Re: boat propulsion - miniature computer-controlled steam plant?

"Peter Fairbrother"  wrote in message news:usi5v7$2ea8v$1@dont-email.me...
On 07/03/2024 00:51, Jim Wilkins wrote:

You machine each blade with two hole saw cuts like this into the rim of the disk:  ((
with a smaller radius on the back one so the blade has a crescent moon profile and sharp edges.

I tried that, but couldn't get it to work with a suitable geometry (for
an impulse turbine) - I had problems with the back edge of the holesaw
hitting the workpiece. If the saw was small diameter it would intersect
the workpiece on both edges, and if the diameter was large enough that
it didn't interfere the turbine blade was too straight.
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I can visualize what you mean, interference limits the blade depth. The blades could be cut deeper with a small end mill if the rotary index holding the disk blank was in a swivel vise (or rotary table) manually turned only far enough to make the cut. The setup might be easier if the disk blank was fixed to a drilled index plate that took up less space, mounted on a vertical surface of a block that centered (or offset) the blank over the vise swivel axis.
I design things like this graphically by drawing the separate shapes in CAD and moving them to touch, for example the front and back circles intersecting at the blank edges, then recording the center coordinates. Trigonometry can refine the precision without much risk of gross error.
I would rough out the gaps first, milling an arc with hand feed pressure doesn't allow much depth of cut and NO climb milling.