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In-Air Recharging

DamoRC

Elite member
Mentor
#41
Secondly I have a new method that should work better for charging. The plane that would be charging would have 2 batteries one that can power the plane for around 30 min and one that would be a main flight battery. The main flight battery would charge at the maximum charge rate decrese time charging and the second battery would power the plane during charging. And could be recharged by the main battery if needed for the flight profile. In order to save weight in the plane needing the charging the striped down charger that would provide the right voltages and charge rate would be housed in the charging plane. The battery being charged would be charged by only main plug.
I'll be honest - I read this two or three times and I'm still not 100% sure what you are proposing. Can you perhaps draw a diagram?

Finally if anyone @DamoRC @Mid7night @localfiendI was just wondering) wants to design a high cargo capacity plane for the project it would be a big help as I don't have much experience in foam bord aircraft design (I kinda know how to build them though and I am able to fly them.).
Might be best to just leverage available plans for bigger planes or just scale them up. The Guinea would be a good option I think.

Forget servos I figured out how to get rid of them!


Edit: more details I think I'll just use air restance to my advantage. It would be easy to impament but pitch would be near impossible with out a nother surface to catch air and provide stability. Any experanced pilots or builders have any recommendations on if pitch is nessesary and if so how to implement it? I plan on having roll stabilization on the receiving end too. That end would also have a funnel so that might correct slight pitch differences between the 2 planes. Also plans are almost done for the boom. After that it is time to make a model for the conector for 3d printing.
I'm not sure, but it sounds like you are planning a rigid boom between the two craft? This could be problematic as any deviation in direction or speed of either plane could cause one or both to come crashing down.

DamoRC
 
#42
I'll be honest - I read this two or three times and I'm still not 100% sure what you are proposing. Can you perhaps draw a diagram?



Might be best to just leverage available plans for bigger planes or just scale them up. The Guinea would be a good option I think.



I'm not sure, but it sounds like you are planning a rigid boom between the two craft? This could be problematic as any deviation in direction or speed of either plane could cause one or both to come crashing down.

DamoRC
Ok cool dirogram coming up in a few min (finishing plans for foam bord boom) thanks for your opinion on the plane also. So the connection between the two planes is not solid. The plane charging keeps a bit more speed and that holds the conector in place to transfer the charge. If the plane charging slows down and or the cargo plane speeds up the planes will separate.
 

JTarmstr

Elite member
#44
Possibly a capasitor or two in the leads to the RX or from batteries could provide power during the time it takes to switch batteries.

Any plans for the boom are moving along well. I think we are going to need a dedicated boom rx and battery to power movement servos and a fpv cam. I came up with a good way to move the boom in 2 axis (roll and pitch)as you will see in the model. Only requires 2 servos and a 2 prong servo head for both axis.
1 thing to remember about capacitors, while they charge quickly, they lose power very quickly too. maybe a small 1 cell or something powering the servos?
 
#45
1 thing to remember about capacitors, while they charge quickly, they lose power very quickly too. maybe a small 1 cell or something powering the servos?
Ya a one cell with a switch. Before the plane swiches batteries before charging you activate the one cell and it powers servos then gets shut off from the curict. I like that!

Also plans have hit a snag. Anyone know how to put a drawing on more than one sheet in fusion 360? Can't seem to figure it out.
 

DamoRC

Elite member
Mentor
#46
Ya a one cell with a switch. Before the plane swiches batteries before charging you activate the one cell and it powers servos then gets shut off from the curict. I like that!.
Need to be careful switching the one cell into the circuit while it is running on 5V from the BEC to stop the 5V from trying to charge the one cell (which shouldn't be charged above 4.2V). A diode would probably help.

Is your plan to keep the tanker in the air all the time while the smaller plane does its thing, comes in for a charge, then flys out and does its thing again? I think the whole switching from one battery to another is perhaps complicating the problem. Why not just keep one battery in the Tanker dedicated to flying the tanker and another battery in the tanker dedicated to charging the receiving plane?

We are also gonna need to start working through some math (sorry) on the power usage by the two planes. Remember that at max, you will be charging the receiving plane at 1.5 to 2C (ideally it would be only 1 C). So its going to take 15 - 30 minutes to charge depending on the size of the battery in the receiving plane. Long time to keep the two of them connected and your burning through Tanker and Receiver flight batteries during that time (unless you do the supercap "thang")

DamoRC
 
Last edited:
#47
I think that the best thing would be to have the actual nose of the charged plane be the probe. You want the size of the docking mechanism to be as big as possible to allow for error.
 
#48
I think that the best thing would be to have the actual nose of the charged plane be the probe. You want the size of the docking mechanism to be as big as possible to allow for error.
That was what I was planning on doing.
Need to be careful switching the one cell into the circuit while it is running on 5V from the BEC to stop the 5V from trying to charge the one cell (which shouldn't be charged above 4.2V). A diode would probably help.

Is your plan to keep the tanker in the air all the time while the smaller plane does its thing, comes in for a charge, then flys out and does its thing again? I think the whole switching from one battery to another is perhaps complicating the problem. Why not just keep one battery in the Tanker dedicated to flying the tanker and another battery in the tanker dedicated to charging the receiving plane?

