Motor Torque Required to Rotate Hanging Load

[HungryDinosaur_imported]

Hi All,

I am working on a mechanism where I need to rotate a load hanging with hoist trolleys on a round/circular I-Beam track. While simple torque calculations can be done by available data, the mechanism is not as simple. The hanging load, trolley roller friction, and load being on the circumference of the circular frame) etc. makes it more detailed.
I tried to find information on hanging loads and rotation, but could not find any. Can someone please advise what will be the torque required at the motor gearbox to rotate this load at 20 rpm? Thanks in advance. Please see attached image/schematic of the mechanism.

Regards,

HD

 

[BrianE22]

Ignoring any swinging back and forth of the hanging loads, you need to overcome the rolling resistance of the trolley wheels. I've used 3% of the normal load for the rolling resistance load for steel trolley wheels on a good I beam surface. Once you have the rolling resistance then multiply it by the 2 loads and the radius of the wheel. Your pinion and gear probably are 90-95% efficient.

I'm not sure how much the circular arc that the I beams are bent to would affect the 3%.

If cost and size aren't too big a constraint then use a generous safety factor.

Can the I beam track keep the proper gear center distance fairly constant?

 

[hydtools]

Any concern about acceleration time? You would need to consider inertia. The above comment addresses overcoming friction force.

Ted

 

[HungryDinosaur_imported]

Gents thanks for the answers, but still there is no clarity on the motor torque.

BrianE22, I am planning to use a center bush to centralize the gear, and I am aware of it, so working on it.

 

[SnTMan]

Recommend you crack your Dynamics textbook. Doing so will lead you to hydtools' response.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[tygerdawg]

The advice of hydtools and SnTMan is spot on.
You must calculate the maximum torque required to move this mass from a rest condition. That calculation starts with the equation T = Jα. The mechanism has a lot of rotational inertia to which you must apply torque in order to accelerate that mass. Therefore it is essential to define your rotary speed and how fast you wish to achieve your rotary speed. You must provide for deceleration also.

TygerDawg
Blue Technik LLC
Manufacturing Engineering Consulting

http://www.bluetechnik.com