 26, 2015 Posted September 26, 2015 So your calling my Skeletallinn a Fiat bambino?
ThirdDrawerDown Posted September 26, 2015 Posted September 26, 2015 Congratulations! The realisation of a long-held dream! We look forward to the production line, now that the protoype is sorted. @@djb, yes, that's what he wrote. Think of it maybe as 'proof of concept'?
Telecine Posted September 26, 2015 Posted September 26, 2015 Good work Andy, glad that it is coming together.
djb Posted September 26, 2015 Posted September 26, 2015 @@andyr looking forward to hearing the finished product
andyr Posted September 26, 2015 Author Posted September 26, 2015 So you're calling my SkeletaLinn a Fiat Bambino? Weeeell, sorry, David ... but I guess if you wanted to be picky, you would say that's what I intended to say. But since your SkeletaLinn is better than most Linn LP12s ... what should we call them? A Gogomobile? :lol: Andy
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