Does anyone have any experience with the work this machine is able to produce? From simple computations I get about 200W-ish at 80psi and 3000RPM, but I don't even know if that's satisfying operation conditions. I am looking to build a bigger scale version of this engine, with a guesstimate of ~5x the cylinder volume (if the above numbers hold water), to deliver ~1kW mechanical work to a permanent magnet alternator, so RPM will be fairly constant over extended periods (in some cases several hours). I'd like points of view on both actual power output of the original model and suitable long-term operating RPM. Anyone?
Cygnet Royal power rating
- Thread starter Kjetil
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I built an engine based on the Cygnet Royal same cylinder dia and stroke but different crank and con rod arrangement and external appearance.
Only thing I can add is that on an air pressure of 60psi it does 2200 rpm
Another point of interest is that if you reverse the air flow in through the exhaust it will run backwords:- only slower.
hope this is of some help.
Stew
Only thing I can add is that on an air pressure of 60psi it does 2200 rpm
Another point of interest is that if you reverse the air flow in through the exhaust it will run backwords:- only slower.
hope this is of some help.
Stew
I guess it would act a bit different with steam as it expands, but take those numbers as a reasonable operating point (exercise), and make the assumption the piston mean pressure over the entire stroke is half the valve chest pressure (guesstimate), using the 2PLAN formula with metric units I get 2 * (413685.438[Pa]/2) * (3[cyl]*0.0254[m/in]*0.5[in])[m] * pi*0.0254[m/in]*((5/8)[in]/2)^2)[m^2] * 2200[rpm]/60[sek/min] = 114.389[W]. That is, if piston mean pressure guesstimate is ~OK.
Under mentioned conditions (air at 60psi, 2K2rpm) I'd be content with ~0.8HP, but aiming for 1HP (745W) in case guesstimates are off. We increase stroke volume by a scale factor (S1) of 745W/114.389W=6.51286.
Since S1 is a [m^3] scale factor, our real scale factor (S2) (for the drawings [m]) would be the cubic root of 6.51286, S2=6.51286^(1/3)=1.8675, no?
Plz assess the maths and assumptions for me, some kind soul. This is all new stuff to me.
Under mentioned conditions (air at 60psi, 2K2rpm) I'd be content with ~0.8HP, but aiming for 1HP (745W) in case guesstimates are off. We increase stroke volume by a scale factor (S1) of 745W/114.389W=6.51286.
Since S1 is a [m^3] scale factor, our real scale factor (S2) (for the drawings [m]) would be the cubic root of 6.51286, S2=6.51286^(1/3)=1.8675, no?
Plz assess the maths and assumptions for me, some kind soul. This is all new stuff to me.
This is a model engineering site, not a R&D one giving free development time and information.
I assume this is maybe for a commercial enterprise, in which case a good donation to the site may help smooth the flow of your questions.
I am sorry to take such a strong attitude to yourself and your questions, but many times before, people have tried to use the expertise gathered amongst members on this site for their own ends and money making schemes.
Bogs
I assume this is maybe for a commercial enterprise, in which case a good donation to the site may help smooth the flow of your questions.
I am sorry to take such a strong attitude to yourself and your questions, but many times before, people have tried to use the expertise gathered amongst members on this site for their own ends and money making schemes.
Bogs
I can assure that this is a 100% non-commercial hobby project. Since you question my motives; I plan to run a steam-electric canoe (cedar strip epoxy canoe actually, with a few reinforcements) with battery pack (12V-48V, >1000Wh) and outboard electric motor. I think the commercial value of such a contraption would be minimal even from an optimistic point of view. Woodfired "Rocket stove" type monotube boiler (explosion safe, can still steam you good thou). I'm a lot in the wilderness during flyfishing hatch periods, and I want speed + electricity (speed; we can paddle along with the motor). With electricity in camp, I can work evenings from the hammock (PC; PCB design) when fishing is dull, effectively extending my vacations. So that's actually a commercial value right there, being able to work while on vacation. But you can't put a price on quality time.
