DCA: Fabracation 6 — Spiral Supports and Base

Because the spirals are mounted with their narrow end at the hub I needed a way to support the large end of the spiral at the end of the rod. I decided to make these supports out of straight lines to contrast a bit with the spirals and circles on the hubs and bowls.

I also wanted the supports to contact the spiral at two points and be adjustable. The two points of contact is important in keeping the spiral rigid and making it less likely that it would bend. The adjustability served two purposes. 1- Since these are supposed to be antenna on a machine I think it would be fun if they could be adjusted to “tune” the machine. 2- I know I’ll need to keep the spiral under some rotational tension so that it held its form as it collapsed when the bows were slid down the rod but I have no way of knowing how much tension is needed.

I had a great insight when I realized that the width of the sides of a piece of scrap angle iron I had been using as a support was exactly 0.2″ which is almost the thickness needed for a 1/4″ 20 thread (0.1887″) . So I cut a 0.2″ length off it making its end square

I then threaded the so that I could accommodate a 1/4 20 nut.

Once it was threaded I then hand cut a thin slit down its length.

Once this threading and cutting was repeated on the other side I attached this V to another another straight piece and then to one of spare square bracket pieces.

These worked really well in supporting and stiffingin the spirals. I’m also quite pleased with the way they look.

In other developments the core piece is now mounted on the base I made a week or so ago.

Once it was mounted I was able to clamp a wrench to the rear drive rod and give it a spin. The initial results were mixed.

The action was great when the bowls were not touching the central band. But when they were touching they were still interfacing poorly even after I adjusted the rod brackets. Specifically, the right bowl which seemed to still be about 1/8″ off. This poor interface cause small amount of load that quickly caused the gears to spin in relation to the rod. So I had to dissemble the drive and drill holes in the rods that the set screws from the gears could penetrate.

It’s possible that I’ll have to do the same for the set screws on the hubs which are really the only thing keeping the bowls attached to the spinning rod.

While drilling those holes stopped the poor interface form spinning the gears it did not solve the root of the problem which is that the bowls (particularly the right one) do not always sit flush with the central band. I’m almost certain that this is because the tension on the side straps is uneven and taking the bowls out of true. I did some experimentation and I think I’ll be able to true it by hand and and get the both to be completely flush. If not then I’ll just have to run it with a slight gap between he band and the bowls.

The base is going to need some supports. I think I’ll need one the back and one under the central band. I don’t think these will need to be very large or thick.

I really like the way the bowls seem to hover when the are on base.