I promised a detailed set of instructions for how I got through the first part of the build. I have yet to complete that. However I did make some more detailed pictures and a mcmaster carr order(see the files list) with most of the things that are consumables for my build.
so MC doesnt sell bricks I got these from home depot and cut them in half on a wet saw. There are other creative ways to load springs but for cost I do recommend the bricks.
There is a 327 buna n oring between each brick because that's what I had in a kit from mcmaster. Dberard recommends viton. But, whatever I just want to get near where he was circa 2013.
I took the 12" X 12" sheets from mcmaster and cut an equalateral triangle. I did this by clamping both pieces together and cutting them at the same time. I cleaned up the edges with 60 grit paper on the floor. Th e holes for the threaded rod are 1/2" drilled 1 inch in and one inch up from the bottom edges and 1 inch down fro m the top. Th mounting holes for the eyes.are a little wider than the ones in the aluminum plate.
I drilled the holes using a divider caliper to mark up the 6 inch aluminum disc. I showwed my trick in the previous post of rotating the disk on a board to find center. I used a centering drill to make the divot in the center. I then used the dividingg caliper to mark the circle I wanted the centers of the eye bolts to hit. You want this circle as big as possible. Ones you pick a size use trig functions to compute the length of each leg of the equalateral triangle that has verticies on your circle. Then set the divider caliper to that number the intersection points with your circle should be where to put your holes.
The magnet I used is not much like the one on the list. Mine was for another project and I just found it worked well for the magnetic braking here. The trick is to use a pretty big rare earth magnet this one is 2 inches in diameter and 1/4 inch thick. You will want to use non magnetic stainless screws to mount it to the wood base. The one on the mcmaster order takes care of most of this and it seems no extra screws are required. The magnet has to almost touch the aluminum to get maximum breaking, which means after the structure is leveled there will be some time spent adjusting the length of the threaded rods to get the spacing right, For this reason use threaded rod to build this(you will need to adjust as you move things around).
The springs i used are garage door springs. These are pretty cheap and wildly available. Most of the things on the list can be found elsewhere if you are on a budget the MC list may not be for you, but it does make this a lot easier. I had been purchasing parts for this thing since before dberards STM made the HAD Blog. I was moving them around from place to place. Some of my build used obsolete parts. I will cover that when I cover electronics.