Yup! I think the 50 volt motor I tested (the green motor, thanks Jerry Martes) might be one of those. At 0.5 volts it rotates about 1 turn every 6 seconds. At 3 volts it turns about 1 rev per second (fancy that) and I can just barely stall it by pinching really hard on the 1/2" shaft.
Yes they will run for hundreds of hours at minimal loads. Search for Maynard Hill and his world records. Very simple rebuilds on these and they are not loud. K&B makes some very quiet engines in the Sportster line now sold by MECOA. It is almost like flipping a switch to get them going.. Try mecoa.com or rjl.com
At what speed? Generally they will put out about (just over) half what they drew - so an 18 volt drill that runs 1 hout on a 1700mah battery uses how much power? 3.2 amps for 1/2 hour at 18 volts is only 57 watts. As a generator, it will put out more like 35. If it only runs
15 minutes under full load on that same battery, it is drawing 115 watts, more or less, and will put out roughly 75.
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Because a 300 watt output water pumping stirling engine af years past was about 6 feet tall - for starters. Atmospheric stirlings are MICROPOWER at best.
Oops. Technician error. The noload speed of that motor is 20550 RPM at 14.4 volts. That's more reasonable for a small motor like that. It also jibes nicely with generator bench test: about 4 volts (no load) when spinning at about 5500 RPM, no problem at all producing 10 amps. It barely got warm.
I saw two of these sell on ebay this last year. Incredibly small 4 cycle, extreeeeeemly cute, and yes, smaller than you lunch bucket. If I recall, the last one I saw went for over $500.00. The story was they were available in 40 and 80 watt configurations, and was developed in a partnership with Sony to power those "newfangled" miniature TV sets in the mid/late 60's. I sure wish I had one !
I had a military generator about the size of a weedwacker... Couldn't find any specific information about it. It was a two stroke engine on a cast aluminum base. The exhaust came out of the bottom of the engine, into the base which doubled as the muffler, then up along side the engine as a 1/2" OD diameter pipe, flush with the top of the rather square cast aluminum fuel tank. It had the typical military spark plug and cable, which by dimension, almost doubled the size of the unit ! My dad thought hat it was a military radio battery charger from WWII, and that it was always transported with the spark plug hole plugged with the plug hanging on the chain. It had a recoil start mechanism on the side, so who really knows how old it was ?
There are the Olsen and Rice Generators..... They were like a large RC airplane engine with a genset. I have seen them at swap meets for $100. There is one on ebay now: Item 150072170032
Beyond all that, You can easily find the Honda 300 watt units (wonderful, quiet, and 4 stroke), as well as the EM series that had
400, 500 and 650 watts. I have an EM500. It will run my 4" grinder or a circle saw, probably because they were from the day when we did not OVER rate Everything.
I'm in San Diego. The book isn't about how to build a bomb it's about how the Nagasaki and Hiroshima bombs were built. Cost me a quarter at a yard sale.
That would be a much better output amp capacity and size/weight match for what he's doing, but it will be more of an engineering challenge. Not that Tom can't do it, mind you, but he's going to have to get a big chunk of AL plate/round and do some fancy milling.
Motorcycle alternators are separate pieces mounted in a cavity off the end of the crankshaft - meaning you have to duplicate that cavity and bolt it to the backside of the weed-whacker engine, so you have the mounting holes for the stator and core in the right place. Then you have to adapt the output shaft of the engine to bolt the alternator permanent-magnet rotor to it, at the right height.
Wire up the original motorcycle voltage regulator, Done. And like the Delco, you can get repair pieces anywhere.
I've read extensively on it. Seal lifetime seems to be the killer. If you lube it like any IC engine, the oil mist gets into the heater tubes and cokes up, eventually ruining the tubes (heat exchanger). I am planning on building a high temperature Stirling engine, running either hydrogen or helium as the working fluid. Rulon seems to be the best seal choice for the power piston. It is a composite of Teflon and rust. The power piston runs at low temperature, and there is a scheme (The Heylandt crown) that keeps the highest temperatures away from the seal area of the displacer, so low-temp materials can be used there, where a really good seal is not needed, anyway. The crank and rods can use sealed bearings and the crankcase can then run dry. For an electrical generator, you put it inside the hermetic crankcase, and there are no shaft seals.
There is a guy in Germany building a home-power sized hi-temp Stirling. I hope he gets it running and can deliver some long-term results on maintenance issues.
In the 70's, Sunpower tried to make the most insanely advanced Stirling (free piston) and ran into all sorts of problems. The biggest was thermal cycling fatigue of large SS structures running at enormous temperatures, with 800 PSI hydrogen on one side and liquid sodium on the other. They delivered several units to a solar power division of Cummins, and then told them that the engines could only safely be run about 10 times, then fatigue would make them an explosion hazard. Cummins was not too amused!
Philips made a bunch of military field power plants in the several KW size that were highly prized as the were practically silent. Ford made some "quad" engines (4 displacers, 4 power pistons) for hybrid electric cars back in the 70's, and ran them in demo units.
20 W should be VERY easy to do with some of the larger "demo" castings kits. With that size engine, you don't have to go to exotic seals and tiny heat exchanger tubes. There was a guy at the 2003(?) NAMES show that had a Stirling engine running from a propane torch, and he was lighting something like a car headlight with it, plus powering the cooling water pump. That's more than 20 W.
Yes, if you use air at atmospheric pressure as the working fluid, the output is small. If you use hydrogen or helium at several hundred PSI, and have good seals on the power piston, that changes everything. I have a simulator that showed a single-cylinder Stirling of 50 cc displacement, running with a
700 C temperature differential and 800 PSI hydrogen working fluid would produce 1 Hp at about 5000 RPM. This simulator included all the known losses, too. 800 PSI hydrogen at 800 C is not to be trifled with, though, and I have scaled back my ambitions a bit after thinking about how hard it would be to build.
You seem to be pretty knowledgeable in an area that I find fascinating. Are you making your own designs? What if a guy wanted to run one off of compressed air instead of straight hydrogen? I have the means to create compressed air up to 9000 psi.
How about CO2? I've always wondered if a guy could manipulate the heat and the pressure to allow a phase change on the low temp side. That should create a vacuum to help move the piston as well add considerable cooling. Has anybody done any work in that area?
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