The Alexander: May Status

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May

This thing looks as if the first thing its done every morning
for the last ten years is saw through a Volvo,
and its screaming occupants.
- Daniel Rutter, describing The Edger
"Sweat"
May was the month of intense perspiration. Not only becuase the shop has been 85F plus, but because it was time to critically test some design elements to see if they really worked. So far, they have. There's been a middlweight robot frame zooming around the streets near my townhouse for the past few weeks, usually at the top speed of 20 MPH. As soon as I get better at driving it under high speeds, I'll surely have the local cat population on the run.

The digital audio versions of this months quote are down here this month; they're so large that I recommend you allow the rest of this page to load before grabbing the files. WAV (143K) or AU (52K).

I received a few comments on the Rolls-Royce robot rumor from last month. Most notable was from photographer and restored MG auto owner Dean Thomas: "Two words why it will never win: Lucas Electric." My inside sources confirm that said 'bot does exist, it was built by an RR employee and funded by the company, at least in part. However in a bizarre twist, it does not sport the legendary automotive logo of its ancestors, apparently at the request of the BBC. I guess they're worried about getting their collective butts kicked by the Yanks come August.

Pictures

	This hacksaw cut took almost 30 minutes. That's becuase the blued chunk of steel I'm holding is coded "O1," a high carbon grade that has already been oil hardened. It's a bit different to work with, most changes involving lots of coolant and decreased cutting speeds. But its toughness makes it an excellent choice for the Ax's prong bumpers, seen below.
	Here is the second bumper on the mill bed, getting its finishing cut. As I mentioned above, the Ax hits 20 MPH at full stick. This makes ramming an attractive attack mode, as opposed to shoving, which the Agamemnon was good at last year. The new "no pinning" rule also favors speed above power, not to mention that fast robots crashing into each other is what the audience is paying big bucks to watch.
	Three late night sessions in the electronics design wing converted a bag of parts into a 900 MHz transmitter, the source of the Ax's reverse video link. And yup, I wound those little red coils myself. The camera, bagged from the dormant Ag, is slated to be mounted on the forearm of the Edger to allow Weapons Officer Dave to see what he's slicing into. We'll certainly provide an audience feed this year in case anyone wants to write the video to tape.
	Ah yes, another famous "using all the clamps in the shop" picture. I really should by stock in ViseGrip. Here I've got the bottom support of the front structural frame jigged up so I can weld it all together. The chunks of 1018 flat stock serve as large alignment tools when not being cut and machined themselves, a useful property of their ground surface dimensions.
	Here the Ax is flipped on its back, revealing some of its internals. Starting in the upper part of the picture, the two black cylinders with silver caps are the drive motors. Note the vents on the end facing you, where the cooling flow exits. Left foreground is the high current solenoid that switches the 25v into the Edger's cutter motor. Center is the shaft clamp that keeps the whole turntable bearing system intact. To the right is the Pittman motor that spins the turntable.
	One of the oft-overlooked rules of the event is to provide an easily accessable on/off switch for the robot. Here is my safety interlock that disconnects the battery power from the speed controllers with a quick yank. The motors I've used draw 80A at full stall, meaning that the 30A lighted toggle switches I used last year weren't an option. I wanted something really solid with low line losses, and safety-judge-approved. In fact, I've used these Anderson connectors with 12ga silicone wire throughout the high current circuits in the Ax.

A couple of long views of the Ax from the bottom. I have the bottom protection plate installed on one end, sporting the experimental paint scheme.

From the start I made provision on the Ax for a small CO2 bottle. It would either be used to drive the not-yet-designed pneumatics, or as cooling for the Astroflight motor in the Edger. This my mini-fill station hooked up to one of the bottles. It holds 4oz of liquid, about 2 cubic feet of 70C gas. Because the vapor pressure of CO2 at room temperature is about 856 PSI, it's the hot ticket for the sub-1000 PSI compressed gas rule. Solid CO2 (aka "dry ice") has over twice the density of liquid CO2, so for a space critical application it would be the superior choice.

What do you do when you can't find the correctly sized U channel for battery brackets? Buying square tube extrusion and chopping it in half is a good choice.

	You're looking at a unique spot on the Ax - unused space. In the design I managed to leave a few small gaps open for any last minute battery or connector requirements.
	Here I have the entire driveline completed and attached. As you can see, the middle wheel on each side is wider than the fore and aft units. This is what happens when the December "Torque was king last year" brain doesn't communicate clearly with the March "Torque is out, speed is in" brain. I could spin out the wheels on the Ag last year, so I didn't want that to happen this year, thus the wide center tires. But since the Ax doesn't present the same amount of torque to the wheels, I'll be switching back to thin tires in the middle, saving over a pound of weight in the process.
	After you're through with this status report, and if you liked Daniel's Volvo quote, jump over to his web page for some interesting content. Your horizons will be expanded.

And now I close with some prelim pictures of the front bumper.
Many people incorrectly believe that bumpers should be flat in Robot Wars.
I disagree: they should be pointy and sharp. Enjoy!

If you have an extra air conditioner, please send it my way.

On to Special Report