On Jan 24, 6:24*pm, Gunner Asch wrote:
On Sun, 24 Jan 2010 14:39:01 -0800, "anorton"





wrote:

"mac" wrote in message
...
My Garmin NUVI 500 for my bicycle uses a ball mount. The one that I
purchase from a third party is hollowed plastic and broke from
vibration. I adapted the broken piece to my light bar and it broke
again at the ball.
I toyed with several methods. One buy a ball turning tool, two find a
ball and mount it to a post. The ball was .670 inches and I didn't
find any one that size.
I decided to make a form tool for a section and move around the ball
shape. The critical section is smooth as the female move up to the
major diameter and that the major diameter size is maintained. The
down side also needs to be smooth for a short distance.
I Machined a rectangle piece of aluminum leaving the head 3/4 inches,
in three direction. The post section is 3/4 X 1/2 inches. Pictures are
here.http://www.billcotton.com/nuvi500.htm

It looks like this worked well enough for you.

In the optical lens industry, spheres and spherical sections are generated
using a cup-shaped grinding tool. The workpiece is rotated, the tool axis is
at an angle to the workpiece and spun more quickly. *The edge of the cup is
aligned over the apex of the workpiece, and then the tool is moved into the
work parallel to the workpiece axis. *Here is a rough diagram of how it
works:
http://www.britannica.com/EBchecked/...68/Cross-secti...
The radius generated will depend on the diameter of the tool and the angle.
It can make very precise spheres that are the ready for (very) fine grinding
and final polishing. *Perhaps you can do this with a tool post grinder on a
metal lathe.

Om a metal lathe..CNC..it can be done in one simple operation.

http://www.omni-turn.com/Pages/Examp...el%20ball.html
Yes if happen to have a CNC around, that would've been my choice.
The history of my home machine shop, It was a belt sander and drill
press with a cross slide vise. I had help a friend set up his three in
one machine. I thought that if I could come up was a reason I would
buy one also. A little while later I read about a free coasting
gearing for a tandem bicycle. I shopped around for a unit to modify
our tandem bicycle. A bicycle shop wrench, that the name they go by,
said that this type is just a couple of BMX free wheeler mounted. The
shop wanted 500 dollars for the set of gears. That was my excuse to
spend 1500 dollars for the three in one. Bolt circles and other
calculation made for a fun take off for my shop.
I docketed many of the projects on my web page and posting on in this
group.

If you think there may ba a market for your new mount..Id be happy to
turn you onto people who could make these and other parts cheaply and
quickly. *You might have a new product!!!

Gunner
Thanks, but I don't see a market, Several are made for motorcycle that
are stronger.
*Whenever a Liberal utters the term "Common Sense approach"....grab your
*wallet, your ass, and your guns because the sombitch is about to do
*something damned nasty to all three of them.- Hide quoted text -

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