There were a bunch of really great comments to my post last night about the next engine and the other project I'm working on and the general topic. Many of them resonated with things I've been thinking of, so much that I thought it would tough to get to them all but there are similarities. Hope this isn't too "me, me, me, me" for everyone else.
There were several comments along the line of building a small but useful engine, and several people referred to a Stirling engine. A useful engine is something I've given a lot of thought to and is part of the reason I'm interested in building that hit and miss engine; it's 2-1/2 cubic inches. I don't know how much power it's capable of, but as a guideline I think a good engine can get 1 HP per cubic inch. I seriously doubt that I could get 2-1/2 HP out of it, but maybe it could be 1-1/2 or 1 HP. Here's what I consider a really important number for you. It's slightly off the exact value but easier to remember.
One horsepower = 750 watts.
I can think of that engine as 750Watt to a 1,125Watt battery charger/power supply. I could wrap a belt around the big flywheel hub visible in that picture and use the engine to drive a generator. (It's more prudent to go with 80% of those numbers because you'll have inefficiencies in your charging system.)
I know that Stirling engines can do useful work, but I don't know how big a Stirling engine to think about to get 750 watts. They definitely have their place, I just don't know what it is. I've seen guys use one to charge a cellphone which to me is touching the bottom end of the useful scale.
WCR, if you have 3HP (2,250 watts) worth of steam, why not use a steam engine instead of a Stirling? There are tons of very capable steam engine designs and every engine builder seems to build at least a couple. Are you thinking of a Stirling engine because of some advantage they have? (that I don't know about...)
Stefan, I think your approach is a cool idea. 500W out of a steam engine to run a generator and charge batteries, is a good, useful size; to a 12V storage battery, half a kW is over 36 amps.
An idea I keep thinking about, but have no idea how to really get there, is the widely available 49cc engines like they use on motorbikes. These "49ers" are almost exactly 3 cubic inches, and the parts are available everywhere. You can buy an entire, ready to mount and run engine for well under $100. If you go to eBay, you'll find all the parts you can imagine. How about a carburetor for $11? The RC model carb on my Webster cost over $30. I see pistons for 7 to $10, too. I just don't know that those parts fit in "any" 49er engine and I can see buying a bunch of parts only to not have them fit together.
I don't know how much the piston in my Webster cost, but among the critical parts in an internal combustion engine is how well the piston fits. The real cost of the piston is the hours of measuring, remeasuring, and generally agonizing over the fit. A ready made cylinder and piston that fits it is really tempting.
And Titaniumboy - I'd never heard of the BAXEDM project. I know of the existence of EDM but not much about what it really can do and do for me. I'll be looking into that.
A PM Research #3 steam engine. Fairly small, at 0.15 cubic inch displacement, but available as fully machined parts so all that's left is to assemble it. Their #6 engine is 4.4 cubic inches, but is castings to machine and assemble yourself.
There were several comments along the line of building a small but useful engine, and several people referred to a Stirling engine. A useful engine is something I've given a lot of thought to and is part of the reason I'm interested in building that hit and miss engine; it's 2-1/2 cubic inches. I don't know how much power it's capable of, but as a guideline I think a good engine can get 1 HP per cubic inch. I seriously doubt that I could get 2-1/2 HP out of it, but maybe it could be 1-1/2 or 1 HP. Here's what I consider a really important number for you. It's slightly off the exact value but easier to remember.
One horsepower = 750 watts.
I can think of that engine as 750Watt to a 1,125Watt battery charger/power supply. I could wrap a belt around the big flywheel hub visible in that picture and use the engine to drive a generator. (It's more prudent to go with 80% of those numbers because you'll have inefficiencies in your charging system.)
I know that Stirling engines can do useful work, but I don't know how big a Stirling engine to think about to get 750 watts. They definitely have their place, I just don't know what it is. I've seen guys use one to charge a cellphone which to me is touching the bottom end of the useful scale.
