Build Your First Combat Bot!

FingerTech’s diagram (Figure A) shows a typical wiring setup with a gearmotor and servo. But we’ll solder our connections, and also add a JST battery connector.

1a. Solder the ESCs to the gearmotors

The Silver Spark motors have one tab near a red dot and another tab without one. This corresponds to the polarity of the motor. Each tinyESC (5) has one purple and one blue wire. Solder one of these wires (which one doesn’t matter at this point) to one tab then the other color to the other tab.

Do the same process to connect the other tinyESC to the other motor, but flip the polarity of the wires. For example, if you soldered blue to the tab near the red dot on one motor, then solder the purple wire to the same tab near the red dot on the other motor.

I recommend adding heat-shrink tubing to cover the joints from potentially shorting and to add strength to the connection.

1b. Solder the power connections

Solder all the red wires from the tinyESCs and the 9V regulator (6) to one of the tabs of the FingerTech mini power switch (1). On the other tab, solder the red wire from the female JST connector. The female is the connector that the other connector goes inside of. This allows the (male) plug on the battery to plug directly into the connector, providing power.

The mini power switch works by tightening a screw which connects the two tabs. Once this screw makes contact the circuit is complete and electricity is able to flow. In order to make sure all components of the robot will turn off once the power switch is loosened, we connect all the red wires to one location, ensuring there is only one way for electricity to flow. We connect the other tab on the switch to the battery to ensure power is being received.

1c. Solder the ground connections
Solder all the black wires from the tinyESCs and 9V regulator to the black wire on the female JST connector. These connections don’t need to be separated by the switch since we already separated the red wires. By connecting the black wires we complete the circuit, leaving only the switch to allow you to turn it on and off.

Congratulations. You’ve now soldered all of the most important connections in the robot!

Connect the receiver leads from the tinyESCs to channels 1 and 2 on the receiver (3). These will allow you to control the drivetrain using the right stick on your transmitter.

Connect the receiver leads from the servo (2) to channel 3 on the receiver. This will allow you to control the lifting arm using the throttle channel on your transmitter.

Connect the receiver lead from the 9V regulator (4) to channel 4 on the receiver. This allows the regulator to power the servo so it can use its full capacity.

3a. Glue hubs into the wheels

Add a dab of hot glue onto the larger half of a 3D-printed wheel hub and insert it into the center of a foam wheel (Figure B).

Flip the wheel over, add a dab of hot glue onto the smaller half of the hub (Figure C)
and insert it into the center of the larger half. Press the pieces together to make sure the hubs properly bond to the foam wheel.

3b. Glue Lite Hubs into the hubs

Add a bit of hot glue to the nylon body of a Lite Hub then insert it into the center of the printed hub in the wheel (Figure D).

Repeat Step 3 for the second wheel.

Add a dab of glue to the bottom of each motor mount in the chassis (Figure E).

Now you’ll heat the rear section of the chassis to insert the Silver Spark gearmotor. Turn on the heat gun and let it come up to temperature. Focus it on one motor well at a time: Once the plastic becomes soft, insert the drive motor into the slot. Ensure the gearbox is thoroughly mounted and sitting in the hot glue. Then bend the plastic in slightly so it helps support the motor. Remove the heat gun and let the plastic cool so it hardens in place (Figure F).

Repeat this process for the second gearmotor (Figure G).

Slide the lifting arm over its supporting arm on the top plate, as shown in Figure H.

Attach the servo horn to the output shaft of the servo. The servo horn is a component that connects to the output shaft’s splines (like gear teeth), which allows you to transfer its power to something else. Slide the servo directly into its mounting area. It should sit snugly next to the lifting arm (Figure I).

Attach M3 bolts through the lifting arm into the servo horn (Figure J). Due to the servo horn’s design you will need to insert one screw first then attach the second one after it. You may need to trim screws to fit exactly.

Screw the servo into its mounting holes in the top plate, using the four #6×½” Plastite screws.

Attach the wheels to the gearmotor shafts by tightening the Lite Hub setscrews using the 0.050″ hex wrench.

Finally, attach the top plate to the robot chassis using the five #4×3/8″ Plastite screws (Figure K). Enjoy your completed Kerfuffle!

So now that you have a completed machine, what do you do with it? First, practice with your robot. Turn it on, using the 3/32″ hex wrench to screw down the mini power switch. Use the transmitter’s right stick to move the robot (front/back and left/right) and the left stick to move the lifting arm servo (up/down).

• • Practice driving. Get the hang of how your robot drives, and become accustomed to how it moves — this will allow you to compete more effectively later on.• Do figure-8s — it’s a great way to get used to the robot’s steering as well as get a good read on its speed.

• • Practice fighting. Because this machine has no dangerous spinning elements, you can easily build clones of it and hold mini sumo competitions where you have timed skirmishes and try to out-drive and out-fight each other.• To attack, approach a raised area on your opponent. Because Kerfuffle relies on lifting (Figure L), it needs to get underneath the other robot, so find areas on your opponent where the arm can get below to maximize lifting ability.• Wait until you are firmly under the opponent to lift. If you try to lift too early it can leave you exposed to attack, so be patient before using the weapon.• If Kerfuffle gets flipped over, use the lifter arm to flip it right-side-up again!

• • Fight at events! Check robotcombatevents.com to find combat robot events in your area. Check when/where competitions are happening and see which ones are hosting “Plastic Ant” classes as part of their competition, such as MACRO’s events held in Severn, Maryland (Figure M). I highly recommend going to events as this is where you will get connected to members of the combat robot community and further learn about the sport.

If you’re looking for tips and tricks, or would just like to meet other combat robot enthusiasts, the Combat Robotics group on Facebook is where many of the builders (especially the ones from BattleBots) discuss robot designs.

With these tips you’re well on your way to entering the world of combat robots! Happy building!

Since I first shared this Version 2 design, Kerfuffle’s shape has changed dramatically as competition pressed further development. You can see Version 3.0 (Figure N), Version 3.3 (Figure O), and newer designs by following my team Bone Dead Robotics on Facebook or
@bonedeadrobotics on Instagram!

Ready for kinetic weapons?

• • First, build a protective test box or safety arena (see page 54).

• • Try building Irkin (Figure P), my plastic antweight vertical spinner bot.

• • Or add new weapons to Kerfuffle, like my sawbot Version 3.1 (Figure Q)! 

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