Pusher Drone!! - Upside Down Motors?! 

Pulling clean air is significantly more efficient than pushing obstructed air. This raging debate has been resettled many times in aircraft engineering. A few aircraft manufacturers who built pusher planes even reverted back to tractor (puller) configurations later. Conveniently, it’s also easier to engineer control surfaces behind a tractor configuration; plus, these surfaces will also have more authority behind, rather than in front of, the blown air. Cooling the motor behind a propeller is another advantage of a tractor configuration that reduces heat wear and improves dependability. I hope this was helpful! I LOVE THIS CHANNEL! Thanks for another fantastic experiment, guys!

I think the biggest difference in how it feels to fly would be in the center of gravity vs center of thrust. When they flipped the drone upside down, they put the lipo on what was the bottom of the frame, putting it on top. So the center of gravity is probably about an inch to an inch or two higher than the center of thrust. This is probably what PDEVX meant by it has a pushy feel and a reluctance to roll.

I've done a bunch of testing on a thrust stand on push/pull, and I've found that pulling is more efficient, likely because the airflow is better over the stator for cooling.

pulling or pushing air through the arms DOES make a difference. Air that is pushed by a fan goes mostly one direction, but air can be sucked from any direction into the fan (that's why we feel a very strong "wind" after the prop, but not before the prop). As for the person who feels a difference, only one way to know if it's placebo : blind test.

Ive been doing this for years. But not many people watch my videos. I even went as far as flying 7" props on a 5" source one with front motors inverted and rear motors normal. Thrust to weight ratio is insane. But i guess i should of sent it to you guys to gain some traffic traction. 😕 it flew great. Even chased some drift cars with it on 6" arms and 8" props

These are the best ones ! Thanks for another fun one :)

Love it, when there's a new RR video. High quality quad entertainment :D

you guys are inspiring me to finally pull trig and start my build! your passion is infectious, great job boys

Yessss that’s the build I’m getting Monday, I’m gonna try this after a regular flight to see if it mitigates prop wash

Classic fun with OG Christian behind the lens!

Mechanically speaking, When you turned it into a pusher, you changed the performance of the motor. Normally when the props are on top It's pulling the shaft up away from the stator reducing mechanical drag. With the motors inverted ... this may heat the motor faster and reduce performance.

You should have had a quad with "normal" configuration as well and compare them directily to eachother. Just speculating if it feels different but not actually testing anything made the Video feel like it had no point lol just 4 Guys under a Gazebo having a blast, flying a quad, chatting a bit Still watched it and I like you guys, not complaining on that side, but the Title had my expectations up a bit. I missed a real conclussion and takeaway..

It will be more efficient, because high speed air from the prop is not blocked by the arms, the slower speed air coming into the prop over the arm has much less resistance.

Also an interesting Idea that I have tried out is if you flip the frame over and put the rear motors on the top. It reduces the amount of turbulent air to the rear motors and changes the characteristic quite a bit.

Just turn the front motors over for best centre of gravity and flight feel and prop wash is better and can still turtle mode it and it also gets props out of view at 45 degrees tilt on a 7inch where you see the motors more than a 5inch

I tested several years ago because it always seemed like a better/more efficient idea to have a pusher style quad. I ended up using a thrust stand to measure the difference the drag of the arms made to the thrust but I found that at higher thrust levels the bells of the motors would come into contact of the housing increasing the drag way more than the arms, but motors are probably a lot better these days.

I've been flying 5" pushers since 2017. Twin Quad Guys CK-SX frame, Botgrinder BOT5, and the Demibot. I plow thru scraggle freely, because frame protection. I bottom battery mount, and use the frame otherwise normal, not inverted.

I love the Dustin of FPV 🙂

I was like "Damn Drew needs a haircut" and BOOM! Drew has a haircut.... Damn I'm good.

Pushers have cleaner air at the end. And they sound different. Plus, you get force being pushed against the inner bell rather than the c-clip/screw holding the bell.

You guys should run reverse motor direction anyway. It flings dirt away from the lens and gives the rears access to cleaner air.

Awesome.

