Recent article on home made gears ?

    Nobody makes their own ordinary gears unless they're into machine shop work
for its own sake.

    However, if you're really good at machine shop work, there are situations
when gear teeth as an integral part of another part can be useful.
See Rosheim's "Robot Evolution" book.

                John Nagle

:     Nobody makes their own ordinary gears unless they're into machine shop work
: for its own sake.


Which was exactly my thought when I read the article, so I didn't
bookmark/notate it.  :-)

I am looking for an alternate way to make my motorized turntable (robot
head). I was looking for a cog-belt type pulley in the range of say 6" OD,
something that would fit on the outside of a hardware store lazy susan
bearing. I haven't seen anything in that size range.

Then I (thought I) rememberd this article, and thought cutting something out
of wood on the scale might work. But I can't find it.



--
==========================================================
Chris Candreva  -- chris@westnet.com -- (914) 967-7816
WestNet Internet Services of Westchester
http://www.westnet.com/

work

The proper cross section for a gear tooth is a cycloid curve, not
a circular curve.  If you made it with a drill, it would be noisy, with
high friction and lots of backlash.  It would be crap.

To make good gears you need a vertical mill, a rotary table and
a gear cutter.  The right tools will probably cost you $500 to $700
new from Sherline or Taig.  You could get them used for maybe
half that.  Of course, you could use them for much more than making
gears, and if you are serious about robotics, you will probably end
up buying a mill, lathe and rotary table eventually anyway.

For small gears, you can buy extruded brass or plastic "pinion wire".
When you need a gear, just slice off a piece.


Maybe a bicycle chain and sprocket?

You can always attach the timing belt sprocket to a central shaft of the
turntable (most turntables don't have a shaft, but you can add one
easily enough). This approach has the benefit of allowing for quite a
bit of misalignments.

Or, a plastic flexible rack -- as in rack-and-pinion -- also works. I
use them in various homebrew animatronics I build for the family. You
glue or otherwise fashion the rack piece to the side of the turntable. A
pinion gear on the motor engages the rack. Alignments are more critical,
and you may need to put the motor on a spring load.

-- Gordon

: You can always attach the timing belt sprocket to a central shaft of the
: turntable (most turntables don't have a shaft, but you can add one
: easily enough). This approach has the benefit of allowing for quite a
: bit of misalignments.

That's what I'm doing now. In fact we beat this part to death a few months
ago (use a torsion spring on the motor, I wanted to use the pot for
tenstion, you said it was a bad idea . . . . :-) This was the pic I posted
http://www.westnet.com/~chris/Robots/RobotHead-3.jpg

Now I feel bad. I REALLY apprecaite everyone jumping in with suggestions --
It just we all went through this already :-) I haven't had time to try out
the list from last time. For some reason this idea came to me this morning,
it was just bugging me that I remembered reading this but couldn't find it.

So I'm going to assume I either made up this article, or it was such an
abysimally bad idea I was right to toss it in the first place.


--
==========================================================
Chris Candreva  -- chris@westnet.com -- (914) 967-7816
WestNet Internet Services of Westchester
http://www.westnet.com/

Now I remember!

This approach will work as long as the pot is not connected to the same
belt as the drive. Otherwise there is too much overhung load on the
shaft of the pot, and it may wear out pretty quickly.

-- Gordon

On 26 Mar 2006 18:01:54 GMT, "Christopher X. Candreva"



If the head only turns something like 180 deg. (not contineous
rotation), then you might could use string secured around the
turntable edges and connected to a double spool on the motor,
Since the string is firmly attached to the spool and the
turntable, you don't have to worry about slipage. The spool both
takes in the string in one direction and lets it out in the
other.

    --You might want to see what Bryan's doing with a cnc controlled
wood router: http://www.bmumford.com/xyz/details/gears.jpg
    

--
        "Steamboat Ed" Haas         :  Concave, convex, con      
        Hacking the Trailing Edge!  :  carne: all is Zen..
                          www.nmpproducts.com
                   ---Decks a-wash in a sea of words---