Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Homemade Crayford

This topic has been archived. This means that you cannot reply to this topic.
21 replies to this topic

#1 Bill Kocken

Bill Kocken

    Messenger

  • -----
  • topic starter
  • Posts: 465
  • Joined: 07 Aug 2004

Posted 19 April 2005 - 11:25 AM

Has anyone successfuly built their own crayford style focuser? Being really cheap, and not all that happy with the rack and pinion focusers on my dobs, I've been toying with the idea of trying to build my own. I have contacted a gentleman to machine a drawtube with a flat on one side, but I'd like to do the rest without resorting to machine shop work. I'd like to do as much as possible in wood. I have table saw, router, drill press and normal assortment of hand tools. I can use metal, but only if it involves simple cutting, drilling and maybe tapping a threaded hole or two.
So, has anyone done this? I'd like to hear about what you did..
Bill

#2 rboe

rboe

    ISS

  • *****
  • Posts: 69020
  • Joined: 16 Mar 2002

Posted 19 April 2005 - 12:02 PM

Bill; Welcome to CN. Has the ice gone of the lake yet? Some folks have built their own. I used to snoop on google and some ATM sites and it's amazing what some folks have built.

The trouble with wood is moisture and the diamension changes it causes. Between summer and winter in Minnesota you could probably convert from 1.5 in. eye pieces to 2 in. with an adaptor - just wait for the seasons to change.

If you insist on wood, I'd recommend a different style focuser - perhaps a custom design to take these problems into account.

That said; there are several commercial units on the market - some fairly reasonable - that will probably be much better than most of us could make and your talents could be better used elsewhere on the scope.

Formaly from Duluth.

#3 Island Mike

Island Mike

    Viking 1

  • -----
  • Posts: 578
  • Joined: 20 Dec 2004

Posted 19 April 2005 - 12:49 PM

Hi Bill,

Yes, welcome. There are cheap imported crayford's now available like this one:

http://www.speednetl...ord Focuser.htm

Cheers,

Mike

#4 Brent Burton

Brent Burton

    Mariner 2

  • *****
  • Posts: 249
  • Joined: 06 Apr 2005

Posted 19 April 2005 - 02:45 PM

Hi Bill, I built my own crayford from wood using the designs from here:

http://www.atmsite.o...r/CrayFocus.htm

It turned out pretty good and didn't cost that much. Around $50 in materials from your local hardware store and hobbie shop.
I'll try to take some pick of it tonight and post them here.
I find that this design allows for the expansion of wood if you choose to use wood. Any expansion of the wood is taken up by the springs pushing the focus rod to the draw tube.
Good luck!

#5 Bill Kocken

Bill Kocken

    Messenger

  • -----
  • topic starter
  • Posts: 465
  • Joined: 07 Aug 2004

Posted 19 April 2005 - 07:03 PM

Hi Brent,
I look forward to seeing some photos. I enjoy the challenge of making something like that on my own. I've made the spider and secondary holder for both of my scopes and am looking for another challenge.
Bill

#6 MMICKELS

MMICKELS

    Aluminum Knight

  • *****
  • Posts: 36075
  • Joined: 20 Jan 2004

Posted 19 April 2005 - 07:08 PM

Welcome to Cloudy Nights Bill. Please post photos of your focuser for us.

#7 rboe

rboe

    ISS

  • *****
  • Posts: 69020
  • Joined: 16 Mar 2002

Posted 19 April 2005 - 07:22 PM

Brent; When you get a chance can you post pics of your focuser? Than unit looked pretty darn nice.

