I spent a little time yesterday making a parabolic cut-out. I'll take it with me to the shops today, on the chance that I find a bowl or something with the same contour.
And a question for the driver gurus;
If I were to piggyback 3 or 4 FET's on the same board, will the 13a have a strong enough drive signal to operate them all?
At least the write-up is already excellent, great reading, that will impress the judges as well :-) , I hope that the mirror will work out in the end. Keep going!!!
Jacks a good looking assistant but he appears to goof of as much as my two assistants. I bet if the three of them got together there'd be a bunch of trouble. Its good to see some progress on the light.
That shallow, long focal length Edmond Scientific reflector looks like it should be used in a retro configuration. The light sources they used in WWII search lights emitted in all directions.
While I was researching making parabolas, I came across the term 'spinning' a few times.
As it turns out, a liquid that is spun at a constant speed in a container forms a parabola on it's surface. The faster the rotation, the shorter the focal point.
This is what I'll be trying next, by using a low viscosity epoxy, or plaster mix.
The key seems to be keeping a consistent speed, whilst the solution sets.
Others of my group did that when I was in Germany, to use as a light gathering mirror. I think we used polyester. It should start as a liquid and not change volume too much when it hardens. I don’t recall how we silvered the surface. Evaporating aluminum on it in a vacuum probably gives the vest shine, but without a vacuum one could stick aluminum foil to the surface.
The 1964 book “Direct Use of the Sun’s Energy” by Farrington Daniels has text about making parabolas and a photo-plate showing how they made a concrete mold to form plastic parabolic mirrors. It’s out of print but cheap if you can find it. Paid $2 for my copy.
Lore from fellow radio nuts has it that the best satellite dish to use as an antenna reflector is the old “Dish 500” model; newer ones have an offset designed in for the receive head location. Parabolic reflector principles are the same for light or radio, same stuff different wavelengths.
Don’t think outside of the box, throw the box away!
A common satellite dish was one of my first thoughts, but for the (yet to be divulged) body, the focal length is too long. I need the focal length to be no more than ~25cm.
I started piecing out a jig to use for spinning up the reflector tonight - hopefully I'll be at the stage where I'm making a test run with it on the weekend.
What a massive effort. Remind me never to get in an argument with you as your persistence is, well persistant. I hope it turns out better for you today. Whats Jacks nickname, Hammer or Chuck?
Thanks, although apparently not enough persistence to embed a couple of videos from Flickr....
I know I've done it before but it eluded me last night, so I jumped ship over to the big G, but even that wasn't straight forward :(
Just had a quick look at the reflector now - it looks OK, but will need to be lightly sanded/dusted, & sealed with something, before the reflective film has a chance of sticking to it.