BRAT Biped

Last modified by Eric Nantel on 2023/02/21 12:24


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Table of Contents


About the Biped BRAT
BRAT stands for Bipedal Robotic Articulating Transport. The robot is a 6 servo biped walker featuring three degrees of freedom (DOF) per leg. The robot can walk forward or backwards and turn in place left or right with variable speed. It can even do lots of Robo-One style acrobatic moves. Our combo kits include everything needed to make an operational robot, however the chassis and servos are available separately for those who want to use their own electronics.

The Mechanics
The robot is made exclusively from brushed, or black anodized aluminum servo brackets from our Servo Erector Set. It also includes an electronics carrier made from ultra-tough laser-cut Lexan.

The Servos
We are providing the walker with Hitec HS-422 servos. Due to the robot's light weight, these servos work well.

Powering Options
As with any walking robot, weight is a major concern. The best approach is to keep the weight to an absolute minimum. We recommend using the 6.0 Volt Ni-MH 1600mAh Battery Pack (BAT-03) and the Universal Smart Charger (USC-01).

Controlling the Biped
The robot is available in two basic configurations, Animatronic (tethered connection to a PC) or Autonomous. The autonomous version includes the BotBoarduino microcontrollre. We have several sample programs that allow the robot to roam without bumping into objects, get up by itself if it falls, and exhibit other behaviors such as boredom or surprise. We even have a "seek and destroy" tutorial showing how to make the robot locate, home in, and kick water bottles. There is also a template program that is easy to edit to add other sensors or behaviors. The PC version uses our SSC-32 and the Visual Sequencer to control the robots motion. It's a tethered configuration but can be made wireless with a wireless serial device such as the Sparkfun BlueSMiRF modem. We have 10 example sequences for the Visual Sequencer to get the robot going right away.

To keep costs down we are not providing printed Assembly Guides. They are provided online, so you will need to print them when you order the kits. By providing the Assembly Guides online we can provide more detailed and up to date information than the old hardcopy method allowed.



  • No of DOF per leg = 3
  • Servo motion control = local closed loop
  • Height (as pictured) = 8.5"
  • Width (as pictured) = 6.0"
  • Ground Clearance = 2.5"
  • Weight (without batteries) = 22.2 oz
  • Range of motion per axis = 180 degrees
  • Accuracy of motion per axis = Servo controller dependent (SSC-32 = .09°)
  • Servo voltage = 6 vdc

User Guide


BRATCA-BLK/BRU Combo Kit Information

Additional Information

Created by Eric Nantel on 2023/01/13 12:45
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