The drive is made up of 4 identical assemblies like this, one for each wheel.
I didn’t really want to mess around trying to cast my own treads onto a custom hub is it looked difficult, and time consuming, and expensive. I decided to use off the shelf 63 shore A castor wheels from Wicke.
They are the same type used in Griffin MKI and I liked them. They were pretty light weight and grippy.
The downside of using off the shelf castor is that I am restricted to the sizes they supply, so I designed around that.
The pulleys and support bushing mount were watercut in aluminium blanks and finished on a borrowed lathe.
They are keyed onto the hex drive shaft.
The live shaft spins on cage bearings press fit into the plastic chassis and side armour.
A Igus plastic bushing sits in the drive motor mount plate to control the engagement between the two spur gears. I also hoped this would support the drive shaft if the bearing on the far end were to get smashed off.
The larger driven spur gear is waterjet from 6082 grade aluminium. This is quite a soft grade, as I knew the waterjet cut quality isn’t as good as a conventional machined finish, and wanted the teeth of the larger gear to wear into the harder teeth of the small gear attached to the motor.
The aluminium teeth should work harden against the harder material of the drive gear eventually.
I made use of the 5 axis waterjet at CWC and added chamfers to the UHMW frame.
At the back this allowed me to keep the rear wheels in contact with the floor if the front end is lifted of the ground.
It also breaks up the boxy shape of stacks of 2D profile cuts.
The hydraulic power pack is a pretty much standard off the shelf unit from Related Fluid power.
I fit my own motor onto it, so had to machine my own coupler to the pump, and design a way to mount this.
I also sealed the breather cap for the reservoir with epoxy, as otherwise it would leak oil when inverted.
The holes on all the shafts for the weapon are oversized on the steel parts, and tight on the plastic.
This way when a force is applied the parts all move around until they hit the steel, which acts as a limit stop.
My thinking is that when impacted, the more parts that are able to move the less concentrated the force is in a single place.
The scoop was lasercut with interlocking locations tabs, for both structural strength and to make welding fast and simple for me.
Here some of the components for the drive assembly are able to be seen a bit better.
The drive shaft was turned from stock Hex bar over at Wycombe Engineering, and case hardened so that it could run directly onto the needle roller bearings seated in the frame.
the wheel is retained by circlips cut straight into the hex stock.