Part 2 of "Making a mechanical Iris."
So if you are not yet completely bored. I will continue.
The second phase was to make the leaves. Eight of them, all machined from 0.25mm brass sheet. As I mentioned in a previous post, Karma decided to raise its annoying head and peek in my direction. Things were going well, all of the previously made parts fitted together well and looked quite good.
So machining the leaf blanks should have been easy, after all what could go wrong? The first two were cut with no problems, however as the third was cut, the brass lifted, jammed the cutter which promptly snapped. I was not happy! I only had one cutter left for the job, so any further problems would seriously put a crimp in the progress for several days while waiting for replacements. as luck would have it all the leaves were finally cut out including replacements for the one damaged by the jammed cutter.
Next the pivots had to be soldered to the leaves. I have some low silver, solder paste for the job, so after making a jig I set to. !mm brass rod was cut into approximately 4mm lengths, and these were placed in the jig. the leaf was then fitted to the pivots, solder paste applied and the joints soldered. I had a lot of problems initially The aluminium I used for the jig, sucked the heat away, way to fast causing the joints to be weak. I tried using a Hydrogen-oxygen micro welder to increase the available heat, but this was way too hot and would simply vaporise the solder. The solution after some trial and error was to max. out the soldering iron and raise the part using an aluminium ring cut from some tube I had handy. During the assembly of the iris, two leaves broke, one spare, and were unrepairable, therefore two spare leaf blanks were cut on the mill and one soldered to form the 8th leaf. Finally each of the slots were filed to allow for smooth movement of the pins, a pin sticking was what caused the two leaves to break, ripping out the pins and tearing the brass leaf.
All was assembled and tested. The mechanism is still a little stiff but this will improve with use. I will machine recesses to allow a better grip on the two arms of the control ring, but all in all, I am happy with the result.
A few details about the iris. The overall diameter is 20mm, not including the grips. The inner aperture is 10mm when open and 2mm when closed, I tried to make it fully close but the spring force meant too much of a recess was needed at this small a diameter with the materials I had to hand.
finally the rest of the pics, and about time to, I hear you say.
But first.. The return of the galactic hitch hiker.
I tried to hitch a ride on the Golgafrinchan B Ark, but the captain said he couldn't stop as he was on his way to an important bath?!
Pics yaaay.....
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