#8 Brent Burton

Brent Burton

    Mariner 2

  • *****
  • Posts: 249
  • Joined: 06 Apr 2005

Posted 20 April 2005 - 09:00 AM

Here are the pics I keep saying I'll get everyone...sorry for the delay.
The focuser body is made from Claro Walnut, the back piece that holds the spring tensioners is made from Curly Maple, the knobs are from Hawaiin Koa and the trim ring around the draw tube is Mahogony.
The draw tube I took out of an old Orion focuser that came from another scope of mine.
It works pretty good. Moves up and down very smooth and is tight enough to hold any eyepiece yet not too tight that it is difficult to use.
The tension can be adjusted to any ones preferance by tightening or loosening the set screws in the T-nuts under the back piece.

Attached Thumbnails

  • 412393-Wood focuser.gif


#9 Chriske

Chriske

    Kijkerbouw Urania

  • *****
  • Posts: 3113
  • Joined: 15 Aug 2004

Posted 20 April 2005 - 10:54 AM

Bill,

No need to make a flat on one side. We tested our new focuser (made out of resin) very thoroughly and it works just fine without it.
We don't use a spring mechanism to push the focuserrod against the focusertube. No need to use springs at all here.
And no, the focusertube don't turn in its holder while focusing.
Posted Image

#10 Jim Svetlikov

Jim Svetlikov

    Vanguard

  • -----
  • Posts: 2033
  • Joined: 06 Oct 2003

Posted 20 April 2005 - 11:01 AM

Nice focuser, Brent. I don't recall seeing that at Table Mountain last year.

#11 Bill Kocken

Bill Kocken

    Messenger

  • -----
  • topic starter
  • Posts: 465
  • Joined: 07 Aug 2004

Posted 20 April 2005 - 11:15 AM

Brent, that is beautiful! Lots of nice woods. I have a few detail questions. :question:
Is the main body one solid block of wood, or did you build it in pieces and glue it together? ( It appears to be one solid block.)
Bill
How are the 4 bearings that position the drawtube affixed inside of the main body?
And, can you describe the tensioning device and how the focus rod is held against the drawtube.

#12 Brent Burton

Brent Burton

    Mariner 2

  • *****
  • Posts: 249
  • Joined: 06 Apr 2005

Posted 20 April 2005 - 12:19 PM

I didn't have it at last years TMSP. I built it this year. You'll get a chance to see it this year though.

#13 Brent Burton

Brent Burton

    Mariner 2

  • *****
  • Posts: 249
  • Joined: 06 Apr 2005

Posted 20 April 2005 - 12:47 PM

Hi Bill, yes the body is one solid block of wood. You can buy bowl turning blocks fairly inexpensively like the one I used.
The bearings are small RC car bearings and they are held in place by simple wood screws with a counter sinc/reversed head. They stuck out the side a little after installation so I just grinded them down flush with the side of the body. (you can see what I'm talking about in a couple of the pics above)
The focuser knobs are attached to a shaft that runs through a couple of plungers that free float in the focuser body and are pushed by the springs against the draw tube.
I also didn't have the need for a flat on the draw tube, the friction on the draw tube from the shaft and the bearings is more than enough to keep the draw tube from spinning.
The springs then loosely fit inside a couple of T-nuts and are kept in the T-nuts by a couple of set screws that thread into the T-nuts.
I've attached a quick blow-up drawing of my focuser to help.

Attached Thumbnails

  • 412666-focuser.jpg


#14 Bill Kocken

Bill Kocken

    Messenger

  • -----
  • topic starter
  • Posts: 465
  • Joined: 07 Aug 2004

Posted 23 April 2005 - 08:54 AM

Brent and Chris,
Thanks for the photos and ideas. I've actually got several good ideas now, and I need to figure out where to go next.
Bill

#15 Bill Kocken

Bill Kocken

    Messenger

  • -----
  • topic starter
  • Posts: 465
  • Joined: 07 Aug 2004

Posted 27 April 2005 - 08:54 PM

I'm going to start with wood. I think I will use layers of plyood. I'll cut holes in the plywood using a circle cutter on my drill press or maybe a hole saw. I can install the four bearings and then laminate the layers together. I'd use a solid block, but don't have a good way to cut a 2.5" or so hole. A forstner bit would be really nice, but I don't have ( or want to buy ) one that large.

