A rolleron is a type of aileron used for rockets, placed at the trailing end of each fin, and used for passive stabilization against rotation. Inherent to the rolleron is a metal wheel with notches along the circumference. On one side, the notches protrude into the airflow. During flight, this will spin the wheels up to a substantial speed. The wheels then act as gyroscopes. Any tendency of the rocket to rotate along its major axis will be counteracted by the rollerons, deflecting in the opposite direction of the rotation.

Rollerons were first used in the AIM-9 Sidewinder missile.

http://en.wikipedia.org/wiki/Rolleron

http://yarchive.net/mil/rolleron.html

Why does the rolleron deserve its own thread Wookie? Just curious.

Witty Rejoinder said:

Why does the rolleron deserve its own thread Wookie? Just curious.

its a point of interest i found recently

it uses gyroscpic motion as a form of creating stable flight in missiles/rockets

i’d not heard of it before

Yeah they’re a clever idea.

its ingenious

Do they spin while the missile is still attached to the plane?

http://blog.makezine.com/2010/02/14/unusual-mechanism-the-rolleron/

The wheel provides precession forces that tilt the fin it’s riding in. This bends the tab that it sits in like an aileron cancelling the roll that produced the precession.

Very elegant negative feedback loop, works like a charm although roll isn’t entirely eliminated.

I know a model rocketeer who did this on a much smaller model rocket, he discovered that it was necessary to blow a stream of air at the rollerons before launch to get them spun up (since it was ground launched, not in an already moving air stream like the AIM-9 is usually. I think he used an air compressor/tank and some tubing to direct a narrow stream at the wheels from above (and to the side, since otherwise it’d hang up).

Helps with onboard video, keeps it from getting totally spinny.

Kingy said:

Do they spin while the missile is still attached to the plane?

as i understand it

no

the missile is sent off and as it speds up it turns the rolleron which in turn then gives the missile more stability in the sense that it stops it rolling around.

instead of doing this you could actually build a gyroscope into the fin, no air required. you could have a small motor that turns the rolleron continuously before launch

the rolleron would be hidden

wookiemeister said:

instead of doing this you could actually build a gyroscope into the fin, no air required. you could have a small motor that turns the rolleron continuously before launch

the rolleron would be hidden

Classic Wookie. Take a simple idea that works and make it needlessly complicated and expensive.

i model rocketry you often see camera footage from the rocket but it spins around in flight

as pointed out you could build rollerons into the model rocket fins and stop that spin and make more watchable footage

the battery could be housed in the nose to increase the stability

i model rocketry you often see camera footage from the rocket but it spins around in flight

as pointed out you could build rollerons into the model rocket fins and stop that spin and make more watchable footage

the battery could be housed in the nose to increase the stability

Kingy said:

wookiemeister said:

instead of doing this you could actually build a gyroscope into the fin, no air required. you could have a small motor that turns the rolleron continuously before launch

the rolleron would be hidden

Classic Wookie. Take a simple idea that works and make it needlessly complicated and expensive.

not at all

the motor driven rolleron doesn’t need the drag caused by the rolleron , its not exposed to the weather because its housed in the fin

an inexpensive motor could be used to drive it

wookiemeister said:

Kingy said:

wookiemeister said:

instead of doing this you could actually build a gyroscope into the fin, no air required. you could have a small motor that turns the rolleron continuously before launch

the rolleron would be hidden

Classic Wookie. Take a simple idea that works and make it needlessly complicated and expensive.

not at all

the motor driven rolleron doesn’t need the drag caused by the rolleron , its not exposed to the weather because its housed in the fin

an inexpensive motor could be used to drive it

you’ve added a motor which you didn’t have before i.e. increased complexity.

poikilotherm said:

wookiemeister said:

Kingy said:

Classic Wookie. Take a simple idea that works and make it needlessly complicated and expensive.

not at all

the motor driven rolleron doesn’t need the drag caused by the rolleron , its not exposed to the weather because its housed in the fin

an inexpensive motor could be used to drive it

you’ve added a motor which you didn’t have before i.e. increased complexity.

yes but have less drag with no moving part exposed to the elements

motors have good reliability.

the fin is allowed to be aerodynamic rather than clunky and drag ridden

you do know how rollerons work wookie?

Boris said:

you do know how rollerons work wookie?

yes gyroscopic forces

yes gyroscopic forces

yes, but how are those forces used to control the missile? it isn’t a direct connection.

the little flap doesn’t move

its the gyroscopic forces that stop the missile rolling around – not pitching or yawing

a gyro resists change

in this case the rolling motion

the little flap doesn’t move

it does. that is why they are called rollerons. you have heard of ailerons? those little flaps move both ways.

