Help for design of rotary system

[Parsnip]

Hiya all,

I wonder if anybody can help me.
I am designing a large cylindrical type object (approx 800mm tall and in about 400 mm in diameter) and that has slots for locating small items. This cylinder needs to be rotated using some sort of drive and motor mechanism. The speed of movement is not all that critical however smoothness and accuracy are.

My questions are:
What sort of system (pully, worm gear, dc motor, stepper motor) would be best.

How do I go about calculating the motor sizes - do I have to know inertia etc.

Is there any sort of design guide that would help me in the correct selection and sizing of the drive system.

Thanks in advance

Parsnip

 

[CoryPad]

Without more details, it would be hard to provide "the best" solution.

How about having an externally splined shaft out of the motor and an internally splined piece connected to the cylindrical object's structure. Then, use a motor control system to rotate the object as needed.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[MintJulep]

"How do I go about calculating the motor sizes - do I have to know inertia etc."

Yes, you do.

"Is there any sort of design guide that would help me in the correct selection and sizing of the drive system."

Yes, it's called and engineering degree.

 

[MotorVib]

HP sizing, we need to know a little more like speed & the Wk². If it is just spining you need vary little HP to do that. The problem is the smaller the motor the long it will take to get up to speed. Most people size the motor on the working load and not the dead load.

Chris

"In this house, we obey the laws of thermodynamics." Homer Simpson

 

[eromlignod]

"Yes, it's called and engineering degree."

Around here it's called *an* engineering degree. ;-)

Don
Kansas City

 

[chicopee]

Motorvib-It would be very hard to comply with the third law of thermodynamics.

 

[zeusfaber]

Another thing we need to understand is what you mean by "accuracy".

Is it important:

a. To get the drum to spin at the right speed?

b. To get the drum to get up to speed or stop at the right time?

c. To get the drum to stop in the right place?

d. To get the drum to stop with a particular amount of overshoot?

A.

 

[BrianPetersen]

e. To get the drum to spin such that its position is synchronized with another independently-controlled function.

 

[MikeHalloran]

In general, projects like this turn into disasters because of normal gear lash and manufacturing tolerances... which have to get extreme as the radius decreases.

Putting the slots in the object is also no fun. Machining from the solid or a tube is expensive. Wrapping from slotted sheet is more attractive... except at the joint, where it gets really messy.

The presence of an "indpendently controlled function" suggests that you have two design projects, or one large system design project... none of which you appear equipped to surmount. No offense intended.

One thing you might consider is just wrap a timing belt around the outside of the drum and drive it with a stepping motor. It will require an idler to get enough wrap on the 'pinion'... but it won't need a monster timing belt pulley on the drum... just two discrete teeth.





Mike Halloran
Pembroke Pines, FL, USA