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Old 02-20-2013, 04:40 PM   #31 (permalink)
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Quote:
Originally Posted by mort View Post
Almost the opposite. "Coupling" is misdirection. Rockets make vertical climbs totally decoupled from ground friction. If the propeller makes more thrust than than needed to climb the hill then you go up.
Air shows often have hopped up crop-duster biplanes that can make vertical climbs. The Piper Cub can make a 45 degree climb, and no road is that steep.
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It's all power to weight ratio, if the thrust exceeds the vehicle weight, then it can climb vertically (but not with a car whose wheels would be spinning long before it reached the vertical portion of the road).

Even though the Cub's nose is pointed up at 45 degrees, the wing's 10 to 20 degree angle of attack means the aircraft's flightpath isn't anywhere near a 45 degree angle.

But propulsion via ground friction allows you to use a "granny gear" to climb up a steep road on very low horsepower. According to my owner's manual, 1st gear allows the 54hp engine in a 67 VW Beetle to propel the 1900 lbs car up a 45% incline (VW beetles are known for their extremely high 1st gears that redline at about 12mph). Show me a 54hp, 1900lbs airplane that can climb out with a flightpath anywhere near that angle.

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Old 02-20-2013, 04:47 PM   #32 (permalink)
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Yup, the good ol' "slow flight" configuration. My instructor made me do HOURS of slow flight. But as promised, it makes you a much better pilot, since your control inputs have to be more precise and "correct".

In fact, we did SO much slow flight practice, he'd pull the fuse on the stall warning buzzer so it wouldn't annoy us!!!
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Old 02-20-2013, 10:34 PM   #33 (permalink)
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Quote:
Originally Posted by basjoos View Post
Even though the Cub's nose is pointed up at 45 degrees, the wing's 10 to 20 degree angle of attack means the aircraft's flightpath isn't anywhere near a 45 degree angle.
You are right about the old J3C Cub, but there are plenty of aircraft that can make a 45 degree angle of climb.

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But propulsion via ground friction allows you to use a "granny gear" to climb up a steep road on very low horsepower. According to my owner's manual, 1st gear allows the 54hp engine in a 67 VW Beetle to propel the 1900 lbs car up a 45% incline (VW beetles are known for their extremely high 1st gears that redline at about 12mph). Show me a 54hp, 1900lbs airplane that can climb out with a flightpath anywhere near that angle.
Again, if the propeller makes enough thrust you go up.

45% grade is 24.2 degrees - about what that Cub (by the way, last built in 1947) is doing with 65 hp. In any case I don't plan to fly up a steep driveway, but a pusher prop would do the job just as well as a "granny gear"

But what the OP suggests is really having a small engine and pusher prop to provide thrust during those cruise conditions where the SUV's engine is way over sized. Assuming use only during cruise conditions, the prop is 85% efficient and the small engine can be designed for 33% efficiency at that power (combined about 28% efficient) compared to the SUV engine at 22% efficiency and drive train about 95% efficient (combined 21% efficient). A tire - prop hybrid could makes sense - in a unicorny way.
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Last edited by mort; 02-21-2013 at 02:53 PM..
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Old 02-20-2013, 10:41 PM   #34 (permalink)
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Quote:
Originally Posted by mort View Post
But what the OP suggests is really having a small engine and pusher prop to provide thrust during those cruise conditions where the SUV's engine is way over sized. Assuming use only during cruise conditions, the prop is 85% efficient and the small engine can be designed for 33% efficiency at that power (combined about 28% efficient) compared to the SUV engine at 22% efficiency and drive train about 95% efficient (combined 21% efficient). A tire - prop hybrid could makes sense - in a unicorny way.
-mort
yes im looking at it for long steady at speed driving at around 40/60 mph
not stop and go town driving.
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Old 02-21-2013, 12:40 PM   #35 (permalink)
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I wish I could hit my enemies with that
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Old 02-21-2013, 02:43 PM   #36 (permalink)
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I wish I could hit my enemies with that
Igor Sikorsky, of the 'other' propeller-vehicle fame, could do better. Developed aerosanis or 'airsleds' for transport and...war!

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Old 02-22-2013, 01:13 AM   #37 (permalink)
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These early Russian snowmobiles look cool. Altough cold weathers are not my cup of tea, I'd like to test-drive it...
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Old 02-22-2013, 01:18 PM   #38 (permalink)
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On the question of climb, here's a 65 HP vehicle that can do vertical climbs: Mosquito Aviation - Home of the Ultimate Ultralight Helicopter : Index
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Old 02-22-2013, 01:48 PM   #39 (permalink)
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...what's the rate-of-climb for an autogyro?

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