Biff
Carpal Tunnel
Reged: 09/04/05
Posts: 2372
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: 52
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: 370
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: 24
Loc: Sweden
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That's just beautiful! nice craftsmanship.
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Skylux 70/700mm Refractor
Astro-3 GEM Mount
4mm, 20mm Plossl, 1,5x Barlow
Sony A300 DSLR Camera
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polaraligned
sage
Reged: 12/26/08
Posts: 227
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
professor emeritus
Reged: 08/17/07
Posts: 691
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: 34
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: 3450
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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: 867
Loc: Easton, PA, USA
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Very nice!
Gary
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Happy-Idiot
Carpal Tunnel
Reged: 04/06/06
Posts: 2801
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: 428
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: 402
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: 2372
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
professor emeritus
Reged: 08/17/07
Posts: 691
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: 5022
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....
Two curious cats
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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: 2372
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: 2372
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
Pooh-Bah
Reged: 11/12/06
Posts: 1087
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Johnny
Spicewood, TX
Sherman Oaks, CA
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Sky Captain
Metal Whisperer
Reged: 11/07/04
Posts: 7180
Loc: Issaquah, WA.
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Nice job Ryan! I'm very impressed. Brilliant design and build.
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Equipment Overload!
Kerry
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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The more I see the better it gets, real craftsman ship, excellent.
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1414
Loc: Sin-sin-atti
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Very clever Ryan!
Did you use a mill to drill your holes? When I drill in the plywood layers the bit always seems to drift a bit.
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Ed Jones
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Gordon Rayner
scholastic sledgehammer
Reged: 03/24/07
Posts: 965
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I made binocular eyecups by boring, and then threading, Delrin, to a depth as deep as allowed by the largest lathe boring bar which fits into that thread size. A form tool cut the curve on the outside edge of the eyecup-to -be, which was then cut off. Repeat, until all of the threaded hole has been used.
Delrin will melt and the threads or surface finish be spoiled, if heat builds. So a water-soluble coolant(I used a laboratory bottle with a 135 degree bend in the nozzle), or one of the air jet cooling ( Coanda or Venturi (?) based) nozzles, is helpful. I use plain water for hand-tapping. Perhaps added dish soap would help?
Delrin-AF, which has imbedded Teflon particles, is easy to cut, but is expensive. I look for remnants. It is a mahogany-like brown color.
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Gordon Rayner
scholastic sledgehammer
Reged: 03/24/07
Posts: 965
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Are you using brad point drill bits? In wood, those wander less, and give cleaner holes when breaking through, than bits for metal. Sets are available at Rockler, Harbor Freight, etc.
They are useful in oak, in which drill bits for metal tend to wander into the easier path between ( or is it in?) the grain lines.
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Biff
Carpal Tunnel
Reged: 09/04/05
Posts: 2372
Loc: Courtice, Ontario
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Ed, no I don't have a mill... otherwise you'd probably be looking at an all aluminum focuser.  I use a drill press.
What holes are you referring to specifically? As has been mentioned brad points help. Also i have a reasonably good set of drills (these). I've found they work much better for accuracy and clean holes vs. what you would get at HD.
Edited by Biff (11/08/09 06:05 PM)
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Roy McCoy
professor emeritus
Reged: 10/13/05
Posts: 642
Loc: Glendale, AZ
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Ryan,
Like everyone has said:
Elegant, nice craftsmanship, good design.
Really nice.
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sarastro
sage
Reged: 08/12/04
Posts: 402
Loc: Seattle
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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
Many thanks for the extra photos!
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Mark Harry
Post Laureate
Reged: 09/05/05
Posts: 3120
Loc: Northeast
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So you're a hack on a lathe....yeah, right!
Nice job!
Mark
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So many projects, so little time!
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StarStuff1
scholastic sledgehammer
Reged: 04/01/07
Posts: 971
Loc: South of the Mason-Dixon Line
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V-e-r-y nice execution of a really cool design ides.
Just curious, any idea of the amount of time involved in the project?
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Tools that make objects very far away appear much closer than they actually are.
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Biff
Carpal Tunnel
Reged: 09/04/05
Posts: 2372
Loc: Courtice, Ontario
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Quote:
Just curious, any idea of the amount of time involved in the project?
Heh a long time (maybe a month) but I wasn't working on it constantly and had a few design changes along the way plus having to get the stuff to knurl... learn to set it up... then make some thing useful out of it... figure out some jigs... yada yada. But if you had all the stuff setup and knew what you were doing it could probably go pretty quickly.
- I'm sure somebody more proficient than myself could machine that draw tube in no time.
- The wooden body is made of 3 layers (1x3/4" and 2x1/2") BB plus the base. I cut some squares glued and clamped and left over night. Now that I know what order to make the cuts in and how to do them, I could do all the cuts on the body in an evening. Then another overnight glueup to glue the body onto the base.
