"Searcher7" wrote in message
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On Apr 11, 8:32 pm, "Ed Huntress" wrote:
"Searcher7" wrote in message

...



I came up with a new design for a video game joystick. The problem
with the original design that I am attempting to improve upon involves
wear of the metal parts that move across each other.

My goal is to A) create it so that the parts that move against each
other are inserts that are easily replaceable. And B) increase the
wear resistance through use of a better metal.

The action of the up/down joystick causes wear at the end of a rod
that turns inside of a matching diameter hole.

If you look at the picture of the joystick assembly in this link, you
will get an idea of what I'm referring to.
http://i290.photobucket.com/albums/l.../Joystick%20Pr...

I know that the easily machinable metals tend not to be wear
resistant, but I'd appreciate ideas on the best metals to use for
something like this. Metals that I can machine on my mini lathe or
mini mill.

Thanks a lot.

Darren Harris
Staten Island, New York.

Can you show us some close-ups of the actual wearing parts? Especially so
if
you have some disassembled. That would make it easier to judge.

--
Ed Huntress

Ok, I just took a picture of the two key parts.

http://i290.photobucket.com/albums/l...s/IMG_0442.jpg

The small "knob" protruding from the piece on the left fits into the hole
of the large piece on the right.

..When in use it only turns within about a 20° range, but over the
course of 100s of thousands of times the hole in the 1/16" wall gets
larger.

Thanks.

Darren Harris
Staten Island, New York.

Hmm. As it appears in the photos, the "knob," or shaft, looks like its
diameter is a lot smaller than that of the hole. Is that correct?

Second, you mention "up and down," and now "turning...within about a 20°
range." Does it do both?

When similar issues have come up before I've recommended a commercial drill
bushing for the replaceable hole, and a hardened steel shaft turning/sliding
in it. That's hardened steel on hardened steel -- the highest-quality
bearing that was used a century ago, when internal-grinding spindles ran in
plain bushings at 10,000 rpm. They didn't even lubricate them. They ran as
pneumo-dynamic bearings on a film of air. But the combination was also used
at low speeds with oil lubrication.

Anyway, the point that Tim brought up is a valid one, but the key issue in
wear bearings is the relative wear of each of the two parts, and the reasons
that softer material (bronze or brass) are often used with steel have to do
mostly with the work-hardening property of the copper-alloy bearings; their
compliance before they work-harden; and their friction coefficient when
running with poor lubrication. There is a material-to-material friction
coefficient that enters into it, and mild steel doesn't run well in
anything, except some plastics. Hard steel on hard steel is one of the best
bearings but it requires accurate fitting. Soft steel on hard steel, or soft
steel on soft steel, are among the worst.

If you decide to try the hardened shaft in a drill bushing, you can get some
tips here on the shaft and sources for bushings. I don't have any such
sources anymore.

Good luck! I'd run over to see it if the damned tolls to Staten Island
weren't such a rip-off. g

--
Ed Huntress