Calling all Mechs! (Torque calculations)

[Jedward45]

Hey,
Here's a challenge for all the Mechs on Delphi:

I'm currently trying to find the correct spring pin size to hold a final stage bevel gear in place. This pin transmits torque from the driven bevel gear, to both a 3" wheel mounted on top of the bevel's hub, as well as to a live shaft inserted through the bevel's hub. (Once again, thats a 3/8" diameter Shaft, within a 1" OD bevel hub, within a 1.25 OD Wheel Hub.) Consequently, the Pin's length would be 1.25", with 2 points of torque transfer (One on each side). The difficulty is that Lateral space to mount the Pin is extremely limited, meaning I need the minimum pin diameter necessary to withstand the torque of the drive train. (with an adequate margin of error)

So, if T=rF, then the radius is .625", but I don't know how to estimate the force.

I know
-the Robot's speed (with a rough overestimate), is 10 feet/sec.
-The robot's weight is 150, but I figure 75lbs maximum on each wheel (4 wheels, but all weight on two wheels in full speed stop)
-Using JVN Design Calc, Robot pushing force is 120lb, and Motor Torque load is 1.9 Nm, Wheel Stall Torque is 14Nm. (sorry I didnt convert)
-Coefficient of friction is 1.4

Once again, I'm looking for the Torque load the Pin will have to endure.
Any help would be great!