Projects In Metal

As The Propeller Turns

One of the more interesting builds that went in to this steam launch is the propeller that moves the launch through the water.
Initially, I did not really put much thought into the propeller, and going through a selection of propellers I had lying around from the radio controlled model gas powered boats that I built at one time or another, I choose a propeller that looked about the right size. Well, wouldn't you know it, when I steamed the launch for the first time, I could not keep a head of steam up. I quickly realized that the pitch of the propeller which was meant for a fast turning gasoline engine was to fine a pitch for a steam engine..

Back in my shop, I did the work-up that should have been done initially, as I realized that I needed a propeller with a pitch meant for a slow turning high-torque steam engine, I rolled up my sleeves and went to work constructing a steam boat propeller. This 4 bladed propeller is 2.5" in diameter, and with a very coarse pitch that is suited to a slow turning steam engine. With the propeller completed and the launch back in the water, it was a whole new ballgame.

With 30 psi showing on the pressure gauge and the throttle wide open, you need to not quite break in to a run to keep up to the launch as it moves along at top speed, and the good thing is that the boiler can maintain a head of steam while doing this.

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