The prop and motor manufacturers love it 👍🏽 Since us mere mortals tend to slam the ground a few times per sesh, it would need some kind of prop/motor protection to be viable I think. Love the concept tho.

WHAT !!!!! I literally was just having a conversation with kebab FPV, not four days ago about this exact thing a 5 inch FPV freestyle pusher quad copter !!!!!!

I thought it was a awesome fun idea Drew!!! The guys didn't seem to supportive but look like a cool try to me! If anything a fun day

I found when I did this with my whoop, it flew just the tiniest tad crisper handling than a standard whoop. But. *Noise.* It turned my stealthy, quiet platform into a screech owl. Also, the props are far more vulnerable on a pusher whoop. Overall, it's the noise that turns me off - not as big an issue with open props, I'd guess.

maybe it comes down to how well the stators/motors can handle drastic push/pull regimes?

Personally I did something similar about 5 years back just for camera to have clear view. My setup was 5" drone running 6" props on 4S. Front motors on the bottom and the rear on top with 3D printed spacers. That was back with DJI Ocusync or Digital FPV System The First digital air unit from DJI.

Bring back the eye liner and colored hair.

You guys should change all motor positions so that the arms don’t have any effect at all. So bottom left motor would be at the base of the quad. The Top right motor would be at the top and the arm. Both other arms vice versa. So that all props will be pushing and pushing air without hitting any arms in the process. I hope that makes sense. You would need some landing skid plates to hold the drone off the floor. Just an idea really.

Dear LeDrip, I think the Arms over the Prop (pusher) does not realy block the Incomming Air. If the arms under The Prop (Normal) it have much more Impact on the Airflow. Becurse the Pressured angled Air is blocked by the Arm. In this Case there are caotic Air circulations spreads in all directions around the arm, and have large Impact on the Thrust flow area around the arm. I think in pusher it is much easier to suck the the Air in the Propeller from evrywhere. Over the Propeller there is a Low Pressure Area, this area suck the air in the Prop from all directions inclusive the Ramair of flight speed. The High Pressure Area under the Prop is pushed in one Direction. The Sucking Area is Sucking of all directions, and the Athmospherik Pressure is helping to "refill the low pressure area" And did you Inverted the Motor Directions in Betaflight? Or swaped the Propellers on the Arm? This could have Impact on flight handling in case of the Yaw axis mixed with other Axis in flight.

maybe the way it feels is the distance of force from the center of gravity. perhaps while pushing there is more throttle necessary to do the same move by like a hair. Would be curious about underslung battery.

"God damn the pusher." -Steppenwolf

If you install the motors upside down in the freestyle frame and mount the battery at the bottom, you can shift the centre of gravity enough to get a balanced freestyle quad.

I'm surprised you didn't try it with the battery mounted underneath. It would make taking off, and landing easier. How it would affect the flight characteristics, is just a guess until you try it.

can you try to make a prototype frame where the lipo slots inside the middle of the frame, resting on the bottom plate? try to come with a solution to put the FC and ESC. it think it wil fly good its like a mid engine racer. widen the frame just a bit so it stil has 2 carbon sides and a hole big enough so half the lipo slots inside the frame. the lipo wil almost be exactly in the middle of the props and between the top and bottom

Absolutely YESSS on 12"19' and you should maybe try to put the arms down instead of on the top.

as my 1st betaflight quad, i've only ever flown a pusher setup. And i'm terrible at it. The fact that 1/2 the pilots can't tell the difference let me know it's not simply motor orientation that's holding me back, lol

Multi rotor aerodynamics are so weird, but as a fixed wing hobbyist I’ve done a bit of studying on pusher props. Aerodynamically, propellers have kind of a weather vane effect; for a plane, you get more longitudinal stability with a pusher prop vs a tractor propeller all things equal (or as equal as possible). Supposedly, doing a “pusher” prop setup would make your kwad more stable, and at that *less* agile in freestyle. Stability is great for a cinema setup but not aerobatics, so in this case, pusher perhaps is way worse for freestyle drones.

