The blade will be 2" x 14" x 0.5" and weigh about   3.5 lbs.  A 7/8" hole will allow it to be duirectly attached to the axle using a 1/2" bore Trantorque bushing.

The top 72 tooth 3mm HTD pulley is from SDP-SI. Its bore is machined out to 7/8" to match the trantorque bush that will secure it in place. 

I scribed the centrelines around each of the gearbox mountings so that I could tell when they were properly positioned for drilling and tapping.

Andrew then scribed a line around each end of the lower tube at the distance we want to locat the screws.

Then drill three holes equispaced (approximately) at each end.

One hole was drilled with a #25 bit and then tapped 10-24 in each mounting.

The scribed line on the mountings allowed us to line up the mounting in the chassis correctly so that we could mark the positions for the other two holes in each part. A little filing of the holes in the chassis allowed any mounting fit ant chassis. The Gearboxs were then secured with three screws each.

Weapon motor mounts were hand fabricated out of some spare Aluminium Channel.

And matching clamps from flat bar.

These secure the HTI  (Speed 700 sized) motors to the side of the chassis.

Both Chassis now have weapon motors. Similar mountings will be made to allow the use of Mini-Ev Motors as well.  A weight test for almost everything the bot will need came to 7.85lbs.  With the Blade weighing about 3.5lbs, the Bot should come in nicely on the correct weight.

We measured the actual pulley to pulley centre distance which came to 127mm minimum. I used solidworks to calculate the actual belt length required and then ordered the nearest larger size - 390mm.