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Old Yesterday, 03:27 PM   #4291
super10018 is offline super10018  United States
diyAudio Member
 
Join Date: May 2010
Hi Mike,

First, usually, a heavy carriage does sound better. But you need to think about other factors as well, such as friction, resonant frequency, and compliance of cartridge. If the friction is zero, the carriage should be as heavy as the resonant frequency and the compliance of the cartridge allow.

This thread is long. I have confused with your previous version of the arm. Now, I saw the latest version of the arm. I have to say it is a very clever design. You have put your mind and passion into the arm. I have been enjoying the process as well. Although the arm is not perfect, I would say the ideas are very creative. Kudos to you and carlo!

Jim
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Old Yesterday, 03:52 PM   #4292
carlthess40 is offline carlthess40  United States
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Join Date: Oct 2017
Location: Lake Mary Florida
Quote:
Originally Posted by Mike56 View Post
Hi Carlthess, i attach hereto pics of the current state with apologies for poor workmanship, its been "adjusted" many many times. It is also made with hand tools only, saw, file, drill.
Some white background aids visibility
Six pictures
1. Rails and balls
2. Cart on rails
3. Cart with pen tip pivots mounted
4. Top parallelogram plate that fits between pen tips
5. Paralellogram on cart
6. Other view

Hope this updates all
M

Thatís some great handy work there. Wish you where here in Florida. Iíd have every tool at hand for you
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Old Yesterday, 04:26 PM   #4293
Mike56 is online now Mike56
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Join Date: Apr 2020
Quote:
Originally Posted by super10018 View Post
Hi Mike,

First, usually, a heavy carriage does sound better. But you need to think about other factors as well, such as friction, resonant frequency, and compliance of cartridge. If the friction is zero, the carriage should be as heavy as the resonant frequency and the compliance of the cartridge allow.

This thread is long. I have confused with your previous version of the arm. Now, I saw the latest version of the arm. I have to say it is a very clever design. You have put your mind and passion into the arm. I have been enjoying the process as well. Although the arm is not perfect, I would say the ideas are very creative. Kudos to you and carlo!

Jim
Jim, i write too much, i promise to be more brief if i can!

Thanks for your thoughts and comments above, and also to other recent respondees. I am pleased it raises interest and that some of you like parts of it.

How about you all (Jim, Carlthess, DD, Carlo, Koldby, Ed, Warrjon etc to name a few in no particular order and apologies if i have missed anyone out) team up to help me make improvements as my virtual design team on this thread? - respond if you wish, not if you don't?

Two topics to start with;
Resonant frequency,
1. how much does it matter and why,
2. is it likely that this configuration compares in any way to a conventional PTA in terms of analysis
3. Maybe there are a series of RFs in various planes in different parts
4. How might i measure it/them
5. What to do about it/them

Friction.
The current configuration has quite low friction. It will only occasionally stick after re-assembly but seems to settle after a few sides and will only stick if i inadvertently dump dirt in the rails. However i would like it reduced and have more tolerance. This is ceramic 5mm balls on anodised aluminium surfaces

1. How can i reduce friction most easily and gain tolerance
2. has anyone tried teflon self adhesve tape on the rails?

BTW, one of my aims is to build with inexpensive parts by hand, depending on what you buy or have there is very little material cost involved here.

Any other areas anyone thinks should take priority?

Best to all
Mike
__________________
PC, to Chordette GEM DAC or O.L. Aurora 4 with Home built Radial LTA or OL Onyx arm Rega Ania to Graham Slee MC pre, to Prima Luna Prologue 1. Troels Gravesen Fusion BAD with Hypex 151's high level input
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Old Yesterday, 04:28 PM   #4294
Mike56 is online now Mike56
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Join Date: Apr 2020
Quote:
Originally Posted by carlthess40 View Post
Thatís some great handy work there. Wish you where here in Florida. Iíd have every tool at hand for you
Its a pity i am not, a kind thought thanks, what do you build?
Mike
__________________
PC, to Chordette GEM DAC or O.L. Aurora 4 with Home built Radial LTA or OL Onyx arm Rega Ania to Graham Slee MC pre, to Prima Luna Prologue 1. Troels Gravesen Fusion BAD with Hypex 151's high level input
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Old Today, 07:34 AM   #4295
Straight Tracker is offline Straight Tracker  United States
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Join Date: Nov 2010
Location: Prescott, Arizona
Quote:
Originally Posted by Mike56 View Post
2. has anyone tried teflon self adhesive tape on the rails?
Hello Mike56,

I would stay away from Teflon tape. Teflon tape would be helpful if the friction you are encountering would be of the "sliding" kind. As you know, you are dealing with "rolling" friction, where the balls would micro indent any soft surface such as tape. The balls would constantly try to climb out of those micro indentations.

