DIY linear tonearm - Page 11 - 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 15th July 2013, 10:17 PM   #101
diyAudio Member
 
Join Date: Nov 2010
Location: Prescott, Arizona
Quote:
Originally Posted by vynuhl.addict View Post
But a total lateral mass of 29.5 grams in (is?) not too shabby
Hello vynuhl.addict,


isn't the total lateral mass of of this type of tonearm equal to the total weight of the tonearm? Also, I would assume that the effective mass in the vertical plane is much less than it is in the horizontal plane?
What effect, if any, does that have on the quality of the sound?

Sincerely,

Ralf
  Reply With Quote
Old 16th July 2013, 12:27 AM   #102
diyAudio Member
 
vynuhl.addict's Avatar
 
Join Date: Mar 2006
Location: Vancouver, BC,Canada
Hi Ralf,


Yes, total lateral mass is the equivalent of total weight of the arm with cartridge. The lateral weight is the hardest to deal with and is also important in an air bearing design too!. The effect it has on sound is given by its ability to keep the cantilever centered, so say on an out of center disk the less mass there is to stop and traverse into an opposing direction the more likely that the stylus will remain close to center which affects stereo imaging.this has also been referred to as "the tail wagging the dog" on higher mass, and or servo controlled arms where there can be a longer delay in response to an off tangent stylus. In a nutshell, better accuracy.

Colin
  Reply With Quote
Old 16th July 2013, 12:48 AM   #103
diyAudio Member
 
Join Date: Feb 2011
Location: Devon, UK
what if rubber o-rings were put over the bearings? Would they twist vertically a little easier?
  Reply With Quote
Old 16th July 2013, 01:19 AM   #104
diyAudio Member
 
vynuhl.addict's Avatar
 
Join Date: Mar 2006
Location: Vancouver, BC,Canada
Cats squirrel,

I think rubber o rings would add friction to inhibit vertical play, along with preventing a mechanical path to ground for resonance control.


Colin
  Reply With Quote
Old 16th July 2013, 03:38 AM   #105
diyAudio Member
 
directdriver's Avatar
 
Join Date: Nov 2005
Clearaudio TT2 showing bearing and armwand. Also notice the convex surface of the bearings.

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 16th July 2013, 03:55 AM   #106
batsong is offline batsong  United States
diyAudio Member
 
Join Date: Jan 2008
Location: St. Louis
The convex shape must allow for free movement along the vertical plane. For a design where the carriage rides on the outside of the running tube, one could mount the tube to the main pillar using another roller bearing (such as larger version of those the carriage rolls on). This would theoretically allow free vertical travel of the arm wand and perhaps improve performance for higher compliance carts.
  Reply With Quote
Old 16th July 2013, 09:02 AM   #107
diyAudio Member
 
Join Date: Jun 2004
Location: sheffield
Send a message via MSN to sq225917
Isn't the convex shape to keep a fixed pivot point in the vertical plane for tracking warps? If they used flat edged bearings the whole assembly would rock front front edge to back as it tracked warps making it much less sensitive to warps and adding lots of noise as the flat surface of the bearing slammed into the runner.
__________________
hoping to pick up some things.
  Reply With Quote
Old 16th July 2013, 09:27 AM   #108
Calvin is offline Calvin  Germany
diyAudio Member
 
Calvin's Avatar
 
Join Date: Nov 2004
Location: close to Basel
Hi,

I´m no mechanical expert, but my guts feeling tells me that a framework carriage like the one shown in #93 should be advantageous over a single arm tube like in #105.

Reasoning:
The feeding force echibited by the stylus (not accounting for the perpendicular to this dragging pull due to the table´s spinning) at point A is orientated perpendicular to the single arm tube, thus exhibiting maximum torque on the midpoint B of a straight line spanning between the two bearings. Also the bending forces on the tube are maximal.
Assumed an infinitely stiff armtube/carriage this torque is translated into forces acting on the bearings parallel to the arm tube and in opposite directions at points C and D. This would push the bearings against the glass tubes wall, thereby lifting them slightly (due to the tubes shape).
Thereby it´d generate a small force in parallel to the glass tube, which then results in a movement of the bearings along the glass tubes length axis.
But most of the torque will be wasted to drive the bearing ´up the wall´.

With the framework as in #93 the bending stress within the two tubes or ribs is lower because not only will the feeding force been shared between the ribs but also will the force component perpendicular to the ribs be smaller.
The bearings will experience a force component immediately pushing in the glass tubes direction. The wasted force component pressing the bearings against the glass wand will be smaller.

I think this applies under the assumption that the points B and B" are kind of fixed, due to mass inertia of the carriage. I don´t know up to which extent this assumption holds and to which extent the assumption fails due to the moveability of points B resp. B".
If it applies, the conclusion would be that the bearings distance of the carriage for a single arm tube should be lower for higher force along the glass tube, while the conditions for a framework would be the opposite --> larger distance between the bearings.

The above lend me to the idea if it weren´t advantageous to use a flexible joint between a single arm tube and the carriage instead of a fixed one?

Is that reasonable, or am I thinking utter rubbish here?

jauu
Calvin
Attached Images
File Type: png Forces on carriage of Cantus.png (22.4 KB, 768 views)

Last edited by Calvin; 16th July 2013 at 09:36 AM.
  Reply With Quote
Old 16th July 2013, 11:11 AM   #109
a.wayne is offline a.wayne  United States
Sin Bin
 
Join Date: May 2008
Location: Front Row Center
Quote:
Originally Posted by moray james View Post
easy way for you to find out is to build both. Look at the parts list for both arms, consider the complexity of the two builds. Measure the finished moving mass of booth arms. Install the same cartridge and listen. After all that you can decide but your preferential choice might not be the same as the next guy. The only opinion that counts is yours, so far as what you like the sound of. Why don't you build an arm which seems to you to be the simplest linear design for you to make and start from there? Best regards Moray James.
Which to build Moray , recommendation ..?
  Reply With Quote
Old 16th July 2013, 11:28 AM   #110
diyAudio Member
 
slowmotion's Avatar
 
Join Date: Nov 2002
Location: Norge
Thanks for this thread, I have to try build one of these.
Colin, what kind of "glass tube" are you using?
__________________
- Jan -
  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
Another DIY Tonearm johnmarkp Analogue Source 0 22nd April 2008 12:07 AM
my DIY Turntables and DIY tonearm Roger Waters Analogue Source 57 22nd January 2008 07:05 PM
Linear tracking tonearm vs. Pivoting tonearm Don Nebel Analogue Source 1 4th November 2007 11:49 PM
Magnetic suspension linear-tracking tonearm? Shaun Analogue Source 5 4th June 2003 11:21 PM


New To Site? Need Help?

All times are GMT. The time now is 12:27 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