Another DIY Turntable - maybe a new idea? - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 2nd January 2006, 10:33 PM   #1
JesseG is offline JesseG  Canada
diyAudio Member
 
JesseG's Avatar
 
Join Date: Jul 2005
Location: Mid coast of British Columbia
Default Another DIY Turntable - maybe a new idea?

Hi all.

I just finished reading almost all of the monster DIY turntable thread, which seems to have ground to a halt last September. Some really great ideas: air bearings, magnetic bearings, floating the platter on oil... great stuff.

Each approach has its problems: Air bearings need top-flite precision and a compressor (or pressurized air source), magnetic bearings need suitable magnets and have all kinds of magnetic field issues, floating on oil could be messy and the difficulty of keeping the platter centered while applying a driving force remains to be solved.

I have been thinking about this problem tho - what we need is an approach that is 1) simple 2) plays LPs well and 3) is buildable.

Also, on looking at the various designs currently in use, it appears that we have become collectively fixated on the idea tha we have to apply the rotational force directly to the platter. Most of the inherent limitations in turntables comes from this basic design feature.

Whenever I have to solve a problem, I tend to look around to see if humans have already solved it. Looking back, it did not appear that any device simmilar to a hifi turntable had been needed or used in human history - until I noticed the Potter's Wheel.

This device uses a very coarse motive force (the potter's feet) and translates it into a very fine rotational machine, capable of amazing precision - and, it is very simple.

This approach has some really attractive features:

1) the rotational force is applied to a flywheel which can be decoupled from the platter in all sorts of ways while maintaining precise speed control

2) any vibrations derived from drive mechanism (motor) can be isolated from the LP/platter interface.

3) the mass of the platter can be configured to best suit the dynamics of playing LPs, not rotating them.

I have attached a first kick at the idea of designing a TT on the principals of a potter's wheel. I'm sure many of you could come up with a better interpretation.

I will look forward to comments on this idea - hope it rings a bell with some of you like it has with me.

HNY

Jess
Attached Images
File Type: gif potter's wheel sm.gif (22.1 KB, 1002 views)
  Reply With Quote
Old 2nd January 2006, 10:56 PM   #2
diyAudio Member
 
Join Date: Feb 2004
Location: Lincolnshire, UK
Too many links in the (drive) chain and alot of bearings IMO.

The subplatter could be driven directly somehow thus loseing the rubber belt from the motor.

The silicone tube....again a possible source of speed variations in the main platter due to stylus drag?

I think there could be mileage in the idea. Heavy subplatter for speed stability driving a light main platter for low energy storage/dispersion.


Paul.
  Reply With Quote
Old 3rd January 2006, 06:56 AM   #3
JesseG is offline JesseG  Canada
diyAudio Member
 
JesseG's Avatar
 
Join Date: Jul 2005
Location: Mid coast of British Columbia
Quote:
I think there could be mileage in the idea. Heavy subplatter for speed stability driving a light main platter for low energy storage/dispersion.
Yep, thats the essence of the idea.

Quote:
Too many links in the (drive) chain and alot of bearings
There are only two bearings in the design as it is. The one supporting the flywheel and the one supporting the platter. However, you may have a point. The concentric bearing for the platter is the least developed part of the concept at this point. Im hoping that some of thr mrchanical wizards out there will come in and help figure it out

Any and all suggestions welcome...

Lets see what develops

Jess
  Reply With Quote
Old 3rd January 2006, 07:26 AM   #4
bappe is offline bappe  Sweden
diyAudio Member
 
bappe's Avatar
 
Join Date: Sep 2002
Location: Furulund, SWEDEN
Hi!

Have a look at the Forsell Air Ref. w flyweel drive. The flyweel is rotatinf at a speed of app. 1500 rpm and is made of brass. this in turn drives the relatively light main platter. If we make the (correct or incorrect) assumption that we have a stiff connection between the flyweel and the platter we get a system that have the inertia equivalent of a platter at 33 rpm with a mass of close to 1 ton, interresting!

BR,
Anders
  Reply With Quote
Old 3rd January 2006, 07:27 AM   #5
bappe is offline bappe  Sweden
diyAudio Member
 
bappe's Avatar
 
Join Date: Sep 2002
Location: Furulund, SWEDEN
Hi again!

Here is a link:
http://pic17.picturetrail.com/VOL826...75/9036152.jpg

/Anders
  Reply With Quote
Old 3rd January 2006, 07:47 AM   #6
maxro is offline maxro  Canada
diyAudio Member
 
maxro's Avatar
 
Join Date: Dec 2004
Location: Survey says: Least happiest city in Canada
Default Re: Another DIY Turntable - maybe a new idea?

Quote:
Originally posted by JesseG
Hi all.
1) the rotational force is applied to a flywheel which can be decoupled from the platter in all sorts of ways while maintaining precise speed control
How can one maintain precise speed control with decoupling? Paul is right, the flexure of the tube you suggest will inherently allow speed fluctuations.

