Weapon System

Currently Ruf Ruf Dougal has only one weapon, it is a spike which protrudes from the front just below his head.
The spike is effectively a 'con rod' driven by a huge flywheel within his body.

Spike

The spike is a 25mm diameter hardened steel driveshaft from a Ford Fiesta. One end of the shaft is ground to a sharp point and the other end carries the 'big end' bearing.

Big End Bearing

The big end bearing is a suspension ball joint. The housing is welded to the spike shaft and the taper on the ball is fitted to a boss in the flywheel.

Sliding Bearing

The spike is allowed to slide directly inside a greased steel tube which in turn is allowed to pivot using a halfshaft bearing. The end of the tube extends beyond the fully retracted spike and is crossdrilled to provide the mandatory safety pin.

Flywheel

The flywheel is a 16 inch diameter temporary car wheel wrapped in lead to bring the weight to about 20kg. It also has a counterbalance weight fitted to balance the spike. The flywheel runs on a standard car wheel bearing supported on a 2 inch diameter scaffold pipe. Drive is by 2 car ABS motors running at 24V and is via a friction / self servo interface.

I haven't calculated the inertia but at 450rpm (7.5 spikes per second) and with a stroke of 8 inches I wouldn't want to get too close!

Spike	Flywheel & Big End Bearing
Pivot Bearing	Flywheel Bearing
Friction Drive Wheel	Motor & Friction Belt