Dan Thomas
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- Sep 17, 2008
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- 6,358
There it is. And those who don't understand wattage will fall for this snake-oil battery.
Help Support Homebuilt Aircraft & Kit Plane Forum:
henryk
Well-Known Member
many,many x 100 $ ...!
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John.Roo
Well-Known Member
3-metre long and 95kg drone is not a toy anymore....
They are really lucky that nobody was injured.
www.flyer.co.uk
They are really lucky that nobody was injured.
AAIB report slams CAA and Airspeeder after demo drone crash : FLYER
AAIB report slams UK CAA and Alauda Airspeeder after demo drone crash at Goodwood public event + VIDEO
henryk
Well-Known Member
EzyBuildWing
Well-Known Member
SureFly Aero's hybrid octokopter had(has) a 4-cylinder ICE providing electrons to its 8 motors....plus also a 5 minute battery to get you down if the ICE failed. Price to be $200k.
Anybody know what happened to it?
Anybody know what happened to it?
Purchased by Moog in 2019 and now doing military demos. I wonder if they aren't moving forward with the commercial market.
EzyBuildWing
Well-Known Member
"Flying Car" is departing the local scene! ...and so is Lear Jet....
henryk
Well-Known Member
=small propellers diameter=low Specific Thrust=many,many Energy !
=CR ,reactionless =good ,energyeffective solution !
Dan Thomas
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- Sep 17, 2008
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I think this electric flight thing is going to have to go through the same evolutionary process that early aviation did. Those first airplanes were way underpowered, structurally questionable, their engines were notoriously heavy and unreliable, difficult to control, and so on. Very few people were willing to risk themselves in them. It took some smart people a lot of years to sort out the bad ideas from the good, and most of the progress was made during the world wars, when improvements made the difference between winning and losing. We entered WW2, for instance, with fabric-covered biplanes and finished it with jets. Six years. Seven years later Cessna introduced their 180, an all-metal airplane built with the same basic airframe technology they're still using 68 years later in the 172,182 and 206.
Electric flying stuff? Don't buy the first versions of it. Same for flying cars.
It is funny because model aircraft are blazing a pretty big trail for electric airplanes too. Brushless LiPO dominated models as soon as it became affordable. Now quadcopter drones are getting bigger and bigger...the controllers were thousands of dollars 10 years ago and are basically nothing now. I see lots of youtube videos of guys scaling up multicopters and flying themselves around in them (yikes!) but then again the Wright Bros took some pretty big risks too.
Dan Thomas
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- Sep 17, 2008
- Messages
- 6,358
Model airplane power-to-weight ratios are awesome, but it doesn't scale up easily. Doubling the size of the airplane increases its weight by the cube. If we take a model with a six-foot wingspan and make it a 36-foot span airplane, the weight goes up 216 times. You need a lot more power for that. It's one reason why airliners need engines that produce tens of thousands of horsepower.
I think those numbers are right. It's still early and I'm only a few minutes into the first cup of coffee.
Hybrid electric does not make sense for current, existing aircraft. The turbofans are capable of getting up to 60% thermodynamic efficiency while flying at -50 C, 30,000 ft. A hybrid electric cannot even match that, fuel cells systems can do only marginally better, but at the expense of much more weight, price and maintenance.
When we're talking hybrid electric to replace piston ICE for GA air-planes, it does not make sense either. If you use a smaller ICE for the hybrid system it will consume about the same quantity of fuel for the range, but at slower Carson speed. So you save maybe 30% of weight on the ICE, but the rest of the hybrid system weights a lot more and you get there later. More about Carson speed.
Pure electric aircraft makes sense only in certain cases:
1. The aircraft mission is short range and duration, up to about 1h. In this case the electric system can even be lighter than the comparable ICE. If the air-frame is built around the electric system, and not a conversion, the resulting aircraft will have less drag.
2. Self launching and motor-gliders. Is much easier to fit an electric system for this purpose.
3. The electrical system enables new functionality to the aircraft - e.g. VTOL. The plethora of multi-copters, manned and not, demonstrates plentily this point of view. I'm not a big fan of multi-copters, yes they are simpler, but aerodynamically they are the worst performing aircraft out there. Considering the low specific energy (gravimetric energy density) of current batteries, aerodynamics plays a big role in aircraft range and endurance. Electric single rotor helicopter outperforms any similarly sized multi-copter, due to disk loading and Reynolds number. Cruise performance is mostly dictated by the aircraft's L/D, helicopters are not so good performers, simple multi-rotors as Ehang184 are even worse. Flying is the most efficient when using wings, due to the high L/D wings have, but historical VTOL aircraft design failures since 1950 shows this is not an easy path to take. This is due to conflicting parameters of cruise and hovering performance: L/D drives the performance in cruise and that means large aspect ratio wings, low wetted area and small propeller size. Disk loading and no flow interference drives the hovering performance and that means large rotors and no wings.
When we're talking hybrid electric to replace piston ICE for GA air-planes, it does not make sense either. If you use a smaller ICE for the hybrid system it will consume about the same quantity of fuel for the range, but at slower Carson speed. So you save maybe 30% of weight on the ICE, but the rest of the hybrid system weights a lot more and you get there later. More about Carson speed.
Pure electric aircraft makes sense only in certain cases:
1. The aircraft mission is short range and duration, up to about 1h. In this case the electric system can even be lighter than the comparable ICE. If the air-frame is built around the electric system, and not a conversion, the resulting aircraft will have less drag.
