Test stand progress.

After tidying the ladders away I realised I shall have to set it all up again. The mounting will have to be lifted off the pier to make room for the top plates of thick plywood. I have some aluminium sheet which could be folded neatly over the top plate to give the appearance of solid aluminium. Though the scrapyard might have a thick enough plate of solid aluminium if I keep looking.

Or, I could cut down the size of the top frame of the stand to match the mounting's own 20mm thick alu. base plate. That would provide more even support and increase the taper of the pier sides. The nearer the sides are to an equilateral triangle the stiffer they should become. While a more square form [less taper] is more prone to lozenging. It already feels surprisingly stiff despite its apparent flimsiness. Being more prone to rocking when not evenly supported at the corners by the undulating surface on which it rests. I deliberately did not cut the internal corners of the angle iron away to allow them to slope. This may become necessary if I increase the taper.

I originally intended to make a heavy timber and plywood [pyramidal] pier but thought it best to start with something easily adjustable to check for OTA clearances and height. A solidly built timber pier with stressed skin [ply] cladding should be much stiffer and better damped against vibration. My tilting, miter saw is ideal for cutting all the correct angles on the timber framework. Assuming I knew what angles to saw.

Today, Tuesday, I set up the ladders and chain hoist again and lifted the mounting. Then I narrowed the top of the stand both ways to match the base plate.  It was more of a struggle to get the screws back through the slots but still manageable.

I have a 10mm thick plate of scrap aluminium to cover the top. The mounting can rest on this. Though I might add at least one layer of 18mm plywood as a further stiffener as well. Plywood has the advantage that it will compress locally where it meets the domed screw heads. Allowing more even support.


Having the mount in pieces allowed me to prop up the PA in different positions. I was trying to increase clearance for a potential lower wormwheel position. While it was possible to achieve clearance I was not very happy with the changed appearance. For the moment I shall continue as before with the upper RA wormwheel drive position. This allows me to retain the 7" diameter clutch between the cylinder and the RA wormwheel.

Today, Wednesday, I made a 3/4" plywood top plate for the mounting to rest on. Then I added a 3/4" ply shelf half way down the pier with more slotted angle iron bolted around it. This is meant as a secure resting place for the AWR drive electronics and a serious stiffener for the test stand legs.

I'm wondering whether I shouldn't use some spare pond liner material as a waterproof cover for the mounting and pier. Not that the electronics will be left in the pier but to ensure no dew runs down inside the pier should it condense on the massive, metal mounting during use. The garden collection bag is waterproof but doesn't reach low enough with the mounting in place. The saddle in particular adds enormously to the height of necessary coverage. Rain and wind stopped play at lunch time. I put my work gloves down on the ground for a moment and they blew away!

Drilled the mounting base plate for 10mm hold down screws/bolts. Then marked through the holes and drilled through the 18mm [3/4"] ply, pier top plate. I added a second plate under the top frame, to form a compression sandwich, with the corners cut away for the bolts. It's not all that pretty but it is stiff and easily manageable.

Click on any image for an enlargement.

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