Angling for 90 - tangential pivot tonearms - Page 51 - 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 June 2013, 03:14 AM   #501
diyAudio Member
 
directdriver's Avatar
 
Join Date: Nov 2005
Default PLT = Pivoting Linear Tracker

Let's move on to more fun stuff!

Our forum brainiac Mark Kelly has been quiet these days so I decided to take liberty (Don't kill me, Mark!) to link his ideas and pictures from another forum on here just to stir up some more discussion. I want to or at least I try to be as encompassing as possible to cover all topics on this genre of tonearms. Below is Mark's diy effort and experiment, along with his comments. Very cool!


Quote:
Posted on October 25, 2012

PLT = Pivoting Linear Tracker.

I've been playing with this concept a while, here's one of my efforts. As you can see this is a proof of concept prototype made with bamboo sticks and scavenged bearings. I would have used better bits for the next version if I hadn't come up with a different design which I like much more.

Click the image to open in full size.

I blue-tacked a pointer to the headshell at 90 degrees to the cantilever. It points directly over the spindle at 60mm radius:

Click the image to open in full size.

And also at 150mm radius, and all points in between to within 0.1mm.

Click the image to open in full size.

BTW the data on these pic files says they are over three years old, so obviously I'm not going anywhere with them. Anyone who wants to use the ideas can.

Your problem will be bearings. The main bearing in the phot is the head drum out of a VCR. The secondary bearing (hidden under the arm at the end) came out of a failed HDD. Neither are good enough for theis application but obtaining the correct bearings has eluded me for years.

Mark Kelly


I owe you another beer, Mark!
  Reply With Quote
Old 2nd June 2013, 03:47 AM   #502
diyAudio Member
 
Join Date: Dec 2004
Location: Fernandina Beach, Florida
[QUOTE=Sprags;3510125]I posted my message after not getting a lot of sleep.

Hi, Sprags
That is what I meant by dumb-o rays, a name invented by my friend, for doing things on too little sleep. Your idea is a very good one, even if part of it was also thought of by someone else. (that someone is Straight Tracker, who was throwing you a compliment).

I got hit by the rays myself in my own post, started at 8AM on too little sleep (the "12-in SME3009" screw-up).
Thanks to our diplomatic host, Direct Driver, I at least got to correct things.

Last edited by awolff761; 2nd June 2013 at 03:51 AM.
  Reply With Quote
Old 2nd June 2013, 04:12 AM   #503
Sprags is offline Sprags  United States
diyAudio Member
 
Join Date: Mar 2013
My ideas come at all times. While working for Boeing Helicopters I came up with a fixture design that was used for both turning and milling rotor links for CH-46 and 47's. Saved immensely on set up times and added to precision of the part. I thought of that one when I couldn't sleep and drove into work at 2AM and had the concept ready for presentation in a 10AM meeting. Just one of many....

Last edited by Sprags; 2nd June 2013 at 04:15 AM.
  Reply With Quote
Old 4th June 2013, 08:55 PM   #504
diyAudio Member
 
directdriver's Avatar
 
Join Date: Nov 2005
Default SchuchTronic

More pictures of this interesting German tonearm. Still in search of that hi-rez picture that shows all the details of the arm....

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.
  Reply With Quote
Old 5th June 2013, 02:02 PM   #505
tnargs is offline tnargs  Australia
diyAudio Member
 
Join Date: Sep 2006
Quote:
Originally Posted by awolff761 View Post
Arms that move on rails do indeed follow the original cutter path perfectly, but that's not the whole story. The entire arm mass (counterweight, pivot housing, arm & pickup) must be moved as well. Since the arm stays perpendicular to a radius, how can its pickup move inward across the record? The answer is, "it can't." The spiral groove pulls the stylus (cantilever) out of position and the mass is dragged by it. This is very bad for the record and stylus, not to mention the sound. "Air-bearings" remove rail friction, but the mass must still be handled.
Based on my readings of Poul Ladegaard, the above is nothing more than a common misconception. But since this is a pivoting tonearm thread (and I love it so much), let's pretend that linear trackers have some kind of inherent issue.
  Reply With Quote
Old 5th June 2013, 06:54 PM   #506
diyAudio Member
 
Join Date: Dec 2004
Location: Fernandina Beach, Florida
Hi, tnargs,
Thanks for checking my post, but my reading of Poul's arm is different. He says (Poul Ladegaard's Air Bearing Tangential Tonearm Page),

"Here, the idea of a new principle of movement had to be tried. The mass of a lead weight was to be transformed into the needed horizontal pull force using a pulley.
The problem now is to control the movement of the arm so as to ensure tangential tracking at all times. A heating wire slowly melting through stearin wax had the necessary properties and could by means of varying the electrical currrent be smoothly adjusted from a full stop to the necessary maximum speed. The wax was placed in a small tray in connection with the pulley wire. A wire in the wax along the edge of the tray was fastened to the arm base and thus it could steer/slow down the turning of the wax tray and thereby the movement of the arm.
The mistracking angle of the arm was measured with a photo cell, whose signal was converted into an evenly pulsating current in the heating wire."

