Electric C/L with Lipo Battery holstered to pilot

[Jim Stratton]

Greetings from Ventura, CA

I was referred to this forum recently as the go-to-place to float this question.

Depending on the type of plane (combat vs stunt/sport) - the weight of the lipo battery/amp/timer can equate to 30%-50%
of the total weight.

Is is feasible to the use the control lines as power lines?
The pilot could have the battery "holstered" to his belt and include the amp and timer functionality.

It would require insulated lines - and any power loss due to line length and increased drag of the lines could be
easily offset (I think) by using a larger battery.     There is probably some electrical engineering formula to
calculate the power loss.

Any feedback would be greatly appreciated.

Thanks,

Jim     

 

[Richard Imhoff]

Only one line needs to be insulated.

[John Rist]

Only one line needs to be insulated.

False.   Years ago when I was flying scale U-control I was sending the throttle signal down the wires.  To save weight I figured that I only needed one of the lines to be insulated.  The insulated line was larger in diameter then the regular line.  It almost worked until I tried to throttle down for a landing.  At this time line pull goes down and the wing drag on the larger line was greater than on the smaller line.  The bigger line was the up line.  Even while giving full down on the control handle the aircraft went up and over and then into the ground.     Any way lines of different diameter is not good.

[John Rist]

Greetings from Ventura, CA

I was referred to this forum recently as the go-to-place to float this question.

Depending on the type of plane (combat vs stunt/sport) - the weight of the lipo battery/amp/timer can equate to 30%-50%
of the total weight.

Is is feasible to the use the control lines as power lines?
The pilot could have the battery "holstered" to his belt and include the amp and timer functionality.

It would require insulated lines - and any power loss due to line length and increased drag of the lines could be
easily offset (I think) by using a larger battery.     There is probably some electrical engineering formula to
calculate the power loss.

Any feedback would be greatly appreciated.

Thanks,

Jim   

The short answer is it won't work.  I have a insulated 60' set of lines left over from my scale flying days.   I measured the resistance of the pair and found them to have 1700 ohms of resistance.  Assuming you need 25 amps to run the motor it would take 42500 volts to drive 25 amps down the lines.  V=IR, V=voltage, I = current, R= resistance.  So V=25*1700. V=42500 volts.  If you did this the lines would probably burn up.  Think about it.  Your house wiring is set up to handle 115 volts.  The average outlet can deliver 25 amps.  Consider the size of wiring in your house. 

[Gerald Arana]

The short answer is it won't work.  I have a insulated 60' set of lines left over from my scale flying days.   I measured the resistance of the pair and found them to have 1700 ohms of resistance.  Assuming you need 25 amps to run the motor it would take 42500 volts to drive 25 amps down the lines.  V=IR, V=voltage, I = current, R= resistance.  So V=25*1700. V=42500 volts.  If you did this the lines would probably burn up.  Think about it.  Your house wiring is set up to handle 115 volts.  The average outlet can deliver 25 amps.  Consider the size of wiring in your house.

That might be just a wee bit heavy for CL............

Jerry

[Dan McEntee]

  I have a Cox Bearcat that flies that way! Well, you can call it flying but it's really whipping on 15 foot lines!. With the current required for a stunt model, your flying lines would act like a fuse element and go "POOF!"  The current flow coming out of these lipo batteries is almost enough to spot weld thin sheet metal! Just not feasible for the power required for a model to fly, even for something like 1/2A.
  Type at you later,
  Dan McEntee

[Arlan McKee]

The short answer is it won't work.  I have a insulated 60' set of lines left over from my scale flying days.   I measured the resistance of the pair and found them to have 1700 ohms of resistance.  Assuming you need 25 amps to run the motor it would take 42500 volts to drive 25 amps down the lines.  V=IR, V=voltage, I = current, R= resistance.  So V=25*1700. V=42500 volts.  If you did this the lines would probably burn up.  Think about it.  Your house wiring is set up to handle 115 volts.  The average outlet can deliver 25 amps.  Consider the size of wiring in your house.

I agree with you in principle, but I think comparing Stainless to copper is more apples and oranges with regards to wire size. Stainless is closer to a heating element than electrical conductor. Can you imagine how hot the battery would get?
I can see the headlines in the local newspaper.......
Man sets self on fire while flying toy airplane.

[John Rist]

I agree with you in principle, but I think comparing Stainless to copper is more apples and oranges with regards to wire size. Stainless is closer to a heating element than electrical conductor. Can you imagine how hot the battery would get?
I can see the headlines in the local newspaper.......
Man sets self on fire while flying toy airplane.

True that copper and stainless is like apple and oranges however flight lines are steel because they are strong.  Copper is truly a better conductor but weak and would not pass a pull test.  So like you say in principle it can't be done.   However I don't say never.   When I learned to fly in 1953 I would have said electric U-control is impossible.  Now that's mostly all I fly.   