Quote:
Originally posted by bappe
Hi!

Have a look at the Forsell Air Ref. w flyweel drive. The flyweel is rotatinf at a speed of app. 1500 rpm and is made of brass. this in turn drives the relatively light main platter. If we make the (correct or incorrect) assumption that we have a stiff connection between the flyweel and the platter we get a system that have the inertia equivalent of a platter at 33 rpm with a mass of close to 1 ton, interresting!

BR,
Anders
I would have to assume that the belt is not a stiff connection between the flywheel and the platter, same problem as the flexible tube.

This flywheel idea was discussed in a recent thread. (light weight plinth?) Paul, did you start it?

Like many things in audio, just because it has been done, does not make it a good idea.

What's wrong with regular old belt drive?

I suppose direct drive is out of the question for DIY.

Max
  Reply With Quote
Old 3rd January 2006, 11:26 AM   #7
diyAudio Member
 
Pjotr's Avatar
 
Join Date: Nov 2002
Location: Netherlands
Hi Jesse and others,

Looks a bit as the Transrotor magnetic drive. In stead of the silicone tube spring they use a magnetic spring as coupler. But such an extra mass and spring introduce an extra mass-spring system with an extra resonance to cope with.

All those mass-spring things are exited by the varying drag of the groove modulation. IMHO a heavy platter which is simply loosely belt driven by a steady running motor still appears to me as the most optimum compromise.

The air coupled flywheel looks very interesting. But I donít think this will give the platter a very high effective mass. It is simply de mass of the platter (-> moment of inertia) driven by the torque as a result of the drag of the coupling air between platter and flywheel.

Cheers
  Reply With Quote
Old 3rd January 2006, 08:46 PM   #8
hybris is offline hybris  Netherlands
diyAudio Member
 
Join Date: Oct 2003
Location: Bleiswijk
For the first design mentioned in this topic I would like to point at the risk of torsion resonance. Kind of overshoot- effect: the response after a sudden increase in stylus drag.

Can be compaired to the main drawback of a bass- reflex speaker.

Oh, by the way I build my own arms and motor units too. In the gallery of V. Engine Y'l find my unipivot balsa- arm.

And at the moment I'm working on a heavy TD160- based motor unit: no floating subchassis but a stationairy one.
__________________
h.
  Reply With Quote
Old 3rd January 2006, 10:06 PM   #9
JesseG is offline JesseG  Canada
diyAudio Member
 
JesseG's Avatar
 
Join Date: Jul 2005
Location: Mid coast of British Columbia
Very ineresting comments from all.

Quote:
Have a look at the Forsell Air Ref. w flyweel drive. The flyweel is rotatinf at a speed of app. 1500 rpm and is made of brass. this in turn drives the relatively light main platter. If we make the (correct or incorrect) assumption that we have a stiff connection between the flyweel and the platter we get a system that have the inertia equivalent of a platter at 33 rpm with a mass of close to 1 ton, interresting!
Thanks for this, Anders. Shows me that soemone else has seen enough merit in the idea to build one.

Quote:
All those mass-spring things are exited by the varying drag of the groove modulation
Yes, I can see the possibility of getting some effect from that. I expect that some experimentation could identify a suitable drive coupling material.

I just really want to find a way to get away from applying the rotational force directly to the platter, thus avoiding all of the latteral force complications that derive from that one engineering compromise.

Let's see what else folks come up with

Jess
  Reply With Quote
Old 4th January 2006, 02:30 AM   #10
maxro is offline maxro  Canada
diyAudio Member
 
maxro's Avatar
 
Join Date: Dec 2004
Location: Survey says: Least happiest city in Canada
Quote:
Originally posted by JesseG
I just really want to find a way to get away from applying the rotational force directly to the platter, thus avoiding all of the latteral force complications that derive from that one engineering compromise.

Let's see what else folks come up with

Jess
Okay,

How about a motor that revolves at 33.3 RPM attached directly to the flexible drive shaft-tube thing. No lateral load and no coupled flywheel transient issues.

I suppose one could mock this up with a DIY platter hovering over a direct drive table with a piece of tubing wedged over the spindle and attached to the underside of the DIY platter.

Or, how about a belt riding around the motor and two idler pulleys forming an equalateral triangle around the platter. No lateral load on the platter, and it has been done before. Just don't use three motors.

Max
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Bipolar stepper motor idea for custom turntable... binspaul Analogue Source 0 7th April 2009 09:43 AM
DIY - Turntable whubbard Analogue Source 17 8th March 2009 07:39 AM
An idea! Fully balanced TDA1541A DAC idea. Please comment! cartman Digital Source 8 17th July 2007 08:18 AM
DIY Turntable ?'s LeBob Analogue Source 3 26th July 2004 03:32 AM
DIY turntable idea DeonC Analogue Source 5 18th March 2004 09:32 PM


New To Site? Need Help?

All times are GMT. The time now is 04:13 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2