- The knobs and thumbscrews took me a long time (again my lathe skills), they took me a few evenings at least. Again it'd faster now, though I suppose you could just buy knobs and screws.
If I had to do it all over again I'd wager I could get it done in 3 or 4 evenings barring no do-overs and no interruptions.
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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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StarStuff1
scholastic sledgehammer
Reged: 04/01/07
Posts: 971
Loc: South of the Mason-Dixon Line
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Thanks for that detailed response. The learning curve is often steep for something new. Most of us have been here and done that!
Your result is impressive. I would bet this is not your last wooden crayford!
Another bet: there will be imitators and imitation is a most sincere form of flattery.
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Tools that make objects very far away appear much closer than they actually are.
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Biff
Carpal Tunnel
Reged: 09/04/05
Posts: 2372
Loc: Courtice, Ontario
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Quote:
I would bet this is not your last wooden crayford!
Probably not. Had I had a mill I would most likely have made an aluminum one but this one (to me anyway) looks kinda classy rather than looking like a compromise. Though I think it would out of place on a fancy all aluminum scope.
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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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Jim Romanski
scholastic sledgehammer
Reged: 01/02/05
Posts: 842
Loc: Guilford, Connecticut
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Very nice focuser.
What about the eyepiece? Did you make your own Nagler 13mm out of wood too? 
--------------------
Jim
17.5" Dob "Project"
13.1" Coulter
8” Cave
NP 101 on a CG-5
25x100 binos
Naglers, Ethos, etc.
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StarGazer235
journeyman
Reged: 09/11/09
Posts: 6
Loc: Montreal, Qc
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Wow! Very, very nice! I'm officially jealous...
I'm also currently building a wooden crayford. I have some stainless tubing, about 1"3/4 ID for the drawtube, but it's nowhere as nice as your drawtube , and I had some leftover pieces of jatoba for the body (harder than maple i think).
How did you put the curve in the bottom side of the focuser? I haven't tackled that yet and I don't know how to...
Also, where did you find the Teflon piece and thumbscrews? Hardware stores are lacking for that kind of stuff...
Did you machine the roller yourself?
Congrats on your fine work!
--------------------
Celestron FirstScope 76mm
(soon: 130mm, maybe 150mm?)
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dpwoos
sage
Reged: 10/18/06
Posts: 206
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I sure would love to see it. Any way to get some pics posted? Thanks.
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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Please lets have finished piccies of your brilliant focuser, if you dont mind I am going to dowload all your pics for my archives, and I shall definately use them for any lectures on Crayfords in the future that I give.
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Biff
Carpal Tunnel
Reged: 09/04/05
Posts: 2372
Loc: Courtice, Ontario
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Sorry for the delay, I'm working on getting the pics reposted.
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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: 2372
Loc: Courtice, Ontario
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Picks are up!
I lost all the text that went with the pics when they were wiped out so I'll try to remember the key points.
Here's the focuser that my nephew was going to get.
A few shots of my crayford.
Fully racked in.
Fully racked out.
A couple with a 13T6 Nagler for scale.
Disassembled picks for Roger:
Draw tube.
Roller shaft with knobs and bearings.
Guide bearing on bolt.
The piece of teflon for friction on the roller. I made it wedge shaped so that when the thumb screw is tightened it would press itself against the edge of the slot that houses it. Further it will press the roller shaft bearings against the side of the slot they ride in which eliminates any slop.
Pic of where that teflon wedge would go (roller shaft removed for clarity).
Some shots of the stripped down wooden body.
Roller shaft assembly sitting in its guides.
And with the teflon wedge in place.
I hope that's all the pics and info replaced. If I left something out, let me know.
Ryan
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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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AV in CMH
sage
Reged: 11/07/05
Posts: 461
Loc: Columbus Ohio
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Really nice.
I am inspired.
Thanks,
Anthony
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Biff
Carpal Tunnel
Reged: 09/04/05
Posts: 2372
Loc: Courtice, Ontario
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Quote:
Wow! Very, very nice! I'm officially jealous...
I'm also currently building a wooden crayford. I have some stainless tubing, about 1"3/4 ID for the drawtube, but it's nowhere as nice as your drawtube , and I had some leftover pieces of jatoba for the body (harder than maple i think).
How did you put the curve in the bottom side of the focuser? I haven't tackled that yet and I don't know how to...
Also, where did you find the Teflon piece and thumbscrews? Hardware stores are lacking for that kind of stuff...
Did you machine the roller yourself?
Congrats on your fine work!
Hmmmm solid hard wood would be NICE!!!
