From: "John Murray" 
To: "'Mirror Matic'" ,
        "Amateur Telescope Makers" 
Reply-To: "John Murray" 


G'day Everyone,
        Well, after a week of experimenting with different turntable and
ecentric speeds(30 - 70rpm T/T, 4 - 20rpm Ecc). 3 different tools (2 x 5, 1
x 6.4"), (different sizes and construction) flipping the blank to give
a flat surface to start with, casting against the original curved surface
etc etc etc. The bloody tools still refuse to spin properly. I believe that
the tool on the outside edge is travelling around 1/2 speed relative to the
blank instead of virtually no relative speed difference on the outside
where the edge of the tool and blank meet. Am I clear there?
        The toggle has been constructed with 3 pieces of oil impregnated
high density vinyl. An inner one, an outer one and a bush which seperates
the other 2 pieces. I've lubed this with water, oil and finally graphite
powder. There appears to be no slop in the toggle and it rotates with no
binding or friction that I can detect. I have tried sweeping the tool
across the blank to no avail, also, stationary overarm with around
1/2" of wag again to no avail. The annoying thing is that the first
spiral cast tool I made spun beautifully. It just fell apart!
        The latest tool (5") with 1/8" gaps seperating the 1" tiles
(laid horizontal) started the blank going very, very slightly convex with
the edge of the tool around 1/8" (no more) overhang from the edge of
the blank? That surprised me. Sweeping had no effect on the tools rotation.
        I'm considering adding a drive to the overarm to drive the tool.
Any thoughts or suggestions? Using the newest feature in the link in my
signature will show some of the tools that have been used, not all though.


Cheers

John Murray
Whyalla
South Australia
Our ATM page is at
http://astronomy.sa86net.com

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