Calculating Torque to Accelerate

[ram18]

Hi,
I need to find out horsepower to accelerate pipe (40ft long) which is fixed with the plate (10ft x10Ft x 1inch) and whole assembly supported with bearing and shaft. I need to accelerate and decelerate this assembly 180 degree in 10 second ?

Plate weight = 4000 lb
pipe weight = 4500 lb
total weight = 8500lb.

bearing and shaft is perpendicular with respect to plate and pipe in the center

I done this calculation but its seems wrong can anybody tell me what i have to do for right solution . where i am wrong ?


Torque = moment of inertia x Angular acee

Power = Torque X angular velocity.

so i find out moment of inertia for plate and pipe .
Plate
Moment of inertia = mass X a X a / 6 = 4080 X 10x10 / 6 = 68000 lb-ft2.

Pipe ,

Moment of inertia = 647441.66 lb - ft2

Total M.O.I = 715441.66 lb - ft2.

i want to rotate this thing 180 degree in 10 second. so i consider 3 rpm .

angular velocity = 2pixn / 60 = 2x3.14 x3 / 60 = 0.314 rad/sec

angular aceen = change in velocity / time interval = 0.314 / 10 = 0.0314 rad / sec2.

avg angular velocity = 0.314 / 2 = 0.157 rad / sec

torque = total m.o.i x angular acee = 715441.66 x 0.0314 = 22464.86 lb-ft2 / sec2

power = torque x avg angular velocity = 22464.86 x avg angular velocity = 22464.86 x 0.157 = 3526.848 lb-ft2 / sec 3.

1 hp = 17696 lb- ft2 / sec3

so 0.30 hp required to rotate whole system in 10 second. it seems wrong. Can you guys give me some direction on that.

Thanks.

 

[tiny-tim]

hi ram18!

I need to accelerate and decelerate this assembly 180 degree in 10 second
…
angular aceen = change in velocity / time interval = 0.314 / 10 = 0.0314 rad / sec2.

doesn't it mean that the angular speed will be zero every 10 seconds, with a constant acceleration for 5 seconds, and then a different constant acceleration for the next 5 seconds?

 

[ram18]

Actually i want to accelerate that assembly 180 degree in 10 second. I think all load is carrying by bearing so how can i calculate how much torque required to rotate this whole assembly. i m so confused now please give me some right direction.

 

[tiny-tim]

Actually i want to accelerate that assembly 180 degree in 10 second.

do you mean from 0° to 180° in 10 s, then from 180° back to 0° in the next 10 s, and so on?

 

[ram18]

Yes tiny tim can u help me on that .

 

[tiny-tim]

ok, then that means that you need constant acceleration from 0° to 90° in 5 seconds, then an equal constant deceleration from 90° to 180° and back to 90° in 10 seconds, and so on …

how much is that acceleration? ​

 

[ram18]

Actually i want to rotate that system 180 degree in 10 second . can u tell me my above calculation is right or wrong for that please.

Thanks,

 

[tiny-tim]

Actually i want to rotate that system 180 degree in 10 second . can u tell me my above calculation is right or wrong for that please.

Thanks,

I don't understand …

what angular speeds do you want it to have at the angular displacements of 0° and 180° ?

 

[ram18]

i am going to use hydraulics motor to rotate that system 0 to 180 degree . And i want to know how much torque required to do that?