Linear tracking turntables, whatever happened?

Curious as to the demise and downfall of the seemingly short lived linear tracking TT.
Just from a geometry point of view I would have thought a linear arm should be superior to one with a fixed pivot that sweeps through an arc.
Obviously there is much more to it than that, sort of the reason for this thread.
I am genuinely interested in trying one out for myself as well.
6db47fb2 f8db 415d a4f7 49a7b6ed12b0Ag insider logo xs@2xuberwaltz
As and ET 2.0 owner for 25 years (Upgraded to 2.5 10 years ago), I have a few observations.  One - it is difficult to completely dial in. That being said after using the Feickert app for azimuth and fine tuning by ear, I've not made any further adjustments to setup parameters in the last six months, other than tiny tracking weight adjustments. I'm just playing records and hearing, as best as I can tell, using a Soundsmith Zephyr MIMC through a Herron VTPH-2a phono stage, virtually all the information in the grooves.  Getting the stylus to exactly match the location and angle of the cutting lathe chisel may be impossible, but unlike a pivoted tonearm, with it's guaranteed tracking error, at least you have a chance.   Two - Pump problems can be solved if you can find room for a 20 gallon shop compressor.  Mine is about 30 feet away in another room connected to the tonearm via 1/4" hose. I turn the compressor on until it fully charges to about 115 PSI.  I then turn it off.  That gives me around 2 to 2.5 hours of listening time as the tank drains, where the regulated pressure at the tonearm is 12 psi.  If I'm still listening, I just turn it the compressor on again for a recharge, which takes about 4 minutes. The setup includes a moisture trap, but there has never been any moisture in the line, ever.  For several years I switched to an oil based compressor, also in the other room.  It was only 3 gallons and was very quiet, so I could leave it on, and it would switch on as necessary.  Over time, it started leaking oil that traveled all the way to the tonearm spindle and jammed it up.  I cleaned the spindle with MEK and went back to the big compressor and I've had zero problems since.  Having heard digital dubs from a Caliburn TT, I do know that where my setup falls short is in conveying the forward momentum / punch that a cost no object drive system brings to the table.  But that's not the tonearm's fault.  Other than that, 50 years into this hobby,  I'm more in awe of what LP's are capable of than ever. It's like sitting at a mixing console, where you can choose to follow any component from the kick drum to triangles to the subtlest background vocals. 
mkiser, your note about being in awe of what LP’s are capable of, rings so true with me as well! It is almost like how can one even complain about any of it, that it works at all, and sounds so good is amazing in itself! Enjoy! 
All this posting got me fiddling with my rabco  st 7 with a BO 20en Mmc. Been sitting 20 years it works but arm leads the notch tried adjusting it but have noticed the tracking wheel is a soft compound looks like it’s got grease in it  actually. Not sure if it’s degraded and I need to replace it or get it serviced but not sure where to turn to. Parts might not be available like to listen to my records again   Any suggestions are appreciated   Bob
Fairly sure early on in this thread when the Rabco was discussed that Ralph or Lew mentioned the tracking wheel is fairly common item needing replacement along with belts.
Might start there?
Yes I’m thinking it’s degraded searched eBay for parts but I have no other leads yet. Ty