# How do I calculate the torque needed for a rotating cylinder?

• AerospaceEng
In summary, the dimensions of the cylinder, mu=42.14 and w=2.62 radians/second, are similar to the dimensions of the cylinder in a previous thread. The cylinder needs to move slowly, so the resistance to rotation due to friction can be calculated using the same equation as for a heavier cylinder. The friction due to a bearing can be calculated in the same way, but the diameter of the shaft has no effect on the friction force.
AerospaceEng
So essentially I'm trying to build a rotating free floating rotating cylinder (like laying a coke can on its side and propping it up so that when it rotates it won't have contact with the ground) I hope this is clear
and I need to figure out what size of motor I need to turn my cylinder by calculating the amount of torque needed

Dimensions of cylinder

m=226.80Kg
radius=0.61m
Length of cylinder=2.44mangular velocity =2.62radians/second
Moment of Inertia=42.14

But I'm not really sure where to go from here, how do I calculate the torque needed? and help is appreciated

AerospaceEng said:
So essentially I'm trying to build a rotating free floating rotating cylinder (like laying a coke can on its side and propping it up so that when it rotates it won't have contact with the ground) I hope this is clear
and I need to figure out what size of motor I need to turn my cylinder by calculating the amount of torque needed

Dimensions of cylinder

m=226.80Kg
radius=0.61m
Length of cylinder=2.44m

angular velocity =2.62radians/second
Moment of Inertia=42.14

But I'm not really sure where to go from here, how do I calculate the torque needed? and help is appreciated

There was just recently a very similar thread. Does it help at all?

https://www.physicsforums.com/showthread.php?t=464235

.

Thanks for the post Berkeman that kind of helped, although I know that Torque is

T=I(alpha)

but I don't understand how I can caculate alpha (the angular acceleration) because if you do some math you'll see that my cylinder turns very slowly, it's suppose to turn fairly slowly for long periods of time so I know to find alpha i do

alpha=w(angular velocity)/time

but that's fine whether it takes 10 seconds or a full min to reach its full speed doesn't matter to me its how much torque does it take to keep it rotating?

AerospaceEng said:
but that's fine whether it takes 10 seconds or a full min to reach its full speed doesn't matter to me its how much torque does it take to keep it rotating?

That would be determined by the friction that opposes the rotational movement. I.e. air resistance and e.g. resistance within ball-bearings. In other words, a complicated matter that also requires a lot more information.

Hi Guys,

I actually have a very similar problem I'm working on at the moment except my cylinder is a lot heavier (2500kg). The dimensions are similar and it only needs to move slowly (30 degrees in 5 minutes).

I've worked out what the resistance due to Inertia is but I'm not sure how to go about accounting for the friction. The cylinder is located on a shaft with bearings at either end; what information do you need to calculate the resistance to rotation due to friction in the bearings.

In it's basic form, friction exerts a force on an object equal to mu.N, where mu = coefficient of friction and N equals the normal force (i.e. weight) of the object. Can the friction due to a bearing be calculated in the same way? Does the diameter of the shaft have any effect on friction force? Or shaft velocity?

Any help or suggestions would be appreciated.

## 1. What is a rotating cylinder?

A rotating cylinder is a type of mechanical device that consists of a cylindrical structure that can spin or rotate around its own axis. It is commonly used in various applications such as engines, turbines, and even amusement park rides.

## 2. How does a rotating cylinder work?

A rotating cylinder works by using a power source, such as an electric motor, to rotate the cylinder at a constant speed. The rotation can be achieved through various methods, including using gears, belts, or direct drive mechanisms.

## 3. What are the benefits of using a rotating cylinder?

There are several benefits of using a rotating cylinder, including its ability to convert energy into motion, its compact size and ease of installation, and its versatility in various applications. It can also provide a smooth and continuous motion, making it suitable for precision tasks.

## 4. What factors should be considered when building a rotating cylinder?

When building a rotating cylinder, it is important to consider factors such as the desired speed and torque, the type of power source, the materials and design of the cylinder, and the intended application. Safety measures should also be taken into account to ensure proper functioning and prevent accidents.

## 5. Can a rotating cylinder be customized for specific needs?

Yes, a rotating cylinder can be customized based on specific needs. This can include adjusting the size and shape of the cylinder, changing the rotation speed and direction, and incorporating additional features such as sensors or control systems. Customization can allow for a more efficient and tailored solution for different applications.

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