Idea: pneumatic tool as prime mover

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Steam Captain
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Idea: pneumatic tool as prime mover

Post by Steam Captain » Wed May 20, 2020 11:34 pm

I accidentally stumbled upon pneumatic tools and did some research of how their inner workings look like. They are rotary vane motors. And although they seem to be quite hungry and they for sure don't look good as an engine, they might be a neat mechanical energy source for some temporary on-board applications like an engine-independent water/bilge pump or something like that. At least for the more unconventional kind of steam boater (is there even a conventional steam boater).

I already see a workshop full of pneumatic tools being tapped to a vertical fire tube boiler before my eyes. :D
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fredrosse
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Re: Idea: pneumatic tool as prime mover

Post by fredrosse » Tue May 26, 2020 7:55 pm

Rotary steam motors, including the sliding vane type, were all the rage when the demand for high speed steam engines was present in the 1890s. This was to find a steam engine appropriate to the high speeds associated with the new technology of electric generators. Virtually all of them were unsuccessful because of their rapid wear and low efficiency, and high speed steam engines were quickly developed for generator service.

When centralized electric generation was developed, steam turbines took over the generation industry, and continues to this day as the most prominent prime mover for electric generation service. About 80% of all the world's electric power is from steam turbines. So much for thinking that the "Steam Age" ended decades ago. Today's steam power is hundreds of times more than the era generally referred to as the age of steam, but it is not seen by the public. I guess it is the same as the USA most popular non-spectator sport, which few people can identify, because it is not seen by the public.

Steam turbines however are less useful in smaller sizes, and hence anything below a couple of hundred horsepower has an efficiency lower than a reciprocating steam engine. Yes, small steam turbines can be made with reasonable efficiency, but that generally requires an operating speed far in excess of a few hundred thousand RPM for a 1 kW machine. Go and find the right gear reducer for that one!

(sorry for the short detour, back to the subject:)


The rotary air motors might make a reasonably functional small source power, as Captain suggests..."they might be a neat mechanical energy source for some temporary on-board applications like an engine-independent water/bilge pump or something like that." If used in steam service the components and seals would need to be good at steam temperatures, and lubrication would be constantly required.
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Re: Idea: pneumatic tool as prime mover

Post by TahoeSteam » Wed May 27, 2020 2:45 pm

The sliding-vane air motors have been used for a few fun albeit inefficient projects out here. I believe Roger McGuire even powered his steam trail bike with one many years ago. I'll have to look in the home video archive and take a look.
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Re: Idea: pneumatic tool as prime mover

Post by Steam Captain » Sun May 31, 2020 4:11 pm

Interesting. Thanks for the input. Yeah, I remember reading the "Douglas-Self" sites. He lists a whole lot of rotary steam engines and they all seem to have suffered from leakage and/or irregular wear at the sealing elements. My idea was my logic: If pneumatic tools are using vanes, they seem to have worked out the sealing problem to a useful extend. The only question is how the change to steam effects the innards (Does it rust fast. Does it get stuck due to thermal expansion.). But it's interesting someone already had the same idea with pneumatic tools. Even though it might not be appealing to many steamboaters using it as the "engine". Imagine inviting the family for a trip on your steam boat and all they see is a small knob being bolted to the keelson: "That's the engine."

I've run some numbers using the given air consumption of those tools and they do need around the full output of a steam launch boiler (I keep it simple with this very general statement). So, it is clear one wouldn't run a pneumatic tool while the engine is running. At least not for all too long. But since pneumatic tools are lying around in many workshops and it doesn't take a whole lot of effort to strap a hose to a boiler and a pneumatic tool, it might be an out-of-the-box option just to try it out.

What enticed me to open this thread was this spontaneous idea in the back of my head while seeing these tools: There are situations when the engine isn't running. For example while being fastened to a jetty. To keep the steam pressure in check, the steam could be run through a pneumatic drill, which drives a bilge pump for example. Or it runs an alternator. OR it is used as a redundant pumping system or one could even design an emergency drive with it.
The applications are just limited by the user's imagination (well, and the boiler's output).

Hello Tahoe: I would really be interested in seeing that video. It doesn't need to be immediately, if you can't find it right now, but if you find it some day, I'd really be interested in watching it.
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