Not a bad design...
... I've seen power supply units which get hotter and give off more steam.
A Swedish schoolboy has built a miniature steam engine to power his Raspberry Pi. It is a piece of absolute engineering beauty. Forum user “Alexzpro”, posting in Swedish on the Svenska Elektronikforumet, put up a video he had made of the power plant for his Raspberry Pi. Alexzpro's generator is a small compound steam engine …
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Not only would a propper drive belt last longer it would be more efficient. The elastic band on the tension side stretches and on the opposite side contracts. The energy to stretch the band will be dissipated as heat in friction as the band passes over the spindle and absorbed into the elastic band as it passes over the flywheel. As a pure guestimate I would say that 30% of the energy is being wasted.
"..Alexzpro's generator is a small compound steam engine... "
Don't think so. A compound uses exhaust steam from a high pressure cylinder to drive a lower pressure one. This means the low pressure cylinder is bigger than the high, and both look the same to me.
Now, some may say that they could be bored out to different diameters. True, but it looks like the exhaust runs from both cylinders, not just one as would be the case with a true compound.
Oh, and it does look like a reversing gear to me too.
al/ waiting for a pint...
And from the footnote:
"The regulator shuts once a small amount of hot steam has entered into the cylinder."
No, it doesn't, the regulator is essentially just a tap, that restricts the flow-rate of the steam. The amount of steam that enters the cylinder is controlled by the valve-gear. In a simple model, it is probable that the cylinder (head) gets filled with steam at (almost) boiler-pressure.
I agree, this is not a compound engine, it is just a dual cylinder engine. Neat though. I made a somewhat similar project when I was ten. My Grandfather gave we a model stationary steam engine. It was originally designed to run on coal but as such never quite raised enough steam to be interesting. My father had created, in his youth, a gas burner for it. This ran on coal gas and looked quite lethal. Not being able to get a supply of coal gas I designed an electric fan driven parafin burner. Actually more like a flame thrower,and quite lethal. You could drive a small generator from the engine. The generator produced just enough to power the fan. Flames would leap from every hole. My Mother screamed with fright while my Father laughed.
My advice to any parent who wants their child to be an Engineer: build them a shed and don't ask too many questions. A few bunt fingers are a small price to pay for the pure joy of making something work.
"[...] wish I still had my meccano stream engine from the 70's"
The standard was the Mamod steam engine with a little meths burner. Not sure why my parents bought me one - probably I pestered - none of my pals had one. Couldn't afford to buy any accessories - and for some reason I never used it to drive things with my No2 Meccano set. Over the years various mechanical projects made me wish I still had the latter with its beautiful brass gears.
Somewhat surprisingly Mamod are still in business. Here's their steam
Back in the 1960's I used a Mamod No 1 boiler to build a Gauge 1 Live Steamer. More like a 'Thomas' loco than anything running on BR but great fun. Ran it on the school track. Far too dangerous for todays softies though. What with all the risk assesments and H&S rules. Shame really.
Gauge 1 is 10mm/foot scale for those who don't know.
" Far too dangerous for todays softies though. What with all the risk assesments and H&S rules. Shame really."
True. I started up by buying radios and tvs at jumble sales, often they needed repairing. My parents often saw me launched across the room after having received a huge shock. They look on smiling thinking that i was a real card. They never tried to curb my dangerous pursuits and it formed me and made me the man I am today.
Nowadays every special forces mission kicks off with a risk analysis and the health and safety officer is consulted. Seatbelts on toilets will be the next thing.
I still have my Mamod engine. It's a basic unregulated one with a hexamine burner and grease bearings. By dripping oil onto the bearing surfaces I could get it to run so fast it would shake itself apart.
Those Stuart models look damn good!
Still got the Mamod engine in the loft - decidedly used, but still in (most of) it's box. An early enough one to have the meths trough and not the solid fuel blocks.
For some reason my grandad decided that it was an ideal present for a 3 year old boy ...
