Dynamic problem building an RC robot

[farhankhan2395]

We are building a 4 motor driven, with the middle wheels being idle for support. The parameters known are :
Mass= 50 kgs
Theta (Angle ) = 60 degree
Acceleration = 0.254 m/s^2
Assuming coefficient of kinetic friction = 0.6

I am attaching the work I have done and where I get stuck.
I am having trouble calculating the normal forces (N) and frictional force so if someone could help me or tell me what am I missing in the free body diagram or the calculation it would be of great help. I am getting a negative value of N2 which doesn't seem correct. Either way if someone could check and confirm my calculation.
I need to solve this so we can choose a motor for our vehicle, so involves calculation of torque which also I have included.



Thank you very so much.

[Cragyon]

Looks like physics homework to me...