Help! Multi rotor competition help

[Andres_r35]

Hello my name is Andres,
I am building a quad copter that will weigh at most 5 pounds. It will need to fly a long way ( not sure but a mile? maybe more), but I am looking for efficient motors with a low amperage take so that the battery will last longer. I was planning to use a 2300Kv motor with a 6" fold-able propeller that has a 35 amp continuous take, but I realized that it was relatively a large amperage take so i started looking at 15 continuous amperage. I was looking for a professionals help on picking a motor for this drone. I am looking for mostly longevity ( so lower amperage take?) that will fly at around 500 feet AGL. I am also looking for a good battery to use, right now I am looking at a 3 cell 5500mAh battery with 50C, but I have to take in account the weight of battery. I am also using a random 4-in-1 ESC with max 40 amps I found since i didn't think it would be that important, but any feedback would be cool too. I was planning to use the 4-in-1 ESC for less weight. We are using the Omnibus F4 pro with a Beitian BN-880 GPS module that I found recommended by INav...is that a trusted GPS module to use? The flight controller comes with a barometer so I was planning to use this all together to program the drone to use the autonomous Way point method or an RTH option. I'm not using any camera. For the transmitter and receiver I was going to use the cheaper option of the TBS crossfire module, which I found to be the FrSky R9 module to extend the range. I am planning to have the drone autonomously going to the way point then manually landing it, but it will go up as high as 5000 feet. Is the FrSky good enough or is the TBS Crossfire going to give me less issues? The transmitter I am using is the Taranis X9D with the FrSky R9 module attached. I am new at drones so any help is highly appreciated on what to get.

 

[ElectriSean]

Hi Andres, a few things to consider. Flying at 5000' is completely illegal in every jurisdiction I'm aware of. The stock FrSky 2.4g system is capable of about a mile in good conditions, but you're smart to consider long range options like the R9 or Crossfire.

You can't choose a motor based solely on current draw, the most important thing to consider is the amount of thrust it produces, You want at least a 2:1 thrust to weight ratio, so for a 5lb copter you're going to need 10lbs of thrust, or about 4500gr. That's about 1200gr of thrust per motor, which is pushing the extremes of what a mini quad motor can produce with a 6" prop. For this sort of heavy lift longer range stuff you would be better suited with a larger, slower motor and bigger props, especially if efficiency is a goal.

 

[MorningViewFPV]

i was thinking bigger props for sure.

 

[PsyBorg]

I would guess to carry 5lbs ( all up weight or minus battery packs?)
Motors in the 850 to 950kv range on 12 or 14 inch props would be far more effecient.

Still not sure that would give you the flight time to go a mile. Gps hover and land and still be able to get back up and rth.

As Sean says 5k altitude is illegal and extremely unsafe. Technically so would flying out of los but if your gear is top spec and reliable....

Anyways.. to be honest if you are here asking basic questions you should really rethink this project until you are far more knowlegable in all of the various aspects of the hobby.

 

[FDS]

The altitude could be due to terrain?

 

[Andres_r35]

I would guess to carry 5lbs ( all up weight or minus battery packs?)
Motors in the 850 to 950kv range on 12 or 14 inch props would be far more effecient.

Still not sure that would give you the flight time to go a mile. Gps hover and land and still be able to get back up and rth.

As Sean says 5k altitude is illegal and extremely unsafe. Technically so would flying out of los but if your gear is top spec and reliable....

Anyways.. to be honest if you are here asking basic questions you should really rethink this project until you are far more knowlegable in all of the various aspects of the hobby.

Sorry, to clarify we are using this drone for a payload competition launched on a runway with a cleared airspace. We are going to be deployed off a rocket at 5000feet but we have a method of slowing down and releasing the drone at around 300feet AGL so our drone won’t start up until then. The problem I am afraid of is when our payload holding our drone comes down, it will be pushed by the wind. So when we release the drone at 300feet it would have to go a long way to hit the target( our competition is to guide our payload back down to a target). Another factor is the constraint of 5lbs, and having to fit this inside of a 6” diameter by 15” long tube. We are planning to make foldable arms and props to make this all fit though. So yes, 5 pounds including everything. Sorry didn’t mention most of this earlier. But props, change to 12”? I am afraid of it not fitting or going over the weight limit.

