Momentum of this rotating gear?

[sophiecentaur]

My solution. I think I have got it now. There seem to be ratings for nominal acceleration on stepper motors. One that I found had a nominal acceleration of 280 steps/sec, which is equal to 504 degrees / sec, which is equal to 8,79 rad / sec. Then I just need to find out whether the moment of inertia exceeds the holding torque by using Torque = nominal angular acceleration * moment of inertia. Got any comments?

I really really don't understand any of this, now. How are you going to deliver power to this free moving motor? I have to repeat my original question - What is fixed to what, what is allowed to rotate and what is fixed to the earth?
You clearly have a picture of this in your head which has more details in it than that basic figure you have provided.

And god only knows what you mean by this. How can a torque be compared with a Moment of Inertia? They have totally different dimensions. And what is "holding torque"? We have suddenly migrated from ideal, theoretical to nuts and bolts (totally practical). V. confusing.

 

[risecolt]

I really really don't understand any of this, now. How are you going to deliver power to this free moving motor? I have to repeat my original question - What is fixed to what, what is allowed to rotate and what is fixed to the earth?
You clearly have a picture of this in your head which has more details in it than that basic figure you have provided.

And god only knows what you mean by this. How can a torque be compared with a Moment of Inertia? They have totally different dimensions. And what is "holding torque"? We have suddenly migrated from ideal, theoretical to nuts and bolts (totally practical). V. confusing.

lol. Are you ****ing kidding me? Torque = angular acceleration * moment of inertia.
A motor has its own lowest acceleration rating. The big gear is rigid, the small gear is not rigid.
The small gear rotates about the big gear, because the motor spins, the small gear thus also have to rotate about itself, as it is in contact with the large gear. That is all the information you need to get into your head.

 

[sophiecentaur]

lol. Are you ****ing kidding me? Torque = angular acceleration * moment of inertia.
A motor has its own lowest acceleration rating. The big gear is rigid, the small gear is not rigid.
The small gear rotates about the big gear, because the motor spins, the small gear thus also have to rotate about itself, as it is in contact with the large gear. That is all the information you need to get into your head.

I could say the same thing.

You have still not described what happens to the body of the motor. You 'agreed' that it is free to rotate (or did not read my question). OK for a thought experiment but now you tell me you have a real motor in mind, with real characteristics. SOOOOOO it needs power from somewhere. Where? A long flexible power lead?
If you cannot actually draw out your apparatus with more than just 'sky hooks then you have to specify, fully, what you have in your head. I suspect that there is something in your imagined set-up that you may not have fully considered (or, at least, keeping secret) - which is why I was after a proper diagram.

You have done the equivalent of drawing an electronic circuit without including power supply voltages and a ground and expecting someone to say how it will function.

 

[etudiant]

lol. Are you ****ing kidding me? Torque = angular acceleration * moment of inertia.
A motor has its own lowest acceleration rating. The big gear is rigid, the small gear is not rigid.
The small gear rotates about the big gear, because the motor spins, the small gear thus also have to rotate about itself, as it is in contact with the large gear. That is all the information you need to get into your head.

It is rude to talk down to people who are trying to help answer a poorly posed question such as yours.
In a class, I'd tell you to sit in the corner. Dunce cap for the next offense.

 

[sophiecentaur]

It is rude to talk down to people who are trying to help answer a poorly posed question such as yours.
In a class, I'd tell you to sit in the corner. Dunce cap for the next offense.

Cheers, but it's water off a ducks back for me. I spent a long time being paid for dealing with hormonal teenagers so I tend not to take offence!

 

[tipsung]

Magnetic Prpulsion

If one had in space 2 (or more) perfectly aligned connected wheels with large magnets that were precisely set to spin effectively by alternating different polarities what, if anything, could this produce?

 

[sophiecentaur]

If one had in space 2 (or more) perfectly aligned connected wheels with large magnets that were precisely set to spin effectively by alternating different polarities what, if anything, could this produce?

Did you have anything in mind?

 

[tipsung]

Yes. Working off opposite repelling particles creating a sort of ion propulsion. I can vision this and draw it out but the mathematics behind it is not my strong suit. I just seem to daydream and come up with several different things all the time never knowing if things will function as I envision

 

[sophiecentaur]

There are many designs for ion drive that do not involve 'moving parts'. Why involve extra complications?

 

[tipsung]

Point taken. Perhaps this magnetic alignment with a motor, coil, rotor and shaft could produce electrical energy and cause acceleration. As the motor accelerates the stronger magnetic field thus causing the motor to go faster and faster... Like I said it was just a thought. Thank you for the replies.

 

[sophiecentaur]

My point is that it would not be a reactiionless drive.