Hi,

I think that I would use a steel disk bored to fit the shaft and bolted to
the aluminium base. I might use two steel disks (one on top one below) and
through bolts. Think pipe flanges bolted on imho. The keyway could be
engaged by a steel pin that would fit into a machined rectangular hole in
the aluminium plate, and be sandwiched by the steel plates. The reason I
say this is, that aluminium is maleable and will not hold its shape around
the shaft, it will develop play rapidly.  This will also make it easier to
machine things I think, you would only need a drill and a metal saw that
fits the round hole to make the elongated hole for the pin. The pin could
be a matching drill bit's shaft (to match the keyhole). You can stack
several pins in the slot if the aluminium is thick enough.

Maybe you can get away with just one steel plate. You do not say if this
is load bearing (axial, bending, etc). Imho think pipe flange. I saw your
radar pages and I wish you good luck. If I'd have to do it I'd visit an
auto scrap yard and buy a wheel with its semiaxle and bearing (not a
driven wheel), take it to a welder and have the semiaxle welded to a base
made of another wheel without its axle and bearing (why not) or some
suitable sturdy base, like a tripod made of 3 short 1.5" pipe segments.
Then I'd build everything on the moving platform on the now horizontal and
free spinning wheel. This is a good quality low friction and low play
bearing that can take about of ton of axial force without too much trouble
and still turn easy.  This trick has been used before to mount antennas
and telescopes.

hope this helps,

Peter

On Tue, 30 Apr 2002, Sean H. Breheny wrote:

>Hi all,
>
>I'm trying to connect a drive shaft to a piece of aluminum plate. The way
>I'm attempting to do this is to pass the shaft through the plate at a 90
>deg angle. The shaft has a keyway in it and I'm going to make the hole in
>the plate have a small tab that will fit into the keyway. I need to find
>out how much torque can be applied before the tab will break off. I know
>this probably has something to do with shear strength (and will involve the
>dimensions of the keyway, diameter of the shaft, properties of the
>aluminum, etc.) but I don't know what method to use to figure this out.
>This is only a hobby project so all I need is a reasonable estimate. Can
>anyone help me out?
>
>By the way, the project (rotating platform for the antenna of my weather
>radar project,
>http://www.rocket-roar.com/BT/wsr.html ) DOES have several PICs in it, so
>this is at least remotely connected ;-)
>
>Thanks,
>
>Sean
>
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