Pulleys connecting a motor and shaft - Determining loads in shafts

In summary, a 5hp, 1755rpm WEG Motor (part #00518OP3E184T) needs to turn another shaft at 1000rpm, 12 inches away. By using a pulley system with a 8" sheave on the motor and a 14" sheave on the shaft, a drive ratio of .5714 can be achieved. However, the problem is determining the loads on the shaft and the necessary components such as bearings and v-belts. More information is needed to determine a complete design solution.
  • #1
MrBlue
1
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Homework Statement


A 5hp, 1755rpm, WEG Motor (part #00518OP3E184T) needs to turn another shaft that is 12" away at 1000rpm.


Homework Equations


Torque=HP*5252/RPM
T=F*r -> F=T/r
Drive Ratio = Driver Pitch Diameter/Driven Pitch Diameter
Sum Forces
Sum Moments


The Attempt at a Solution


I plan on using a pulley (aka sheave) system with v-belts. I want to use a 8" sheave (7.95" pitch diameter) on the motor and a 14" sheave (13.95" pitch diameter) on the shaft that needs to turn 1000rpm. This will give me a Drive Ratio of .5714.

1755rpm*.5714=1000rpm --- Which is what I want.

My problem is, I don't know how to figure out the loads in the shaft. Since I know the torque in the motor (Torque = 5hp*5252/1755rpm=14.96ft*lb=179.52in*lb), I thought I might be able to figure out a force at a point on the motor sheave diameter by knowing that T=F*r so that F=T/r. However, when I do the calculations, I get that the force on a point on the outside of the sheave is F=179.52in*lb/(8in/2)=44.88lb. This sounds like too small of a force.

I also think that that might not even be what I need. I think I need to figure out the tension in the v-belt? Basically I need to figure out how many v-belts I need (do I need just 1 belt or 2 or 3, etc.?), and the loads on the shaft that I need to spin at 1000rpm. If I can get the resulting loads on the shaft, I can figure out the type of bearings I need to support the shaft and such.

I don't know where to go with this and could greatly use some help. Any help at all would be helpful. Thanks so much in advance.
 
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  • #2
Hi MrBlue, welcome to the board. I'm not sure I understand the question. What class is this for? Is this a design problem that you're supposed to determine a design solution to? If so, to what degree do you want to extend this design solution? As you say, there are a number of issues to consider, such as drive ratio (you have that), shaft sizes for stress and fatigue analysis, bearing analysis, V-belt or other belt selection, part selection, mounting bases, belt tensioning device, etc... If you can clarify what you're expected to do I can probably help you out.
 

1. How does a pulley connect a motor and shaft?

A pulley is a simple machine that consists of a grooved wheel and a rope or belt. It is used to transfer motion and force from one part of a machine to another. In the case of connecting a motor and shaft, a pulley is usually attached to the motor's shaft and the other end of the belt or rope is attached to the shaft, allowing the motor's rotational force to be transferred to the shaft.

2. How do you determine the loads in a shaft?

To determine the loads in a shaft, you need to consider the forces acting on the shaft, such as the weight of the object being lifted, the force from the motor, and any other external forces. You also need to calculate the torque required to rotate the shaft and the speed at which the shaft needs to rotate. This information can then be used to determine the maximum load that the shaft can handle without breaking.

3. What factors affect the load capacity of a shaft?

The load capacity of a shaft is affected by several factors, including the material it is made of, its diameter, length, and the type of load (e.g. tension, compression, or bending) it is subjected to. Additionally, the operating conditions, such as temperature and speed, can also impact the load capacity of a shaft.

4. How do you choose the right pulley size for a motor and shaft connection?

The size of the pulley needed for a motor and shaft connection depends on the desired speed and torque of the shaft. A smaller pulley will result in a faster rotation of the shaft but with less torque, while a larger pulley will provide more torque but with a slower rotation. It is important to choose a pulley size that can handle the desired load and provide the necessary speed and torque for the application.

5. Can the angle of the pulley affect the load capacity of a shaft?

Yes, the angle of the pulley can have an impact on the load capacity of a shaft. A pulley that is at an angle can create additional force, called the side force, which can increase the load on the shaft. It is important to consider the angle of the pulley and its effect on the load capacity when designing a motor and shaft connection.

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