# Time required by a motor to reach the torque

1. Jan 23, 2014

### subbby

I have :
Cylinder : 958,000 lbs
Motor 200 HP
required RPM : 5
time : 60 seconds

Torque: 18,757 lbs-ft

What to find ?

Time required by the motor to reach that torque

Doubt :
• Is there a chart or a graph that gives this value ?
• is there any eqaution / formula that helps finding this time ?
• or is 60 seconds the answer ?

Also, 18,757 is the torque and a 18HP is what is required to reach 5 rpm in 60 seconds. How do you calculate the torque required to keep it running. Isn't, 18,757 the just the start-up torque ?
Assuming no friction or energy losses, how to calculate this running torque?

2. Jan 23, 2014

### cjl

That all depends on the specifics of the motor design. Electric motors can make peak torque effectively instantly, while internal combustion engines may take some time to develop the peak torque after the throttle input is applied (how much time depends on the details of the motor design).

As for the running torque? If there are no frictional losses, the torque to maintain a given speed is zero. All torque used to maintain a constant speed of rotation is purely to counter the losses in the system.