Duplicating (mostly) a real part - which CAD program ?

I'm mounting new front calipers on my motorcycle, and the calipers on
this bike (83 Goldwing) mount to an unusual "swinging arm".

The new calipers will require a new swinging arm .. no way to use the
current one and modifying it is not really a good idea (in case this
slightly mad idea doesn't work out).

This means a block of Al 3" x 3" x 8" with maybe 80% milled away. (No
chance I'd trust this to a casting).

Lacking drawings or dimensions for _anything_, the final shape will be
determined ad hoc.

However, the initial shape (in plan view) and the location of three key
mounting holes _is_ predictable, and it would be nice to CNC this initial
shape.

I see taking a pic from straight above, feeding it into a CAD program and
then tracing the outline.

However, I do not know of a (free or low cost) CAD program that allows me
to put a picture down as background and trace around it on another layer,
creating a DXF out of this layer.

Any thoughts ?

Thanks in advance.


Alan


--

Alan Rothenbush
Academic Computing Services
Simon Fraser University
Burnaby, B.C., Canada


The Spartans do not ask the number of the enemy, only where they are.

Agix of Sparta