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#171
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Electrically Powered Ultralight Aircraft
jimp wrote This is probably a historic moment. Normally what happens when thread drift begins is that it increases at an increasing rate such that what was originally zepplin aerodynamics becomes the best recipe for strawberry preserves... LoL ! Thanks, I needed that! -- Jim in NC |
#172
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Electrically Powered Ultralight Aircraft
"Dan Luke" wrote Pardon the intrusion on this interesting discussion, but just how *does* added weight in a car impose extra load on the powerplant besides via bearing friction and tire deformation? It isn't. He failed to include bearing resistance (only tire deformation) in the original assessment of increased rolling resistance. -- Jim in NC |
#173
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Electrically Powered Ultralight Aircraft
On Aug 18, 12:24 am, "Morgans" wrote:
Nope, lots of problems to consider before we start considering an electric aircraft. Lots more than we can maybe even consider, at the moment, even if we were to figure out a way to make a practical airplane electric powered, don't you think? -- Jim in NC Oh, definitely. We are nowhere near a practical electric airplane. But I think the potential is there (no pun intended), and I hope they keep working on it. |
#174
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Electrically Powered Ultralight Aircraft
In rec.aviation.piloting Morgans wrote:
"Dan Luke" wrote Pardon the intrusion on this interesting discussion, but just how *does* added weight in a car impose extra load on the powerplant besides via bearing friction and tire deformation? It isn't. He failed to include bearing resistance (only tire deformation) in the original assessment of increased rolling resistance. I didn't include it because the increase in wheel bearing friction (the only bearing friction effected by weight) is negligable in modern vehicles. The total bearing friction, i.e. all the bearings in the vehicle is around 10% of the total drag forces trying to slow a car. Adding a little weight to a 2000 to 3000 pound car causes an insignificant change in the wheel bearing friction. -- Jim Pennino Remove .spam.sux to reply. |
#175
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Electrically Powered Ultralight Aircraft
wrote)
Normally what happens when thread drift begins is that it increases at an increasing rate such that what was originally zepplin aerodynamics becomes the best recipe for strawberry preserves... So you're saying zeppelins should take advantage of jam-jet propulsion technology? ....when in season, of course Paul-Mont Usually needs to snow twice before I get the drift ~~~~ |
#176
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Electrically Powered Ultralight Aircraft
On Aug 11, 9:47 pm, "Bill Daniels" bildan@comcast-dot-net wrote:
... I've already made a cell holder for A123 Systems "A1" cells. That's the lithium phosphate nano cathode one used in 36V DeWalt power tools. You can buy a couple of new DeWalt 36V power packs for $50 or so on Ebay. Then, dismantle the pack to retrieve the individual cells. My pack will be 13.8 volts and 11AH weighing 3 pounds. It will be the same size as a 7AH 12V SLA but weigh less than half as much. Don't forget to add a brick of lead to the bottom of your new battery pack, to keep the CG in the right place ;-) Best Regards, Dave "YO" |
#177
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Electrically Powered Ultralight Aircraft
wrote)
In cars, weight matters most in acceleration and doesn't matter in any significant amount with modern tires in cruise. Speculate please: 1. Two 3,600 lb cars - good tires 2. Traveling 60 mph (no wind) 3. 4cly - 150 hp (Honda Accords) 3. Flat highway in North Dakota 4. Fuel flow meters hooked up to both vehicles (Honda #1) Driver ................ 105 lbs Fuel .................... 15 lbs TOTAL .............. 120 lbs (1/30th of 3,600 lb car) (Honda #2) Driver ................. 300 lbs Passengers ........ 700 lbs Luggage ............. 100 lbs Fuel ................... 100 lbs TOTAL ............. 1,200 lbs (1/3 of 3,600 lb car) ....BTW, BTDT! g If both vehicles were monitored for 50 miles, would their fuel flow be (approx) the same, in cruise? Paul-Mont |
#178
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Electrically Powered Ultralight Aircraft
("Charles Vincent" wrote)
According to SAE studies, aerodynamic drag accounts for 60% of the resistance that must be overcome for highway cruise, with tires being 25% and driveline friction making up the last 15%. Semi: Tires ........... 18 Footprint ..... big per tire Weight ....... 80,000 lbs Drag .......... HUGE!! MPG .......... 5 (loaded) Minivan: Tires ........... 4 Footprint ..... smaller per tire Weight ....... 4,000 lbs (for easy math) Drag .......... MUCH less + no cab/trailer drag MPG .......... 22 I've never really understood why an 800 lb motorcycle/rider gets (only) 50 mpg and a fully loaded semi can get (about) 5 mpg? Motorcycle: Tires ........... 2 Footprint ..... very small per tire Weight ....... 800 lbs (with rider) Drag .......... It's a motorcycle! g MPG ........... 50 Paul-Mont |
#179
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Electrically Powered Ultralight Aircraft
Montblack wrote:
("Charles Vincent" wrote) According to SAE studies, aerodynamic drag accounts for 60% of the resistance that must be overcome for highway cruise, with tires being 25% and driveline friction making up the last 15%. Semi: Tires ........... 18 Footprint ..... big per tire Weight ....... 80,000 lbs Drag .......... HUGE!! MPG .......... 5 (loaded) Minivan: Tires ........... 4 Footprint ..... smaller per tire Weight ....... 4,000 lbs (for easy math) Drag .......... MUCH less + no cab/trailer drag MPG .......... 22 I've never really understood why an 800 lb motorcycle/rider gets (only) 50 mpg and a fully loaded semi can get (about) 5 mpg? Motorcycle: Tires ........... 2 Footprint ..... very small per tire Weight ....... 800 lbs (with rider) Drag .......... It's a motorcycle! g MPG ........... 50 Motorcycles have a terrible coefficient of drag given their shape and the shape of the rider. A fully faired bike is much better, but still much worse than most cars. My K1200LT is one of the better motorcycles and its Cd is above 0.5 with the windshield fully lowered and I believe it is closer to 0.6 with the windshield at the highest setting. So even with the relatively small frontal area as compared to a car (although not as much smaller as you might think as the bike is taller than most cars), the drag coefficient is so high that the total drag is quite high in comparison. Matt |
#180
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Electrically Powered Ultralight Aircraft
Montblack wrote:
I've never really understood why an 800 lb motorcycle/rider gets (only) 50 mpg and a fully loaded semi can get (about) 5 mpg? Motorcycle: Tires ........... 2 Footprint ..... very small per tire Weight ....... 800 lbs (with rider) Drag .......... It's a motorcycle! g MPG ........... 50 Paul-Mont Check this: http://www.bgsoflex.com/airdragchart.html Matt |
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