DC motor - Enough torque to rotate load?

[dalou]

Hi all,

I am new here as i want to ask something about an engineering project i am working on. I need a motor to rotate a 200 grams cylinder which will be hanging from the motor's shaft (vertically). I wanted less than 100 rpm so the motor I chose is a 2.1W 6V DC motor with a 50:1 reductor that leads to 60 rpm and 12.5Ncm. Will that be enough to keep that load rotating? I have no idea how much 12.5Ncm is and have nothing to compare it with. Moreover, what kind of coupling should I look for to fix the shaft of the cylinder to that of the motor? Will regular couplings be strong enough or will the cylinder fall down eventually? Thanks a lot for any responses, I really need your help here to make sure I won't buy anything wrong!!

[dalou]

nothing? please any comment would be helpful, i really need an opinion here..

[dawin]

Hi all,

I am new here as i want to ask something about an engineering project i am working on. I need a motor to rotate a 200 grams cylinder which will be hanging from the motor's shaft (vertically). I wanted less than 100 rpm so the motor I chose is a 2.1W 6V DC motor with a 50:1 reductor that leads to 60 rpm and 12.5Ncm. Will that be enough to keep that load rotating? I have no idea how much 12.5Ncm is and have nothing to compare it with. Moreover, what kind of coupling should I look for to fix the shaft of the cylinder to that of the motor? Will regular couplings be strong enough or will the cylinder fall down eventually? Thanks a lot for any responses, I really need your help here to make sure I won't buy anything wrong!!

What's the torque of the gearmotor? The inertia of your cylinder? So the motor comes with a gear reducer or you're adding it yourself? Regardless, gearing it down will increase your torque; which you won't need much of once you get the cylinder actually moving.

Coupling depends on what it has to do. Regular coupling, what do you mean? Can you drill a holes into your cylinder and is it long relative to the drive shaft? If I could, I'd pin it right through the drive shaft (which will probably be pretty short), or use a set screw. If you can do a through-hole down the entire cylinder you can use a clamp at the base; whatever you want to do.

[dalou]

First of all thank you for your response..

The gearing comes integrated with the motor. From the motor's datasheet:
Supply Voltage: 6V
Power Rating: 2.1 W
Output Ratio: 50:1
Output Speed: 60rpm
Torque: 0.125Nm (This number includes the gearbox, i.e. it is already increased due to the use of gerbox)

The inertia of the cylinder is around 3.4 * 10^-5 Kg m^2. Moreover, the cylinder will be dipped and rotating in an aqueous solution. And I dont mind about acceleration rate, as long as it is able to get started rotating.

The drive shaft is around 1cm long. The cylinder is ~ 10cm long with a steel shaft put in its middle. How would you fix the one shaft (that of the cylinder) to the rotating one of the motor. I had in mind something like that:
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=3258189#header
would that work ok? Or would the weight of the cylinder be too much to be supported by this?

Thanks a lot,

dalou