Posted 19 April 2005 - 11:25 AM
So, has anyone done this? I'd like to hear about what you did..
Posted 19 April 2005 - 12:02 PM
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.
Posted 19 April 2005 - 02:45 PM
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.
Posted 19 April 2005 - 07:03 PM
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.
Posted 19 April 2005 - 07:08 PM
Posted 19 April 2005 - 07:22 PM
Posted 20 April 2005 - 09:00 AM
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.
Posted 20 April 2005 - 10:54 AM
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 20 April 2005 - 11:01 AM
Posted 20 April 2005 - 11:15 AM
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.)
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.
Posted 20 April 2005 - 12:19 PM
Posted 20 April 2005 - 12:47 PM
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.
Posted 23 April 2005 - 08:54 AM
Thanks for the photos and ideas. I've actually got several good ideas now, and I need to figure out where to go next.
Posted 27 April 2005 - 08:54 PM
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,
Posted 03 May 2005 - 12:30 PM
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.
Posted 07 May 2005 - 12:17 PM
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.
Posted 09 May 2005 - 06:17 PM
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.
Posted 10 May 2005 - 08:51 PM
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.
Posted 10 May 2005 - 08:52 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 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 10 May 2005 - 11:37 PM