I’m toying with the idea of a car engine + generator for power backup

[james_s]

IIRC propane also has a higher octane rating than gasoline, so you can run a higher static compression ratio to get some of that power back. Granted you can't really just adjust the compression ratio at will, but if you're ever building an engine to run on propane it's something to keep in mind.

[james_s]

Over here due to zoning you will almost always need to use a road to get your tractor from the farm to the field, so it is a road vehicle that needs to be registered and road worthy. Farmers have to buy diesel just like everyone else, but they do get a bunch of subsidies back on a lot of stuff instead.

Heating oil is colored red here to make it easy to tell apart, and you do get in trouble if you are found having it in the tank of your vehicle. It's not just diesel with a die, the stuff is less pure and is generally only a good idea to put into old simple diesel engines. Seen plenty of 50 year old tractors that ran on only heating oil and they still run. Yet since a generator is not a vehicle its perfectly legal to run on cheep heating oil here.

The massive diesel engines in ships also tend to run on so called fuel oil (same stuff). Those use extra tricks too such as switching the engine mapping once out in sea where they escape strict emissions standards. So they crank up the compression to get more efficiency out of the same amount of fuel while making lots more NOX

I'm not a farmer but I believe there is a provision in the law here that allows transporting farm equipment on public roads without licensing them as a road vehicle. You're not allowed to commute to work on a tractor or take it on a highway but you can drive it on local roads as needed for agricultural purposes.

I thought ships typically ran on bunker oil? Nasty sludgy stuff that is left over from refining the lighter hydrocarbons into other fuels.

[langwadt]

why is that? I don't see why an engine properly tuned for propane shouldn't make just as much power as on gasoline

80% is actually optimistic for many engines because of more complex factors, but the simple analysis is that for two otherwise equivalent engines, the propane both displaces more air and produces less energy per equivalent mass of air due to the C/H ratio.  The assumption is that the two 'equivalent' engines are pumping the same volume of charge gas, whether that be air with a small fraction of evaporated gasoline or air with a larger fraction (volume) of propane.

With liquid injection the charge will be cooler and denser, the octane rating is higher so it can handle higher compression ratio and because it is slower burning more needs ignition advance, but that of course requires more substantial engine changes

[james_s]

Well ignition advance is usually pretty trivial to provide. With a turbocharged engine you can increase the boost easily, which has a similar effect to increasing the compression ratio.

[bdunham7]

but if you're ever building an engine to run on propane it's something to keep in mind.

I've (re) built a fair number, and LPG/propane (not exactly the same thing depending on where and when you are) and conversions of existing designs really had issues, largely thermal.  Many older engines would have valve issues and overall shorter engine life unless severely derated for power and run at slower speeds.  Forklift engines, for example, were run at power to displacement levels that are pitifully low compared to modern gas auto engines.  They also needed special lubricants when used with 'sour' fuels, which were common.  A more modern, efficient, high compression ratio engine with customized camshaft profiles and engine controls would probably improve things, but I don't know of anyone making anything that advanced.  It seems the emphasis is on CNG, which has its own challenges. 

[John B]

but if you're ever building an engine to run on propane it's something to keep in mind.

I've (re) built a fair number, and LPG/propane (not exactly the same thing depending on where and when you are) and conversions of existing designs really had issues, largely thermal.  Many older engines would have valve issues and overall shorter engine life unless severely derated for power and run at slower speeds.  Forklift engines, for example, were run at power to displacement levels that are pitifully low compared to modern gas auto engines.  They also needed special lubricants when used with 'sour' fuels, which were common.  A more modern, efficient, high compression ratio engine with customized camshaft profiles and engine controls would probably improve things, but I don't know of anyone making anything that advanced.  It seems the emphasis is on CNG, which has its own challenges.

Were the valve issues due to the fact that no fuel spray was cooling the valves in port injected engines?

If so, you simply need to add compression ratio increasing, valve cooling water injection to the DIY fuel-converted-car-motor 3 phase inverter generator project.

The real hurdle is integrating it with cloud based services.

[langwadt]

but if you're ever building an engine to run on propane it's something to keep in mind.

I've (re) built a fair number, and LPG/propane (not exactly the same thing depending on where and when you are) and conversions of existing designs really had issues, largely thermal.  Many older engines would have valve issues and overall shorter engine life unless severely derated for power and run at slower speeds. 

seems odd to have thermal issues with less power. Timing set too low, power wasted out the exhaust burning up the valve on the way?

