Arm board No. 3
With the second arm board, a functional working layout was realized. This arm board uses the same dimensional layout as the second board. This is why you won't see any trammel photos on this page. Once these pieces were assembled and the arm mounted, a tonearm cartridge alignment was quickly realized. What is different with this board is the material in use. Phenolic. More specifically, Grade LE Garolite Sheet. The material is composed of several layers of a fine weave cotton fabric that is compressed , heated and cured in phenolic resin. The end result is a material with tensile strength figures more comparable to metal than wood. Cuts like it too. It machines readily with metal cutting tools. Definitely harder than wood.
above photo 1: Retaining the detachable top plate layout as with previous boards. The base layer is 3/8 inch thick phenolic. The top plate is 1/8th inch thick phenolic. The 1/16th inch thick aluminum washers can be seen against the sub-chassis. These three washers are glued into place with neoprene based contact cement.
above photo 2: two plates prior to assembly.
above photo 3: the base plate phenolic has a top layer of 1/64th inch thick lead sheet. The lead is glued with contact cement. Mounting screws are allowed to make contact with the lead.
Note. the lead sheet was not found to be helpful and was eventually removed from the next version armboard. #4.
above photo 4: Top plate is secured with 4 flat head countersunk wood screws. The phenolic material is much harder than wood. Consequently it is necessary to size the screw holes as if it were a tap drill.
above photo 5: Tonearm is assembled. The suspension has been adjusted. The tonearm is aligned. Ready to go.
above photo 6: A close up view.
I ordered this sample sized 3 inch x 6 inch piece of 1/8th inch thick carbon fiber when I ordered the phenolic plates.