hello
i used the premotec, because this motor was laying around and it was the easiest way to do. quick and dirty solution..
so i guess it could be done better.
also important was that all my rubber wheels and idler pucks where not in best shape.
so some 4mm round rubber string is cheap and easy to mount.
also if you attach a motor make sure you isolate the motor by rubber somehow.. if motor is attached with rubber suspension, silent blocks and then with a belt you should have minimal rumble.
but torque transmission could become a problem. but i had acceptable results with this solution.
the best mod. would be to use the strobo marks and feed them to a small microcontroller to add a feedback loop back to premotec motor.
extra bonus mod...plus a stable quarz clock. then you can get quarz locked turntable drive...
if you go with original 60hz motor buy a 50/60 hz converter. they exist for hammond organs.
exactly same problem a 60hz/115v motor and there are many organs out in europe running on converters.
problem could be noise over the power line. not sure how good emi protection is. but they have also sine version....
[url]http://www.keyboardpartner.de/hammond/products.htm[/url]
[url]http://www.keyboardpartner.de/hammond/diagrams/SWC60-3.pdf[/url]
flo
Hi Mark,
- 30 watts@1800rpm
- 0.116711111 foot pound force @1800rpm
- 1.61358 kg/cm @1800rpm
? ( I used this article: http://www.vettenet.org/torquehp.html and this calculator for these conversions: http://www.asknumbers.com/TorqueConversion.aspx).
Also must the pulley be stepped and does it really have to be 1800rpm for a direct drive?! If i just make a pulley of, let's say 0.5 inch fixed size, i can change the rpm's by powering up/down the DC motor right? And for a 0.5 inch pulley i need a motor capable of doing max 2496 rpm's to get 78rpm's (http://www.temecularodrun.com/ref/rpm_calc.asp, using 16inch platter size) which then should have a HP of at least 1/18 HP (to be precise 0.055466667 HP, using the formula in the above article again: (2496rpm * 0.116711111 needed torque) / 5252)), so it provides the same torque at that speed (man i hope i all got his right.. already calculating for an hour now
).
...sorry for so many new questions .. i still have so much to learn about all this. Don't feel obliged to answer any of them, i'll keep reading and researching myself of course!
Joost
Check, great to hear this is a realistic option! I s*ck in maths, but 1/25HP@1800RPM is the same as:markrob wrote: The brushless DC motor idea should work out great. As far as torque, just make sure the motor is capable of 1/25 hp at the shaft speed you will be running (1800 rpm if going with direct drive). If you can find a motor that can be mounted in the same space as the Bodine, that is the easiest solution. You will probably need to machine a new stepped pulley to fit the motor shaft.
- 30 watts@1800rpm
- 0.116711111 foot pound force @1800rpm
- 1.61358 kg/cm @1800rpm
? ( I used this article: http://www.vettenet.org/torquehp.html and this calculator for these conversions: http://www.asknumbers.com/TorqueConversion.aspx).
Also must the pulley be stepped and does it really have to be 1800rpm for a direct drive?! If i just make a pulley of, let's say 0.5 inch fixed size, i can change the rpm's by powering up/down the DC motor right? And for a 0.5 inch pulley i need a motor capable of doing max 2496 rpm's to get 78rpm's (http://www.temecularodrun.com/ref/rpm_calc.asp, using 16inch platter size) which then should have a HP of at least 1/18 HP (to be precise 0.055466667 HP, using the formula in the above article again: (2496rpm * 0.116711111 needed torque) / 5252)), so it provides the same torque at that speed (man i hope i all got his right.. already calculating for an hour now
).I think that will make sort of sense since there's no direct contact between motor and platter, but then why is most of all the expensive TT gear rim driven? Why didn't Presto (and Neumann, Scully, expensive Garrard's, Lenco's, etc) use a belt in the first place?!markrob wrote: The disadvantage of this approach is that you will still be running a rim drive system and be suject to the need for the rubber idler pucks. Also, I suspect that you will have much better motor vibration isolation if you use Flo's approach and go with a belt drive. That seems to be a problem with my 6N.
Mark
...sorry for so many new questions .. i still have so much to learn about all this. Don't feel obliged to answer any of them, i'll keep reading and researching myself of course!
Joost
- There's no B-side on a blank -
Hi Flo,
Thanks very much for these insights.
Joost
Thanks very much for these insights.
I think i'll buy a sheet of Sorbothane for that, I read somewhere on this forum it's great for damping......flozki wrote: also if you attach a motor make sure you isolate the motor by rubber somehow.. if motor is attached with rubber suspension, silent blocks and then with a belt you should have minimal rumble. but torque transmission could become a problem. but i had acceptable results with this solution.
