History

This is the diary of the rebuild of my first combat robot, Roadkill1A, into the significantly mightier Tin Lizzie Borden.

Roadkill 1A, while a sound design overall, suffered from a few bits of painfully bad engineering.

The drive control consisted of 16 alarm relays which were wired in parallel pairs in a dual H-bridge formation. The things I failed to consider here, were the current involved and the fact that the relay contacts don't all close at exactly the same rate. This resulted in the swift destruction of almost all of the relays as the current welded and melted the contacts. Not having a reliable way of measuring significant DC current, I guestimated more than a bit too low. I have since discovered that my tiny Black & Decker screwdriver motors, when run at 12 volts, have a stall current of somewhere in excess of 25 Amps each. Figure 3 per side and it's not hard to see why my little alarm relays failed so spectacularly. Add 16 gauge wire to the mix and the drivetrain was doomed from the start.

The complete failure of the drivetrain might not have been quite so bad if my few landed hits had been worthwhile, but alas my engineering failed me there, too. Roadkill 1A was equipped with a pneumatic axe, powered by CO2 at 150 PSI. The driving force was provided by a modified screen door closer piston. The problem with the system was one of volume. I had no low pressure buffer tank, and I was trying to feed the piston from the regulator, through a solenoid with a small orifice, and using tubing with about 3/16 inch I.D. I could easily develop the pressure required, but the piston was severely starved for volume and developed no real force.

Overall, a dismal failure. I was able to compete in 1 individual round, where I wiped out my relays. I was able to get the relays replaced for the rumble, but did not fare any better there.

This leads me to the reconstruction of the bot formerly known as Roadkill 1A. A rebuild of this magnitude, although not total, requires a new christening. Henceforth, the resurrected robot is named Tin Lizzie Borden. I hope you enjoy reading this as much as I enjoyed building it.