Understanding Gear Ratios and Torque in Torsional Problems

[Alistair McCheyne]

Hi, this is a question from a previous past paper that I am having trouble with. Am I meant to just use the number of teeth from each gear to find a ratio and use this to find the effective inertia at point C. Then use this to find a torque and take away the torque of the constant load.
My exam is tomorrow so any help would be greatly appreciated.

Here is my working
https://scontent-lhr3-1.xx.fbcdn.net/v/t34.0-12/13162482_10156888512910486_1882077086_n.jpg?oh=08e752c6546ce7cb6b8917d83a1d6d77&oe=57313006

Thanks

 

[haruspex]

Your notation is confusing... I_b=I_b+I_a(r^2)?!
More importantly, you are thinking about the ratios wrongly. As gear B turns once, how often does gear A turn?