That was certainly my take on the physics. Unless, of course, the petroleum based engine is VERY inefficient at highway speeds.
Posted on 02/20/2011 6:08:28 AM PST by saganite
No doubt air resistance is a factor. But engine efficiency is also a factor. Most cars reach optimum mileage performance around 60 miles an hour. The wind resistance is certainly higher at 60 MPH than at 30 MPH but the mileage is still better at 60. The reason for that is the engine efficiency is better at 60 than at 30.
.and it’s all due to wind resistance (which increases much faster than speed).
I throw in with y'all's wind resistance rebut to Intercept Point's Point. At higher speeds a larger and larger proportion of the motive power is dedicated to overcoming it, to the point where the inefficiency is greater at high speeds than at start-and-stop, recovered-energy, low speeds.
Also decreasing the mass of the accelerating vehicle will have greater ramifications at lower repetitive acceleration speeds than in the higher "wind resistance regime."
A related point, high strength-low weight materials have profound ramifications in all sorts of energy venues.
Good issue, good replies.
I worked on the Abrams M-1 program back in the 80s.
We did a lot of development with the 0W20 synthetic based hydraulic fluid for the transmission and engine.
The Army wanted to be able to fire up @ -60F.
I’m sure they were considering they might need to operate in Alaska or Siberia.
The lube worked well but it tended to be more leak prone when warmed up to operating temp. Your gaskets and seals had to be perfect.
One old German engineer used to joke that if they had that stuff back in WWII their tanks would have cruised right into Moscow.
If Hitler hadn’t diverted resources from Central Army Group and stopped the drive on Moscow to help out Southern Army Group he would have cruised on in to Moscow anyway. But that’s another thread entirely!;^)
What the hell is an FE or an FS you alphabet soup idiot?
I worked on a project like this in the 80’s while in college. The engine did not provide power to the drive train but to the compressor. The engine was set to run at the most efficient rpm all he time. I would think that the energy gained in stopping the truck would be needed to start it again in stop and go traffic. But remember who wrote the article , does the reporter have any clue about what they are writing.
Those hanging out in the Rockies on ocassion might easily guess that FS is Forest Service in the context of "road". Lots of on-line maps label such as FS 131, for example.
The engine is not directly connected to the wheels. It is connected to the hydraulic pump. I would guess they can tune the connection so that the engine sees a load that matches its optimum conditions for rpm and torque. In stop-and-go city conditions (which is what it would be optimized for) it would charge the hydraulic reservoir and then stop running. The truck would run off hydraulics until pressure dropped to the point where it restarts the engine.
Speed squared will give a good comparative value for wind resistance(drag).
Example: speed =10 ,drag =100 and speed=20, drag=400,
Example: speed=40, drag =1600 and speed =50, drag=2500.
You mileage any vary.
An actual free market wouldn’t even make this type of thing a concern. With all the government regulation preventing both drilling for oil here where we know we have massive deposits of natural gas and oil and with the government preventing new inventions for transportation, we get little to nothing except the government demanding to regulate even more.
The Ford FE engine. http://en.wikipedia.org/wiki/Ford_FE_engine
That was certainly my take on the physics. Unless, of course, the petroleum based engine is VERY inefficient at highway speeds.
A little puzzle once in a while is good exercise for the mind, plus it is code for those in the know to be able to recognize who is a member of the fraternity (or not).
TNNJA.
I thought about that, but thought that it was way out of context and too far in rapidly receding history to be on anyone's radar. Guess not. ;-)
Yes, anyone who has worked with finely-controlled power hydraulics — which has been around since the jet age — wonders why we haven’t gone this way sooner.
UPS trucks, garbage trucks, city buses, etc. would be good candidates for such a system.
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