He is using an "active" system, not a passive one. A falling lead weight pulls the arm, coupled by a pulley. The rate of fall is modulated by a heated wire in wax, said head controlled by optical feedback. When there is mistracking, the system tries to correct it.
This his "Arm 2", and there is likewise nothing in his other designs that suggests he violated either logic or the laws of physics.
Back then, he also did not treat articulated-head or moving-plinth designs.

Andy

Last edited by awolff761; 5th June 2013 at 07:01 PM.
  Reply With Quote
Old 5th June 2013, 10:07 PM   #507
LFM is offline LFM  Canada
diyAudio Member
 
Join Date: Oct 2004
Location: Sault
Default Angling for 90

I've wanted to bring this up in this thread for some time but haven't for fear of getting flamed. I have owned many Shure cartridges that incorporated that stabilizer brush assembly. I assume since it was used on the most expensive models that it was not detrimental at all to performance. I know of no reported tweaks to improve them which involved removing the brush. I'll mention as well that I used a cleaning device in the 80's called a dust bug which consisted of plastic arm with a brush and the brush tracked the LP grooves and traversed and cleaned as it went. The bristles followed the grooves and didn't require antiskate.
Could these principals not be used to propel the arm across the record and shoulder a large portion of the lateral force that normally would be transmitted to the cantilever? It would most like be best for it to float up and down like the Shure devices. By being several grooves wide it would sort of average the transverse forces so that the stylus will never be far from tangent and I think it would really help when the spindle hole was not drilled on center.
  Reply With Quote
Old 6th June 2013, 12:31 AM   #508
diyAudio Member
 
Join Date: Dec 2004
Location: Fernandina Beach, Florida
Hello, LFM
Your idea is excellent. Just HOW excellent is shown by Shure's never-used follow-up to their brush patent (which was #4275888). That patent recalled other patents using pads, et al, to clean and stabilize the pickup.
The newer patent (#4514836) was more like your idea and answers your question about the old brush's good or bad side. It states, in part:
"Frequent cleaning of the brush is required. In addition, excess lateral force, as from manual error, causes the bristles to bend and possibly disengage from the groove, or cause side thrust on the stylus affecting the tracking of the stylus in the groove and increasing stylus and record wear."
In other words, the bristles may introduce problems. And they may help or hurt side thrust.
There is a common principle in the world: you may not find out what's wrong with something until a) the competition points it out or b) the company itself makes (or intends to make) a better version.
[Note: Shure originally didn't understand how the bristles worked. By the time of the newer patent, they did.]

Hope this answers your question!

Andy

Last edited by awolff761; 6th June 2013 at 12:36 AM.
  Reply With Quote
Old 6th June 2013, 01:50 AM   #509
tnargs is offline tnargs  Australia
diyAudio Member
 
Join Date: Sep 2006
Hi LFM, note that Shure recommend leaving the brush up (off) for the best sound quality.

The idea that the stylus has problems 'dragging' a linear tracking arm across the record is, IMO, a furphy. As I mentioned above.
  Reply With Quote
Old 6th June 2013, 02:11 AM   #510
diyAudio Member
 
directdriver's Avatar
 
Join Date: Nov 2005
Quote:
Originally Posted by LFM View Post
I've wanted to bring this up in this thread for some time but haven't for fear of getting flamed.
Not on this thread, at least not by me. You're more than welcome to chime in. We don't bite.


Quote:
Originally Posted by tnargs View Post
The idea that the stylus has problems 'dragging' a linear tracking arm across the record is, IMO, a furphy. As I mentioned above.
Care to elaborate your claim that horizontal mass has no effect on performance? Besides sonic performance, how do you deal with eccentric records? Enlighten us.
  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
GLIDING FOR 90 - mechanical linear tonearms: no airpump, no servo directdriver Analogue Source 29 3rd May 2014 06:24 AM
Angling of ports and/or drivers? Dave McReeferson Full Range 11 27th March 2012 08:45 PM
String suspension vs. uni pivot or gimball tonearms nghiep Analogue Source 26 13th August 2011 05:27 AM
Angling drivers left and right in a vertical line-array???? ozziozzi Multi-Way 12 16th January 2009 05:23 AM
Need Amp For 90-0-90 V DC Drafance007 Solid State 15 12th October 2003 09:03 PM


New To Site? Need Help?

All times are GMT. The time now is 07:10 PM.


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