Jensen 20G Model Steam Engine | Live Steam
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Published 2022-11-25
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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Playlists:
Stirling & Hot engines: • Stirling & Hot Air Engines
Model Steam Engines: • Steam Engines
Steam Turbines: • Steam Turbines
Internal Combustion Engines: • Internal Combustion Engines
Electric Motors: • Electric Motors
Fischertechnic Inventions: • Fischertechnik Inventions
Thermal Imaging: • Thermal Imaging
Mindboggling Physics: • Mindboggling Physics
Vintage Computing Technology: • Vintage Computing Technology
All Comments (21)
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What a wonderful machine! Thank you for sharing, sir!
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I had a toy steam engine fired by alcohol when I was a kid. I'd love to build a model tug boat powered by something like this ... RC of course.
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Had a similar one back when I was 11. It got me interested in boilers and steam generation. Later in life I became a 3rd Class Power Engineer and went on to a lucrative career in building maintenance.
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I still have my Jensen engine I got for Christmas as a kid!😃👍🛠️
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This has a lovely sound!
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you have all the cool toys
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I had a Wilesco, and did infact set the carpet on fire in my room running it. A Jensen will not give a boy that life lesson. But it sure looks nice!
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Wow a regulator and a reverser. Nice.
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Easily the most elaborate way to power a lightbulb. From electricity to heat to rotational energy to electricity to lightbulb
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had mine for 50 years no gen. and mine burns fuel tablets some of the good old toys
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Wow
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Looks pretty 😍
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I should get out prob one of the rarest engines out there, the 1939 Mamod SC3 I acquired some years ago, in its original box and all complete save missing a drive band and works like a champ, only a handful were ever made due to war breaking out almost the same time and Mamod became a war effort factory turning out precision parts for weaponry and aircraft. After WW2 the design was never resurrected making it uber rare in steam engine circles.
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...They eventually figured out there was a more efficient way to power the lightbulb.
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this model has a larger cylinder diameter, so there is more torque
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Making electricity from electricity. Develishly clever.......................
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Hat die Maschine eine echte Kreutzkopfführung?👆👆👆👆👆😀😀 Viele Grüße aus Germany
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How can u change the speed and make it go slower?
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How can I purchase steam engine locomotive small
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Much Vibration.
