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View Full Version : How much power has a toy steam engine?

EinsteinsHund
06-01-2011, 01:29 PM
A friend of mine has developed a nice educational program which uses a toy steam engine like this (http://wilesco.de/wilesco/index.php?option=com_content&view=category&layout=blog&id=2&Itemid=4&lang=en). We are both wondering how much power such an engine can provide. Here are the technical specs (http://wilesco.de/wilesco/index.php?option=com_content&view=category&layout=blog&id=117&Itemid=129&lang=en) for the engines, but unfortunately, power is not given. I googled it to no avail, so I'm counting on my fellow dopers to know the answer.

Scumpup
06-01-2011, 01:38 PM
I had one of those when I was a general science teacher. They'll run at a pretty high number of rpm's, but no real power. Mine came with a little generator, manufactured by the same company, that the steam engine was supposed to turn causing a flashlight bulb to glow. The engine didn't generate enough power to turn the generator, even at a full head of steam. Putting any load on it at all would stall it. So, basically those toy steam engines produce just enough power to turn their own flywheels.

XT
06-01-2011, 01:44 PM
I'm not sure how to calculate it from those stats, but IIRC Power is work over time, where work (force times distance) is in a unit like joules and time is in seconds. I suppose you could use F=MA to calculate force, then using that over some distance get work...then use work over time to get the power. That's off the top of my head though and it's been decades since I took physics in college.

BTW, as an aside those little 'toy' steam engines can be kind of dangerous sometimes. They aren't really toys and need to be treated like any tool that could be potentially dangerous.

-XT

EinsteinsHund
06-01-2011, 01:50 PM
BTW, as an aside those little 'toy' steam engines can be kind of dangerous sometimes. They aren't really toys and need to be treated like any tool that could be potentially dangerous.

-XT

Oh, don't worry, the training is for adults and is to be held in a professional situation.

EinsteinsHund
06-01-2011, 01:54 PM
I had one of those when I was a general science teacher. They'll run at a pretty high number of rpm's, but no real power. Mine came with a little generator, manufactured by the same company, that the steam engine was supposed to turn causing a flashlight bulb to glow. The engine didn't generate enough power to turn the generator, even at a full head of steam. Putting any load on it at all would stall it. So, basically those toy steam engines produce just enough power to turn their own flywheels.

So one can assume that the power is less than 3 to 5 W, if it's not enough to light a flashlight bulb?

UncleRojelio
06-01-2011, 02:25 PM
These steam powered R/C toys (http://www.crabfu.com/steamtoys/) generate enough power to move themselves.

FasterThanMeerkats
06-01-2011, 04:21 PM
A couple hundred My Little Pony Power (MLPP).

Snnipe 70E
06-01-2011, 11:12 PM
It has been to many years to remember how to calculate the power of a steam engine, but you do not have enough information.
You need to know The mean effective pressure in the cylinder. RPM, bore and stroke.

Francis Vaughan
06-02-2011, 02:08 AM
There are a range of toy steam engines. The most common use a simple oscillating cylinder and a similarly trivial valve system - consisting of nothing more than a couple of holes in the cylinder. They use a spring to hold the moving cylinder against a stationary mount, and thus can maintain only trivial cylinder pressure. They are pretty idiot proof. These steam engines produce essentially zero power. As observed, they can just about keep themselves running, or with very high gear ratios move something very slowly. Typically trying to run even a small generator will stall them as soon as the generator is connected to an appreciable load.

The steam engine in the link shows a proper valve gear and would likely produce some small but useful power, and probably would run a small generator. But as noted above, there isn't enough information to know what they power would be. In small models like this frictional losses can dominate, and so a theoretical power may turn out to be still very optimistic. If you have a running system, just load the generator with a set of known resistances and calculate the power. There is a nice little educational experiment in doing just that. (I would expect that there will be a peak power found with one particular load, and loads both larger and smaller will result in less overall power delivery.)