Fixing Roll

[MikkOwl]

I thought a larger influence was that the airflow from the propeller is not straight, but spirals rearwards across the fuselage and wings. It strikes the stabilizer from one side constantly for example, pushing the tail in that direction. I don't know if these forces are contrary or reinforce the actual torque effect from the propeller.

[Wolf_Rider]

its like this:

A helicopter had to have the tail rotor put on it for what reason?

that's right... to prevent the main rotor and the main body (housing the engine) from spinning in opposite direction.

double main rotor 'copters spin in the opposite direction: why?







and there is no prop on the ever popular car anology, when the engine is revved hard causing lurch.

piston drives the cranshaft which turns the prop. the piston moves down bwcause the explosion, which causes the movement because it forces the piston to move down using the block/ head as the base. the engine block is mounted securely to the vehicle, etc, etc, etc

[bongodriver]

and there is no prop on the ever popular car anology, when the engine is revved hard causing lurch

no but there is a large 'flywheel' so it's not completely invalid.

for the spitfire it's like this....


torque: prop rotates clockwise, aircraft rotates anti-clockwise, has the smallest effect of all 3.

propwash: causes the aircraft to yaw left with increased power...right rudder required to counter

gyroscopic precession: pitch up causes yaw right, pitch down causes yaw left, this seems to be the strongest effect, if you are trimmed with a pitch up bias the aircraft will want to roll right.

all these forces will change according to power setting and control inputs, only rudder and elevator can be trimmed, therefore there will tend to be a requirement to keep hands on stick to counter all the secondary roll forces induced by yaw, and this is largely felt as a roll right, even a fixed aileron 'tab' will only be effective at a set speed range.

[Wolf_Rider]

flywheel is part of the crankshaft though and has no air drag as such


"torque: prop rotates clockwise, aircraft rotates anti-clockwise"

crankshaft rotates (on which the prop is attached) clockwise, inside the engine block. the crankshaft rotates because of the pistons driving the shaft, the pitons push against the engine block, because the pistons/ cranshaft is the movable object when the engine block is securely mounted on a firm surface. when there is no firm mount, the engine block floats... so the crankshaft/ pistons pushes against the engine block which in turn is moved in the opposite direction

prop wash is applicable until airspeed is greater

[bongodriver]

torque is not really an effect purely of air resistance, it is more to do with inertia, the flywheel is a heavy mass (just like a prop) and causes resistance to the power of the engine, that energy needs to find its way somewhere, inevitably it will cause the whole engine block to rotate in the opposite direction, I know.. I've seen it, an engine on a static test bench being revved will lurch in the opposite direction of crankshaft rotation, essentially we are in agreement on this effect but with slightly differing perceptions on its cause.

propwash is a factor as soon as the power is applied and is harder to control at low speeds because the aerodynamic controls havent got a 'bite' on the airflow

[Wolf_Rider]

basic law of motion... "For every action there is an equal and opposite reaction"





http://www.aerospaceweb.org/question...s/q0015a.shtml

might help/ might not

[bongodriver]

Me personally no, I studied enough of that on my ATPL theory, so I am fully up to speed on all these effects.

[b101uk]

Originally Posted by Wolf_Rider

its like this:

A helicopter had to have the tail rotor put on it for what reason?

that's right... to prevent the main rotor and the main body (housing the engine) from spinning in opposite direction.

double main rotor 'copters spin in the opposite direction: why?

and there is no prop on the ever popular car anology, when the engine is revved hard causing lurch.

piston drives the cranshaft which turns the prop. the piston moves down bwcause the explosion, which causes the movement because it forces the piston to move down using the block/ head as the base. the engine block is mounted securely to the vehicle, etc, etc, etc

helicopter have main gearbox fixed in the body which turns torque threw 90deg, so the engine has little to do with it with regards to its own flywheel effect as the load from pushing the blades one way is put into the main body by the gearbox case wile the tail rotor counters main body yaw and engine only counters input shaft load and is 90deg out of sync with you example!

If your then talking about vehicles like cars, trucks etc, agene the engine is mostly fixed to the gearbox which has its own mounts and the small amount of rock you get from sharply revving the engine when there is no load is minuscule in comparison to the amount of torque from the gearbox output shaft which will in fact twist the gearbox case and thus vehicle body/chassis the opposite way wile the engine that is rigidly fixed to it is only countering a smaller input shaft load.

Also with gearbox in the equation with lower output ratios resulting in increased output torque (like trucks, helicopter, turbo-props, etc etc etc) if you input say 500NM and get out 1500NM then ware dose the difference in output torque have an effect and ultimately go, via the gearbox case into the rest of the vehicle by any chance wile the engine is only countering a smaller input shaft load.
.

So forget the engine we are only interested in ware the force from pushing a prop one way ultimately ends up!

Originally Posted by Wolf_Rider

basic law of motion... "For every action there is an equal and opposite reaction"

http://www.aerospaceweb.org/question...s/q0015a.shtml

might help/ might not

you are 19 post behind

The effects of gearbox and high load and a vehicle twisting in the opposite direction to its propshaft

http://www.youtube.com/watch?v=pUVEH7AoEnw