[DenzilPenberthy]

My 2p worth for OP:

 Get a Honda Eu2000i. They really are very impressively quiet.  If you want to run it off propane to avoid issues with stale fuel, than you can get a kit to convert it to propane.


 Alternatively, if you want more power, get an old small tractor and a generator to fit on the 3 point linkage and PTO shaft. If you want a hobby project then  a classic tractor might fit the bill. If you've got heating oil on site, then you could find a 1940 or 50s one that runs on kerosene.

[bdunham7]

seems odd to have thermal issues with less power. Timing set too low, power wasted out the exhaust burning up the valve on the way?

IC engines are an advanced science and management of the thermal issues is a complicated subject.  Yes, the burn time is an issue and you can't completely solve it with more and more spark advance.  But there is also a phenomenon called a 'quench layer' where the propagating flame is extinguished just short of a combustion chamber boundary and the remaining unburned area serves as an insulating layer.  Propane mixtures don't quench as easily, so more heat is transferred.  Older engine designs often rely on a 'quench' feature to control combustion and introduce turbulence, which is accomplished by having part of the piston come very close to the cylinder head.  Unless you make this clearance very tight, the quench doesn't work as well with propane.  This is similar to what happens when you run an engine on a lean mixture at high power levels--things melt.

[james_s]

Getting a tractor just to generate electricity seems to be a bit Rube Goldberg-esq.

I think if I were going to take the hobby route I'd look for an antique diesel stationary engine or a steam engine and fire the boiler with natural gas then run the exhaust steam through a heat exchanger to heat the house. Not very practical but it sounds like fun.

[Circlotron]

But there is also a phenomenon called a 'quench layer' where the propagating flame is extinguished just short of a combustion chamber boundary and the remaining unburned area serves as an insulating layer.

That quench or boundary layer is pretty important. It's what allows you to use aluminium pistons despite the high flame temperature present. If detonation occurs, that insulating layer gets swept away by the extremely violent gas movement therefore allowing much greater heat transfer to the piston, ending up with a hole melting in it.

[David Hess]

IIRC propane also has a higher octane rating than gasoline, so you can run a higher static compression ratio to get some of that power back. Granted you can't really just adjust the compression ratio at will, but if you're ever building an engine to run on propane it's something to keep in mind.

The same issue occurs with high ethanol content gasoline.  An engine intended for E85 could support higher compression so E85 vehicles which run on either E85 or standard gasoline are less efficient than they could be on E85.

I think if I were going to take the hobby route I'd look for an antique diesel stationary engine or a steam engine and fire the boiler with natural gas then run the exhaust steam through a heat exchanger to heat the house. Not very practical but it sounds like fun.

I have seen recommendations to get one of those very old single cylinder "Lister" mechanical injection diesel engines.  The US banned their import a couple years ago.  They are something like this:

https://www.purusharthdieselengine.com/single-cylinder-water-cooled-diesel-engine.html

[bdunham7]

The same issue occurs with high ethanol content gasoline.  An engine intended for E85 could support higher compression so E85 vehicles which run on either E85 or standard gasoline are less efficient than they could be on E85.

That was true before variable cam timing became popular, but nowadays you actually can vary the effective compression ratio fairly easily by delaying the closing of the intake valve, as well as reducing combustion temps by leaving some exhaust behind.  There are production gasoline motors with open multivalve combustion chambers, 12:1 compression ratios and superchargers.  Obviously that would blow up pretty quickly at low speed and high torque without some valve timing wizardry.  I don't know how many current E85 vehicles have these features since E85 isn't such a big deal anymore. 

[james_s]

I have seen recommendations to get one of those very old single cylinder "Lister" mechanical injection diesel engines.  The US banned their import a couple years ago.  They are something like this:

https://www.purusharthdieselengine.com/single-cylinder-water-cooled-diesel-engine.html

The Lister engines and copies are great, they're dead simple and will run forever, and they look cool. It's a shame they banned the import, and kind of strange too, it's been a niche thing for many decades, it's not like everyone has one and runs it all day.

[Berni]

Yep gasoline engines are very optimized for gasoline(even a certain octane rated one) so running most other fuels in one of those tend to need some derating or adjustment. You could tweak a lot of modern engines to better run on it tho since electronics control so much of it now. All it needs is a ECU flash to crank up the boost on that turbo, adjust the fuel quantity, ignition, valves etc. Then again such a high tech engine is the last thing id want as a backup generator.

