Biff
Carpal Tunnel
Reged: 09/04/05
Posts: 2407
Loc: Courtice, Ontario
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I'm making a small scope for my soon to be 8 nephew. After doing some final modeling it turns out the focuser I was going to use was way too tall for a good IF so after some thought I decided I'd try my hand at making a focuser. It's only a 1.25" as a 2" would be a waste, with this I'm barely able to get 70% at the edge of a 26mm plossl (without using a large secondary) so just good enough. I don't consider myself a good woodworker and I'm a hack on my lathe. I used wood for the body because I don't have a mill to work with aluminum but TBH I think it ads a bit of "character". This was also my first crack at knurling so the knobs and thumbscrews aren't perfect.
I'm posting this in hopes that somebody can get some ideas from it and also for some feed back on what's right, and mosty importantly what's wrong. I'm not much of a photographer and I'm using my wife's new lens so I'm not sure how the pics are going to look on your end. It's not very forgiving though as I can see some flaws in the shots that aren't noticeable when holding the unit in my hand. I still need to blacken the inside of the draw tube and varathane the wood but at least the build is done.
Here's the focuser he was going to get.
At the end of the day I got the EP ~1.75" closer to the secondary and that will help a lot with the IF so mission accomplished but It's not going to be easy to give it away. One last comment on the motion... It's really nice! I may even take apart my JMI and Wyorock and redo them to match this focuser to bring their performance up to par.
Again any question, comments, and constructive criticism welcome.
Ryan
Edited by Don W (11/12/09 08:03 PM)
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DavidinFL
member
Reged: 08/28/09
Posts: 53
Loc: Navarre, FL
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That looks great! If there are any flaws (like you said) I'm having a hard time seeing them.
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Orion XT8 - Orion StarMax 102 EQ
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 591
Loc: UK
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Hey man thats brilliant!!, I am going to steal your idea for future focusers, a very neat piece of work, it shows what can be done with wood, but that is what the Crayford is all about. John Wall. 
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Husbyggarn
member
Reged: 12/12/08
Posts: 47
Loc: Sweden
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That's just beautiful! nice craftsmanship.
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Skylux 70/700mm Refractor
Astro-3 GEM Mount (DIY Motrized RA with Steppermotor)
32,20,12,6,4mm Plossl, 1,5x Barlow
Sony A300 DSLR Camera
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polaraligned
sage
Reged: 12/26/08
Posts: 324
Loc: P. R. of New Jersey
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I think it came out very, very nice.
Enjoy it!
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RossSackett
scholastic sledgehammer
Reged: 08/17/07
Posts: 756
Loc: Memphis, TN
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Nice craftsmanship, but also REALLY nice elegant design. It would work in a variety of materials, including aluminum, delrin, or a fiber-reinforced plastic.
Ross
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"A craftsman relies on science when the state of knowledge allows it, tradition and experience when it does not, and makes art whenever he can."
12 scopes from 4.25 to 18" and a 24" in progress. 12 ATM awards. Webpage: http://stardazed.com/ Some more scope pix at http://www.flickr.com/photos/8315630@N04/
Anagrams: Amateur astronomer = A mature moon-starer; Dobsonian maker = Debonair as monk
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cloudmagnet
member
Reged: 12/04/08
Posts: 47
Loc: Georgetown, Texas
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Great work Biff!!!
A coupla questions about the 3 brass thumbscrews:
The outer 2 adjust pressure on the shaft bearings, right?
The center one ...?
What material did you use for the friction roller that moves the focusing tube?
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Wes James
Post Laureate
Reged: 04/12/06
Posts: 3961
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Beautiful worksmanship, Biff- VERY nice!!
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Wes
Atlantic Beach, FL
Some bino’s from Miyauchi 5x32 Binon's up through Garrett 20x110 Signature's,
Some telescopes from a Stellarvue 80mm NHNG up through a couple of 8” reflectors…
And a wonderful 4.25" Delmarva Shiefspiegler!
Some good friends, made here on C/N.
Oh- several cats and a wonderful wife!
Anyone want a cat???? :-O
"When your work speaks for itself- Don't Interrupt" -Gamble Rogers
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Gary Fuchs
scholastic sledgehammer
Reged: 05/22/06
Posts: 921
Loc: Easton, PA, USA
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Very nice!
Gary
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Happy-Idiot
Post Laureate
Reged: 04/06/06
Posts: 3072
Loc: 3rd Rock
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Very cool, you have a very lucky nephew. 
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Brian
A small scope that gets used often is a better investment than a big scope that stays in the closet.
Unitrons, you spend more time looking at them than you do through them.
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Moki
super member
Reged: 11/06/05
Posts: 449
Loc: Under the Clouds
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Well done, Biff! Elegant and simple.
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"In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual." Galileo
12.5" F5.3 Dob on EQ platform
8" F7 planetary Dob / EQ Platform
Current ATM projects:
Xtal-Controlled EQ platform motor drive - finished... It works!
Motorized focus for planetary (moved to the bottom of the list for now)
10" F5.5 Verylight PushTo
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sarastro
sage
Reged: 08/12/04
Posts: 442
Loc: Seattle
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Very nice Biff!
Do you have any disassembled pics of the focuser? I would be very interested in the inner workings, particularly the roller assembly.
