Calculate Torque Needed for 100lb 11ft Propellor @ 1RPM

In summary, the conversation discusses calculating the necessary torque for a motor to rotate a 100lb, 11 ft diameter propeller at 1 rpm. It is suggested to make hand measurements of the torque required and use that information to size the motor. The use of speed reduction gears, a DC motor with PWM control, and a Freewheel coupler is also mentioned. The propeller must be able to run nonstop for two weeks, and the discussion touches on the use of hand-assist to get it going, the orientation of the propeller, and the type of bearings being used. The conversation also includes a link to more information on Freewheel couplers.
  • #1
Metahedron
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Good day!
How do I calculate how much torque I need in a motor for my project?

I must rotate a 100lb propellor, which is 11 ft in diameter, at 1 rpm .
 
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  • #2
Welcome to the PF.

You only need torque to spin up the propeller to speed, and to overcome bearing friction. Does the apparatus exist already? If so, you could just make hand measurements of the torque required, and then use that information to size your motor. Will you be using speed reduction gearing to get that slow rotation rate?
 
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  • #3
I do not have the apparatus presently, just the designs. I do plan to use speed reductions gears, but I was also hoping to use a dc motor with pwm control. Is there a most ideal technique for this? It has to be able to run non stop for two weeks.
 
  • #4
When you start it up, can you use a hand-assist to get it going? Then you basically only have to overcome friction of the bearings. Is the propeller vertical or horizontal? What are you using for bearings?
 
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  • #5
BTW, how are you planning on coupling the geared-down motor shaft to the propeller? If you make that coupling with a Freewheel coupler, then you could spin up the propeller by hand to a little over 1rpm, and let bearing friction slow it down to where the motor takes over through the Freewheel coupler...

https://en.wikipedia.org/wiki/Freewheel

480px-Freewheel_en.svg.png
 

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Related to Calculate Torque Needed for 100lb 11ft Propellor @ 1RPM

1. How do I calculate torque needed for a 100lb 11ft propeller at 1 RPM?

To calculate the torque needed for a propeller, you will need to use the formula: T = (F x D)/2π, where T is torque, F is force (in this case, 100lbs), D is the diameter of the propeller (11ft), and π is the mathematical constant pi. Plugging in the values, we get T = (100lbs x 11ft)/2π = 554.3 ft-lbs.

2. What is the unit of measurement for torque?

The unit of measurement for torque is typically foot-pounds (ft-lbs) or Newton-meters (Nm). In our case, the torque needed for the 100lb 11ft propeller would be measured in ft-lbs.

3. Does the RPM (revolutions per minute) affect the torque needed for a propeller?

Yes, the RPM does affect the torque needed for a propeller. The higher the RPM, the more torque is required to rotate the propeller at that speed. In our case, since the propeller is rotating at 1 RPM, the torque needed would be lower compared to if it were rotating at a higher RPM.

4. Can I use the same formula to calculate torque for a different weight or diameter of propeller?

Yes, the formula used to calculate torque for a propeller can be applied to any weight or diameter of propeller. Simply plug in the appropriate values for force (in lbs), diameter (in ft), and π (the mathematical constant) to get the torque needed in ft-lbs.

5. What other factors may affect the torque needed for a propeller?

Other factors that may affect the torque needed for a propeller include the type and design of the propeller, the viscosity of the fluid in which it is operating (such as air or water), and any external forces acting upon the propeller (such as wind or currents). These factors may require additional calculations to accurately determine the torque needed for a propeller.

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