Diesel doesn't care so much since there self ignition is required rather than problematic. So compression can be cranked up as high as the engine components can survive without breaking (Until emissions laws step in). The only challenge there is that the fuel system runs at insane pressures so it might not survive moving any fuel. A possibly even more fuel universal engine are turbine engines where they also just simply need a fuel that can burn, but does not need nearly as high pressures in the fuel system. Tho i am pretty sure the neighbors would not appreciate the noise it makes and they are not the most efficient of things(the small ones). It also sounds like the kind of insane project someone like Colin Furze would make.

I'm not a farmer but I believe there is a provision in the law here that allows transporting farm equipment on public roads without licensing them as a road vehicle. You're not allowed to commute to work on a tractor or take it on a highway but you can drive it on local roads as needed for agricultural purposes.

I thought ships typically ran on bunker oil? Nasty sludgy stuff that is left over from refining the lighter hydrocarbons into other fuels.

When it comes to vehicles the laws are sometimes tight ass ridiculousness here in Europe. They don't even let you put a aftermarket sport air filter in your car without a bunch of paperwork. Even a bicycle legally involves paperwork if you fit an electric motor with >300W of power on it since it becomes a 'motorcycle'.

Yes fuel oil is a general term for all the messy crap that is too dirty to be called diesel. The heating/furnace oil is the cleaner variety of fuel oil, the bunker fuel that the ships can run on would probably gum up a typical home furnace burner. Then again when an engine the size of a house has injectors the size of a persons leg, that probably makes it easier to handle a much messier/gooeyer fuel.

[brucehoult]

The whole idea is not that bad in my opinion. You can buy generators that connect onto the PTO output shaft of a tractor(Used for backup power or power out in the field). They do tend to be in the 10 to 40 kW range

No one was quite sure what was going to happen at Y2K and farmers were worried about things such as being able to milk their cows if the electricity system was disrupted. My father bought a tractor mounted 3-phase generator which I think was around 40 or 50 kVA. He got his milking shed set up to be able to take power from it. He also offered to provide neighbouring farms with electricity from the generator in the event that something happened, and changed them essentially an insurance premium in advance for this. There were enough takers to pretty much pay for the generator I think :-)

Of course in the end a lot of computer programmers put in long hours and did actually find and fix a number of bugs, and nothing bad happened.

[brucehoult]

Personally I got a Honda EU2000i inverter generator a few years ago and it's a lovely little machine. Despite the fact that it is also a small air cooled engine they have done a remarkable job of making it quiet, and since engine speed is decoupled from the frequency of the generated power, it spends most of its time near idle. It's quiet enough that I can let it run all night long without disturbing my neighbors. With it sitting out in front of my garage I can't hear it at all inside the house.

Nice and small and cheap at around US$1300, but it's not enough to power a house -- it's not even enough to run a hairdryer or kettle. It's also pretty inefficient with the fuel. The 7 kW model for $5549 looks like a much better deal long term. Enough power to actually run things, and about 50% better fuel economy thanks to fuel injection.

[electr_peter]

Personally I got a Honda EU2000i inverter generator a few years ago and it's a lovely little machine. Despite the fact that it is also a small air cooled engine they have done a remarkable job of making it quiet, and since engine speed is decoupled from the frequency of the generated power, it spends most of its time near idle. It's quiet enough that I can let it run all night long without disturbing my neighbors. With it sitting out in front of my garage I can't hear it at all inside the house.

Nice and small and cheap at around US$1300, but it's not enough to power a house -- it's not even enough to run a hairdryer or kettle. It's also pretty inefficient with the fuel. The 7 kW model for $5549 looks like a much better deal long term. Enough power to actually run things, and about 50% better fuel economy thanks to fuel injection.

Consider portability factor as well.
Several Honda EU2000 units can be connected in parallel (there are 4mm banana sockets on front panel) to boost output. They are very silent for generators and pretty good overall. EU2000/2200 is the biggest model one can still call truly portable. There is also lower power and lighter EU1000i unit - very portable as well with 4mm parallel sockets. 3-7kW units are only "portable" in the sense that handles are attached. Depends on your needs, of course.

[AaronD]

But there is also a phenomenon called a 'quench layer' where the propagating flame is extinguished just short of a combustion chamber boundary and the remaining unburned area serves as an insulating layer.

That quench or boundary layer is pretty important. It's what allows you to use aluminium pistons despite the high flame temperature present. If detonation occurs, that insulating layer gets swept away by the extremely violent gas movement therefore allowing much greater heat transfer to the piston, ending up with a hole melting in it.

