Moment of Inertia

What do you mean with "input and output moments of inertia"? The moment of inertia of the motor rotor and of the mechanism after the gearbox?

That I know, you can't calculate the moment of inertia of a gearbox only with the information that you have. If the gearbox is standard you have to find its datasheet or contact the manufacter. If you made the gearbox by yourself, you can use the formulas given by Snygolfgs, but you have to know the moment of inertia of all the gears: measure their mass and assume that they are cylinder.

Thanks for replying. I have now got the info to solve my problem.

I concurr.... use the manufacturers spec in the case of off the shelf. However understand that the calculations are not an exact science.

I also agree.... if you are designing it you need a whole bunch of info including bearing specs and fluid specs of the lubrication.

If you are looking at an existing box that you can't get specs for.... get your wrenches out! You'll need to measure a whole bunch of stuff inside.

Other than that you could get the box tested at a lab. I was just at a gearbox maintenance shop yesterday. They were set up pretty good and even they wouldn't be abel to do a test like that.

OR... just throw in a factor! If your designing an entire driveline you will be dealing with some standard friction coefficients and safety factors anyway.

just my 2 cents

Guy

Thanks, I can now work it out from the information on the site you gave me.

The manufacturer of the gear box (I assume it's a reducer).

When I was in the automotive conveyor game I needed the I/O moments of inertia for some further calculations.

Now I work for a builder of mega yachts in the Pacific Northwest. About a year ago I had to come up with the moments of inertia for the MTU 16V4000's as well as the ZF gear reducers.

The moment of inertia is a composite moment of inertia for the whole drive train, not the mass of steel. Think of it as replacing the gear box with a box with just the input and output shafts - but the shafts have to have the same moment of inertia (resistance to turning or being turned) as the intact gear box.

It's kind of an obscure value and application that is not required very often.

Travis

Say you new the moment of inertia for a gearbox (from manufacturer catalogue). How do you use the to determine the amount of required amount of torque to start turning the gears from rest?

Is that the use for it? Please outline any other uses and how to apply them.