Eminent Technology ET-2 Tonearm Owners

@pegasus. 
The bearing tower/manifold is in the concept phase at present.
Some features are almost locked in.....
> The air feed into the manifold will be like a flattened funnel to slow the airs velocity before it gets to the bearing sleeve. The original jet of air has to cause turbulence where it first contacts the sleeve. This funnel will probably be lightly packed with wool. The manifold will be undercut to allow for a multi wrap of filter paper around the sleeve to further smooth/ equalise air delivery to the capillaries. The manifold will also have, as per my current version, the cap screw and shim metal locking arrangement between the manifold and sleeve to lock the two o'rings.
> The manifold and tower will be a male/female VEE slider arrangement with a single capscrew locking them in place. This will ensure that the manifold stays exactly horizontal at all VTA positions. It also gives a very solid join between the two parts. A vertical capscrew between the two providing for VTA adjustment. The slider will be straight. 
> The tower will have one fixed, parent material, foot and two PVC adjustable feet. The PVC feet provide for alignment of the tower to the platter surface. The single, parent material, foot provides a "virtual" single point of contact with the arm board.
> Parent material will be either zinc or aluminium and will have machined galleries containing damping material.

This is a long term project. I will keep you posted.

Re radically raising the arm to 20 degrees. I get the stiffness issue. Would the wedge idea work as desired? Do we not want the vertical pivot point to be in line with the cantilever. Maybe I missed something in your initial or your latest discussion  on the topic.  

cheers.       

Thanks for the captivating infos!
- Although I agree on the idea of eliminating turbulence - isn't damping it not also introducing an additional flow resistance which will upset the  "balance" of implicite air flow resistances from air feed via calibrated air beaing openings to bearings air film? Personally I'd be very (self-) critical when changing this, I like to be double on the safe side about changing such crucial areas (at least with my limited understanding of air bearings).
In fact I'd contact Bruce about his thoughts regarding keeping the correct pressure on the distributed points/air openings when introducing additional flow resistance.

- raising the arm bearing: I meant lifting the back of the arm, and correcting with a 20 degree wood wedge between arm and cartridge (the wedge pointing to the front of the arm),

Pegasus

My techno-intuitive thought on this is:
- The lower the resonance of the i-beam, the wider the frequency range over which the bearing/cartridge resonance can be controlled by it.
- the higher the resonance, the closer together both resonances and the more resonant interaction instead of control.

Does Bruce have the model? Or should I ask my more MATLAB-experienced son?

Pegasus
The model for the original I Beam was in part influenced by business priorities. We know this. This limitation is no longer there.  

Why don't you send your theory and questions to Bruce direct and let us know what he says ?

brucet (at) eminent-tech (dot) com

I am interested in your, John and others impressions of Bruce' Long I Beam.

Harry and I seem to be in sync.
Also, still am interested in seeing pictures of your dual path wiring setup.

Cheers Chris

@pegasus 
I agree, there is likely to be a small reduction in air pressure entering the  capillaries due deltaP across the wool and filter paper. Easily sorted by increasing the input pressure slightly.  The arm can be operated with and without the wool/paper to test its efficacy.
Much has been written in this thread  about the need for a stable air supply. It seems that the ET is very sensitive to any perturbations in the air stream. This design is simply taking this trait and seeking to ameliorate it further. Look inside the manifold at the small hole which connects the air supply to the manifold cavity. Air entering thru this hole jets across the small gap and hits the sleeve then circulates around the boundary between the manifold ID and the sleeve OD. This design change is an effort to deliver smooth air to all of the capillaries. It may not be of benefit, but I intend to find out.

Cheers 

Bruce's second run, long I-Beam delivered yesterday.  Much better fit for the weight clamp.  Sounding good. 
Cheers