Question for Brent, did you use any sort of bearing for the focuser shaft, or is it simply riding in a hole bored through the body. I also assume that the hole is slightly oversized to allow it to be adjusted against the drawtube.
If it is supported by some sort of bearing, then it needs to be able to move somehow.
thanks for any help,
Bill

#16 Brent Burton

Brent Burton

    Mariner 2

  • *****
  • Posts: 249
  • Joined: 06 Apr 2005

Posted 03 May 2005 - 12:30 PM

Sorry for the late reply. I've been busy lately.
The focuser shaft is ridding in the holes that go through the nylon plungers just ahead of the springs (see diagram).
The hole bored through the body is larger than the shaft to allow the shaft to move back and forth.
So the shaft is essential spring loaded against the draw tube.
As long as your springs are stiff enough you should have plenty of tension against the draw tube to hold heavy eyepieces and give a nice smooth feel.
Hopr this helps let me know if you have any more Q's.

Brent

#17 Bill Kocken

Bill Kocken

    Messenger

  • -----
  • topic starter
  • Posts: 465
  • Joined: 07 Aug 2004

Posted 07 May 2005 - 12:17 PM

I had missed the fact that the nylon plungers have holes drilled for the focuser shaft. That makes a lot more sense to me now.

I got some very nice small bearings from that big auction site. $10 for 10 bearings, including shipping. I was going to buy router pilot bearings, but they were about $5 each at my local home improvement store.

Bill

#18 Brent Burton

Brent Burton

    Mariner 2

  • *****
  • Posts: 249
  • Joined: 06 Apr 2005

Posted 09 May 2005 - 06:17 PM

That is a good deal on those bearings.
If they don't work out for you then you can also get small RC car ball bearings at your local hobby store. That's where I got mine from.
They weren't $1 each but there not as expensive as in the hardware stores.
Another good source for hardware is mcmaster.com they have EVERYTHING you could ever want and at not too expensive prices as well. Good source for raw materials.
Post some pics as you go along. I'd like to see as would every one else too.
Good luck.

#19 Bill Kocken

Bill Kocken

    Messenger

  • -----
  • topic starter
  • Posts: 465
  • Joined: 07 Aug 2004

Posted 10 May 2005 - 08:07 PM

Post deleted by Bill Kocken

#20 Bill Kocken

Bill Kocken

    Messenger

  • -----
  • topic starter
  • Posts: 465
  • Joined: 07 Aug 2004

Posted 10 May 2005 - 08:51 PM

Here are pics of my project so far. Warning, I'm working on this V E R Y I N T E R M I T E N T L Y.

The bearings camoe off of the auctin site. They are .125 ID x .375 OD x .1562 width. (inches). The focuser tube was sourced for me by a machinist friend. He started with an aluminum tube and cleaned it up on a lathe and he milled the .25" wide flat. The dimensions are 2"ID x 2.25"OD x 3.25" Long.

#21 Bill Kocken

Bill Kocken

    Messenger

  • -----
  • topic starter
  • Posts: 465
  • Joined: 07 Aug 2004

Posted 10 May 2005 - 08:52 PM

Let's try the pics again.
Here are pics of my project so far. Warning, I'm working on this V E R Y I N T E R M I T T E N T L Y.
The bearings came off of the auction site. They are .125 ID x .375 OD x .1562 width. (inches). The focuser tube was sourced for me by a machinist friend. He started with an aluminum tube and cleaned it up on a lathe and he milled the .25" wide flat. The dimensions are 2"ID x 2.25"OD x 3.25" Long.
Posted Image
Posted Image

#22 rboe

rboe

    ISS

  • *****
  • Posts: 69020
  • Joined: 16 Mar 2002

Posted 10 May 2005 - 11:37 PM

Bill; If you click on the Edit button you can go back and try to attach your pictures without posting again. Good way to edit blunders too.


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics