December 2003

Saturday 20th December 2003

I finally found some time from Christmas activities to have a look at the damage I'd received in the recent Worthing event. One drive sprocket had been bent, but I managed to hammer it more or less flat again once I had removed the axle assembly from the robot. I had noticed that the other drive wasn't working, but this was due to an electrical problem, not a mechanical one this time.

I was hoping it wasn't the motor controller that had died, but on closer inspection I found that one wiring block terminal that connected the motor wires to the controller was all melted. While at the Worthing event the left hand side motor connectors had become loose, but I didn't check the right hand side while I was at it. It seems that the screw terminals were loose on this side too, but instead of the motor simply not working at all, the connector must have been arcing and eventually overheated and melted the plastic surrounds. This eventually insulated the wired from the terminal and the motors failed to run. I had to cut the terminal block out and replace it with a new one, after which the drives worked on both sides.

Melted motor wire connector

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Monday 29th December 2003

For a while I have been mulling over how I might manage to gain access to the gas bottle once it is fitted within the Hog, so that I can turn the gas on and off without either removing a front panel, or sliding my hand under the flipper. Having recently looked over Paul Cooper's M2 robot at the Worthing event, I noticed that he had attached a hexagonal nut to his gas bottle fitting instead of the normal nobly round handle grip, and had drilled a hole opposite this in the outer panels. He could then simply turn the bottle on and off using a box spanner or socket on a short extension.

19mm nut welded to a place that fitted onto the gas tap

I decided I could do a similar thing so welded a 19mm nut to a plate of metal that I had filed a square hole in. This now screwed onto the square shaft on the top of the gas bottle tap.

I next had to cut away a part of the chassis because the gas bottle lined up nicely right behind a cross member. I welded a couple of other supports to strengthen the member I had butchered, leaving me with the last job of cutting a hole in the outer panel.

Modified strut to give access to the gas bottle from the outside
Hole cut in front side panel to give access to the gas bottle tap

The trusty tank cutter made quick work of the polyprolene panel and I was now virtually there. The only thing to consider now was whether to make a purpose built tool to turn the gas bottle on and off, or to simply use a conventional socket and lever, but this decision I can leave until another day.

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