I once had a TT which had this kind of technology, it was a cheap Japanese kind of player (have to look it up). Maybe i can buy one of those again and re-use it's parts for such a system. Also i see there's a thread going on here: https://lathetrolls.com/viewtopic.php?t=2629&highlight=motor&mforum=lathetrolls where JayDC is trying to accomplish the same thing if I'm right. I'll follow that closely.flozki wrote: the best mod. would be to use the strobo marks and feed them to a small microcontroller to add a feedback loop back to premotec motor.
extra bonus mod...plus a stable quarz clock. then you can get quarz locked turntable drive...
That might be a relatively cheap solution as well. I also found one here in the Netherlands for less and is capable of handling more power: http://www.haltronics.nl/webshop/product_info.php?products_id=655 (100watts).flozki wrote: if you go with original 60hz motor buy a 50/60 hz converter. they exist for hammond organs. exactly same problem a 60hz/115v motor and there are many organs out in europe running on converters. problem could be noise over the power line. not sure how good emi protection is. but they have also sine version....
http://www.keyboardpartner.de/hammond/products.htm
http://www.keyboardpartner.de/hammond/diagrams/SWC60-3.pdf
Joost
- There's no B-side on a blank -
Hi,
I didn't check your math, but I think you have the right idea. You want to look at the torque at the platter speed to get a better idea of the actual forces involved. You are also correct that if you go with a variable speed motor, you won't have to use a stepped pulley. This type of arrangement also allows you to be less precise with your pulley dimensions as you will be able to adjust your speed to compensate using a strobe disk. Also opens up options for half or reduced speed mastering.
I don't doubt that there are great rim drive systems out there. My Dual 1219 is pretty good. Just not trivial to make things work correctly. I suspect the mechanical noise on my 6N is due to age of the motor and idler pucks. There is good deal of discussion on the web over the merits of rim, direct, and belt driven systems. Like most things there are many tradeoffs to consider.
I would probably opt for keeping the rim drive only becuse the mechanics are so much simpler as long as you can find a motor that fits in the space and you are able fabricate a proper mounting adaptor. Also, if you do the mod right, you should be able to return the lathe to its original setup if you decide to sell later.
As far as the need to match torque at 78, I would just use the 1/25hp number as I doubt that the 6N designers cut things that closely. In fact, since the available torque is less at 78 vs. 33, I suspect they selected the motor based on this speed. If you plan of driving the head from an external motor to allow variable pitch (as some have done), I'll bet you could reduce the motor size even further. The fact that an SL1200 provides enough for most cutting needs is proof of that. You also want to look at the torque/ speed curve for the motor and drive you select as it will probably not be constant. The fixed speed Bodine does not have to deal with this issue. Make sure you have enough available torque over the speed range you intend to run. I'm thinking that a 5:1 range would cover 78 rpm to 16 rpm (for half speed mastering). If that turns out to be a problem, then a stepped pulley will help solve that.
Mark
I didn't check your math, but I think you have the right idea. You want to look at the torque at the platter speed to get a better idea of the actual forces involved. You are also correct that if you go with a variable speed motor, you won't have to use a stepped pulley. This type of arrangement also allows you to be less precise with your pulley dimensions as you will be able to adjust your speed to compensate using a strobe disk. Also opens up options for half or reduced speed mastering.
I don't doubt that there are great rim drive systems out there. My Dual 1219 is pretty good. Just not trivial to make things work correctly. I suspect the mechanical noise on my 6N is due to age of the motor and idler pucks. There is good deal of discussion on the web over the merits of rim, direct, and belt driven systems. Like most things there are many tradeoffs to consider.
I would probably opt for keeping the rim drive only becuse the mechanics are so much simpler as long as you can find a motor that fits in the space and you are able fabricate a proper mounting adaptor. Also, if you do the mod right, you should be able to return the lathe to its original setup if you decide to sell later.
As far as the need to match torque at 78, I would just use the 1/25hp number as I doubt that the 6N designers cut things that closely. In fact, since the available torque is less at 78 vs. 33, I suspect they selected the motor based on this speed. If you plan of driving the head from an external motor to allow variable pitch (as some have done), I'll bet you could reduce the motor size even further. The fact that an SL1200 provides enough for most cutting needs is proof of that. You also want to look at the torque/ speed curve for the motor and drive you select as it will probably not be constant. The fixed speed Bodine does not have to deal with this issue. Make sure you have enough available torque over the speed range you intend to run. I'm thinking that a 5:1 range would cover 78 rpm to 16 rpm (for half speed mastering). If that turns out to be a problem, then a stepped pulley will help solve that.