 

[PsyBorg]

Things to ponder..

5lb mass freefalling 4500ft. (Speed kills.)

Prob 1. Tumbling.
Prob 2. Motor freewheeling backfeeding power to the esc.
Prob 3. Possible overspeed damaging motors
Prob 4. Prop blades shearing off or total destruction of them.

I would say your craft must exit your launch module under power.

First to stop tumbling. Second to keep torque on the motors so they and or your props do not self destruct. Specially folding props that are signifcantly weaker.

I suppose you could paradrop it and release the chute just after powering props so it does not come down tumbling or at terminal velocity.

Either way you need to control the motors freewheeling and protect them props somehow until the fall is arrested to keep them intact.

Still 6 inch props carrying 5lbs seems a stretch to achieve this goal. Again far lower kv and bigger pitch if not bigger size should be considered.

A final note for the radio. No matter what power gear you use once a direct los is broken control becomes less once objects get between tx and rx. At a mile range that can be a huge if not total loss of control.

 

[Piotrsko]

What could possibly go wrong here?
I guess payload is ejected out the nose end possibly along with the recovery chute for the boost vehicle. Some separation time.........

Oy this makes my head hurt.

 

[Andres_r35]

Things to ponder..

5lb mass freefalling 4500ft. (Speed kills.)

Prob 1. Tumbling.
Prob 2. Motor freewheeling backfeeding power to the esc.
Prob 3. Possible overspeed damaging motors
Prob 4. Prop blades shearing off or total destruction of them.

I would say your craft must exit your launch module under power.

First to stop tumbling. Second to keep torque on the motors so they and or your props do not self destruct. Specially folding props that are signifcantly weaker.

I suppose you could paradrop it and release the chute just after powering props so it does not come down tumbling or at terminal velocity.

Either way you need to control the motors freewheeling and protect them props somehow until the fall is arrested to keep them intact.

Still 6 inch props carrying 5lbs seems a stretch to achieve this goal. Again far lower kv and bigger pitch if not bigger size should be considered.

A final note for the radio. No matter what power gear you use once a direct los is broken control becomes less once objects get between tx and rx. At a mile range that can be a huge if not total loss of control.

We were planning to use a 6" diameter by 15" inch tube that the drone will be inside until we release it. Once ready, the parachute would be released until slowed down for the drone to be released.

 

[cranialrectosis]

I'm thinking (if you can) a small glider with a foldable prop and foldable wings so when it drops out of the tube the wings unfurl and you fly home.

I think two folding wings and a folding prop are simpler solutions than a parachute, 4 folding arms and 4 folding props. I also think the fixed wing with a 25" wingspan and 10" folding prop is going to be WAY more efficient at altitude, payload and distance.

 

[PsyBorg]

No matter how ya look at it this whole concept and idea is super sketch. Far to many uncontrollable factors with high potential for disaster.

Keep ideas going tho. The more we can meld together a better chance for success and less chance of causing more drama about our hobby.

Just remember we get 10% of the darpa funding if you win!!

 

[Andres_r35]

So from the parts that we have right now, I am assuming our drone will weigh 2 pounds. The maximum distance it will need to go is 2,400 meters or 1.5 miles. The frame that was suggested to us has maxed 7" propellers that have foldable arms. Should we look into other frames that support larger size propellors? Any other factors I might be missing that I should look into?

 

[ElectriSean]

2lbs is much more realistic with 7" props.

 

[Andres_r35]

2lbs is much more realistic with 7" props.

So with these 7" x 4.5 props I was thinking of using a 1600kV motor. How would I find the thrust to weight ratio of this?
How do I know what kV pairs with what motor or does that comes with experience?

 

[ElectriSean]

So with these 7" x 4.5 props I was thinking of using a 1600kV motor. How would I find the thrust to weight ratio of this?
How do I know what kV pairs with what motor or does that comes with experience?

Every motor should have a thrust chart that shows how much thrust it produces with a variety of props and battery voltages. https://www.miniquadtestbench.com/ has also done a ton of independent testing, check there also if you're having problems finding data for the motors you're looking at.