Roger
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Biff
Carpal Tunnel
Reged: 09/04/05
Posts: 2407
Loc: Courtice, Ontario
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Quote:
Nice craftsmanship, but also REALLY nice elegant design. It would work in a variety of materials, including aluminum, delrin, or a fiber-reinforced plastic.
Ross
There's an idea. Can Delrin be machined with wood working tools or would it melt/gum up or cause abnormal wear on bits & blades?
Quote:
Great work Biff!!!
A coupla questions about the 3 brass thumbscrews:
The outer 2 adjust pressure on the shaft bearings, right?
The center one ...?
What material did you use for the friction roller that moves the focusing tube?
Yes the two outer ones apply direct pressure to the bearing for the roller shaft. The center one puts pressure on a bit of teflon that's in there for friction. The two bearing screws aren's really required. Using just the center thumbscrew to put pressure on the roller shaft and so put pressure on the flat side of the draw tube will work but the center thumb screw needs to really be cranked down. Using the extra thumbscrews on the bearing gives me a little more adjustment freedom.
Quote:
Very nice Biff!
Do you have any disassembled pics of the focuser? I would be very interested in the inner workings, particularly the roller assembly.
Roger
I'll take some disassembled pics and post them.
Thanks for the comments all!
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Ryan
Antares 200mm f/6 Dob & 130mm f/5 Travel Dob.
Projects on the go...
- a couple 80mm SS refractors on the back burner.
- a few small mirrors awaiting polishing
- 260mm f/7.15 mirror... still polishing
Member of DRAA
 My house.
 DRAACO
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RossSackett
scholastic sledgehammer
Reged: 08/17/07
Posts: 756
Loc: Memphis, TN
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Delrin has the reputation of being very easy to machine.
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"A craftsman relies on science when the state of knowledge allows it, tradition and experience when it does not, and makes art whenever he can."
12 scopes from 4.25 to 18" and a 24" in progress. 12 ATM awards. Webpage: http://stardazed.com/ Some more scope pix at http://www.flickr.com/photos/8315630@N04/
Anagrams: Amateur astronomer = A mature moon-starer; Dobsonian maker = Debonair as monk
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Achernar
Postmaster
Reged: 02/25/06
Posts: 5211
Loc: Mobile, Alabama, USA
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Very nice work Biff! I'm sure it works as well as it looks. It looks like you got the roller bearing off some defunct router bits.
Taras
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15-inch F/4.5 Dob under construction
10-inch F/4.5 Discovery Dob
6-inch F/8 Homebuilt Dob
4 1/4-inch F/4 Homebuilt reflector
A whole bunch of eyepieces, filters and other accessories....
One curious cat
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KevinP
super member
Reged: 06/25/07
Posts: 170
Loc: Edmonton
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Nice looking focuser Biff!
Are the socket cap bolts threaded directly into the wood or do you use threaded inserts to capture them?
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Kev
Sketches
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Antares 200 mm / f5
ATM 82/700 refractor in progress
Bushnell 10x50
Celestron 15x70
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Biff
Carpal Tunnel
Reged: 09/04/05
Posts: 2407
Loc: Courtice, Ontario
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Quote:
Very nice work Biff! I'm sure it works as well as it looks. It looks like you got the roller bearing off some defunct router bits.
Taras
Ha ha ha! Good eye! That's where I stole them from. I was going to pick some up but when playing with ideas I 'borrowed' some off of a CRAPsman router bit set. I just got lucky they are 1/2" O.D. and 3/16" I.D. which is exactly what I wanted. I doubt I'll ever use those bits anyway.
Kevin, The ones for the bearings are direct into the wood since all the force is to the side of the hole anyway. The 4 holding the back plate on use inserts because I was afraid the force the thumbscrews would pull the screw out if they were directly screwed into the wood. For the screws going directly into the wood the holes were treated with CA that has the viscosity of water. I then tapped them, reapplied the CA and then cleaned the holes out again with the tap. TBH it's probably as strong as the inserts.
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Ryan
Antares 200mm f/6 Dob & 130mm f/5 Travel Dob.
Projects on the go...
- a couple 80mm SS refractors on the back burner.
- a few small mirrors awaiting polishing
- 260mm f/7.15 mirror... still polishing
Member of DRAA
My house.
DRAACO
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Biff
Carpal Tunnel
Reged: 09/04/05
Posts: 2407
Loc: Courtice, Ontario
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Hope that's what you were looking for. If you need anything else let me know.
Ryan
Edited by Don W (11/12/09 08:02 PM)
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johnnyha
Carpal Tunnel
Reged: 11/12/06
Posts: 1539
Loc: Sherman Oaks, CA
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Johnny
Spicewood, TX
Sherman Oaks, CA
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Sky Captain
Metal Whisperer
Reged: 11/07/04
Posts: 7770
Loc: Issaquah, WA.
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Nice job Ryan! I'm very impressed. Brilliant design and build.
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12" Lightbridge : SC 8" f4 : 12.5" f2.35 Astrograph : TAL RS 4" f10 : WO EZT : Atlas EQ6
35 & 22 Panoptic : 14 & 8.8 Meade UWA : 8 to 12 Speers Variable : Antares 1.6x Barlow
Kerry
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