Linear Tracker ...I was wondering

Sorry to disappoint you, CT. I was reporting a conversation with an expert who realized the limitations of his design, and warned me against it when I asked. A true gentleman, Tom Fletcher.

You are of course correct that the Trans-Fi is a hybrid linear tracker. But, I note that the two plane air bushing is usually compromised by a relatively stiff air hose to pressurize that bearing, so I can’t agree that it is the most linear. That hose generates large forces relative to other forces on the stylus.

Big problem, or so it seems to me, considering Hooke’s Law (as the air hose acts like a spring); displacement is linear in force, but restoring force is proportional to offset from the centre, so it changes as the air bushing traverses the beam. Assuming that the air hose is centred at 4 cm from the rim of the record, this causes the stylus to press into the left channel, decreasing to 0 force at centring, and increasingly press into the right channel.

Trans-Fi finesses this problem by pressurizing the beam on which the saddle rides, and taking care of vertical motion by very low friction pivots. The only external force on the saddle is the tonearm’s cable - still a spring, but a very, very tiny one! The pivots only need to handle a few grams each - I like copper for the Koetsu, nylon for the Miyajima. Agreed that air would be best here too, but it’s not obvious how to do it.

What do you think?

I have discussed the weaknesses of this design in other postings, but overall I like the compromises which this design represents. My main modification is another support at the end of the beam, which allows me to adjust horizontality to 1 minute of arc, and maintain that setting.

Terry9
But, I note that the two plane air bushing is usually compromised by a relatively stiff air hose to pressurize that bearing, so I can’t agree that it is the most linear. That hose generates large forces relative to other forces on the stylus.

Terry
You are referring to the Kuzma - which I believe is the one Fremer was referring to in my previous post- LOL - don't quote me on that someone check back if they care....but I am pretty sure.

What do you think ?

Well I like pictures, so.
Clues to what I think lie in the attached picture. Kuzma Airline versus a Eminent Technology 2.5  

Note the huge differences in design especially inside the red circles.

https://photos.app.goo.gl/3EtMfiUdgQpAGL1f8

So
One needs its air line and wiring for damping (Kuzma), as you reference above - the other does not (ET 2.5)

IMO 
The heart of 360 air bearing lies in its manifold design supporting the air bearing. It's the engine.

One in the picture has small, moving manifold - Kuzma
The ET 2.5 the opposite. A large stationary manifold.
This also results in customers being able to order the tonearm from the factory with a 3 - 19 psi range setting. Their choice. The Kuzma comes in one setting. 

The bearing differences between the two - night and day. The ET is the smoothest/slipperiest bearing I have encountered. This can be good if one is good with setup, or very bad IMO if one does not know how to set it up. The crazy bearing Bruce designed. will highlight set up errors. So a weakness of the arm is - the audiophile needs to learn the arm first. Read the manual.  How many do that? .  

So what do you think Terry on the two designs ? .

Cheers Chris  

CT, you are so right! Perhaps I was thinking Air Tangent, although I'm not certain as I've never seen one. But for some reason I forgot everything I ever knew about the ET design. Thanks for correcting my error - alas, all to common at my age.

But, we still have a cantilevered beam. The Trans-Fi is easy to fix with a support on the free end. The ET requires another bushing on the other side, which in turn means a great long massive bearing shaft between the two air bushings. I saw some Chinese audiophiles demo something of the sort, and I was about to build one when I discovered the Trans-Fi.

The big advantage of the Trans-Fi is how accurately one can set azimuth - a few minutes of arc - not that I can hear better than about 15 or so. I tried to engineer something as good, but it ended up mighty clunky. So I bought someone else's solution and modified it as above.

Maybe we should host a thread on linear trackers and their mods?

Actually,the best air bearing arm is the Walker. It had the lightest horizontal mass. The air bearing is stationary and large. It uses a lower pressure (less noise). The arm is made out of some type of very light composite. The turntable section is actually the original Air Force, air bearing platter, air bearing suspension etc.  https://walkeraudio.com/proscenium-black-diamond-v/
Unfortunately, Walker also sells a bunch of BS on their web site and I refuse to support that. I find it odd that the press has not compared the Black Diamond to the Air Force 1.

Surprised there is no mention of Advanced Analog MG1. An affordable linear tracking option. Their site is under construction. But there is info there.

adanalog.com