You can see that the quad was flying much better when shawn first started. By the time Bubbys turn came up it, you could see jello just flying straight the level. Wonder if the vibration was impacting the FC enough to hurt performance? Maybe the off-set prop disc made the vibs worse or if it was the stack of the vibs and the offset?

At 9:27 you can see that the props are flipped appropriately. Also having the arms on top does not impact the airflow into the props as much as being on bottom and affecting airflow out. The biggest difference is going to be center of gravity change and the tune, compared to each pilots regular rig. Get two of those side by side, one up and one down, then blind test it as best you can.

What if the motors are pushing friction into the bearing more and thats why you dont get the pop or the faster throttle

Amazing well done 👏 🎉🎉🎉🎉

I would like to see the motors spaced up an inch above the frame, more even with the middle of the battery. The way it would carry the center of gravity might allow for even tighter turns and even quicker roll rates, it might even stabilize better? Its similar to balancing a basketball on a concave surface vs a convex surface. What surface takes more effort to keep the ball in the middle? Fun fact: When you learn how to balance a tennis ball on top of a beach ball, then you'll understand the concept of how to fly a helicopter.

@rotor riot what about a mid mount frame but make it a pusher!!! That would be fun 🤔

i think it looks cool

Highly doubt theres going to be much of a flight differance. What there however will be is a massive reduction in crap that gets into the motors, when chasing things with a lot of gravel/drit/rubber like motocross, rally or drifting. I have had rocks jam up motors, and iv had to clean out melted rubber from the bells. Yet when i flew a Avata during a Swedish folkrace event the motors were as smooth as if i never was there. Normally id have to tear the motors apart and clean them out with bluetac/possible even replace the bearings if its fine dust/really dry at a race.

I started with the Avata a “pusher” and got a lot flight hours in.. When I transitioned to a freestyle drone with motors on the “ bottom “ the freestyle drone of course had more punch but less stability on low end hover.. from what I can see from your goggle footage, it looked like an Avata flying with a lil more power. Rates did seem slow and could be making the biggest difference… Just my 2 cents experience lol 😅

Suction is omni-directional, and thrust is is directional. There would definitely be A difference. But with the amount of work the flight computer does. Probably very hard to quantify. Do a weight lifting comp with both types!

1. Invert only the front motors. 2. mount the motors upside down, not just turn the frame around and change configuration in BF. on a couple of my O3 quads, to get the props out of view, I just invert the front motors, leave rear motors as is. and it should have been a true blind test.

Nice video, PEDVX is like "Chorão" singer of Charlie Brown Jr. band of Brasil!!!

Props out, bottom mount lipo. 👌🏼

When you inverted the motor did you also invert the props ???

Cool idea 🔥🔥🔥

If anything the motors seem starved of air by pulling in air over the arms. Might explain the performance difference. Clean air going out for better prop wash but with the tuning for normal setup already takes into account prop wash from the air going over the arms. I suspect you need to re tune for it pulling air from the arms. But it definitely seems starved of air hence the lack of peppyness.

Pusher are preferred because propellers are not disturbing camera view. It will feel underpowered because it is pushing over the cushion on air it pushes below it.

Hi guys! Are you 100% shure the props where mounted correctly, so that the rounded side is up and flat side at bottom when the quad is in ready to flight position? (the props should be facing the same as before the pusher changes)… I ask because it would be an easier mistake because you are not used to screw them on reversed.. 🤷🏻‍♂️ This could explain the lack of power

The propellers are pulling air across the arms, yes, but it doesn't really matter because the propellers are also ramming the frame into air as it flies forward.

I was wondering what was happening to the bearings in the motors, are they uni directional thrust or bidirectional thrust capable?

Is it possible to flip over a cinawhoop and the props to fly upside down? Either by flipping the flight controller orientation or flipping the fc itself? I want to turn my pavo20 into a more freestyle type quad by removing the prop guard and maybe the entire drone so i dont hit props on the ground trying to take off, i suppose i could make a stand for taking off that cradles the battery instead lol but still curious to try it

8:25 what Shawn is saying is exactly what I thought you meant in the beginning of the video. Confused why they didn't do it this way?

