Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

DIY linear tonearm
DIY linear tonearm
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 1st March 2020, 07:57 AM   #3521
niffy is offline niffy  Europe
diyAudio Member
 
Join Date: Nov 2013
Location: Dartmoor
Hi Dahlberg,

When I was using my steel on steel bearings I used them with a little bit of petroleum jelly. They seemed to run just a little bit smoother with it although this difference could have been within the error bar of my test rig. To be honest I couldn't hear any difference in sound with or without lubrication.
With ballrace bearings they definitely work better dry. With pin bearings it doesn't make a significant difference, not significant enough to be heard. As Warrjon mentioned, grease will trap dust. When I took the steel bearings off the arm after several months of use the petroleum jelly did look a tad hairy.

I would probably not use lubrication if I were to use steel bearings again.
I run the sapphire tungsten carbide bearings dry.

Niffy
  Reply With Quote
Old 1st March 2020, 10:36 AM   #3522
niffy is offline niffy  Europe
diyAudio Member
 
Join Date: Nov 2013
Location: Dartmoor
Quote:
Originally Posted by dahlberg View Post
Prototyping looks like this at this moment. Titanium armtube (100x6x4mm),
aluminum carriage and cartridge mounting plate (70/75 alloy, 8mm thick).
Carriage should weigh in at 50-60g incl cartridge and counter weight.

Rods will be polished 6mm H6.

The arm will rotate at the base and there will be some additional functions
added as well.

Click the image to open in full size.

http://www.dahlbergaudiodesign.se/images/linear_18.png
Hi Dahlberg,

I seem to have missed this post. Looks like a good design. One of my earliest versions of the arm (which I didn't get working) used a rotational base. I do like the idea of rotating the arm away from the record either horizontally or vertically as with the clearaudio. A slide mechanism, as I use, requires an additional structure for the bars that will inevitably have a resonant character. A sliding system is simple and makes the dressing of the arm cables easier. My early prototype never seemed to lock into the same place meaning that the LTA varied. This is more a reflection on my design than on the idea of rotation.

If you are using 2mm wide wheels you will have a contact angle with the rail of over 40. Ideally I think that the contact angle should be 20-30. The absolute maximum would be 45 which you should just squeeze under depending on the edge profile of your wheels. Using 3mm wide wheels will reduce the contact angle to 30 but will dramatically increase vertical friction. During my testing period I built a rail and set of wheels that were 3mm wide with a contact angle of about 30. I actually built this rail expecting it to fail just to see if it would fail as predicted. It did. Vertical friction was too high causing vertical motion to be over-damped leading to a flattened sound. I would recommend using 4mm rods for your rail. I initially used borosilicate glass before moving on to tungsten carbide. A quick scan found this. It is also h6 tolerance.

Metric Silver Steel

Niffy
  Reply With Quote
Old 1st March 2020, 01:36 PM   #3523
dahlberg is offline dahlberg  Sweden
diyAudio Member
 
dahlberg's Avatar
 
Join Date: Jan 2005
Location: Sweden
Thanks, that's relevant information. I was a bit hesitant myself but it's still on the drawing board so no harm done.
__________________
Some Music I Like:
https://play.spotify.com/user/dahlbe...tm_medium=open
  Reply With Quote
Old 1st March 2020, 04:02 PM   #3524
niffy is offline niffy  Europe
diyAudio Member
 
Join Date: Nov 2013
Location: Dartmoor
Hi Dahlberg,

Have you calculated the vertical location of the centre of mass of the carriage Inc cartridge? Ideally it wants to be level with the vertical pivot point which will be a little over a millimetre above the bottom of the wheel (assuming you have 2mm wide wheels and a contact angle of 30). There is an argument for having the centre of mass slightly lower than the pivot point for stability reasons. It's not clear from the plan you posted what the mass distribution will be. It looks like the centre of mass will be above the pivot.
Another point that Jim raised a while ago is the importance of having a derail preventing mechanism. During normal play back this is not so important but during record changing it is. Jim nearly took out one of his collection of cartridges when he was changing a record on his early mechanical linear arm.

Niffy
  Reply With Quote
Old 1st March 2020, 04:42 PM   #3525
super10018 is offline super10018  United States
diyAudio Member
 
Join Date: May 2010
Here is a suggestion for the protection mechanism.

Jim
Attached Images
File Type: jpg p.jpg (28.5 KB, 162 views)
  Reply With Quote
Old 1st March 2020, 06:56 PM   #3526
niffy is offline niffy  Europe
diyAudio Member
 
Join Date: Nov 2013
Location: Dartmoor
Quote:
Originally Posted by super10018 View Post
Here is a suggestion for the protection mechanism.

Jim
Hi Jim,

Perfect. It doesn't add unnecessary mass to the carriage and also acts as a dust guard for the rail.

Niffy
  Reply With Quote
Old 1st March 2020, 07:28 PM   #3527
warrjon is offline warrjon  Australia
diyAudio Member
 
Join Date: Feb 2011
Location: Terang Vic
Quote:
Originally Posted by super10018 View Post
Here is a suggestion for the protection mechanism.

