Electric Aircraft

[Minuteman]

Haha, it's not just the Truck though, the trailer needs a major overhaul as well... can we say boundary layer separation. And then every trailer out there needs to be like this.

Also as to the hybrids, I do not mean a hybrid like these retarded battery and gas things are. I mean a small diesel motor powering a large generator, running electric motors that drive the wheels. Just like trains work. No part of the IC engine provides movement. That is a terrible design(which is probably why they went with that for cars).

True. I did see a truck the other day that looked like someone had taken a bunch of coroplast, zipties & bailing wire and made an "aerodynamic skirt" for their semi-trailer. It looked like an accident waiting to happen, but there might have been some gain to be had before then.

I would imagine the size of the diesel engine needed to supply enough power to run an electric motor would be just about the same size as the existing diesels. The power band of the existing diesels is probably already quite narrow because they have have a history of marrying them to transmissions with a brazillion gears. But the diesel still has to accommodate a wide range of torques, which means changing mass flow and the turbocharger speed.

There may be some gain to be had with a hybrid system where the instantaneous power demand of the diesel motor is evened-out by spinning-up a flywheel (like F1's KERS) or charging a capacitor or battery during the low-demand segments, then drawing on that reserve when climbing a hill or running from the highway patrol when they see what the company has done to their trailer.

 

[Mark815]

I don't know. You ever tried to turn an electric motor without any current on it. Takes a ton of torque. Not saying that it isn't possible, just something that would also have to be taken into design consideration.

Thats why I posted what I did. I just pictured a dying battery driven motor as the blades slowed down, but I'm sure it would be just as it is now where you would still have the ability to autorotate.

 

[deadstick]

IIRC Schweizer is working on a POC electric 300C and Cessna is working on an electric 172.

 

[fish314]

I don't know. You ever tried to turn an electric motor without any current on it. Takes a ton of torque. Not saying that it isn't possible, just something that would also have to be taken into design consideration.

Thats why I posted what I did. I just pictured a dying battery driven motor as the blades slowed down, but I'm sure it would be just as it is now where you would still have the ability to autorotate.

You know, that's an angle I hadn't thought of... good point. I guess there would either have to be some kind of one-time breakaway type device (so you could autorotate once, but then have to get it reconnected on the ground) or you'd have to come up with some kind of transmission/clutch setup, which would probably waste some energy to friction, and add some weight to the design.

Probably still doable... but it would add a wrinkle, wouldn't it?

 

[Minuteman]

You know, that's an angle I hadn't thought of... good point. I guess there would either have to be some kind of one-time breakaway type device (so you could autorotate once, but then have to get it reconnected on the ground) or you'd have to come up with some kind of transmission/clutch setup, which would probably waste some energy to friction, and add some weight to the design.

Probably still doable... but it would add a wrinkle, wouldn't it?

I don't think it would be a huge hurtle. My (limited) understanding of the Robinson helicopters is that they have a belt drive between the recip. motor and the rotor shaft, with a clutch that disengages during motor startup, ground idle, and maybe also during autorotation (otherwise, the rotor would be fighting the compression strokes in the motor).

 

[Schinpop]

I don't know. You ever tried to turn an electric motor without any current on it. Takes a ton of torque. Not saying that it isn't possible, just something that would also have to be taken into design consideration.

Most electric motors will spin freely when there is no field current (DC) or load on the output (AC). You just have the drag of the bearings. Perhaps I mis-read your post, but this would be much less drag than the compression stroke(s) on an ICE.

 

[DaveC]

I don't think it would be a huge hurtle. My (limited) understanding of the Robinson helicopters is that they have a belt drive between the recip. motor and the rotor shaft, with a clutch that disengages during motor startup, ground idle, and maybe also during autorotation (otherwise, the rotor would be fighting the compression strokes in the motor).

Yup, they have an over-running clutch that allows the rotors to turn freely even if the engine seizes completely. For startup there's a clutch switch that the pilot uses to engage the clutch belts.

 

[Minuteman]

Yup, they have an over-running clutch that allows the rotors to turn freely even if the engine seizes completely. For startup there's a clutch switch that the pilot uses to engage the clutch belts.

Ah, thanks! There goes the idea of using autorotation to try to recover some energy in the batteries.