Mark
i think 30 watt is a little low. better have some reserve 50W-60W.
especially if you want to varii the rpms..
scully uses belts...
neumann until vms70 used direct drive with a motor on its limits...if you cut deep grooves with heavy lateral modulation you can easy get to the lyrec's limit.. only with sp02 and denon drive you have better results..
or with vms80,82 brusehed dc motor
lenco tt's are shit (sorry to say that and i guess now i got lots of opposition...) but technically they have almost no torque. garrard and thorens are way better, but same friction wheel.
and big difference to your presto :
they just play back. no power variations. imagine you cut heavy lateral amount tracks... no way...)
so friction wheels might be ok or good for playback but not for recording.
and i would say those turntables got their very good reputation of other mechanical qualities. i guess if thorens made a direct driven td124 this model would be the king of turntables....
japaense and korean high end scene even prefer old neumann lathes to the garrards, thorens emts....
they just used this technique because it was a cheap technique. high pole synchronous motors are super heavy and fxxxxx expensive. there was nothing else at that time.. dcbrushless came a little bit later...
and presto was never a high end machine. itwas made to be portable...
and it worked good enough for mono acetate laquers...
especially if you want to varii the rpms..
scully uses belts...
neumann until vms70 used direct drive with a motor on its limits...if you cut deep grooves with heavy lateral modulation you can easy get to the lyrec's limit.. only with sp02 and denon drive you have better results..
or with vms80,82 brusehed dc motor
lenco tt's are shit (sorry to say that and i guess now i got lots of opposition...) but technically they have almost no torque. garrard and thorens are way better, but same friction wheel.
and big difference to your presto :
they just play back. no power variations. imagine you cut heavy lateral amount tracks... no way...)
so friction wheels might be ok or good for playback but not for recording.
and i would say those turntables got their very good reputation of other mechanical qualities. i guess if thorens made a direct driven td124 this model would be the king of turntables....
japaense and korean high end scene even prefer old neumann lathes to the garrards, thorens emts....
they just used this technique because it was a cheap technique. high pole synchronous motors are super heavy and fxxxxx expensive. there was nothing else at that time.. dcbrushless came a little bit later...
and presto was never a high end machine. itwas made to be portable...
and it worked good enough for mono acetate laquers...
Great! All clear and a nice piece of information on old days motor usage!
Since we're in 2011 now, i think an upgrade to a belt system would be the way to go then.
Wouldn't it be possible to use a belt driven dc motor in it's current location, like:
I think this should work, what you think?! It is a minimal change and it would also give me the ability to restore everything back to the original state if ever needed (although there are more parts on the Presto which aren't original anymore, but nevertheless).
@Flo I read you moved the motor to the place of the playback arm, why is that? I guess because of needed room for the amp?
And alright i say it with you: Lenco's are SHIT!
..well that's out of the way.. what a relief.
Since we're in 2011 now, i think an upgrade to a belt system would be the way to go then.
Wouldn't it be possible to use a belt driven dc motor in it's current location, like:
I think this should work, what you think?! It is a minimal change and it would also give me the ability to restore everything back to the original state if ever needed (although there are more parts on the Presto which aren't original anymore, but nevertheless
).@Flo I read you moved the motor to the place of the playback arm, why is that? I guess because of needed room for the amp?
And alright i say it with you: Lenco's are SHIT!
..well that's out of the way.. what a relief.- There's no B-side on a blank -
[quote]@Flo I read you moved the motor to the place of the playback arm, why is that? I guess because of needed room for the amp? [/quote]
it was because my 6n was not in original condition. so the arm was missing and the motor fitted just inside. only drill 3 new holes...
sure i havent done it like this when i have a mint presto... then i guess i would have bought a freq. converter....
to put in the amp was another lucky thing..it just fitted in.
so more or less a very improvised solution..
it was because my 6n was not in original condition. so the arm was missing and the motor fitted just inside. only drill 3 new holes...
sure i havent done it like this when i have a mint presto... then i guess i would have bought a freq. converter....
to put in the amp was another lucky thing..it just fitted in.
so more or less a very improvised solution..
-
andyburnout
- Posts: 16
- Joined: Sun Apr 25, 2021 10:22 pm
- Location: Melbourne
Re: Presto 6N Motor / Speed Controller update options
Has anyone recently done a belt drive conversion? Surly 10 years later it had happened, anyone have any advice?
I’m in Australia running 50hz and also have a lot of motor noise, I thought this might be a better option.
I’m in Australia running 50hz and also have a lot of motor noise, I thought this might be a better option.
Last edited by andyburnout on Wed Jul 13, 2022 3:18 am, edited 1 time in total.
Re: Presto 6N Motor / Speed Controller update options
This one is converted to direct drive. It is MRC16, not 6N but the platter works in similar way https://www.lathetrolls.com/viewtopic.php?f=15&t=8200&p=53005&hilit=presto+mrc#p53005