Servo - May 2009

A better alternative are chargers with delta peak detectors. These can tell when the battery is charged and then will switch it over to trickle charge and turn on an indicator light to let you know.

The cheapest ones have low output current and so need several hours to bring your battery to full

charge, but you can plug your battery in and forget about it. If you have a slow charger, you may need two or more batteries to get your robot through a full day of fights. You can also buy higher current chargers that will recharge your battery in an hour or less but they will cost you more.

The pursuit of energy density will ultimately lead you to Lithium Polymer (LiPo) batteries which have the best performance available. However, LiPo batteries and their chargers are outside the scope of an article about cheap power. SV

All photos are courtesy of Michi Mathias.

ROBOT PR FILE

THE ULTIMATE ANT

Due to circumstances beyond my control (plus a bit of laziness), I’ve been out of building insects for about four years. I follow the technology escalation on various forums, particularly the Antweight forum on Delphi Forums (http:// forums.delphiforums.com/ant weights). As I creep back into building, I realized the state-of-the-art in components moved on without me. So, I started a thread to garner the fruits of the best insect bot building brains. “We” (they) built the parts list for the 2009 Ultimate Antweight full combat bot. There was surprising little disagreement on the top one or two brands of hardware in each area.

As we’re taking a short break from our “Top Bot” profile series, (due to the apparent exhaustion of Event Organizers, who slipped a bit

After being battle tested in 51 fights through three major upgrades, Babe was very competitive in the 2005/2006 season.

● by Kevin M. Berry

in getting brackets into BotRank), I decided to use this wealth of data to profile the 2009 Ultimate Ant.

My baseline is my tired old 2005 machine Babe The Blue Bot. At the time, as a box bot, it approached the Ultimate level of technology. Now, it’s hopelessly out of date except for possibly in a few areas. Babe has appeared numerous times in SERVO, both in my articles and as a standard header in another series. Here are the specs:

• Drive Motor: Four Copal 60:1 gearmotors

• Wheels: 1.75” Lite Flite

• Hubs: 4 mm Lynxmotion

• Drive ESC: Sozbots Classic

• Drive Batteries: 350 mAh LiPoly Triple Cell 3S 11.1V pack

• Weapon: 0.040” Ti 6Al-4V wedge

• Armor: 3/32” hardened kevlar honeycomb with 0.012” 6Al-4V titanium overlay

• Radio System: JR Quattro 75 MHz PPM with GWS four channel receiver

• Power Switch: RadioShack

• Fittings/Parts: Zip ties, hook and loop, aluminum, UHMW

I went in thinking the only components on Babe that might still be state-of-the-art quality are the armor and the LiPoly pack. Sneak peek at the results: Lite Flites are

still current and I’m not giving up on my Lynxmotion hubs.

For pumping the forum’s expertise, I laid down the following ground rules (which later caused some trouble, explained under the Motors heading).

“Assuming the following: unlimited budget for components (but value matters too, not just cost); two driven wheels; spinner (drum, disk, horizontal, vertical, whichever); 2.4 GHz radio system; Robot Fighting League compliant. Don’t worry about raw materials or manufacturing unless very specialized.”

This post accomplished exactly what I desired. Eleven builders posted their lists, along with some advice from other seasoned veterans. The results were surprisingly consistent.