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Milamber

By Milamber
in DIY Astronomer

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Milamber

Milamber

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I have this week received a 10" f/5 mirror to play with (for another project) so am taking the oportunity to make a scope from the bottom up since the mirror is a good one while the OTA was pooh. I'm starting on the focuser since I had some spare time with the lathe today as the mill was being "looked at" (sorted now). I had thought to use four of the bearings I have laying around from the remote control car days but the more I think about it the more I'm leaning towards teflon bearings under pressure from the focus shaft through the tube. What do you people think? Were I to use bearings I'd likely only go with three anyway but the more I think about it the more I like the teflon strips idea...

Arthur

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barkis

barkis

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I think you could do a lot worse than use Teflon Arthur. It is a remarkable material, and well suited as a bearing medium. It will never seize up, as metal bearings are prone to do. Your focuser will finish up a beautifully engineered device, and buttery smooth in it's operation.

You must already know that this Teflon stuff has uses way beyond a non stick frying pan. :smiley:

Ron.

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Milamber

Milamber

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Ron - I used to make PTFE bearings when I was 16 (long time ago) and converted my bike to use them :smiley: That was when we had to use mandrels and fillers and packing and huge presses and ovens and stuff. When you were "allowed" to get your hands dirty at work!

Yup, I like the stuff and do wish it had more and better press but such is life. Ball bearings ultimately will fail, ptfe just needs a gnat's whisker of a turn on the tension screw!

Arthur

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barkis

barkis

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Yes, I remember getting my hands dirty. Even though I had overall sleeves down and press studded around the wrists, I could still get mucky up to my elbows. I must have just been a dirty git, it never seemed to happen to anyone else. :smiley:

:evil:

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barkis

barkis

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... I'm also thinking that if I use four teflon pads rather than four bearings I will be able to collimate the focuser - it'll be a bit like having all-round independent suspension on a car!

Arthur

What, like 4 iindependant Teflon grubscrews? Good Idea. It's surprising how often the focuser is left out of the equasion when collimating. Odd that, since the final part of the light path is in there. :smiley:

:evil:

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Milamber

Milamber

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To be honest, I already have a focuser collimator in testing/development - the issue being that up to maybe the 285-based cameras, it's sort of OK if your focuser is not dead true. Once you go to the bigger chips any out of trueness shows progressively out from the centre of the image. I like the idea of collimatable focusers but if you don't have one then (ordinarily) you are out of luck. All strictly hush-hush though :smiley:

There's a whole lot happening here in the AM thinktank atm - watch that space over there!

Arthur

PS - if this is deemed as commercial guys, feel free to remove it!

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Milamber

Milamber

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OK - first pic is the machined tube and main body blank (although the bore has been finished)

Second and third pics are basically a rough idea of what I am after - I find it easier to do this stuff in 3D rather than on paper, helps to picture things mentally. There's quite a heavy workload on the mill atm but I think I can sneak this on later today to at least get the outside shape sorted. I have pretty much decided that the four teflon/ptfe pads under stainless grubscrews is the way to go - less moving parts, smoother action, and that collimation angle clinches it.

Keep watching!

Arthur

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Milamber

Milamber

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OK - if anyone's interested, here's how it goes:

Pic 1 - Put your lump of aluminium into the machine and find the middle of it...

Pic 2 - Get your "3D" imagined item into the machine somehow (Cartesians - dead easy) and start cutting

Pic 3 - Continuing...

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barkis

barkis

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Very nice too Arthur. I could stand and watch that machine work all day.

I bought a 3 in 1 Super B from Chester UK a while ago. It has a vertical milling machine incorporated into it, unfortunately every action has to be manually implemented, and If it were possible I would convert it too. Now I know that's silly. But I can dream can't I?. :smiley:

It would be nice to see some video of your robot at work.

Ron.

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Milamber

Milamber

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This is a PowerCentre KM80 Rob, a wonderful bit of kit about the size of a small caravan :smiley: I also have the Mazak SQT10M which is a 3 axis cnc lathe - first lathe I ever had that I can turn square parts! (on purpose I mean :evil: ) Has driven tooling in the turret - great fun!

Arthur

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