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Old Nov 30, 2002, 01:52 AM
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Joined Nov 2002
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Teflon, Aceril (Delrin)

Hi all,

I've been trying to make some bearings out of Teflon or Delrin tubing. I found the thread to some 20 GA Teflon at: http://www.allelectronics.com/. In the thread this is bored out to .055" ID. I need something that would go up to .125 ID. There's this stuff at: http://www.daburn.com/dtt500.html that starts at .022" and goes up to .75" in like .006" increments but the minimum order is 100' and I'll need a few different sizes.

Anyone know where to get this stuff in smaller lots? Maybe I can talk my way into some engineering samples.

Thanks.

Richard
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Old Nov 30, 2002, 09:37 AM
It's a spiderweb of knit lines
Souderton Pa. USA
Joined Mar 2002
2,641 Posts
Teflon heatshrink tubing

Richard,
I've been able to make teflon bearings by shinking over the appropriate size rod. The wall is very thin and I was never able to get the bearings to stay in place. If you have a lathe I would try turning a bearing with a shoulder on them. 1/8
inch shaft is kinda large what's it for? Another
thought, maybe you could heat form a shoulder on the tubing?
Good luck
Mike cross
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Old Nov 30, 2002, 04:09 PM
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Teflon, Aceril (Delrin)

Hey Mike,

It's for a counter rotating shaft set up so the outer shaft will get kind of big. I'm not so sure it will reach .125" but I just picked that as a arbitrary upper limit. I wanted to use ball bearings but thought that would get really big. Maybe roller bearings?
On second thought maybe the inner could be teflon or delrin and the outer could be roller or ball.
This place has a lot of solid round delrin and teflon: http://www.onlinemetals.com/
It's just the precision boring involved. I do have a Unimat SL.

Richard
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Old Nov 30, 2002, 05:19 PM
It's a spiderweb of knit lines
Souderton Pa. USA
Joined Mar 2002
2,641 Posts
That's not going to be easy! If a heli, have you thought about the old design (full scale) that used 2 counter rotating rotors NOT on coaxial shafts? Each shaft was slanted out and the rotors were geared to mesh.
If you need efficiency, ball bearings will be easier to deal with than trying to make bushings, especially if they will be between the 2 shafts. But small ball bearings aren't easy to find.
As far as materials go, Teflon is slipperier but cold flows. Delrin will resist cold flow better but is not as slick. Some kinds of Polyproplyene are pretty slick and resist cold flow well.
Thanks for the link, I haven't heard of them before.
Mike Cross

Edited to add: Can you do the precision on the outside of the shaft to mate with the bore size you end up with?
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Last edited by mcross; Nov 30, 2002 at 05:23 PM.
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Old Dec 01, 2002, 01:55 PM
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Teflon, Aceril (Delrin)

Yah it hasn't been easy. This all started when I saw this site about a Italian racer prototyped in the '30s with counter rotating props and foreward sweep. I grew up with the Pogo ( and Ryan Vertijet) and was always fascinated with foreward sweep by the Germans during the war and the X-whatever after (someone has a foreward sweep model flying too). I considered the side by side rotor idea but liked the tech challenge of co-axial.
I also saw these sites:
http://home.att.net/~dannysoar2/Payen.htm
http://home.att.net/~dannysoar4/PayenKeller.htm
http://home.att.net/~dannysoar/FantasySectionIntro.htm
I was blown away that there are groups that are into building things that have never actually flown.
I have two working prototypes. One built on a GWS IPS gearbox. (nice small ballraces here made China but other sizes available from who? ) BTW the nice long shaft from BG Micro item FAN1037 seems to be an exact match for the IPS shaft. Nice snap ring groove in it, other end you're on your own. There's a latching hall effect device in this motor also that was very helpful in some CD-ROM motors I played with but that's another story. The shafts are pretty conventional, steel (piano wire) in brass and brass on brass all from standard hobby stuff all running in the IPS races. The other has ball race outers salvaged from an Omron fan. Had to pare down the brass OD to fit the IPS bearings .120 or thereabouts and bore out a piece of aluminum tube .375 X .035" (from that online metals site) to accept the Omron bearings about .350". BTW those sites came from links found looking for Unimat parts. Any way the overall OD is pretty big hence the look at Teflon or Delrin. I see that American Science Center has some Derlin bushings and I live about 15 minutes away, so maybe I'll be turning down some Derlin (which seems to be a combination of Teflon, Polyoxymethylene, Formaldehyde Homopolymer and Delrin). Hope it turns better than virgin Teflon. The problem is usually the boring. To get it precise requires buying some precision size drifts to true up the bore. They do have a 1/32 bore already, so that could help. Turning down 5/16 OD will be a pain. Still 8 for $2....

Richard
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Old Dec 01, 2002, 04:57 PM
It's a spiderweb of knit lines
Souderton Pa. USA
Joined Mar 2002
2,641 Posts
Hey Richard,
Sounds real interesting, what are you using for gears? I used a diff from an RC car once for counter rotating props for an airplane. It was easy cause the gears and bushings were already there. I had trouble making props thou. Are you
trying to make a pogo? Cause that would be neat!
Mike Cross
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Old Dec 01, 2002, 07:33 PM
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Joined Nov 2002
67 Posts
Teflon, Aceril (Delrin)

Mike,
Mostly the gears are from Dave Lewis and GWS. I also have a ton of gears I've salvaged from VCRs, printers, floppies etc.
As far as props are concerned, I've cut some from styrofoam with a hot wire cutter. I also subscribe to Microflight and read an article about making props out of 1" plastic miniblind slats, a hunk of carbon rod and a square stock brass hub. This has the advantage of allowing you to vary the pitch by rotating the rod in the brass. Usually I just hot glue the slat to a piece of plastic I beam. Works great. I have a blind that's getting shorter and shorter.
As to the Pogo, yah that would be a great model, especially since many motor battery combos are now able to prop hang. That said I'm more of a gearhead experimenter type than a pilot.

Richard
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