Sounds crazy? Sure. It's a crazy world.
Guess the next step will have to be to buy proper drawings and make a SolidWorks model, I can actually put a programmable scale factor on it in SW so I can use the scale I calculated and correct it later until we start to cut.
And I would still be very thankful if anyone has power data of some sort, even if it's just from a car alternator on pulley into some resistive loads. And if anyone notice obvious mistakes in the math, please do tell.
Sounds crazy? Sure. It's a crazy world.
Guess the next step will have to be to buy proper drawings and make a SolidWorks model, I can actually put a programmable scale factor on it in SW so I can use the scale I calculated and correct it later until we start to cut.
And I would still be very thankful if anyone has power data of some sort, even if it's just from a car alternator on pulley into some resistive loads. And if anyone notice obvious mistakes in the math, please do tell.
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Guess I'll just go for 2:1 scale, doubling the drawing dimensions. It is such a compact nice little engine, and there is no harm in overdimensioning it a bit.
Will it be OK to ask advice on this forum during build (regarding materials, etc), or should I try elsewhere?
Will it be OK to ask advice on this forum during build (regarding materials, etc), or should I try elsewhere?
Thanks. I'll probably not go your route with a flashy cylinder using inlays etc, just plain iron cylinders (and pistons) keeping it simple and solid, alu is i guess OK for cylinder cover where you don't have the thermal expansion concerns. But I'll go for external copper tubing like you did, most definitely. I read somewhere you wanted to use brass but had a spacing issue, i guess that was simply for appearance? The rest of my steam tubings are copper so I guess copper is fine for me and way easier.
KJ, I have to say that you have me a bit confused. The way that I interpret what you are wanting to do is two-fold, (1) that you wish to generate electrical power for a camp site environment and (2) are wanting to generate and use same to power a small water craft. My confusion comes into play attempting to separate the two. For such a small craft as a canoe it seems rather silly to me to have to convert heat (a fire source) into steam and then convert that into electrical power, only to have to store said power in batteries and then use that to operate an electric motor to power the craft. Now, having said all of that, can you clarify for us what general arrangement you have in mind please. Is the generating station going to be land based and the power cells charged there and transferred into the water craft or are you planning to have the genset in the boat at all times? If so, how did you plan on getting power to your campsite from it? Would it be possible for you to show us a Crap-O-Cad of the setup you have in mind so we all could get a better understanding and perhaps be of more assistance to you.
Thanks
BC1
Jim
Thanks
BC1
Jim
I have to make the engine and the boiler a common module possible to detach, since the canoe must be transported upside down on a car roof, as a typical vertical fire tube boiler or a monotube boiler as I have in mind will both be a good bit higher than the canoe hull thus making upside-down mount on car roof impossible. I don't have every answers when it comes to condenser tank and water pumps connections, I'll probably have a water inlet through the hull, feeding the boiler pump through some flexible tubing with a valve and connector, or something along those lines.
But, even modulized for car transport, it does not have to be a matter of minutes to assemble/disassemble. It will only be at the start and end of each trip, I'll keep the boiler/engine/alternator module separate from the boat only in car transport and in storage. Battery pack will be separate from the boiler/engine/alternator module, answering your campsite question since battery pack can be brought to the lavvo (tent), genset left mounted in the boat. My campsites are usually by the water anyways, but - no problem.
Steam-electric is inefficient yes, but I cannot have an inboard propeller in a canoe, and still use it for normal paddling, pulling it up on the shore, not to mention transporting it across terrain (a small 2-wheeled cart stuffed in the canoe is used for the purpose). But, my fuel is usually in abundance, so I battle efficiency where I can and leave the rest. Besides, even if I used an inboard prop for propulsion, I'd still need a generator and batteries for my electronics, albeit with better propulsion efficiency, granted. The thought have evolved around countless campfires, thinking about all that energy yet I had little or no electricity (not only PC for work, but flashlights, GPS, phone, possibly some music, etc).
