Thrust Vectoring With Compliant Mechanisms Is Hard

June 16, 2019 by Lewin Day 19 Comments

Thrust vectoring is one way to control aerial vehicles. It’s become more popular as technology advances, finding applications on fifth-generation fighter aircraft, as well as long being used in space programmes the world over.[RCLifeOn] decided to try and bring the technology to a prop-powered RC aircraft, in an unconventional way.

After attending a lecture on compliant mechanisms and their potential use in space vehicles for thrust vectoring control, [RCLifeOn] decided to try applying the concept himself. His test mechanism is a fixed-wing with a single-piece motor mount that has enough flex in the right places to allow the motor (and propeller) to be moved in two axes, achieving thrust vectoring control.

After printing a compliant motor mount in a variety of materials, one was selected for having the right balance of strength and flexibility. The vectoring mechanism was fitted to a basic flying wing RC aircraft, and taken to the field for testing. Unfortunately, success was not the order of the day. While the mechanism was able to flex successfully and vector the motor in bench testing, it was unable to hold up to the stresses of powered flight. The compliant mechanism failed and the plane nosedived to the ground.

[RCLifeOn] suspects that the basic concept is a difficult proposition to engineer properly, as adding strength would tend to add weight which would make flight more difficult. Regardless, we’d love to see further development of the idea. It’s not the first time we’ve seen his 3D-printed flight experiments, either. Video after the break.

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DIY Falcon Heavy 2nd stage test flight of BPS.space

Rocket Science With The Other SpaceX

September 18, 2018 by Steven Dufresne 29 Comments

When you say that something’s not rocket science you mean that it’s not as hard to understand or do as it may seem. The implication is that rocket science is something which is hard and best left to the likes of SpaceX or NASA. But that’s not the hacker spirit.

[Joe Barnard] recently had an unsuccessful flight of his Falcon Heavy’s second stage and gives a very clear explanation of what went wrong using those two simple concepts along with the thrust, which in this case is just the force applied to the moment arm.

And no, you didn’t miss a big happening with SpaceX. His Falcon Heavy is a homebrew one using model rocket solid boosters. Mind you, it is a little more advanced than that as he’s implemented thrust vectoring by controlling the engine’s direction using servo motors.

And therein lies the problem. The second stage’s inertia is so small and the moment arm so short that even a small misalignment in the thrust vectoring results in a big effect on the moment arm causing the vehicle to deviate from the desired path. You can see this in the first video below. Another issue he discusses is the high drag, but we’ll leave that to the second video below which contains his explanation and some chart analysis.

So yeah, maybe rocket science is rocket science. But there’s no better way to get your feet wet then to get out there and get building.

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You Need A Self-Righting Thrust-Vector Balloon Copter

December 25, 2015 by Elliot Williams 15 Comments

Cornell University’s microcontroller class looks like a tremendous amount of fun. Not only do the students learn the nitty-gritty details of microcontroller programming, but the course culminates in a cool project. [Brian Ritchken] and [Jim Liu] made a thrust-vector controlled balloon blimp. They call this working?!?!

Three balloons provide just enough lift so that the blimp can climb or descend on motor power. Since the machine is symmetric, there’s no intrinsic idea of “forward” or “backward”. Instead, a ring of eight LEDs around the edge let you know which way the blimp thinks it’s pointing. Two controls on the remote rotate the pointing direction clockwise and counter-clockwise. The blimp does the math to figure out which motors to run faster or slower when you tell it to go forward or back.

The platform is stabilized by a feedback loop with an accelerometer on board, and seems capable of handling a fairly asymmetric weight distribution, as evidenced by their ballast dangling off the side — a climbing bag filled with ketchup packets that presumably weren’t just lifted from the dining halls.

It looks like [Brian] and [Jim] had a ton of fun building and flying this contraption. We’d love to see a distance-to-the-floor sensor added so that they could command it to hover at a given height, but that adds an extra level of complexity. They got this done in time and under budget, so kudos to them both. And in a world full of over-qualified quadcopters, it’s nice to see the humble blimp getting its time in the sun.

Yep, you heard right… this is yet another final project for a University course. Yesterday we saw a spinning POV globe, and the day before a voice-activated eye test. We want to see your final project too so please send in a link!

Collective Pitch Thrust Vectoring On A RC Plane

November 15, 2013 by James Hobson 59 Comments

The RC plane shown above is hovering in that position. And that’s about the least impressive thing it can do. This is the power of Collective Pitch Thrust Vectoring… on a plane.

So what exactly is Collective Pitch Thrust Vectoring anyway? Put simply, it’s like strapping a helicopter rotor to the front of a plane. We think the basic mechanism behind this is called a Swashplate (as found on a helicopter rotor), which allows for thrust vectoring, meaning the propeller blades can actually change their pitch cyclically, while still spinning at high speeds! This is what allows helicopters to do crazy tricks like barrel rolls.

A normal RC plane can only increase or decrease thrust with the speed of the engine. But with this, the thrust can be changed cyclically as the blades spin allowing for thrust vectoring (advanced steering). Couple that with some huge control surfaces and wing stabilizers and that means some seriously crazy aerodynamic feats.

Watch the video after the break, it’s amazing.

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