A question about electric motors in the interwar years, Aircraft.

So, what I would like to ask about here is electric motors for turning aircraft propellers, while the electricty is generated by some other form of engine.

The main reason for this is to have a multi propeller aircraft that doesn't have huge and heavy engines built into it's wings. This is both to attempt to keep aerodymamic streamlining as clean as possible, but to reduce engine vulnernability, and keep the center of gravity within the aircraft fuselage.

I know I read about this concept somewhere, but have not been able to word my google search properly to get the result I am looking for.

Help.
 
This issue has been discussed extensively on www.homebuiltairplanes.com.
With 2016 technology, manufacturers are just starting to manufacture light, two-seater airplane's that can fly for one hour on lithium batteries.
You could use a petroleum-powered generator, but they are only 80 percent efficient at converting chemical energy to electricity.
 
Problem is that the required electrical motors are also very big and heavy. An electric motor built using the technology of the time and capable of giving the power output of a Merlin engine would weigh at least 2 tonnes and have a similar frontal area to a Merlin, before you start looking at the generation system. Even with modern technology you're looking at something weighing more than 800 kg (I don't want to go into too much detail because the actual numbers are commercially sensitive). This sort of system is only just starting to become practicable for anything bigger than a model aircraft in the next few years, although there is quite a lot of work going into it at the moment behind the scenes.

One other point - shifting mass from the wings to the fuselage is very bad news. The lift comes from the wings, so putting the engine in the fuselage means you have to make the wings stronger to carry the lifting force from the wings to the fuselage. If you distribute the mass of the engines through the wings you can build the wing structure to be much weaker and hence a lot lighter.
 

longsword14

Banned
As pdf27 said, the weight vs power balance was firmly on the side of the IC engine. For aircraft electric motors are not feasible because they never give the required thrust anyway.
The problem with putting anything only in the middle of a beam is that it ensures the highest bending moment and thus the maximum stress in the structure holding the wings to the fuselage. Once the engines keep increasing and thus the weight, putting it all in the middle would be illogical.
 
For aircraft electric motors are not feasible because they never give the required thrust anyway.
Errr... no, building an electric motor to give the required torque and speed characteristics isn't hard (witness the fact that the USN had half a dozen battleships with turbo-electric propulsion in service by this time). The problem is simply that given the technology available at the time, it'll be enormously heavy and require a hell of a lot of maintenance to change the brushes all the time.
 

longsword14

Banned
Errr... no, building an electric motor to give the required torque and speed characteristics isn't hard (witness the fact that the USN had half a dozen battleships with turbo-electric propulsion in service by this time). The problem is simply that given the technology available at the time, it'll be enormously heavy and require a hell of a lot of maintenance to change the brushes all the time.
That is what I meant anyway. The weight vs performance balance does not favour scenarios where the upper limit is low. Any statement made above was for planes only. Any combustion to electric propulsion system would not give enough thrust and still be within the weight limit.
 
Top