The tube I'm using is ~7.75" diameter. What I did was put a 7.25" blade in my tablesaw and push the wood over it side ways. I clamped (really tight) a straght edge to the table top just in front of and perpendiclar to the blade. I started with the blade just barely skimming the wood on the first pass and only raised the blade a smige for each pass. I didn't want any large chunks torn out or and layer delaminated should there be a little catch also I didn't want the blade biting in and launching it through the garage door. I was working from the side so at least I was out of the line of fire should something have gone wrong. It went a lot smoother than what I expected. Just wanted to add that this was cut out of the middle of a 'board' and then trimmed to shape so that it would always ride on a flat surface.
Obviously the radius of the cut doesn't match the radius of the tube but it's pretty darn close for a good fit. You can use a larger blade and push the wood through on an angle to simulate a smaller curve but you end up with the end of an ellipse instead of a perfect round but I if the results aren't close enough for your liking then tape a peice of sand paper to your tube and for the focuser base against it to clean up the curve.
The teflon was part of a small scrap sheet I bought at a local plastics place, ad cut to shape in my tablesaw.
I machined the thumbscrews of of 1/4" brass bar. But I think Mcmaster Carr would be a good place to look for some.
The roller shaft is a piece of 3/16" drill rod.
--------------------
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
Edited by Biff (11/15/09 05:16 AM)
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StarGazer235
journeyman
Reged: 09/11/09
Posts: 6
Loc: Montreal, Qc
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Using a table saw "laterally" to grind a curve... that's brilliant! I'll see if I can fit a 5"1/2 blade to my table saw (my tube's OD is 136mm, 5.36").
For the teflon, I bought some table/chair pads and cut one to size - I think'll work ok.
My initial design turned out too complicated to build - I wanted something kind of like this : http://www.atmsite.org/contrib/Sapp/Focuser/CrayFocus.htm
Turns out the precise drilling required for the support bearings is beyond what I can achieve with my skills/equipment...
Oh well, take two will be inspired by your design!
Thanks for the info!
--------------------
Celestron FirstScope 76mm
(soon: 130mm, maybe 150mm?)
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Biff
Carpal Tunnel
Reged: 09/04/05
Posts: 2372
Loc: Courtice, Ontario
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Quote:
Using a table saw "laterally" to grind a curve... that's brilliant! I'll see if I can fit a 5"1/2 blade to my table saw (my tube's OD is 136mm, 5.36").
Just remember tablesaws can be extremely dangerous! Think it through before you make the cut should anything go wrong the piece of wood won't end up in you and finger won't end up in the blade.
Quote:
For the teflon, I bought some table/chair pads and cut one to size - I think'll work ok.
Also places like Lee Valley etc. sell bits of plastic (I think it's UHMW) for making jigs and such that's supposed to be pretty slick. I think the same stuff it used in furniture sliders as a low cost alternative to teflon. It may not work out a smooth as teflon but maybe you won't be able to tell the difference.
Quote:
Turns out the precise drilling required for the support bearings is beyond what I can achieve with my skills/equipment...
For mine I made a jig for the drill press to keep everything aligned and in the right spot, if you want I can post something on it.
--------------------
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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StarGazer235
journeyman
Reged: 09/11/09
Posts: 6
Loc: Montreal, Qc
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Quote:
Just remember tablesaws can be extremely dangerous! Think it through before you make the cut should anything go wrong the piece of wood won't end up in you and finger won't end up in the blade.
Damn right! My router table is probably _the_ tool that commands the most caution from me though - it even sounds scary when running - but the table saw should not be underestimated for sure (many a piece it has angrily flung across the shop...)
I'm guessing you placed the straight edge so the motion of the blade would press against it, right?
Quote:
For mine I made a jig for the drill press to keep everything aligned and in the right spot, if you want I can post something on it.
I would definitely be interested by that jig layout! I hadn't built a jig yet but had blocks held in place with C clamps - for take two I'll use jigs, less hassle, more precise
--------------------
Celestron FirstScope 76mm
(soon: 130mm, maybe 150mm?)
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orion63
super member
Reged: 12/10/07
Posts: 139
Loc: Lima, Peru
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Beautiful work, and very inspiring!
I also lack the tools for metal working, and think I'll borrow some ideas for future projects. Using bearings from dead router bits is a great idea.
Thanks for sharing!
Gonzalo
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Crayfordjon
Inventor
Reged: 06/17/09
Posts: 370
Loc: UK
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You can replace the teflon pad with lightly oiled felt, I did this on my early CF,s, the action is nice and smooth. Later I gave up using ball races for the spindle bearings and substituted oil impregnated sintered bronze bushes that go under the name of "Oilite bushes", These supply the right amount of friction in themselves. You can also use teflon bushes of course, and I have used this method too. A word of interest, if you make a focuser using ball races for the spindle bearings and leave out the friction pad, you get an incredibly sensative focusing action which is too good for practical application, but might have some use for a system that requires this sensitivity.
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