# Calculating Gyration forces on a propellor shaft

• RussellJ
In summary, the conversation discusses the method for calculating the forces exerted on a prop shaft as a plane goes into a turn or incline/decline. The moment exerted on the propeller is calculated using the formula Mz = Iprop * \varpiprop * \varpiplane, where \varpiplane is determined based on the radius of the turn and airspeed of the plane. The conversation also discusses the calculations for the moment of inertia of the propeller and whether the results seem reasonable.
RussellJ
I am a Co-op student trying to calculate the forces exerted on a prop shaft as the plane goes into a turn or incline/decline.

this is my method of finding the moment exerted on the propeller for a plane in a turn

If the propellor is rotating about a horizontal axis (X) and the plane is in a turn, rotating about a vertical axis (Y) then there is a moment exerted on the propeller about a axis perpendicular to both the Y and X axis (Z axis) which is calculated by:

Mz = Iprop*$$\varpi$$prop*$$\varpi$$plane

where $$\varpi$$plane is calculated based on the radius of the turn the plane is making and the airspeed of the plane then $$\varpi$$plane = speed of plane / radius of turn * unit conversion to rad/s

Is that the extent of the forces?

Sorry if this isn't very concise

Maybe if i write out my calculations it will be easier to understand.

The prop rotates at 1000RPM so that's 9.551 Rad/s

the plane has a minimum turning radius of 1.5 Miles and an airspeed of 374 dividing the speed by the radius and converting gives ~ .069 rad/s.

to calculate the moment of inertia of the prop I assumed the propeller blades were triangles 2.166m high with a .3048 wide base and a thickness of .0508m and all four blades roughly weigh 500lbs total. This gave me a density of 3436.3.

I then calculated the moment of inertia using a triple integral of r^2 dV where r^2 = x^2 + y^2 and dV = dz*dy*dx with bounds Z: 0 to 0.0508, Y -(.3048/(2*2.1336)x to .0714x, and x 0 to 2.1336 and ten multiplying it by the density. This yielded a moment of inertia per blade of 129.3.

I then took all these values and subbed them into M=I*(rotational speed of plane)*(rotational speed of prop) to get M=225 N/M or 15.417 lb/ft which seems very small.

Does this seem reasonable? are my calculations correct?

## 1. How do you calculate gyration forces on a propellor shaft?

To calculate gyration forces on a propellor shaft, you need to know the mass of the propellor, the speed at which it is rotating, and the distance from the center of the propellor to the axis of rotation. You can then use the formula F = m x w^2 x r, where F is the gyration force, m is the mass, w is the angular velocity, and r is the radius or distance from the center.

## 2. What is the importance of calculating gyration forces on a propellor shaft?

Calculating gyration forces allows engineers to determine the structural integrity and durability of a propellor shaft. It also helps in designing and optimizing the propellor for maximum efficiency and performance.

## 3. Can gyration forces on a propellor shaft be negative?

Yes, gyration forces can be negative if the propellor is rotating in the opposite direction. This can happen if the propellor is in reverse or if there is a counter-rotating propellor on the same shaft.

## 4. What factors can affect gyration forces on a propellor shaft?

The main factors that can affect gyration forces on a propellor shaft are the speed of rotation, the mass of the propellor, and the distance from the center of the propellor to the axis of rotation. Other factors such as the shape and design of the propellor can also have an impact.

## 5. How can gyration forces on a propellor shaft be reduced or controlled?

Gyration forces can be reduced by using a lighter propellor or by decreasing the speed of rotation. Reducing the distance from the center of the propellor to the axis of rotation can also help in controlling the gyration forces. Additionally, proper balancing and alignment of the propellor and shaft can also minimize gyration forces.

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