EEEElectrical Engineers .

[M Spencer]

RIGHT . Having flown Electric back in 75 .
A - R T P slot car motor all sheet piper cub 

And thinking of national grids . Would these electric stunters be best runing A C , down the lines . or three phase . 
that just slipped in. Had been thinking do you gotta have Three Lines for A C . With a rectifyer in the aerolane .
And the Pilot Plugged In .

With the little RTP you got massive voltage drop , on 12 V slot car system . we ran it on a battery charger , I think .
But thats the point of AC , isnt it .

So , all the sums need a bit of calculation . Wouldit Work . AC to batteryless plane . And a NEW ERA of Lite Wt. P. A. dawns . 



This is a traditional stone age rectifyer .

[Brett Buck]

With the little RTP you got massive voltage drop , on 12 V slot car system . we ran it on a battery charger , I think .
But thats the point of AC , isnt it .

  Actually, no, that is not the point of AC, or at least not directly. If everything else is equal, AC loses more power in transmission than DC, from reactive impedance and from corona discharge at high voltages. What made AC attractive is that you could easily jack up the voltage for transmission purposes compared to DC. Trying to distribute 117 volts AC is no less impractical than trying to distribute 117 volts DC, and would not work any better. AC was used because you could generate it and transmit is at very high voltage, and then easily step it down as the destination. 13800 volts at the transformer on the pole in the USA gets stepped down to 240 to go to the house. AC is easy to raise and lower using transformers, DC is very difficult and inefficient aside from rare cases

     What you really want is higher voltages, AC or DC is not critical. EV vehicles typically have 400 volt or higher batteries to reduce the required current and save some weight, Formula 1 hybrid batteries are reported to run something like 1200V.

     Brett

[M Spencer]

The thought was , sorta , With modern componentry ,  ' would down the lines  power ' work , for F2B / P. A. , these days .

Id meant to mention ' capacitor ' . These things are supposed to mean you dont need a battery in the thing .


With this one , Its like I read " were you educated at Eaton " ?

reply " That would be a matter of opinion " .     
Most of this English Rubbish WASNT , if treated with respect . But seven kicks to restart stalling at the lights in traffic , might give you doubts . Usually one or two did it .


THEREFORE , What would we need , to have the battery at the pilot , and have the lines not melt. Or is it still impractable , for competition use . ?    thanks .
The pictures are merely illustrative , modern transisterised rectifiers & capacitors , and presumeably what ever else required , are miniturised & more durable . 

[Brett Buck]

Id meant to mention ' capacitor ' . These things are supposed to mean you dont need a battery in the thing .

   That say "Lucas" right on it, how many warning signs do you need?

    I think what you are poking at is the possibility of using a "supercap", IOW super capacitor, instead of a battery. It's sort of like a halfway between a battery and a true capacitor, charging and discharging very rapidly using fast chemical reactions, as opposed to just storing the charge on a plate.

I would have to do some math, but it looks like the energy density of a supercap is about 1/20th - 1/10th that of a lithium-ion battery. Meaning to get the same total energy, it would have to weigh 10x as much.

      Brett

 

[katana]

Had been thinking do you gotta have Three Lines for A C .

Actually you need 4 lines - 3 for each phase + a neutral. Probably more weight and drag than would be sensible. Plus have to use insulated lines or never loop!

[CircuitFlyer]

F2B? No.  Although not impossible, impractical and very expensive. https://www.vicorpower.com/resource-library/articles/uav/design-guide-powering-tethered-uavs

[John Rist]

F2B? No.  Although not impossible, impractical and very expensive. https://www.vicorpower.com/resource-library/articles/uav/design-guide-powering-tethered-uavs

All good but how do you get a 400 v DC power source.  A tethered UAV can be driven from a gas powered generator on the ground.  Also the tether drag for UAV is weight.  For U-control it is weight and wind drag.  Power down the flying lines, for now, is a bad ideal.  Improved battery technology will be the next step up for us.   

[Ty Marcucci]

In the SCCA they called Lucas "Lord Lucas, the prince of darkness"..

[Brett Buck]

Actually you need 4 lines - 3 for each phase + a neutral. Probably more weight and drag than would be sensible. Plus have to use insulated lines or never loop!

    If you were going to use AC, you would certainly not use 3-phase for exactly that reason, you would use single-phase like any consumer device.

     Brett

[Brett Buck]

All good but how do you get a 400 v DC power source.  A tethered UAV can be driven from a gas powered generator on the ground.  Also the tether drag for UAV is weight.  For U-control it is weight and wind drag.  Power down the flying lines, for now, is a bad ideal.  Improved battery technology will be the next step up for us.   

   400VDC?  No problem, as long it was on the ground. 266 AAA-size batteries, 100 iPod-sized lithium-ion cells, etc. Energy is energy, the only reason it weighs more than a current flight pack is the packaging, you could handle 10 lbs without noticing it and do all your official flights on one charge.

   People have been looking at power through the flying lines for 50+ years, and while I don't have any specifics to give, I am sure people have done it multiple times, and the bit about high voltage reducing the size of the lines is absolutely nothing new. There was a thread on RCO about in stunt. I also note that the FAI has a rule somewhere about the maximum allowable voltage, I think it is 42 or 45 volts.

     Brett


p.s. 42V https://stunthanger.com/smf/open-forum/hybrid/msg635682/#msg635682