[Dave Hull]

It was done successfully a long time ago for small, light, indoor models by Addie and Tony Nacarrato. Maybe good for initial training, and certainly a novelty. If that genre is what you are considering, then I'd say yes. Guys here mostly think in terms of much bigger, much higher performance models....so, nobody's done that yet to my knowledge. However, I agree with the "never say never" comment. As an example, various companies have been dumping money into developing carbon fiber nanotubes. These have some amazing properties--including very low electrical resistance--along with low/moderate weight and good strength. So far, the technology hasn't scaled for reasons you can go study up on....

Dave

PS--If you go research remotely powered RPV's you should be able to find a very early attempt by Raytheon Company to power a small plane via microwaves. "Look boss, no strings attached!"

[GERALD WIMMER]

Hello RTP (Round the pole) electric models were very popular when I was young with frequent plans published in the UK Aeromodeler magazine . As a youngster I made a RTP Rearwin Speedster and added a bellcrank and used about 20 ft copper enameled lines. The power supply was a motorbike battery in my school back pack feeding power through a slot car controller/handle and the electric motor in the plane was from a slot car .
It flew a lot in the local park with many people having a go at it as it was easy to fly and the speed could be controlled easily. Best it could do was a very wide semi overhead loop. Did fly a traditional style RTP profile Mustang in our lounge 20 years ago but it scuffed up the ceiling as it had no elevator control when I gave it a bit much voltage.

Regards Gerald

[John Park]

I remember seeing a young girl (maybe twelve years old) flying an electric (power-down-the-lines) version of a curiously ugly little C/L sports model called the Stoneleigh Classic.  She had the battery in a shoulder bag.  The model flew, but clearly wasn't capable of anything except round-and-round level flight.  This must have been thirty or forty years ago, in England.  I can't see any way of improving on this until somebody finally comes up with that great game-changer, ambient-temperature superconducting materials!

[dave siegler]

the answer is that it would work, but you probably would not like the performance. 

As others have said, stainless steel lines are poor conductors.  Copper wire is a good conductor, poor at providing pull strength. 

for a higher performance system, the wires from the battery are 12 or 14 gauge. 

You would need fairly heavy wire.  Like 10 or 12 is needed. 

12 gauge bare wire weights about 20lbs / 1000 feet.   

2 strands of 12 gauge at 60feet is roughly 40 oz of weight just for the power wires.

[John Rist]

On this BB there are discussions on how long the battery leads be can between the battery and ESC.  it has something to do with lead inductance and ESC input filtering.  I think 60' is a bit of a stretch.   

All of the attempts to do this in the past have been with DC motors and no speed controller.  Just an ON-OFF switch on the handle.

[Tim Wescott]

The short answer is it won't work.  I have a insulated 60' set of lines left over from my scale flying days.   I measured the resistance of the pair and found them to have 1700 ohms of resistance.  Assuming you need 25 amps to run the motor it would take 42500 volts to drive 25 amps down the lines.

Or, conversely, you can calculate the voltage needed so that the lines only lose a percentage of the total power.  For a 50 ounce stunter (550 watts peak) and a 10% loss in the lines, you only need to develop 3000 volts right at your hand, to drive around 200mA down the lines to the plane.

So, aside from the fact that you'll kill yourself, that the insulation on the wires will need to be about 1/8" thick, and that the power conversion circuitry in the plane will weigh about as much as a 5S 3000mAh pack -- everything will work fine!

[Tim Wescott]

True that copper and stainless is like apple and oranges however flight lines are steel because they are strong.  Copper is truly a better conductor but weak and would not pass a pull test.  So like you say in principle it can't be done.   However I don't say never.   When I learned to fly in 1953 I would have said electric U-control is impossible.  Now that's mostly all I fly.   

Hard-drawn copper, or some copper alloy, may have a much better strength/density/conductivity ratio.  Probably less if you insist on good fatigue resistance and no toxic metals like beryllium.  But I don't think that you're going to crack the power transmission problem any time soon.

[Ken Culbertson]

Maybe if the long thick wires made the plane fly poorly you could move the battery into the fuselage and use thinner lines.

Today's houses are wired with 14 gauge which is the same wire you get on a 4s Lipo pack except it is solid.  A 5 or 6s will probably have 12 gauge.  A set of .018 lines weigh about 2oz.  A set of 14 gauge will weigh 35.  So to save 16oz in the nose you are going to add 33oz of line and God knows how you are going to get the leadouts back far enough to account for the rake.  Then, you are going to probably have to add 12oz of lead to the nose to get the CG right.

Sounds like a plan - Ken