WCR, if you have 3HP (2,250 watts) worth of steam, why not use a steam engine instead of a Stirling? There are tons of very capable steam engine designs and every engine builder seems to build at least a couple. Are you thinking of a Stirling engine because of some advantage they have? (that I don't know about...)
Stefan, I think your approach is a cool idea. 500W out of a steam engine to run a generator and charge batteries, is a good, useful size; to a 12V storage battery, half a kW is over 36 amps.
An idea I keep thinking about, but have no idea how to really get there, is the widely available 49cc engines like they use on motorbikes. These "49ers" are almost exactly 3 cubic inches, and the parts are available everywhere. You can buy an entire, ready to mount and run engine for well under $100. If you go to eBay, you'll find all the parts you can imagine. How about a carburetor for $11? The RC model carb on my Webster cost over $30. I see pistons for 7 to $10, too. I just don't know that those parts fit in "any" 49er engine and I can see buying a bunch of parts only to not have them fit together.
I don't know how much the piston in my Webster cost, but among the critical parts in an internal combustion engine is how well the piston fits. The real cost of the piston is the hours of measuring, remeasuring, and generally agonizing over the fit. A ready made cylinder and piston that fits it is really tempting.
And Titaniumboy - I'd never heard of the BAXEDM project. I know of the existence of EDM but not much about what it really can do and do for me. I'll be looking into that.
A PM Research #3 steam engine. Fairly small, at 0.15 cubic inch displacement, but available as fully machined parts so all that's left is to assemble it. Their #6 engine is 4.4 cubic inches, but is castings to machine and assemble yourself.
1 HP per CuIn is a pretty lofty number. For years, auto manufacturers chased that magic combination with big cams, custom exhaust, and high compression. Granted, it is quite common today, but there is a whole lot of mechanical / electrical voodoo going on - ie: variable cam timing, multi-valve heads, tuned runner intakes, etc, etc.
ReplyDeleteCase in point: my old school Vulcan 3.0 Ford engine makes 165-172HP out of 182 CuIn. My DOHC 3.0 Duratec makes 220HP out of 181 CuIn.
The 49cc engine is also a two stroke, so twice as many power strokes as a typical Briggs engine. It appears as though that 49 has a reed cage and castings for transfer ports. That type of two stroke has a lot of engineering into it, regarding the intake charge timing and crankcase pressurization. A lot more than I have space to try to poorly explain. Lets just say there is a lot of complexity in its simplicity.
I'm sure there is a way for you to put your own spin on the old hit & miss engine. My take would be a modular design out of billet, not castings. At least that way, it something were to go awry, you would only need to repair / replace a single piece - rather than scrapping a whole (expensive) casting.
Leigh
Whitehall, NY
I've reluctantly concluded that the only practical advantage a Stirling has over the Northern Tool branded version of the Yamaha inverter generator is sufficiently less noise to avoid envy. Therefore, perhaps spend your effort constructing a better muffler system?
ReplyDeleteTip: to avoid gumming up the carburetor in storage, dump the inexpensive pump gas out of the tank, put in a half-cup of "storage gas", and run it dry. A 500W Halogen is a load that won't be hurt by losing power.
That's an excellent point and one I hadn't thought of. They are quieter, although they still do make noise. If one was big enough to be powering a few kW generator, it might be rather loud.
DeleteWith a muffler, you still have noise from the engine block and other things banging around.
The noises are part of the inefficiencies of the engine.
I need to find a good book on Stirling design.
The NASA Stirling design used on space probes has the moving parts hung on flexible springs rather than sliding or rotating bearings, which solves a lot of lubrication and seal-wear problems. https://en.wikipedia.org/wiki/Stirling_engine#Free-piston_Stirling_engines Also google "nasa stirling flex bearings", "free-piston stirling".
DeleteThanks, Anon. Looks like a good starting point.
DeleteThe guys who publish Home Shop Machinist have a set of four books called Steam and Stirling, but I'm not sure how much concise detail is in there.
Saw this in a quick search I did, for hit & miss HP ratings. Pretty interesting paper, even though he failed to reach the desired outcome of his project.