Jim

Hi Jim,


That works well. I have an acrylic dust cover on my current setup attached to the rail with a channel machined into it for wheel clearance, it also prevents the carriage from de-railing.
__________________
SP10, ...... DIY Linear tonearm, ......Stanton 881s with D3000 stylus, .....BHL phono,.........Pass B1,
MODULUS 86 power amps x4,.............Active line level OX,......... bi-amped OB speakers with Mark Audio Alpair 12P
  Reply With Quote
Old 2nd March 2020, 06:50 AM   #3528
nocdplz is offline nocdplz
diyAudio Member
 
nocdplz's Avatar
 
Join Date: May 2010
Location: italy
carriages, carriages
Hi all, watching at your incredible works I had an attack of "improve-algia"- Having finally found where to buy the square carbon tubes (R&G in Germany) I'm toying on these hypotheses (attachment) for a possible hyper super Lil Casey mk last.
Already made some quick prototypes and some tests with a kind of "sine bar" - simply various thickness-gauge blades put under one rail support to start the motion (stiction), o rto maintain it (friction) - Behaviors* are rather different from those seen with the inverse pendulum.

A solution - Total weight = 16 gr
friction - runs with a tilt of a 0,35 shim / 300mm rail. angle=04'1" = 0,067 decimal --- μ=0.0012
stiction - starts with a tilt of a 0,75 shim / 300mm rail. angle=08'36" = 0,143 decimal --- μ=0.0025
B solution - Total weight = 14 gr
friction - runs with a tilt of a 0,70 shim / 300mm rail. angle=08'1" = 0,141 decimal --- μ = 0.0024
stiction - starts with a tilt of a 1,10 shim / 300mm rail. angle=012'36" = 0,200 decimal --- μ = 0.0035
C solution - Total weight = 12 gr
friction - runs with a tilt of a 0,25 shim / 300mm rail. angle=02'52" = 0,047 decimal --- μ = 0.0008
stiction - starts with a tilt of a 0,65 shim / 300mm rail. angle=07'27" = 0,124 decimal --- μ = 0.0022

after all, not so bad for such common means, and a 5000 years old tech. The A solution is quite similar to the mk2, the B instead completely disappointing, the C may be the right one, even if difficult to make properly with my tools (better, without some tools)

carlo
*the measures are an average, obtained alternating the shims under the left and right support, to compensate for any deficiencies in the leveling of the base.
sine bar angles - calc
Sine Bar & Sine Vise Calculator - LittleMachineShop.com
angles - degrees to decimal - calc
Degrees,minutes,seconds to decimal degrees converter
Attached Images
File Type: jpg LC mk3 rails.jpg (125.0 KB, 142 views)

Last edited by nocdplz; 2nd March 2020 at 06:58 AM.
  Reply With Quote
Old 2nd March 2020, 08:12 AM   #3529
dahlberg is offline dahlberg  Sweden
diyAudio Member
 
dahlberg's Avatar
 
Join Date: Jan 2005
Location: Sweden
So here are some alternative solutions with material that I actually have or have ordered (the rings haven't arrived yet). I only have one 5mm rod.
From left to right:
1: Dual rings and 6mm rods. Hight difference rings/rods 0,53mm.
2: One ring dual 6mm rods. Hight difference rings/rods 1,3mm.
3: Same but rods 1mm appart. Hight difference rings/rods 2mm.
4: Dual rings rods 1mm appart. Hight difference rings/rods 0,86mm.
5: 5mm rod dual rings 2mm appart. Hight difference rings/rods 0,6mm.
6: 5mm rod dual rings 2,5mm appart. Hight difference rings/rods 0,8mm.

Click the image to open in full size.

http://www.dahlbergaudiodesign.se/images/linear_19.png
__________________
Some Music I Like:
https://play.spotify.com/user/dahlbe...tm_medium=open
  Reply With Quote
Old 2nd March 2020, 08:41 AM   #3530
dahlberg is offline dahlberg  Sweden
diyAudio Member
 
dahlberg's Avatar
 
Join Date: Jan 2005
Location: Sweden
Dual 4mm rods vs dual 2mm rings

Click the image to open in full size.

http://www.dahlbergaudiodesign.se/images/linear_20.png
__________________
Some Music I Like:
https://play.spotify.com/user/dahlbe...tm_medium=open
  Reply With Quote

Reply


DIY linear tonearmHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Linear tracking tonearm vs. Pivoting tonearm Don Nebel Analogue Source 5 31st May 2015 03:55 AM
Another DIY Tonearm johnmarkp Analogue Source 0 21st April 2008 11:07 PM
my DIY Turntables and DIY tonearm Roger Waters Analogue Source 57 22nd January 2008 06:05 PM
Magnetic suspension linear-tracking tonearm? Shaun Analogue Source 5 4th June 2003 10:21 PM


New To Site? Need Help?

All times are GMT. The time now is 12:38 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright ©1999-2020 diyAudio
Wiki