3 ms·
Ouch. Note that the 4 pounder is only outputing 3 HP so at a pound and a third per hp a denardis equivalent would weigh a bit more than 9 lbs. Note that the d
by VLM 10y ago
Ouch. Note that the 4 pounder is only outputing 3 HP so at a pound and a third per hp a denardis equivalent would weigh a bit more than 9 lbs. Note that the denardis spec includes the accessories that make the engine work and the picture in the article does not. Likely an installed operating denardis would weigh less.
There's a trick you can play with engines that only engineers really understand. A good engineer can fluidly trade economy, reliability, and mass. So if you want a couple ounce model airplane engine that outputs a couple HP and might run for ten hours before burning out at insane RPMs with awful fuel economy specs, those are widely available and fairly cheap. Or you can buy an inboard diesel that'll push a motorboat for insane cruising distances under hurricane conditions and maintained with a shoebox of cheap tools, but it'll be expensive and heavy, like 5 HP and it'll be 100+ pounds.
I have no question someone can build a 4 pound engine that outputs 3 HP or an 11 pound engine that outputs 7 HP. The only question is how long, and how much gas it'll burn. Something tells me neither of them would run my commuter car for 200+K miles OR get 30+ MPG, which is pretty easy for my extremely high tech, but heavier engine, commuter car.
- jws 10y agoThe denardis 40cc 7hp engine says it burns 610g of fuel per kilometer driving a pocket bike. That is around 3 mpg for those of us with strange units. It's safe to say they traded away efficiency.
- walrus01 10y agoIt's a two stroke engine with oil mixed into the fuel, I don't think the intended users (there's such a thing as competition racing micro motorcycles??!) care too much about fuel efficiency...
- Animats 10y agoThat's what Moller, the flying car guy, did. His "Rotapower" engine[1] is an overdriven Wankel. Lots of power, but a short life, which is why the engine never went into production. (The Freedom Motors site looks convincing, until you compare it with their site from 11 years ago. That's Moller - Real Soon Now forever. Over 40 years of Real Soon Now on the flying car.) [1] http://freedom-motors.com/ http://freedom-motors.com/ [2] https://web.archive.org/web/20050411075152/http://www.freedom-motors.com/ https://web.archive.org/web/20050411075152/http://www.freedo...
- walrus01 10y ago> but it'll be expensive and heavy, like 5 HP and it'll be 100+ pounds. tl;dr: affordable, efficient, light weight: Pick any two ?
- userbinator 10y agoI have no question someone can build a 4 pound engine that outputs 3 HP or an 11 pound engine that outputs 7 HP. The only question is how long, and how much gas it'll burn. For an even more extreme example, a Top Fuel dragster engine can make over 10000HP and weighs less than 500lb, but has a lifetime measured in seconds and fuel efficiency better measured in GPM instead of MPG.