Slightly off-topic, but could that be what happened to my '97 fuel-injected Jeep?  I'd think that the FI computer would have enough sensors and smarts to prevent it, but I'm on my second engine now because the first one did that.  Lost a ton of power on the highway, billows of smoke, and when I took the pan off and looked up, I could see valves.

My conclusion at the time was that cooling system insisted on leaking and so I couldn't keep water in it.  I replaced a lot of that, so it doesn't anymore, but your comment got me wondering.

(the temp. gauge on the dash always showed good, so I figured it was reading wrong for lack of water )

[Jester]

If I ever do this I’m going to try to keep the budget under 1k. I think should be able to get a severely wrecked civic or Corolla preferably a roll-over for about $500-700 Salvage the motor, computer, cooling and exhaust system and then send the carcass to the wrecker for scrap metal. There seems to be countless free non working small generators available (because people leave them filled with gas for a few years and they just want them gone) however I like the idea of the 4 pole and that will be harder to find hopefully I can find one for a good price with a dead engine. Then it’s just chain and sprockets, scrap metal and welding supplies. Control board and stepper another $100. I think the key will be to find a 20 or so kW 4 pole generator.

Look at this:  https://www.ebay.ca/itm/144318753004?hash=item219a1168ec:g:KqAAAOSw-VlhXWQN

[NorthGuy]

Honda EU2000i inverter generator

It's also pretty inefficient with the fuel.

It is very efficient. Unlike a normal generator it can adjust the rotation speed depending on the load. This saves lots of fuel at lower loads.

[NorthGuy]

That would allow me to run the engine a little bit slower for a 1:1 tailshaft-to-generator connection at 3600rpm, but with a redline of 5k, that speed is also inside of the normal operating range for this engine.

You can also run it at 1800 rpm. Look, for example, at this Kohler generator based on GM car engine.

[langwadt]

If I ever do this I’m going to try to keep the budget under 1k. I think should be able to get a severely wrecked civic or Corolla preferably a roll-over for about $500-700 Salvage the motor, computer, cooling and exhaust system and then send the carcass to the wrecker for scrap metal. There seems to be countless free non working small generators available (because people leave them filled with gas for a few years and they just want them gone) however I like the idea of the 4 pole and that will be harder to find hopefully I can find one for a good price with a dead engine. Then it’s just chain and sprockets, scrap metal and welding supplies. Control board and stepper another $100. I think the key will be to find a 20 or so kW 4 pole generator.

Look at this:  https://www.ebay.ca/itm/144318753004?hash=item219a1168ec:g:KqAAAOSw-VlhXWQN

how fast can you run a chain before you need to start looking at running it in an oil bath?

[BrokenYugo]

If you can find a 20 kw 4 pole genset cheap you'd be better off fixing the industrial engine in it (which likely has excellent parts support if it isn't super old) than using some auto engine not really designed for the purpose with limited, if any, long term parts support. That industrial stuff is a whole different, better world.

[AaronD]

how fast can you run a chain before you need to start looking at running it in an oil bath?

I was wondering that too, which is why I suggested a belt.  The general rule, to me, seems to be: fast = belt, slow = chain.  So you could have one of each on either side of a gearbox.  An el-cheapo riding lawnmower, for example, which my brother and I as kids took the drivetrain out of and put in a home-made go-kart, with an oversized pulley on the crankshaft and an oversized sprocket on the transmission output.  I did a lot of math (for a kid) to determine the right sizes, and got it just about perfect.  When it worked, it would go about 30mph according to a handheld GPS, almost wide-open at the engine's rated speed in 5th gear.

That was also a good lesson in parts being designed for the actual load of the intended application and not the maximum possible load.  (most of the power went to the mower deck, and it didn't take much to drive the wheels)  The original 5-speed gearbox was constantly breaking in our go-kart, somewhere different every time because we would reinforce it and then something else would go, etc.

It was essentially a complete manual transmission car, minus the safety features and any instruments.  The clutch was a spring tensioner for the belt that connected the engine to the transmission, with a pedal (gate hinge) in the normal position to pull it away from the belt.  A loose belt would hardly transmit any power at all, and a tight one could stall the engine at full throttle without slipping.  You might do something similar for a DIY genset, or you might have an electrical disconnect before any distribution, that essentially does the same thing.

For an industrial application, I've seen about 10 discrete 1/2" V-belts running in parallel between a dedicated 200-hp 480v 3-ph motor and an extruder screw.  I didn't see a way to tension each one individually, but it seemed to work just fine.  The pulleys were single-piece 20-groove or so.