Page 105 - Build Your Own Combat Robot

Build Your Own Combat Robot
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Comparing SLA, NiCad, and NiMH Run-Time Capacities
In this chapter, a comparison between 4 different battery types that have 6-min-
ute run-time capacities between 4 and 6Ahr. With these batteries, you can draw
40 to 60 amps for 6 minutes. All are 12-volt batteries or 12-volt battery packs.
This is a common motor voltage and eliminates having to scale the readings to
make the comparisons here. For this comparison only, the selected batteries/
packs are listed here:

PowerSonic, part number PS-12180, SLA 17.5Ahr
PowerSonic, part number PS-12120, SLA 12Ahr
Panasonic, part number HHR650D NiMH 6.5Ahr, pack of 10 D-cells
Panasonic, part number P440D NiCad 4.4Ahr, pack of 10 D-cells

Comparing Amp Hour Capacity

First, let’s compare the Ahr capacity verses run time of these batteries. Figure 5-2
shows what happens to the capacity of the battery if you change the rate at which you

True Story: Jim Smentowski and Nightmare
Jim Smentowski guesses that he’s invested well over $30,000 into his robots,
though it’s hard to pin him down to an exact figure. “I stopped counting,” he admits.
“Then again, this is an obsession, so you aren’t supposed to keep track.”
Although Jim has always been mechanically minded, he didn’t have an easy start
with robotics after seeing Robot Wars for the first time in 1996. “I got into it because
the concept of fighting robots fascinated me. I had no idea how to make it happen, I
just knew, somehow deep inside, that this was something I had to do. I just started
doing research. On the web, talking to other builders, talking to manufacturers of
parts, picking up all the info I could from anywhere I could. It took a lot of time, and
nobody ever just handed me the info I needed, I had to spend a lot of time and make
a lot of mistakes before I got to where I am.”
But where he is is a good place, indeed. The man behind such renowned robots as
Nightmare, Backlash, and Hercules, he’s a top-rated competitor on BattleBots.
Nonetheless, when asked to recall one of his most exciting moments under the
lights, Jim chose an early competition that, as he explains, was “an exciting moment
that was not a win at all.”
“Back in 1997,” he explains, “I had the chance, as a rusty rookie builder, to face
one of the top robots in the sport, Biohazard, in the rumble. He beat me, of course,
but I was the last to fall of all the other bots in the rumble, and Biohazard had to
work hard to defeat me. It was then that I knew that I might have what it takes to
actually build a machine capable of winning. I’ve been on that quest ever since.”
Jim adds, wistfully, “Oh, and I still haven’t defeated Biohazard... But I’m getting closer.”