Combat Robotics has always and forever long been a great passion of mine. From childhood i wanted to build a rather large sized combat robot myself but due to lack of skill and funds was unable to do so. Recently i decided that it was time and I undertook a challenge to build a 30 Kg combat robot within $100.

I am going to give you guys a complete rundown of my build. Hope you guys find it innovative.

Features

2' x 2.5' x 1' Dimensions
28 Kg Weight
1 ft/s Velocity
High Power
Front Wedge
Front Raiser
2 Hours run time
24 v 9 Ah Battery System
Stable Rugged Design

Step 1: Parts and Tools

Well basically the robot is built out of threaded rods and hard wood.

Parts Required

12mm Threaded Rods (approx. 35 ft) Web Page
2" x 2" Hard Wood Lengths (approx. 12 ft)
12mm Nuts and Washers (approx. 100) Web Page Web Page
10" Wheels with 12mm Hub
Motor Cycle Main Sprocket Sets Web Page
Motor Cycle Chain Web Page
Car Wind Shield Wiper Motors Web Page
2mm Steel Sheet Pieces Web Page
Sealed Lead Acid Battery Web Page
9g Servos (3 pieces) Web Page
High Power Lever Switch (12 pieces) Web Page
High Power Wires Web Page
Spade Terminal Connectors Web Page
Caster Wheels Web Page
5v Regulator Web Page
Card Board

For me the cost for all these parts was around $100. I saved a lot on the motors as i got them from the junkyard. Other parts i bought all from local stores which were much cheaper.

Tools

Hack Saw
Wood Saw
Drill Press/Hand Drill
Wrenches
Hot Glue
Crimping Tool
Screw Drivers
Metal Shop (I went to the one near my home)

Step 2: Planning and Layout

Before starting out on the final design i test fitted some of the pieces just to get an idea of how and where the things will go. I sketched many plans on paper to get a rough idea of the placement. Unfortunately i threw them so have nothing to show.

The images are just some test fits to check the wood pieces are right and to get a rough idea of the size and weight.

Step 3: Fitting the Sprocket to the Wheels

I started off by attaching the sprockets to the wheels. This was a critical part and had to be sturdy so that it doesnt break during operation. I basically drilled holes in the wheels and matching holes in the sprocket. Then i used pieces of the threaded rods to attach them.

Step 4: Cutting the Wood

I cut the wood into 6" blocks. Then i made holes for the threaded rods. The holes were made according to the placement of the block in the robot.

Step 5: Prepping the Motors

The Wiper motors need some work to be installed in the bot. First of all you need to open up the motor and remove the ground from the body of the motor. I used the low power wire and used that for ground. Then you need to mount the motors on a 6" x 6" steel sheet. I drilled holes and mounted the motor. Then on to the sprocket. For that i cut up the piece that was pre mounted on the motor hub and then had it welded centered on the small sprocket. Then i mounted the sprocket on the motor. I also drilled holes for mounting the motors on the robot.

Step 6: Main Assembly

I assembled all of the parts together. Had to open it up or change stuff many times. The images are pretty self explanatory. I mounted the motors as well. The chain were cut according to size and then clipped on. The motors can be moved forward and backward to increase or decrease tension in the chain.

The chain is dangerous. Keep hands clear while operating.

Step 7: Adding Battery + Electronics

You might notice in the images that the position of the wedge and caster wheels change. Well that is true because i was experimenting with various designs. I will explain the final one later on.

The batteries chosen were two 12 V 9 Ah Lead Acid Batteries. They have good results and weight wasnt and issue. I fitted them in two small compartments using foam and then secured then first by a metal strip and later by a metal sheet.

For the electronics i used spade terminal connectors all the way round. I used a basic switch and a fuse for safety. As for the motor controller i experimented with PWM H bridge motor controllers but a few "Pops" later i gave up and turned to a reliable and cheaper solution. I used servos with a mechanical H Bridge Switch Assembly. I connected the servos directly to the hobby remote and easy peasy. I was in business.

Step 8: Finalizing

Now that all is done i finalized the bot. I attached a metal sheet on the top and bottom. Also a sheet for the front wedge. I placed the caster wheels on the front most piece for better stability. Here you may also notice the different designs in the photos.

Move on the next step for some "Inner Info"

Step 9: Stages in Wedge Design

1. First I had the wedge in the front and caster assembly in the centre. But there was an issue. Whenever weight was but on the wedge the caster wheels became a pivot point and the rear wheels lost traction. So not effective.

2. Then i moved the wedge at the back and had caster wheels on both sides of the main wheels but that was not good too as on un-even surface the main wheels lost traction.

3. The final design was one with a front wedge but the caster wheels below the wedge giving not pivot point. Hence there was maximum traction

Step 10: Done But Not Complete

So i have this inner bug in me that does not rest until its comfortable. I was feeling that the bot was too simple and too "empty". If it got stuck or something it wont be able to do anything so i decided to add a front arm which would revolve to raise the bot up and down.

For that i used another motor. Did the same "mods" on it and then mounted it. I used a smaller chain as i had it available. Use the threaded rod for the arm. Gave it a 90 degree bend and then attached it to the bot. Made another motor switch assembly and then i was done.

Step 11: Final Version

This is the final look. Some foam here and there for shock protection. This is a combat robot so its main purpose is COMBAT. I made it in a way that it can sustain all weapons. Flippers will be useless as the bot runs on both sides. This design is like that. Cutting weapons wont be effective as the rods are hard to cut. Rammers and wedges might be effective but this bot hat great torque. Speed is low, perhaps a slower than i would have wanted but torque is high.

Step 12: Conclusion

Well the main challenge to build a working bot was successfully accomplished. Now all that is left is to take it face to face with other bots. I will post videos soon.

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