Watch the Jensen 20G electrically heated steam engine power plant running and driving a small generator with a lamp post.
Jensen Steam engines hold an interesting position in the market of model steaming. Build quality is typical of American-made hardware: very robust, somewhat overbuilt, not too many decorative details. No flimsy parts that break easily, and no tinny boilers. All important parts are made from thick gauge materials. This model steam engine power plant oozes quality, from the hardwood plywood base to the boiler and engine. Sure, it doesn't have the "Stuart models" attention to detail and historical authenticity. But it's robust, very easy to operate, and has lots of playability. And it's a lot less expensive than a Stuart steam engine plant.
Specifications
The double-acting cylinder's bore and stroke are 3/4" (19 mm), so this is considerably more powerful than typical "toy" steam engines; and it's not a toy, but more of a collector's item. As you can see in the clip, its a quite powerful and fast steam engine capable of driving a small generator. It can also drive multiple accessories. The steam for the large cylinder is generated by a 660 watt electrical heater inside the boiler.
Advantages of electrical heating
Using an electrical heater for a model steam engine is perhaps not for the steam purist who would say that model steaming must involve the combustion of some sort of fossil-based fuel. However, there are very significant advantages of using electrical heating: It's much less expensive, and it's much safer. No fuel tabs, no methylated spirit burners, no candles, no gas canisters and no fumes. You can run the engine indoors in the kitchen and it will barely smell any different than a water cooker. Just add water to the boiler and plug in the engine to a wall socket, and the electrical heater will build steam in a few minutes.
Other interesting features
Some other aspects that I haven't seen on other commercially available finished steam engines is the Stephenson reversing mechanism and a genuine large AC generator with a lamp post. This is a very nice touch. There's no "cheating" by using a cheap DC motor for a dynamo. This generator is clearly made by Jensen for generating AC power for their engines, and being able to watch the large coils of the generator as it spins and generates power adds to the authenticity and learning experience.
A lesson on steam engine efficiency
Using an electrical heater actually adds significantly to the learning experience: Since we know that the boiler is heated with a 660 watt heating element, and since we can measure the voltage and current on the lamp post, it is obvious that the steam engine's energy conversion efficiency is quite low. If we assume we can power a 1 watt bulb, the system's efficiency is 0.15%, which is appallingly low. In effect, we're spending 660 watts to generate 1 watt of power. Where is the energy lost? Some is lost in the boiler as some heat is simply dissipated to the surroundings instead of being converted to steam. Some is lost in the steam pipe and in the engine due to being cooled down. Some is lost on account of steam leaks from the boiler, whistle, steam valve and due to leaks in the engine itself. But the vast majority of the power is lost in the exhaust pipe: Water in steam form contains lots of energy, so lots of energy is lost simply because steam is released to the atmosphere. If you want to know more about the thermodynamic theory, search for "Carnot cycle".
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24 ноя 2022
