03-09-2015, 11:31 AM
(03-09-2015, 10:29 AM)JustJohn_imp Wrote: No comprende. As a life-long fan of stationary engines, huge diesels, ship engines, etc I'm seeing a few holes in this story. Ok, for example: I lose whats left of my mind and install a 2500 H.P. Funny Car engine in an overseas vessel. I fully expect it to perform as well as a giant Volvo inline 6 diesel. A slow turning, torque laden engine. I wouldn't even get out of the port of call. Not looking for an fight at all. But not seeing it.
John,
Modern funny car engines produce substantially more than 2500 hp, they're probably approaching double that figure and they are so highly stressed that they must be completely rebuilt after every four second quarter-mile run. So you probably wouldn't get out of port unless you could do it in about four seconds. And the frictional losses involved in transmission gearing to use a 10,000 RPM funny car engine to turn a massive ships propeller 100 RPM would be astronomical. That funny car engine is highly stressed and wears out extreemly fast. The massive diesel engine in a ship is designed to run near it's rated power for weeks on end without stopping and because they turn at very low RPM the frictional losses gearing them down to turn the slow-moving propellers of modern ships would be far more modest. So the funny car engine is not suitable to drive a slow turning ships propeller but it would be a poor choice for reasons other than power. For the same reason, that big 2500 HP inline six Volvo diesel would be a poor choice for a funny car but again, for reasons other than power.
But for the sake of argument, if the gearing horsepower losses were equal to get to a final prop speed of 100 RPM (or whatever RPM that ships propeller requires), it doesn't matter a whit whether the 2500 hp required to move that ship is generated by a massive Volvo diesel, a funny car engine, or wound up rubber bands. Horsepower is a measure of work, it has a finite value that is as absolute as 1 pound of weight.
What you are attempting to argue is that 100 pounds of feathers would have to weigh less than 100 pounds of lead. Even if it's hard to grasp, they both weigh 100 pounds. Believe it or not, understand it or not, a 2500 hp gasoline engine in a top fuel dragster, a 2500 hp Rolls-Royce Merlin engine in Reno air race plane, and a 2500 hp Volvo diesel in an oil tanker all have the exact same amount of peak horsepower which is their ability to do work.
Let me turn your example around. Do you think your massive Volvo in-line six diesel would ever be able to propel a car through the quarter-mile in under four seconds? In this case even if that big diesel didn't weigh any more than the funny car engine, it's slow RPM would require overdrive transmission gearing so steep that again, frictional losses would be astronomical. But assuming that gearing horsepower losses were equal, and assuming that your big diesel and that funny car engine were the same weight, and assuming they had the same horsepower, they would both propel both that ship and that funny car at the same velocities. 100 pounds of weight is 100 pounds whether it's feathers or lead. 2500 hp is 2500 hp regardless of what type of engine we are talking about.
Again, horsepower is an absolute measurement of energy, no different than a calorie, or a watt, or a volt. 100 W of electricity produced by a windmill will light a bulb precisely as bright as 100 W of electricity produced by a hydroelectric dam.
All the best.
Chip