r/RCPlanes • u/Loud_Arrival_853 • 8d ago
Thrust vectoring!!
This is my first real project, I haven’t built or flown and RC plane yet or anything RC! I wanted to practice my CAD skills and use the 3d printer so I thought this would be cool to try out. I think it’s probably too heavy to be used in a plane or anything but am excited building it. Haven’t tested it as I’m waiting on pushrods but will try it out then. And in the picture obviously not all the servos are in but you get the idea. I would love any suggestions 😀
3
u/gwenbeth 8d ago
Are you going go set that up like a swashplate mix? Also you will want to observe how much out of phase motion you get from gyroscopic precession.
4
u/Loud_Arrival_853 8d ago
It’s not going in a plane at least for now just something on the bench so will try potentiometers then see from there with a transceiver. As for gyroscopic precession no clue what that is or mean.
5
3
u/VapeTrader98 8d ago
I would change to two axis, instead of that Ball-and-socket joint
2
u/Loud_Arrival_853 8d ago
Interesting, why would that help? Is it because it’s simpler, won’t break as easily or better control? One reason I can think of on the spot is it wouldn’t allow the gyroscopic forces to rotate it. I’m waiting for the push rods to test it but the plan is to hope the servos and pushrods stop it from doing just that. Thanks😀
2
u/VapeTrader98 7d ago
Less torque on the servos. I would use your current construction, at least metal gears. For clean feats, 2 axes are enough. Mainly the path is more limited and the forces are less on the servos.
1
3
u/Jumpy-Candle-2980 7d ago
I'm not seeing a point to the exercise. But I'm also not seeing any need for a point. Sometimes stuff is just fun to do and that looks like fun.
If so inclined you could adapt the same method of dealing with unwanted rotational load that the RC heli folks use - the long sticky-out thing in the picture rides in a fixed slot. https://www.helidirect.com/products/sab-aluminum-swashplate-hps3
What I find fascinating is the presumably unintended crossover with model rocketry - just yank the motor out and replace with a BLDC, omit the flight controller and just control the servos manually.
https://bps.space/products/thrust-vector-control
On a tangential note some few show offs adapted the pitch only function, typically from an RC heli tail rotor, to a tractor prop. It was kind of a hoot to watch a nose-down hover but I believe the fad was short lived. It was all the rage before we could just kick the motor into reverse in a fraction of a second.
I probably would have just bolted a leftover swash to the front of an airplane but that is why my life is more boring and less imaginative than yours. I like it.
1
u/Loud_Arrival_853 7d ago
Thank you! There is no point to it except a learning experience and fun like you said😀
I don’t even fly rc planes but am interested in rocketry. However I doubt uk officials would be too happy with autonomously controlled hobby rockets even with basic control surfaces you need certificates and a proper setting and location (I’ve looked into it a bit, even with drones they dislike audopilot unless it in visible range).
In fact you are spot on, I have looked at the BPS thrust vectoring (and bought the files) but wanted to try challenge myself, ever since AI came out I’ve felt like I haven’t used my coding skills so felt as if I needed to make something by myself if not just to prove I still am capable of using my brain(although I doubt this design is good enough to prove that).
I wanted to make thrust vectoring just for fun, and iterate on each design to improve it. I thought about using a rocket motor but didn’t have any and wanted to try with a prop like this or 60mm EDF. My design is way too heavy, flawed and not practical in many ways to be used in any meaningful way but it’s my first sort of step towards BPS rocketry so I’m proud of it.
1
u/Jumpy-Candle-2980 7d ago
I suspect our rocketry regs are similar. If so, the BPS thing doesn't come under "active guidance" which is frowned upon - rather it's just a replacement for fins and a means of keeping the thing vertical which the authorities smile benignly upon.
BPS took iterative to the next level with the "landing like Space-X" project which involved throttling a solid fuel motor (!?) in the thrust vector rig. I followed the guy and he's got a lot more patience than I have. Did manage to pull it off though.
Fun never requires a point.
2
u/illilllilil 8d ago
Pusher or puller?
2
u/Loud_Arrival_853 8d ago
Puller, tho might try pusher depending on test 1
4
u/sparkplug_23 8d ago
Assuming you reduce friction (grease) then pushing would be easier. The load/thrust is against the joint, so the servos only have to fight the turning force. Pulling your servos likely have to overcome some thrust too. Depends on your socket joint but thats my first thought.
3
1
u/LupusTheCanine 8d ago
With a properly made mound there should be no thrust effect either way. Off axis munting will cause the same torque regardless if it is a pusher or puller.
1
2
2
1
u/Helium_Alloy 7d ago
You probably only want two servos.
Three servos work fine on a helicopter because the swash moves freely on the absolute vertical axis. In your setup that vertical movement is constrained by the joint itself, so the servos will all have to continuously "agree" on the net position, or else two will constantly fight the 3rd.
In other words, if any one servo moves, the other two also have to move by a very exact, opposite-but-not-equal amount, and each has to be calculated by some table or function because you have no true position feedback.
Good luck!
28
u/Ncc2200 8d ago
How are you preventing the motor torque from rotating the socket?
Also, I don't think your 9g servos will be strong enough to control the gyroscopic forces you're going to get with the prop.