Boris said:

the little flap doesn’t move

it does. that is why they are called rollerons. you have heard of ailerons? those little flaps move both ways.

not according to these guys

spinning wheel resists lateral forces acting on it. In this case, the gyroscopic motion counteracts the missile’s tendency to roll — to rotate about its central axis. The simple, cheap rollerons steady the missile as it zips through the air, which keeps the seeker assembly from spinning at top speed. This makes it a lot easier to track the target

Boris said:

the little flap doesn’t move

it does. that is why they are called rollerons. you have heard of ailerons? those little flaps move both ways.

not according to these guys

spinning wheel resists lateral forces acting on it. In this case, the gyroscopic motion counteracts the missile’s tendency to roll — to rotate about its central axis. The simple, cheap rollerons steady the missile as it zips through the air, which keeps the seeker assembly from spinning at top speed. This makes it a lot easier to track the target

The wheels aren’t meant to stabilize the whole missile, just the ailerons they are mounted in. In the last picture you can see that they are hinged at the front (the brass rectangle at a 45* angle). Imagine you are watching the missile from behind as it flies along. If it starts to rotate clockwise, the precession would cause the top aileron to move to the right, toward the direction of rotation. All of them would move in the direction of rotation, actually, creating an aerodynamic force to spin the missile the other way. If it rotates too far counterclockwise, the ailerons would move the other way, rotating the missile back again.

A rolleron is a type of aileron used for rockets, placed at the trailing end of each fin, and used for passive stabilization against rotation. Inherent to the rolleron is a metal wheel with notches along the circumference. On one side, the notches protrude into the airflow. During flight, this will spin the wheels up to a substantial speed. The wheels then act as gyroscopes. Any tendency of the rocket to rotate along its major axis will be counteracted by the rollerons, deflecting in the opposite direction of the rotation.

the wiki reference makes no mention of the flap moving at all

the air turns the roller but thats it

i thought originally that the rolleron caused the flap to move to act as a flap on a wing but i couldn’t find any reference to this happening, i then relaised that it must be purely the motion stopping the rolling motion not anything to do with flaps moving

A rolleron is a type of aileron used for rockets, placed at the trailing end of each fin, and used for passive stabilization against rotation. Inherent to the rolleron is a metal wheel with notches along the circumference. On one side, the notches protrude into the airflow. During flight, this will spin the wheels up to a substantial speed. The wheels then act as gyroscopes. Any tendency of the rocket to rotate along its major axis will be counteracted by the rollerons, deflecting in the opposite direction of the rotation.

the wiki reference makes no mention of the flap moving at all

the air turns the roller but thats it

i thought originally that the rolleron caused the flap to move to act as a flap on a wing but i couldn’t find any reference to this happening, i then relaised that it must be purely the motion stopping the rolling motion not anything to do with flaps moving

you can see how they are fitted and how they would work.

Boris said:

The wheels aren’t meant to stabilize the whole missile, just the ailerons they are mounted in. In the last picture you can see that they are hinged at the front (the brass rectangle at a 45* angle). Imagine you are watching the missile from behind as it flies along. If it starts to rotate clockwise, the precession would cause the top aileron to move to the right, toward the direction of rotation. All of them would move in the direction of rotation, actually, creating an aerodynamic force to spin the missile the other way. If it rotates too far counterclockwise, the ailerons would move the other way, rotating the missile back again.

as i mentioned thats what i originally thought but i couldn’t find anything to substantiate that

as i have read it is purely the motion of the wheel nothing to do with the flap moving into the airstream

you’d need a larger mass to effect the rotation.

Boris said:

you’d need a larger mass to effect the rotation.

well thats i thought but supposedly its the high rpm that means it doesn’t matter

i’m looking at it more now

most references say nothing about the flap moving

the wiki and make magazine articles aren’t that great

the wiki and make magazine articles aren’t that great

Wookie you need to adjust your tremor control, double posts akimbo.

Skunkworks said:

Wookie you need to adjust your tremor control, double posts akimbo.

i press the button

i wait

i wait some more

finally nothing happens

i click again and then i have two posts instead of one

the more the merrier

Press submit, then press vbt.

google rollerons and go down results until you get to the nasa pdf. open and read.

looks as if my first understanding was correct

its a gyro actuated aileron

i re read the make magazine and wiki reference and concluded that no moving part other than the wheel existed, overiding my initial understanding.

i would still have an electric motor in it

if the aircraft is flying along then i guess the rolleron is actually moving in flight before launch

unless its got some kind of min airspeed before it works

if the aircraft is flying along then i guess the rolleron is actually moving in flight before launch

doesn’t matter if it is as the missile isn’t trying to rotate around its axis.

an electric motor would mean that you could keep the rpm of the rolleron at the best speed based on the missiles air speed and air density

you’d need four plus wiring plus power source plus computer etc. this is simple and does the job and looks like nothing much to go wrong. all that is needed is to unlock the cager before firing and off it goes.

Boris said:

you’d need four plus wiring plus power source plus computer etc. this is simple and does the job and looks like nothing much to go wrong. all that is needed is to unlock the cager before firing and off it goes.

the computer to run the motors could be an arduino micro controller that uses batteries housed in the fin

all the arduino need do is know the air pressure being fed from the brain upfront and then do a calculation to keep the fin at the right speed

Boris said:

if the aircraft is flying along then i guess the rolleron is actually moving in flight before launch

doesn’t matter if it is as the missile isn’t trying to rotate around its axis.

I was wondering if the rollerons affect the plane they are attached to.

It could be unfortunate for a fighter plane if its own weapons forced it to fly straight and level.

all the arduino need do is know the air pressure being fed from the brain upfront and then do a calculation to keep the fin at the right speed

and yet this works and is being used without being that complex. ideal when your life may depend on the thing working.

the rolleron is locked with a cager.

google rollerons go down to the PowerPoint presentation from uni of florida

Boris said:

the rolleron is locked with a cager.

google rollerons go down to the PowerPoint presentation from uni of florida

Ok, ta.