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There's nothing like facts...

Test, redesign, and retest. That's the plan.

The most unusual part of my 'bot is the saw blade, so my development process began with testing the saw blade. I built a test stand out of hardwood plywood with plenty of room to install the saw blade and prototype components. Part of the blade can be exposed by removing a cover plate, allowing me to bring test targets into contact with the blade.

The test stand

This thing is about thirty pounds of plywood, most of it doubled up and epoxied together.

The test stand (800x600 JPG)

In the first configuration, I used a surplus motor, the famous "EV Warrior", with a fan-belt transmission.

The first test (2.2M QuickTime movie)

At roughly 500 RPM, about one-tenth of the target speed, the blade is easily able to chew through soft steel. The test piece is a piece of steel channel from the hardware store. The blade took chips about a quarter-inch wide and a few thousandths of an inch thick. Subsequent modifications to the blade hub reduced friction and vibration, bringing the blade speed up to a measured 900 RPM. That's about as far as I could go with the EV Warrior, which is not terribly strong.

In the final configuration, I plan to drive the blade with an electric motor turning at 15,000 RPM through a 3:1 reduction gear to yield a spin rate of 5,000 RPM-- a tip speed of about 180 MPH, with a stored kinetic energy of about 11,000 Joules. The motor I plan to use should be able to bring the motor up to full speed in twenty seconds, but it'll be moving fast enough to do serious damage within just a few seconds.

Great Balls of Fire! (5.7M QuickTime movie)

Here's my first big pyrotechnics show. The blade, turning here at about 1,000 RPM, is cutting into a small titanium plate, about 4"x4"x0.60", mounted to a swinging arm controlled by a string. Titanium burns nicely when it gets hot enough, and the chips flying off the plate were certainly hot enough. The video clip includes a view of the plate after the cut. Even in just a few seconds with very light pressure, the titanium plate was cut halfway through. The wood behind the titanium plate was charred pretty good, too.

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