6wheel servo flipper antweight combat robot (150 gram)

Files and a guide to build your own antweight combat robot (150 grams). This robot has had over 50 fights, always doing well and a lot of fun so I am sharing it with whomever wants to give combat robotics a go. This robot is very low and stable. The forks get under any other robot and with the powerful servo you'll be throwing your opponent around.

This robot was not necessarily designed to be easy to build so please read all the instructions carefully. I apologize for the length of these instructions but didn't want to leave anything out that might be useful. Please feel free to ask questions and I'll try to answer them.

I get most of my parts from AliExpress, combat robotics stores online and LiPo batteries I get from the local RC hobby shop.  

For electronics I use:
    E-flite 200mah 2S battery
    fingertech switch
    2x n20 gearmotor 6V 500rpm
    Malenki nano or llamaforge control board
    PTK 9495 Metal Gear Servo ( or KST DS215MG alternatively)
    connectors for battery and servo and 22 awg multistranded silicone wire.

I strongly feel that you should use one of the suggested servos as they are strong, reliable and fast and the robot has been designed to fit them. I also suggest you stick to 6v 500rpm n20 gearmotors. Lower rpm motors might be a bit too slow and higher rpm motors might struggle to turn the robot effectively.

Other hardware I use
    1.9mm brass rod and/or 1.8 mm spring steel rod
    M2.5 (3.5mm OD) knurled heat set inserts
    M2.5 6mm button head bolt
    M3 x 16 hexagonal bolt
    m3 nylon locknuts
    m3 washers (.5mm thick)
    22mm mini-Z tires (wide) or 24mm x 14mm well known brand of Danish toy tyres

Start by printing all the parts. A .4mm nozzle, 3 walls, 3 top and bottom layers should be plenty strong. I highly recommend using PLA+ because it's a lot tougher then standard PLA. I use polymaker Polymax.

Insert the M2.5 (3.5mm OD) knurled heat set inserts with a soldering iron and tweezers. Heat set insert are great but can be tricky to install so it's good to do this first.

Drill out any of the small holes with a 2mm drill bit so that you can more easily push the rod in later.

Dry fit and then glue (I use 5minute epoxy) the m3 16mm hexagonal bolts. Make sure they are pushed in all the way and use something straight to verify that they all line up.

Invert the tyres and carefully cut them down the middle so one wide tyre becomes two narrower ones. Remove supports from the wheel hubs. Glue the tyres to the wheel hubs and the wheel hubs to the wheel gears. A little glue goes a long way.

Install your electronics. I cut off the rear tab on the servo and sanded it flush to fit it in the robot.  Don't install your servo horn until you power it up for the first time. Make sure to limit the servos movement (endpoints) and that it moves in the right direction (forward to flip). Now is also a good time to check that the gearmotors spin in the right direction. If using a malenki nano (or llamaforge control board) and turning feels a bit sluggish then I suggest turning off onboard mixing and doing your own mixing in the transmitter so you can turn at full speed.

Almost there. You'll need 3 pieces of rod. The holes for these rods should be drilled with a 2mm drill bit if you haven't already. One rod is at the front the full width of the body and holds the swivel arms there. Then a shorter one (about 47mm long) goes through the other end of the swivel arms with the spacer in between. Same size rod goes through the servo horns second hole (assuming you have the exact same servo horn) Please refer to the pictures of the internals.

Push the drive gear onto the gearmotors. This should be a fairly tight fit. Leave a small gap between the gear and the body of the robot to limit friction. Now bolt on plate left and right to keep all the electronics in place. To install the idle gear use a washer, then idle gear then washer and then use the m3 nylon locknut. Tighten the locknut till fingertight and then back off half a turn. Everything should spin freely if done correct. Same for all the wheels. Lastly push the lifting arms onto rods and secure in place with top plate.

Please be aware that this combat robot was not designed to face destructive opponent (with metal spinners) but the same robot printed in TPU has done quite really well and even won some of our local monthly meets.

Have fun!