Anodized aluminum is a good way to go if the tool marks on the surface of the aluminum rail were oriented parallel to the direction of travel of the carriage, prior to anodizing. In the US, machinists refer to that as "lay"

Sincerely,

Ralf
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Old Today, 07:41 AM   #4296
Mike56 is online now Mike56
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Join Date: Apr 2020
Quote:
Originally Posted by Straight Tracker View Post
Hello Mike56,

I would stay away from Teflon tape. Teflon tape would be helpful if the friction you are encountering would be of the "sliding" kind. As you know, you are dealing with "rolling" friction, where the balls would micro indent any soft surface such as tape. The balls would constantly try to climb out of those micro indentations.

Anodized aluminum is a good way to go if the tool marks on the surface of the aluminum rail were oriented parallel to the direction of travel of the carriage, prior to anodizing. In the US, machinists refer to that as "lay"

Sincerely,

Ralf
Thanks Ralf, great to have your input, i have anodised aluminium at the moment and with the marks going longitudinal with the rail. it is already quite good, i am just seeking better! - i have wondered about light polishing but worry about going through the coating, at the moment all i have done is clean thoroughly.
All input gratefully recieved
thanks
Mike
__________________
PC, to Chordette GEM DAC or O.L. Aurora 4 with Home built Radial LTA or OL Onyx arm Rega Ania to Graham Slee MC pre, to Prima Luna Prologue 1. Troels Gravesen Fusion BAD with Hypex 151's high level input
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Old Today, 07:56 AM   #4297
warrjon is offline warrjon  Australia
diyAudio Member
 
Join Date: Feb 2011
Location: Terang Vic
Hi Mike,

To test arm / cart resonance, HFN test LP has resonant frequency test tracks on side B. If you don't have that LP then pink noise will also identify arm / cart resonance.

The test tracks are easy as you can hear it. Pink noise you would need to use your spectrum analyser.
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Old Today, 08:01 AM   #4298
warrjon is offline warrjon  Australia
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Join Date: Feb 2011
Location: Terang Vic
It's actually not friction you need to be low it's rolling resistance more importantly stiction.

If you had no friction then the balls would slide on the rail, which you definitely do not want. Stiction is the resistance to commence moving and is critically important in a passive LTA, you want this as low as possible. Increasing the diameter of the balls will lower torque required to commence movement.
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Old Today, 08:07 AM   #4299
Mike56 is online now Mike56
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Join Date: Apr 2020
Quote:
Originally Posted by warrjon View Post
Hi Mike,

To test arm / cart resonance, HFN test LP has resonant frequency test tracks on side B. If you don't have that LP then pink noise will also identify arm / cart resonance.

The test tracks are easy as you can hear it. Pink noise you would need to use your spectrum analyser.
many thanks Warren, i have played the 23 to 6 Hz track several times and also watched the output at those frequencies on the spectrum analyser. at the start you can just hear the 23 Hz rumbling away and then that goes sub audible, but i hear and see nothing else. So looking at the spectrum analyser zoomed as close as it will go i see the tone and it simply sits there as a peak and gradually reduces in frequency through the sweep, level reduces slightly and consistently through the sweep, but i see no sudden peaks of resonance in that frequency area. As i write this i wonder if i should be playing those frequencies but looking elsewhere for resonant harmonics?
Thanks as always
Mike
__________________
PC, to Chordette GEM DAC or O.L. Aurora 4 with Home built Radial LTA or OL Onyx arm Rega Ania to Graham Slee MC pre, to Prima Luna Prologue 1. Troels Gravesen Fusion BAD with Hypex 151's high level input
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Old Today, 08:15 AM   #4300
Mike56 is online now Mike56
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Join Date: Apr 2020
Quote:
Originally Posted by warrjon View Post
It's actually not friction you need to be low it's rolling resistance more importantly stiction.

If you had no friction then the balls would slide on the rail, which you definitely do not want. Stiction is the resistance to commence moving and is critically important in a passive LTA, you want this as low as possible. Increasing the diameter of the balls will lower torque required to commence movement.
Understand thanks. Useful again thanks Warren. i have 5mm at the moment, do you have any experience to suggest the best size to use please? i am also considering what might be a better surface than simple natural anodised aluminium for the rails, all budget materials of course! i guess in some cases surface roughness will increase both stiction and friction and one assumes surface smoothness is therefore important and i don't feel the arrangement i have ever has a tendency for the balls to slide, the contact is constant and that seems unlikely so if low stiction comes with low friction i feel its worth a try, Mike
__________________
PC, to Chordette GEM DAC or O.L. Aurora 4 with Home built Radial LTA or OL Onyx arm Rega Ania to Graham Slee MC pre, to Prima Luna Prologue 1. Troels Gravesen Fusion BAD with Hypex 151's high level input
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