He's using a linear regulator (plain 7805), which, apart from simply dissipating the voltage difference as heat, has a current limit of one amp. Which is just a tad low for booting a Pi, and some extra capacitors won't help you there.
On the forum they're talking about him having to fit a switching regulator instead.
"On the forum they're talking about him having to fit a switching regulator instead"
The "buck" down converters are very cheap from the Far East - about £2. The standard module accepts up to 35 volts DC and you can adjust the output right down to a couple of volts. Max current about 2amps.
They also sell "buck" up converters. The one I bought had an output capacitor marked as 35v - and it exploded during initial adjustments while I was trying to get a reading on the meter. Others advertised with the same nominal max 35 volt output had a 50v capacitor - which seems more sensible.
From the article:
> the Pi's greater demand for juice when it boots causes a voltage drop big enough to force the mini computer to reboot.
I'm amazed that such a small steam engine can produce enough power to run a minicomputer as well as a microcomputer. Is the minicomputer lurking in his dad's attic?
I'm amazed that such a small steam engine can produce enough power to run a minicomputer as well as a microcomputer.
I can't readily find actual power output numbers for the D10, but doing a bit of arithmetic with dimensions and data for other models, I end up with 300..400W at the crank*. With a suitable generator and voltage regulating gear you might indeed be able to run a last-generation '11 CPU with a bit of memory and a modern** disk.
It won't be a fully kitted-out /70 with a bunch of RM05s and a TS11.
* But as I'm not a steam engine surgeon, this could be totally off.
** SATA interfaces vividly remind me of SDA.
the Pi's greater demand for juice when it boots causes a voltage drop big enough to force the mini computer to reboot
I assume "the mini computer" refers to the Pi*. So what you're saying is that the Pi's demand for juice when it boots causes it to reboot. Whereupon its demand for juice causes it to reboot.
I'll have to stop there, as I can't stand typing "demand for juice" any more.
* Unless there's a PDP-11 or the like in the setup, which rather detracts from its simplicity.
"I've noted your comment and instead of using a hydro-carbon source, I've adapted the engine so that it runs of geothermal energy instead. With the assistance of my father, I've bored a hole through the floor of the school gymnasium, through several layers of topsoil, alluvial deposits and bedrock until the shaft is sitting just above an active lava tube that I identified through a series of seismic surveys."
"And that provides the heat to power the engine?"
"Good lord, no! The temperature at the termination of the bore site it a mere 90°C. No. We need far more heat energy than that. The bore hole is where I'm going to ram this small thermo nuclear charge in order to crack open the Earth's crust and reactivate the dormant volcano about three miles to the south of the town... the resultant volcanic eruption will provide enough energy to boot the computer and we should hear it auto-playing Für elise through the midi-emulator for about 20-30 minutes. Before we all die of sulphurous gas emissions, and ash suffocation."
He's using too small a regulator. The generator is capable of delivering 17V at 1A, so 17W, but he's using a 7805 linear regulator with a current-limited output. A larger capacitor won't help; a switching regulator would be able to convert 17V @ 1A to 5V @ 3A, which would run the Pi without dropping out.
And a bleed resistor for a low-voltage buffer? Total overkill.
Bicycle dynamos perform just fine, generating AC without an exciter coil. Most motorcycle dynamos also have a permanent magnet with a stationary coil; only Bosch-type generators use an exciter coil for which you theoretically need the battery to have some charge to bootstrap the process (but often the rotor tends to have enough permanent magnetism to do so even without a battery).
Generators with an exciter coil are easier to regulate to a particular output voltage even with a simple mechanical voltage regulator. For a dynamo you'd need a hefty zener or robust stuff that shorts the output.
I think the steamnote is a little incorrect.
The regulator is a throttle, you open and close it to control engine speed overall.
The description in the steam note relates to the Valves, opening for a short time, determined on some engines by a variable cutoff adjustment (e.g. a great big lever on a steam locomotive).
This then allows the steam to expand, expending its energy pushing down the piston.
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