ReplyDeletehttps://corescholar.libraries.wright.edu/cgi/viewcontent.cgi?article=1006&context=honors
"John Deere Model E, 3hp (horsepower) which is a four-stroke, internal combustion, hit-and-miss, and naturally aspirated gasoline engine. The engine displacement is about 62.8 cubic inches, or 1.03 liters. Its compression ratio is 9: 1 with a 4" bore and 5" stroke."
That is a pretty large engine, and came in at 338 lbs, dry.
( source: https://www.gasenginemagazine.com/gas-engines/the-john-deere-model-e-gasoline-engine/ )
At 2 1/2 cubes, I don't think the PM Research engine would produce a useful power output. Would it be cool? Absolutely. That is reason enough for people of sufficent talent to build such things. Which is why we all come here.
Leigh
Whitehall, NY
3 HP out of 62.8 cubic inches, with a 9:1 compression ratio? Wow. That makes my first car, a '72 pinto with a 2 liter engine, sound like a super car. IIRC, it was just over 100 HP (and about 120 CI).
DeleteIt sounds like if I want a 1 HP battery charger, I need to go to Briggs and Stratton. Or one of those 49cc engines. I took a look at some motorbikes being sold as street legal, trying to find the HP ratings. The first one that came up said 2.2kW which is almost exactly 3 HP (2,238W). I have to be careful with that because that term (street legal) has a couple of meanings. I think in Florida, no license vehicles are limited to 5 HP.
You also have to figure that hit & miss engine has an operational rpm of 450 rpm. RPM has a direct correlation to HP output.
DeleteHorsepower = Torque x RPM / 5,252
Also, a H&M engine lacks a truly constant RPM, even at the governored speed. It looks more like a low amplitude sine wave than a flat line. The large flywheel helped mitigate it somewhat, but the long stroke and low RPM cause it to be a bit more pronounced.
The difference of RPM is also why the little 49cc two stroke can make 3HP out of so little displacement. From what I read; they top out at 8500 rpm with no load, but they "peak" right around 7000 or so. Below 4000 rpm they are said to fall on their face. That is typical of a two stroke as well, as they have a rather narrow power band.
I rode a CR250 Honda once. If you treated it like a four stroke, it was a dog. Bring the RPM up, getting it up on the pipe, and it would go : "rrRRRRIIIIIIIIPPP!" It was scary fast, IF you rode it like you were mad at it.
Leigh
Whitehall, NY
Oh, goodness....PM Research has kits that are Fully Machined!
ReplyDeleteThe temptation is strong here, SiG!
Agree with Leigh. 1HP/cuin is a High Specific Output. These are not high performance auto engines. If you got .2HP/cuin you might be doing good....
If you only knew the power of the dark side...
DeleteNitromethane and nitrous?
DeleteWOW! I like the way you think, SiG. ;-)
Leigh
Whitehall, NY
Hey SiG,
ReplyDeleteI'll give your suggestion of using a steam engine instead of a sterling engine a strong consideration when I get to that point in the process.
Thanks,
WCR
Came across this and immediately thought of you.
ReplyDeletehttps://laughingsquid.com/steam-of-consciousness-a-steam-powered-kinetic-skull-sculpture/
Pretty bizarre little sculpture, but I probably would have made it do more.
DeleteThere is also the Predator 212...essentially a copy of the Honda GX200. It makes an honest 6.5 HP, and can be modded to your heart's content relatively cheaply. A YouTuber with the handle Robot Cantina walks his audience through the process of installing and multiply upgrading it so his 1300 lb car can make 50 mph top speed with it. He the promptly yanks it and puts in one roughly double the power.
ReplyDeleteDamn, I must be leading a sheltered life. I've never even heard of this!
DeleteNot to mention I have a Horrible Freight store two miles from me.
I just saw that on sale for 90 some dollars! Sorry I sold the kid's go-cart I made them.
DeleteI used to run a tube fab shop and a guy called looking for 2" SS tube.
I gave him some scrap.
He was making a jet engine for an RC plane.