Torque calculation for a new loading mechanism

In summary, to design the loading mechanism of a new machine, you will need to calculate the torque required for rotation. This can be done by first calculating the static forces and torques, followed by the acceleration forces and torques. It is important to consider both static and dynamic forces in order to determine the necessary torque. The weight of the loading table and workpiece, as well as the distance of their center of mass from the axis of rotation, will also affect the required torque. Additionally, the chosen drive system and the desired accuracy of rotation will also play a role in determining the torque needed. This is an iterative process and may require adjustments and calculations multiple times.
  • #1
Yevhenii
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TL;DR Summary
Torque calculation
I'm designing loading mechanism of new machine and need to know what the torque will be.
Here is the sketch of my mechanism.
Distance from centre of shaft to the top of loading table is 200mm. Distance from the centre of mass of workpiece to centre of the shaft 50 mm. Max load is 400 kg. Weight of loading table is 50 kg.
Do I need (at first) calculate moment of inertia and then angular speed, and after I will know what torque i need? Or I just need to multiply force on distance?
This mechanism should rotate to 180 deg. n=14 rpm
Thanks
1610076047931.png
 
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  • #2
I'm not clear as to exactly what you are doing. Please show an isometric view in the starting position, and another view partially rotated.

A general procedure for machines that move:
1) Calculate static forces and torques.
2) Calculate accelerations and speeds.
3) Calculate acceleration forces and torques.

If the static forces are sufficiently larger than the dynamic forces, the dynamic forces can be ignored. If the dynamic forces are sufficiently larger than the static forces, the static forces can be ignored. You have to calculate both static and dynamic forces and torques in order find if you need to calculate both.
 
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  • #3
Also, are these numbers correct? I must be misunderstanding something...

Yevhenii said:
Max load is 400 kg. Weight of loading table is 50 kg.
 
  • #4
berkeman said:
Also, are these numbers correct? I must be misunderstanding something...
Weight of loading plate is 50 kg (aluminium). Max weight (of workpiece) is 400 kg.
 
  • #5
jrmichler said:
I'm not clear as to exactly what you are doing. Please show an isometric view in the starting position, and another view partially rotated.

A general procedure for machines that move:
1) Calculate static forces and torques.
2) Calculate accelerations and speeds.
3) Calculate acceleration forces and torques.

If the static forces are sufficiently larger than the dynamic forces, the dynamic forces can be ignored. If the dynamic forces are sufficiently larger than the static forces, the static forces can be ignored. You have to calculate both static and dynamic forces and torques in order find if you need to calculate both.
I need to know how to calculate torque, if center of mass of workpiece will be higher than shaft center of mass (+50mm).
And if center of mass of workpiece will be on the same axis with shaft, then how do I need to calculate? F*r?
 
  • #6
1610354211986.png
 
  • #7
The maximum moment will happen when the table and the work piece have rotated 90°.

The weight of the table times the distance of its center of mass to the axis of rotation (it may be more than 200 mm), creates a moment that opposes the moment created by the weight of the workpiece times the distace from its center of mass to the axis of rotation (it may be different than 50 mm),

Installing enough counter-balance on the botton of the table could eliminate the resulting moment; although it would change the moment of inertia some.
 
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  • #8
Now that you have calculated the static moment, the next step is to calculate the torque to accelerate and decelerate. A typical step by step process is as follows:

Step 1: Decide how you are going to drive the unit. Some (not all) possibilities include induction motor and gearbox with contactor, induction motor and gearbox with VFD drive, servomotor and gearbox, hydraulic rotary actuator with solenoid valve, hydraulic rotary actuator with servovalve and servo controller. Each of those has advantages and disadvantages. Some of those have full ability to control acceleration, others do not. Your OP indicates that you have very little experience with this, so expect to spend at least 100 hours of concentrated effort on this step. How accurately do you need to rotate it - +/- 1 degree, +/- 0.1 degree, +/- 0.01 degree?

Step 2: Calculate the acceleration, velocity, and position vs time curves for your chosen drive.

Step 3: Check the peak velocity against gear ratio, RPM, or flow rate (if hydraulic). Adjust as necessary.

Step 4: Calculate acceleration torque from the mass moment of inertia.

Step 5: Plot acceleration torque and static torque on same axes. The sum of those two torques is the total drive torque.

Step 6: Check peak torque against the drive specifications. Adjust if necessary.

And yes, this is an iterative process. Machine design is like that.
 
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  • #9
jrmichler said:
Now that you have calculated the static moment, the next step is to calculate the torque to accelerate and decelerate. A typical step by step process is as follows:

Step 1: Decide how you are going to drive the unit. Some (not all) possibilities include induction motor and gearbox with contactor, induction motor and gearbox with VFD drive, servomotor and gearbox, hydraulic rotary actuator with solenoid valve, hydraulic rotary actuator with servovalve and servo controller. Each of those has advantages and disadvantages. Some of those have full ability to control acceleration, others do not. Your OP indicates that you have very little experience with this, so expect to spend at least 100 hours of concentrated effort on this step. How accurately do you need to rotate it - +/- 1 degree, +/- 0.1 degree, +/- 0.01 degree?

Step 2: Calculate the acceleration, velocity, and position vs time curves for your chosen drive.

Step 3: Check the peak velocity against gear ratio, RPM, or flow rate (if hydraulic). Adjust as necessary.

Step 4: Calculate acceleration torque from the mass moment of inertia.

Step 5: Plot acceleration torque and static torque on same axes. The sum of those two torques is the total drive torque.

Step 6: Check peak torque against the drive specifications. Adjust if necessary.

And yes, this is an iterative process. Machine design is like that.
Thanks for help. I calculated static moment and its much more larger than torque I calculated through moment of Inertia.
As I understood, bigger value will be the peak moment?
I will use worm gearbox, ratio 100. Output torque is 750 Nm
 
Last edited:

Related to Torque calculation for a new loading mechanism

1. What is torque and why is it important in a loading mechanism?

Torque is a measure of the force that causes an object to rotate about an axis. In a loading mechanism, torque is important because it determines the amount of force needed to move and lift heavy loads.

2. How is torque calculated for a new loading mechanism?

Torque is calculated by multiplying the force applied to a lever arm by the distance from the pivot point to the point where the force is applied. This can be represented by the formula: torque = force x distance.

3. What factors should be considered when calculating torque for a new loading mechanism?

The factors that should be considered when calculating torque for a new loading mechanism include the weight of the load, the distance from the pivot point to the load, and the angle at which the force is applied.

4. How can torque be optimized in a loading mechanism?

Torque can be optimized in a loading mechanism by increasing the distance from the pivot point to the point where the force is applied, using a lever arm or gear system to increase the force applied, and minimizing friction in the mechanism.

5. Are there any safety considerations when designing a loading mechanism based on torque calculations?

Yes, safety should always be a top priority when designing a loading mechanism. It is important to ensure that the torque calculations are accurate and that the mechanism is built to handle the calculated amount of torque to prevent accidents and injuries.

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