"we're out of video ideas, ok".. lolol

AMAZINGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG

@letsflyrc waiting for that Tanq dead cat bro 👊😎👊

Did you change the props for Bubby after the crash?

Did you use a pusher style prop in the video?

Moving the motors should change the mass moment. If you increase the mass moment, you will increase the the force required to change direction. DaveM

This is literally the only way to fly now guys, a truly ground breaking discovery that has now forever changed the FPV community standards

The reason it's used on some of the small "whoop" type drones, is because they are designed to fly slow, like inside, etc. The "pusher" effect creates an air cushion when flying close to the ground/floor, kinda like a hover craft effect. I have several I-flight drones, pusher and standard types. The little Protec 2.5 pusher is fun inside, but like others said, kinda "mushy" outside.

I was thinking, is it more efficient? More flight time?

The flat carbon fiber rod to the motor is not aero dynamic at all. Try 3D print aerodynamic V shape on both sides where the prop is, and then try with both configurations, and as pusher, make sure motor rods are on top to ch he weight balance. There’s a reason dji drones have aerodynamic rods to the motors.

The pid need to be re-tuned, for each setup as the COG is different you can't compare with tune.

try draw on paper flip one with props up, and one props down, and thing about gravity center, i guess fliping wth props under its harder but more stability in line, props on top gravity center under props give more stability in rolling but not so on flat , same like trust on rocket engine, ,rolling hard but more stability (props under) sorry for low lvl Language :D

You should tape a mini skateboard in the bottom

I think that the props are made "to suck air" rather than push. It's a different geometry when you use them upside down. Not sure but just a guess. I did the same experiment with a "first gen carbon frame", and it feels just a bit "mushier", but not especially bad. I think that the props are designed to push air in a specific direction, not the other way around. Just a theory.... Greetings from Germany!

Did you flip the props when you reoriented the motors? I saw BF config props-in at 3:27 and at 4:10 it looks like the props were mounted upside down (right side up when the quad was upside down 🙃) Those props did not look like 3D or symmetrical props and this could really mess with your performance as the airfoils have a clear thrust efficiency preference. ~Shaznoid

Wow first video I've seen rotor riot use the goggles 2 and 03 unit instead of the walksnail in their video

How much of a difference does it make due to the fact that the arm is not blocking thrust but instead blocking the air above the prop

Ihave been building like this for years , no props in view and i prefer it

Personally I have been wanting to set my Shendrones Squirt up like this though it is definitly a different style. Does have thin arms.

What if you mount the motors normally and make the drone a pusher by configuring it upside down in betaflight. Then only change the camera angle and fly it upside down.

Does anyone know what park this is in Orlando?

Pretty sure an aero engineer can make that work in ways u can't imagine reduce the surface in top of the props the thinnest u can and u will see the difference air needs to Flow both ways guys equally

I have experienced the same thing as Bubby. Every "pusher" feels slower then equivalent "puller"

5:00 for more thrust and efficiency... i thought we all knew this lol

Actually I have been thinking of doing similar mod on crux35 just because the battery is bottom mounted. Flip the motor, swap the props and change the direction of motor in BF.

Remember when folks were actually experimenting with frames that allowed for pusher prob configs??

way to going

Analytics!

With gps and some code you would have a nice autonomous lawnnmower Drone

Yea its shaky bubby after drew throttled it into the ground 😅😂

Drew! dead cat wins! 🎉 El gato muerto!!

I fly cinewhoops so alot of my drones have this so yea

tpu nut covers for skids bros. :)

Did you flip also the props? :D That could be why it flew so lazy

A lot of what they seem to be describing are the rates, and Bubby is describing a drone that full throttle to the earth

Put the motors on the bottom and the battery as well to keep the cg

But how would it feel it you put the front motors on the bottom and rear motors on the top ? Hmmmmm

I think you guys missed a serious point in your setup unless uiu just didn't show it,, You have to tune it differently when you push instead of pulling through the arms vs pulling accessed for the push Hensel the "Slower responses" to movements up the rates and use good solid supermarket on power input!;-)) thanks for the ideas 💡 guys Bravo miss that stuff 👏 👍 😉 😄

i want to see pulling props but on an upside down frame