Doctorbass said:
I am looking to find the perfect motor to build a 5kW ultra compact generator to cary with a zero motorcycle for long distance . I could use one of these 130kV 7kW turnigy motor combined with it...
Any idea for the compact 7hp ICE ?
Doc
Ok, I looked at that engine, your goals and what's available commercially and what you are proposing is a significant challenge.
An off the shelf generator would use a 200 to 250cc 4-cycle engine and weigh more the 50 Kilos.
You seem to have a pretty good handle on the electical side of things
, so let's look and small powerful engines, something I know a little about.
That little Zenoah certainly a powerhouse, but perhaps a little high strung for your application.
High output 2-cycle engines attain their outstanding power to weight ratio by focusing subsystems[induction, ign., exhaust] to combine over a narrow rpm range[notice the sharp, peaky power-band]. Tuned correctly, max. output is a function of a resonance created by negative exhaust pressure waves boosting the induction flow[fuel and air is heavy].
What this means to your application is that high output 2-cycle engines don't like to run a stationary rpm. They really prefer to be moving up or down the
power band.
And then the is the matter of the fan cooling. I guess it's sufficient, but 2-cycle engines tend to develop "hot-spots. The fuel is a big part of the cooling and jetting is going to be critical. Remember this is a race engine and race engines tend to run best when on the knife-edge. Fall off and they burn-up. And as such[a race engine], I rather doubt you can warranty it.
But the clincher is the fore-mentioned exhaust system, or expansion chamber. Those HP numbers were achieved with one of these bolted on, which they don't show in the picture.
http://www.oneillbrothers.com/rc-car/pipes/jetpro-hpi-baja-5t-pipe.html
Unsilenced no doubt, ouch, ear-splitting.
What you need to do, is stay with a 2-cycle, but trade some more displacement for something running a little more slowly. Something that would be more reliable and less finicky. And something that will meet you requirements without a 2 ft. long snaky pipe that rings like a bell.
But that is not as bad as it sounds. While a 50cc engine will be bigger, it won't be 2X as heavy. The only heavy[steel]parts are the rotating pieces[crank and con rod], the cases, piston, carb, etc are all alum.
So which engine? I have already given you a hint.
I would look at 50cc scooter engines, something like this,
http://www.partsforscooters.com/220-52_Minarelli_Style_1E40QMB_Engine?sc=2&category=77295.
Just like there are times for stealth with Ebikes, there is a need to be stealthy when building a street scooter to fall within the limits of State "moped" laws.
A racing pipe screams "look at me\'.
I've build these to get into the low 40's mph[sorry Doc, old school here, I think in Amer. Standard]with simple bolt-on additions like a big bore piston kit[63cc's], mild porting and a high-compression cylinder head while maintaining the stock, quiet exhaust system. So I'm thinking they must be close to 7 hp.
If you have the time, it's possible to locate crashed scooters. What you do would be to cut off the CVT[belt drive]case. If you buy a new engine, you could sell the new unused parts. There would not be bosses to mount the engine to a horizontal surface, so something would have to be fab'ed there. The shrouded forced-air cooling system is designed to function encased in scooter panels, so no worries there.
The biggest problem again would be the exhaust system. The stock member is constructed of heavy gauge steel, it's a chunk. I know of no light-weight, quiet, untuned mufflers that exist or have been built. Anyone interested in weight reduction would just buy a racing pipe. Since it is untuned[no reflective cones], dimensions would not be critical, only volume. I thinking something welded up from heavy gauge alum with lots of sound absorbing material[fiberglass]inside. Perhaps one baffle.
If this is a route you want to explore, let me know. I can supply you links, engine models, appropriate hop-up parts and modifications.
Piece of cake for me.
EDIT-check out Arlo's earlier gas/electric scooter conversions to get an idea of the size and construction of the core engines[the guy is a heck of a machinist, welder, fabricator].