Endurance should be two weeks possibly even more. I can't carry along batteries for the ride, and solar power ain't made for northern countries like mine. Hence steam.
No crap-o-cad drawings just yet, envision a fairly large canoe with a seat at the stern I will use (with the outboard motor). At my legs; some bags of fuel wood, in front of me the boiler (facing me), and in front of that the engine (alternator on bow end of the steam engine). I'm thinking of using a piece of heavy wood bench plate as base for the both motor box and boiler, with steel screen under the boiler and behind it against the box, the engine and alternator will be boxed in a wooden box. The hull of the boat will get some epoxy/woodstrip laminated knees (for baseplate to rest on / mount to). In front of the engine is just cargo capacity and seats (two seats in front of the engine, one of them removable for more cargo space).
But first ofcourse comes the engine itself (will take time) followed by matching it to a permanent magnet alternator (easy), and the DC/DC battery management, which could also function as a load management as we can regulate charge current with charge voltage (electronics and uC prog, easy). But the canoe is the envisioned end use, I was originally going to leave that part out for people not to see me as completely mad.
But, even modulized for car transport, it does not have to be a matter of minutes to assemble/disassemble. It will only be at the start and end of each trip, I'll keep the boiler/engine/alternator module separate from the boat only in car transport and in storage. Battery pack will be separate from the boiler/engine/alternator module, answering your campsite question since battery pack can be brought to the lavvo (tent), genset left mounted in the boat. My campsites are usually by the water anyways, but - no problem.
Steam-electric is inefficient yes, but I cannot have an inboard propeller in a canoe, and still use it for normal paddling, pulling it up on the shore, not to mention transporting it across terrain (a small 2-wheeled cart stuffed in the canoe is used for the purpose). But, my fuel is usually in abundance, so I battle efficiency where I can and leave the rest. Besides, even if I used an inboard prop for propulsion, I'd still need a generator and batteries for my electronics, albeit with better propulsion efficiency, granted. The thought have evolved around countless campfires, thinking about all that energy yet I had little or no electricity (not only PC for work, but flashlights, GPS, phone, possibly some music, etc).
Endurance should be two weeks possibly even more. I can't carry along batteries for the ride, and solar power ain't made for northern countries like mine. Hence steam.
No crap-o-cad drawings just yet, envision a fairly large canoe with a seat at the stern I will use (with the outboard motor). At my legs; some bags of fuel wood, in front of me the boiler (facing me), and in front of that the engine (alternator on bow end of the steam engine). I'm thinking of using a piece of heavy wood bench plate as base for the both motor box and boiler, with steel screen under the boiler and behind it against the box, the engine and alternator will be boxed in a wooden box. The hull of the boat will get some epoxy/woodstrip laminated knees (for baseplate to rest on / mount to). In front of the engine is just cargo capacity and seats (two seats in front of the engine, one of them removable for more cargo space).
But first ofcourse comes the engine itself (will take time) followed by matching it to a permanent magnet alternator (easy), and the DC/DC battery management, which could also function as a load management as we can regulate charge current with charge voltage (electronics and uC prog, easy). But the canoe is the envisioned end use, I was originally going to leave that part out for people not to see me as completely mad.
mklotz
Well-Known Member
With unlimited fuel and all that cooling water available, I would look into the possibility of using a Stirling engine. It would be so much less hassle than trying to run a steam engine in the wilderness.
IIRC, Stirling-powered gensets were air-dropped to the French partisans during WWII. They used them in the forests to power the radio transmitters used to transmit intelligence to the Allies.
IIRC, Stirling-powered gensets were air-dropped to the French partisans during WWII. They used them in the forests to power the radio transmitters used to transmit intelligence to the Allies.
Stirling would be cool, but suggest to me a 1HP+ Stirling engine suitable for a wood burning stove. I've seen Volo's project, but that is a work in development. Steam just seem much easier to realize.