We are also gonna need to start working through some math (sorry) on the power usage by the two planes. Remember that at max, you will be charging the receiving plane at 1.5 to 2C (ideally it would be only 1 C). So its going to take 15 - 30 minutes to charge depending on the size of the battery in the receiving plane. Long time to keep the two of them connected and your burning through Tanker and Receiver flight batteries during that time (unless you do the supercap "thang")

DamoRC
The tanker has two batteries one for flight and one for charging. As for the plane that needs charging you can refer to the diagram above. Thanks for all your help!!
 
#49
So I have been thinking that getting the planes needed for this project can't be done on the budget I have. So I think the extent of my work will be everything involved in the charging and connectors. After that I think i might hand this thread over to someone else who wants to finnish the project by eventually doing a recharge in flight. If it is possible I might send the stuff I have developed and the nessesary items to the person that takes over the tread (if that is allowed). This will allow the project not to be shelfed after everything I can do on the budget is done. If anyone is interested in this plan please pm me and if no one wants to take over or the mods won't allow it then once a pretend charging happens on the ground with the parts I can develop the thread would close.

Thanks for understanding.
 
#50
I would suggest to Swap the battery instead of recharging in flight. You could have 2 batteries in your airplane. One would be powering the plane, and the other would be ready to replace it.. And then your refuling plane would come up. Pass off a fresh battery. And your plane would drop the dead battery. Kinda like bullets in a gun.
 
#51
Ok well I made a recharging boom but it was my first time making my own plans so it kinda worked. As for the self leveling system with out servos that was a falure so it now the pilot just needs to be very skilled. I am not even posting the design for the boom as it totally sucks and I sure some members here could make one 10 times better than mine lol but for what I am doing (mainly testing electronics) it works. So next up is ordoring some wire and electronics.
 
#52
So, the design I had in mind is rather different to the probe-and-drogue setup @DamoRC showed. What I envisage is a pair of hooks on the receiving 'plane that stick up and curl backwards. Then the drogue has a pair of stubby wings, and as the tanker overtakes the receiver, this 'towed-glider' drogue drags across the top of the receiver and gets snagged by the hooks. Then either the two wing-hook contacts carry the power, or maybe the hooks pivot backwards to push the drogue down into some waiting connector (sweepback on the stub wings will provide a centring force as the cable is under tension). To release, the hooks pivot forwards so as to let go of the drogue.
The further apart the hooks are mounted, the less precisely the link-up needs to be flown as the drogue will centre itself as long as it's somewhere between them.

As for 'charging while inverted', you could use something like a bridge rectifier to make the receiving 'plane 'polarity agnostic'...
 

b-29er

Well-known member
#55
You know, as much as i hate giving apple credit for doing something correct for once

how about some magnets? Here's my thought process here:
1. I think you are going to find that a pair of thumbsticks are an entirely different realm of control authority. While a fighter jet can make very fine maneuvers, your RC is not going to want to, considering play in control surfaces, and i don't know a lot of pilots who do 'delicate' maneuvers, especially with rudder. Something that works with you (read guides the aircraft towards itself/guides itself towards the aircraft, self-orients to correct polarity or automagically rejects connection) might be handy
2. You can polarize the leads (make one side positive, one side negative with rare earth magnets) to always get a correctly polarized connection. No FOOL BRIJE REKTIFIAH, no diode voltage losses
3. low enough weight that it would work well with probe and drogue.
4. if the receiver aircraft does...aircraft things, there is a breaking force, i.e. your lead aircraft won't wind up with a dead elephant on its tail on landing, and the receiving aircraft will break away if it tugs at the magnets.
5. PLENTY OF SURFACE AREA: consider you are trying to pump a (relatively) large amount of amperage, and you wind up with just this tip of a radius to tip of a radius connection. you may wind up with sparks and other funness.

also as a thought, maybe have dual rates at like 15% for probe and drogue action and back to 100% for yank and banking fun. also, size is your friend. Making one or both aircraft large will make them more stable in turbulence.
 
#56
You know, as much as i hate giving apple credit for doing something correct for once

how about some magnets? Here's my thought process here:
1. I think you are going to find that a pair of thumbsticks are an entirely different realm of control authority. While a fighter jet can make very fine maneuvers, your RC is not going to want to, considering play in control surfaces, and i don't know a lot of pilots who do 'delicate' maneuvers, especially with rudder. Something that works with you (read guides the aircraft towards itself/guides itself towards the aircraft, self-orients to correct polarity or automagically rejects connection) might be handy
2. You can polarize the leads (make one side positive, one side negative with rare earth magnets) to always get a correctly polarized connection. No FOOL BRIJE REKTIFIAH, no diode voltage losses
3. low enough weight that it would work well with probe and drogue.
4. if the receiver aircraft does...aircraft things, there is a breaking force, i.e. your lead aircraft won't wind up with a dead elephant on its tail on landing, and the receiving aircraft will break away if it tugs at the magnets.
5. PLENTY OF SURFACE AREA: consider you are trying to pump a (relatively) large amount of amperage, and you wind up with just this tip of a radius to tip of a radius connection. you may wind up with sparks and other funness.

also as a thought, maybe have dual rates at like 15% for probe and drogue action and back to 100% for yank and banking fun. also, size is your friend. Making one or both aircraft large will make them more stable in turbulence.

True, regarding the dead elephant, I am not sure if this real or not, but can a C-130 Hercules as shown in the movie Air Force One, do what it did to keep Air Force One in the air long enough to get the people off the plane? They did this with a tow line. So I would say the Refueling Tanker, this case, the Re-charging Tanker Needs to be super strong and have enough horse power, just in case of these situations, also as you said about earth magnets, have some sort of quick release system in case of problems.