The Bool Audio Blog
Another month has passed. This time around, we will look at the arm mounting collar and how it allows you to adjust the VTA. We will also briefly examine the support pipe assembly. It has been a busy month, working on various projects, so this month's post is just a quick update!
"Applying downward pressure results in lateral clamping force."
Here is a translucent model of the arm mounting collar showing the internal clamping mechanism for the VTA. When you tighten the hex screw from above it puts force down on the clamp actuator that in turn applies pressure to the support pipe clamp.
This method of clamping the support pipe allows you to make adjustments from above with a hex driver and also requires less torque than a standard sideways grub screw. Additionally, this method does not cause any damage to the support pipe, as the clamp locates to the support pipe with a smooth matching radius.
All the clamp parts are made from silver steel and heat-treated for durability, apart from the grub screw, that is made from 14.9 hardened steel.
We really like the idea of having the support pipe laser engraved with 1.0mm or 0.5mm graduations so that height adjustments can be made easily and repeatably.
A small batch of clamp actuators and some support pipe clamps.
The adjustment screw is located just under the main body.
That's basically it for the VTA clamping system. It's a very simple concept that, when applied correctly, creates a highly reliable and sturdy clamping system. However, it's important to note that the system does require some reasonably close-fitting tolerances for it to function correctly.
We have also been working on making all the parts for the support pipe assembly, that will hold the sapphire double cup bearing.
Most of the parts have been completed for the support pipe assemblies.
The 3d render above shows the internal parts that make up the support pipe assembly. This bearing support design is inspired by the Aro tonearm support, but with some slight differences..
The support screw on the end with the zirconium bearing inset has been made to screw into a counterbore for a more compact form factor. This really helps with the limited space inside the mounting collar, and it can be removed with a flat head screwdriver. Nickel silver has been chosen for the support screw and sapphire housing for its durability, corrosion resistance and workability.
A zirconium ball bearing has been chosen instead of stainless steel for its hardness and durability. The end of the bearing support has also been hardened and lapped to a very fine, flat finish.
Next month will hopefully be the start of our 4th-axis CNC build. This has been on the back burner for quite some time now as we just haven't had the space in the workshop to access the CNC control cabinet because there is a compressor in front of it that runs the automatic tool release system for the CNC.
We have put together a small external storage shed that will act as an enclosure for the compressor. We plan to add some ventilation and sound-proofing to help keep the noise down.
That's it for this month If you have any further questions, feel free to get in touch at the email address below.