At the end of the day, the ultimate test is to balance the tonearm and fine tune the leveling until there's no tendency to spin in any direction. A few years ago I made an air bearing based tangential tonearm and believe me, I know very well what leveling means 
If it wasn't for the fish tank air pump buzz and the tiniest grain of dust making the tonearm skip the groove, I would have never give it up. It sounded fantastic!
If it wasn't for the fish tank air pump buzz and the tiniest grain of dust making the tonearm skip the groove, I would have never give it up. It sounded fantastic!In my post #1548 I said it's almost impossible to replicate Frank's LT TA. I said "almost" because I had a hint it's doable even without high-tech tools and the original blueprints. After analyzing and mathematically replicating its geometry, I'm sure it is!
After all, we DIY-ers should never say never and at all times, think out of the box
Have a look at the attached image. It's obvious the red path is anything close to a circle, but using a technique widely applied in digital 3D animation and robotics, called inverse kinematics, it's rather easy to get it right.
This image also highlights some interesting facts:
1) No Birch-type TA, using a variable shape quadrilateral, will ever be able to obtain perfect tracking. Not even Thales Statement or Reed 5A can do it. The initial Thales model probably did, but it was so cumbersome that Micha Huber eventually gave it up.
2) Frank's genius made it possible to do it reducing at the same time from four to two the number of vertical bearings needed. With the added bonus of the damping provided by the magnetic coupling.
After all, we DIY-ers should never say never and at all times, think out of the box
Have a look at the attached image. It's obvious the red path is anything close to a circle, but using a technique widely applied in digital 3D animation and robotics, called inverse kinematics, it's rather easy to get it right.
This image also highlights some interesting facts:
1) No Birch-type TA, using a variable shape quadrilateral, will ever be able to obtain perfect tracking. Not even Thales Statement or Reed 5A can do it. The initial Thales model probably did, but it was so cumbersome that Micha Huber eventually gave it up.
2) Frank's genius made it possible to do it reducing at the same time from four to two the number of vertical bearings needed. With the added bonus of the damping provided by the magnetic coupling.
I think it may be off the topic to talk about Birch-style tonearm here.
I would say it is possible to replicate if you are willing to pay for the magnetic rail at any cost. My question is do you need to?
This topic had been covered in DD's excellent thread, Angling for 90° - tangential pivot tonearms.
In my thread, Building a Tuthill/Reed 5A Tangential Tracking Pivot Tonearm, the maximum tracking error for my 6B is only less than 0.1 degrees, which may be smaller than the construction tolerance for DIYers. For 6C, its tracking error is even smaller. Old Thales tonearm should have no tracking errors in theory, but not Reed 5A. Frank's LT and Reed 5A should have similar tracking errors. I am pretty sure that my 6B has less tracking errors than Frank's LT and Reed 5A in theory, not to mention my 6C. My 6C has the smallest tracking errors. However, small tracking error is not the only factor for performance.
In my post #1548 I said it's almost impossible to replicate Frank's LT TA. I said "almost" because I had a hint it's doable even without high-tech tools and the original blueprints. After analyzing and mathematically replicating its geometry, I'm sure it is!
After all, we DIY-ers should never say never and at all times, think out of the box
Have a look at the attached image. It's obvious the red path is anything close to a circle, but using a technique widely applied in digital 3D animation and robotics, called inverse kinematics, it's rather easy to get it right.
This image also highlights some interesting facts:
1) No Birch-type TA, using a variable shape quadrilateral, will ever be able to obtain perfect tracking. Not even Thales Statement or Reed 5A can do it. The initial Thales model probably did, but it was so cumbersome that Micha Huber eventually gave it up.
2) Frank's genius made it possible to do it reducing at the same time from four to two the number of vertical bearings needed. With the added bonus of the damping provided by the magnetic coupling.
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Hi,
Agree, the Frank s execution is really genius as technical solution and also as design and minimalist good look.
Rgds
Adelmo
It plays very well, I had several good turntables and none of them played so well. There are silver VDH cables in the arms and they are connected to WBT-0210Ag RCA Sockets. Only now you can really hear the differences between the gramophone cartridges, so I'm still looking for better ones and these are a lot of money. I dream of a Lyra Etna, but £10,000 is out of my reach.
The drill in wood has a tendency to run away and at such a length it will never be perfectly straight, so it is best to cut a square or several, for example 25 mm x 25 mm, and only after drilling, mount it in the centers of a wood lathe and then after turning you will have a hole in the middle.
Drilling in a lathe is more accurate (but even so its a big ask), I wonder if a pilot hole can be laser-drilled? (Not with a CO2 laser for a hole that deep, note, the fumes absorb the beam completely).
One approach is take a thicker stock, lathe-drill the hole, then use the hole as centres for turning down the tube, but then you have the problem of needing centre-rests and great care not to ruin it.
Pencils are made by gluing two half-tube sections together - this is probably the best approach.
One approach is take a thicker stock, lathe-drill the hole, then use the hole as centres for turning down the tube, but then you have the problem of needing centre-rests and great care not to ruin it.
Pencils are made by gluing two half-tube sections together - this is probably the best approach.
Hi Mark,
A variation of that would be to use a straight grained piece of wood and split it lengthwise, mill a groove into each half and glue it back together.
I have not tried that method but it might work. If done correctly, one should not be able to see how it was done.
Sincerely,
Ralf