2. Self launching and motor-gliders. Is much easier to fit an electric system for this purpose.
3. The electrical system enables new functionality to the aircraft - e.g. VTOL. The plethora of multi-copters, manned and not, demonstrates plentily this point of view. I'm not a big fan of multi-copters, yes they are simpler, but aerodynamically they are the worst performing aircraft out there. Considering the low specific energy (gravimetric energy density) of current batteries, aerodynamics plays a big role in aircraft range and endurance. Electric single rotor helicopter outperforms any similarly sized multi-copter, due to disk loading and Reynolds number. Cruise performance is mostly dictated by the aircraft's L/D, helicopters are not so good performers, simple multi-rotors as Ehang184 are even worse. Flying is the most efficient when using wings, due to the high L/D wings have, but historical VTOL aircraft design failures since 1950 shows this is not an easy path to take. This is due to conflicting parameters of cruise and hovering performance: L/D drives the performance in cruise and that means large aspect ratio wings, low wetted area and small propeller size. Disk loading and no flow interference drives the hovering performance and that means large rotors and no wings.
“Whales can never supply all the oil we’ll need if we want to light every house...”
Tech changes, and while I agree right this moment the numbers don’t work, they never do in the beginning. These are all pre-first generation proof of concepts but clearly lots of companies want to see if there is something there.
Aesquire
Well-Known Member
There are 2 annoying physics issues that wishful thinking can't change.
power to weight ratio.
It's why 777 airliners don't use steam engines.
More stuff = more weight.
Gravity is a Harsh Mistress.
A Prius only has to accelerate the complex multi part drive train. Not lift it.
power to weight ratio.
It's why 777 airliners don't use steam engines.
More stuff = more weight.
Gravity is a Harsh Mistress.
A Prius only has to accelerate the complex multi part drive train. Not lift it.
henryk
Well-Known Member
Attachments
The original tail rotor consumed between 1.4 to 3kw or more of power using gearbox.
Electric used 1.4 kw and is controllable and has redundancy.
From Kiwiflyer magazine.
PredragVasic
Well-Known Member
Without any heavy math and number crunching, it is fairly easy to realise that the Prius-style hybrid cannot save any weight and may well be worse than normal aircraft engine.
Hybrids work for cars for a very good reason. The car engine needs to operate well outside of its optimal speed almost all of the time. We have gears to optimise its use, but it still only delivers the best torque at a very narrow range of RPM. A hybrid drivetrain allows the ICE engine to run at much more optimal RPM, supplying kinetic energy to a generator that then converts it into electricity to drive efficient electric motor(s), with much broader range of torque and greater efficiency. So, the overall efficiency in a regular car is fairly low, well below 50%, and hybrid can improve by optimising the ICE RPM.
Aircraft engine, on the other hand, operates at almost ideal RPM, squeezing the most energy out of the supplied fuel. It would be quite impossible to get any more of it out by running a generator, instead of a propeller, and then powering an electric motor to drive that propeller.
Hybrids work for cars for a very good reason. The car engine needs to operate well outside of its optimal speed almost all of the time. We have gears to optimise its use, but it still only delivers the best torque at a very narrow range of RPM. A hybrid drivetrain allows the ICE engine to run at much more optimal RPM, supplying kinetic energy to a generator that then converts it into electricity to drive efficient electric motor(s), with much broader range of torque and greater efficiency. So, the overall efficiency in a regular car is fairly low, well below 50%, and hybrid can improve by optimising the ICE RPM.
Aircraft engine, on the other hand, operates at almost ideal RPM, squeezing the most energy out of the supplied fuel. It would be quite impossible to get any more of it out by running a generator, instead of a propeller, and then powering an electric motor to drive that propeller.
tspear
Well-Known Member
Actually that is incorrect. What you are discussing is a hybrid in series or range extender concept. There has only really been one mass produced version of this in the USA. That was the Chevy Volt Gen 1. The Prius, Volt Gen 2 and all other cars do not sacrifice the the efficiency by doing the energy conversion from ICE to electricity to mechanical energy. Instead, the ICE is connected to directly to both the wheels and the generator. The ICE is designed to provide enough power for normal cruise plus a small amount of generator capacity, this was originally called the Synergy drive by Toyota.
Hybrid cars initially got their efficiency but allowing for a much smaller ICE engine using electric power to assist in high power situations where a small engine loses efficiency. Think acceleration from a stop, or climbing a mountain. Later plugin aspect allowed the car to gain even more efficiency by further reducing the size the ICE and its ability to charge the battery at cruise.
Tim
Aesquire
Well-Known Member
Diesel locomotives use a series hybrid, engine spins generator & electric motor spins wheels.
That, as discussed above, is not as efficient as just the IC engine alone, but efficiency isn't the Only criteria you weigh in the design process.
The Range extender idea works but there's a cost. Double the money than straight IC, maybe more weight than you can lift, etc.
There should be some benefit from electric to go this path.
Multiple motors or small pod mounts remote from power source.
Government funding from the guys that approved lesbian chinchilla studies.
Or buzzwords for your fund raising website with CGI versions of aircraft that don't exist, in exotic locations like Cancun or the Louvre.
just a few examples...
That, as discussed above, is not as efficient as just the IC engine alone, but efficiency isn't the Only criteria you weigh in the design process.
The Range extender idea works but there's a cost. Double the money than straight IC, maybe more weight than you can lift, etc.
There should be some benefit from electric to go this path.
Multiple motors or small pod mounts remote from power source.
Government funding from the guys that approved lesbian chinchilla studies.
Or buzzwords for your fund raising website with CGI versions of aircraft that don't exist, in exotic locations like Cancun or the Louvre.
just a few examples...
Bille Floyd
Well-Known Member
- Joined
- Sep 26, 2019
- Messages
- 529
Your like a : "Wake-Up call" for Reality ; i Like it !!...
just a few examples...
Bille
