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Nickf_Zar

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- TL;DR Summary
- Calculating the torque required for an agitator/scraper.

Hi All,

I must calculate the torque and for an agitator motor. An anchor type agitator/scraper, removing crust off the edge of a tank.

My instinct is the max or startup torque will be = (Moment of Inertia) x (Angular Acceleration) + (Drag force of the submerged impeller)* Max radius + (Frictional forces on the edge of the tank)* Max Radius

Tmax = ( I * α ) + [ ( Cd * A * ρ * V² * ½ ) + (µ * F) ] * D/2

• The motor has a soft start but is operated at constant RPM.

• The idea is to get a worst-case scenario to design from.

• Please suggest if you think this problem can be solved with a better solution.

I have very little experience with this type of stuff and would greatly the feedback.

• Is this analysis correct?

• What would be an acceptable coefficient of drag to use for a plate with cut-outs in it without doing an experiment

• What would be an acceptable coefficient of friction to use, for the solidified sealing compound attached to the walls?

I must calculate the torque and for an agitator motor. An anchor type agitator/scraper, removing crust off the edge of a tank.

My instinct is the max or startup torque will be = (Moment of Inertia) x (Angular Acceleration) + (Drag force of the submerged impeller)* Max radius + (Frictional forces on the edge of the tank)* Max Radius

Tmax = ( I * α ) + [ ( Cd * A * ρ * V² * ½ ) + (µ * F) ] * D/2

• The motor has a soft start but is operated at constant RPM.

• The idea is to get a worst-case scenario to design from.

• Please suggest if you think this problem can be solved with a better solution.

I have very little experience with this type of stuff and would greatly the feedback.

**My Questions to the community**• Is this analysis correct?

• What would be an acceptable coefficient of drag to use for a plate with cut-outs in it without doing an experiment

• What would be an acceptable coefficient of friction to use, for the solidified sealing compound attached to the walls?

**Thank you**