EDIT: When it comes to efficiency, I had an idea about an operating mode I might try, to directly drive a BLDC motor with the 3-phase alternator output (no sensor feedback from the BLDC motor at all, just brute force), but that would probably need a carefully matched BLDC since we have no feedback. This would phase lock prop RPM to a ratio of engine RPM, and we'd be about 70% efficient (relative to steam power) with a good alternator. I haven't really gone into the details of that plan yet, it might work it might not (we could also use tachometer feedback btw, for an electronic control loop). But plan A is using batteries.
EDIT: When it comes to efficiency, I had an idea about an operating mode I might try, to directly drive a BLDC motor with the 3-phase alternator output (no sensor feedback from the BLDC motor at all, just brute force), but that would probably need a carefully matched BLDC since we have no feedback. This would phase lock prop RPM to a ratio of engine RPM, and we'd be about 70% efficient (relative to steam power) with a good alternator. I haven't really gone into the details of that plan yet, it might work it might not (we could also use tachometer feedback btw, for an electronic control loop). But plan A is using batteries.
Looking at the Stuart Sirius (similar rpm but very different setup), claims span from 1/3HP to 0.4HP at 2800rpm / 80psi with 2 cylinders and 1 bore / 1 stroke. Reverse solving the 2PLAN formula for the Sirius ratio valve chest pressure to mean effective pressure yields 1 / 4.45 to 1 / 5.34. If the Cygnet Royal had these numbers, the 2:1 scale model would only yield between 415W to 498W at 3000rpm / 80psi where I expected >1.6kW. I definitely need some help testing, sourcing or calculating power output of the original scale Royal engine before settling on scale, cuz these numbers are all over the place :-[
EDIT: I get ~ 1 / 4 pressure ratio for the Brotherhood engine which is probably more comparable. Far from my 1 / 2 expectation thou.
EDIT: I get ~ 1 / 4 pressure ratio for the Brotherhood engine which is probably more comparable. Far from my 1 / 2 expectation thou.
Seems like I can expect the mean effective pressure to be in the ballpark of 1/4 valve chest pressure on these types of engines, judging by random observations. This means scale will have to be 2.5 to get targeted power, and this will give satisfactory results even down to a ratio of 1/6 so chances of being surprised are low. At this scale, I'll have to machine the crank box from ø130mm aluminum barstock, just the machined crank box will weigh about 1kg, and with my crude half-made iron cylinder models weight grows to about 4.7kg. 
I'm starting to feel confident on the scale so consider topic solved. I'm gonna start with the crank casing as it's really a frame for everything else, and also the biggest, most complex part. Thanks to Stew for showing how to do this in his build thread, which was very helpful when making a CAD model (see attached pics). I'm also looking at your crank arms too Stew, very inspiring work.
Things will move very slow, as I'm not a machinist myself but I work with a guy running a crazy nice CNC workshop. They have a busy schedule so I'll probably be waiting a lot. I'll start a build thread sometime.
By building the crank casing first, I also have some time to settle on how to make the cylinders. I'm thinking about iron linings instead of massive iron cylinders, that would also make it easy to machine and assemble the linings, in order to be able to assemble everything else (piston, crank arms, shaft etc), while having even more time to figure out how to make the cylinder casings. I'm thinking I'll probably save that (and tubings/covers) for last.
Things will move very slow, as I'm not a machinist myself but I work with a guy running a crazy nice CNC workshop. They have a busy schedule so I'll probably be waiting a lot. I'll start a build thread sometime.
By building the crank casing first, I also have some time to settle on how to make the cylinders. I'm thinking about iron linings instead of massive iron cylinders, that would also make it easy to machine and assemble the linings, in order to be able to assemble everything else (piston, crank arms, shaft etc), while having even more time to figure out how to make the cylinder casings. I'm thinking I'll probably save that (and tubings/covers) for last.
