Introduction: How to Build an Electric Battlebot Using Batteries
Have you ever wanted to build a robot built for destruction? This instructable will show you how to build our succesful bot, Roulette. Don't let the title fool you, it may be electric but this battery powered beast was tested using past bots. We knew we had a winner when it tossed an old bot 6 feet in the air. This build should cost less than 500$ if you already have the tools. You can watch a match of Roulette here:
Here is also a video of the best match of this competition:
Step 1: Selecting Materials
Our best weapon oriented Battlebot, Roulette, was built using aluminum for the chassis and titanium for the weapon. The weapon was donated by a local business. We picked these materials because they are light and we had to stay under a 15lb maximum weight. Your Battlebot may be lighter or heavier so your choice of materials is up to you. Keep in mind some materials are harder to use than other. We pick aluminum because of how easy it is to machine. As seen in the video, material choice makes a huge difference. The other team broke our titanium bar with a steel one, most likely S-7 Tool Steel. They made a better material choice and thus did much better in the competition. However, we still took 3rd.
Step 2: Design
This league of battlebots is about original design and learning to make. The teams with the best design usually do better, however sometimes simpler is better. Our bot Roulette is a relatively intermediate design. Some skill is required to build, but most of the work is in getting everything put together correctly. If your bot is for recreational use you don't really have to focus on saving weight, however if you plan to enter this bot at a local competition you may need to consider the weight of your materials and adding holes to save weight. I have provided the design for the layout of our bot in case you just want to build a bot with no extra effort.
Step 3: Building
Now that we are building its time I give you a list of tools needed
They are as follows:
A tool capable of cutting through 1/8in aluminum or other 1/8 bendable material. i.e. Hacksaw, Air tools, etc.
A drill capable of cutting through 1/8in aluminum or 1/8in bendable material.
Several drill bits: including 1/4in, 1/8in, 1/2in. and other basic drill bits
Something to bend the frame together with
Whatever tool is needed to drive the fasteners you will use (Hex, phillips, etc.)
Minimum list as well as:
Drill Press with drill bits up to 1in size
CNC mill (we used this to save time, you can do all of these without a cnc, but it speeds things up)
TIG welder to join the edges of the folds
Sheet metal brake capable of bending 1/8in thick material
Step 4: The Frame
Using the layout provided in the "Design" step, take your material and cut it to match the image and dimensions provided.
Or if you walk to the beat of your own drum, cut out your own layout. There are also other styles of joining pieces, our newest design bolts together instead of requiring bending, but it does require a CNC mill instead. Fold together designs are the easiest to make, also make sure all the components we will be adding later on will fit in your layout, our layouts are usually 12in x 12in to make sure everything will fit without a doubt.
If you folded everything correctly and you followed the provided layout, you should now have the frame of the bot and it should have 2.5in sides and a front wedge to match. At this point you can weld the corners to solidify the frame, if you don't have a welder, you don't have to weld these corners they are pretty strong without the welds. However, if you plan to compete with this design, it might be a good idea.
Step 5: Component Placement
Once the frame is complete, check to make sure all components fit. This means you should make sure wires reach long enough to reach what they need to reach. If they aren't long enough prepare to add more wire.
Components needed to run:
Battery powerful enough to sustain the other components
2 motors, an extra one is needed if you wish to run a weapon system
2 gearboxes, unless you are going with a direct drive system. An extra one is needed for a weapon system
1 or 2 speed controllers depending on the capabilities of them. An extra one is needed for a weapon system.
A transmitter, to control the bot from a distance.
Step 6: Adding Components
You will have to find a way to mount the motors whether it be a gearbox like we use or a direct drive system. You will also need wheels of some sort to roll on. We use Banebots green wheels, they are designed for high traction. We also use banebots 20:1 gearboxes for drive systems and 4:1 gearboxes for our weapon system. We use bolts to hold our gearbox in place, all the other components are velcroed down with high strength Velcro. You will have to drill holes into the frame to accommodate a banebots gearbox. If you already know how to wire an RC system you're one step ahead, if not follow this tutorial on RC wiring: https://www.instructables.com/id/How-to-install-ele...
Battlebots are like heavily armored RC cars, so if you need any additional help with wiring you can consult a number of tutorials here on instructables or else where on the internet. On our battlebots we use Deans connectors because of their snug fit for combat. The components will need some sort of connector for easy connections. This part will require soldering. You will also have to make what we call a "Squid connector" Where there switch connects to the battery and speed controllers. This instructable: https://www.instructables.com/id/30lb-Fighting-Robo...may help with visualizing the wiring setup Just remember these connections:
Battery -> Switch
Switch -> Speed Controllers
Speed Controllers -> Motors
Speed Controllers -> Receiver
Here is a list of links to our components:
Speed Controller: http://www.r2hobbies.com/1-10-rc-car-300a-hv-brush...
Brushed Motors: http://banebots.com/pc/MOTOR-BRUSH/M5-RS550-12
Weapon Speed Controller: http://www.hobbyking.com/hobbyking/store/__19686__...
Weapon Motor: http://www.hobbyking.com/hobbyking/store/__24426__...
Weapon Gearbox: http://banebots.com/pc/P60K-S5/P60K-4-0004
Drive Gearbox: http://banebots.com/pc/P60K-S5/P60K-54-0004
Once all the components are hooked up, you have to bind the controller to the bot using the controller's bind button and putting a bind plug in the receiver. Once it is connected you can take the plug out and use it normally. Also the connections made to the receiver by the speed controllers MUST be correct, our team lost several speed controllers due to members plugging them in upside down. The receiver we have listed has an arrow to show which way is up.
Step 7: So, You Want to Add a Weapon
Adding Weapons to battlebots is highly dangerous, never ever install weapons with the robot on. Also never test the weapon unless there is something sturdy between you and it. We never test unless we have a solid door between us and the bot. We also added a weapon key which prevents the weapon from moving even if the weapon switch is bumped. Just remember, if it's strong enough to break metal, it's also strong enough to break you. This step is entirely optional. Now that you are aware of the risks involved with these weapons....
To add a weapon you will have to add arms to the side of the bot to hold a weapon bar. A weapon bar is usually a half inch thick rod with something attached to it. We usually use whats called a beater bar. It is basically a metal "8" lying on its side spinning on the bar. The arms should be very secure, 1/4 in material minimum. There should also be a hole in each arm big enough to hold a bearing that can hold the bar. You will also need a belt and two pulleys. One pulley for the bar and one for the weapon motor. You will also need to cut a hole on the flat side of the frame opposite the wedge to let the belt move through. For safety puposes, drill a hole through the center of the belt and put a bent rod through the hole, the rod should be big enough to catch on the hole in the frame for the belt. This will prevent the weapon from running unless you are ready. It may take a few minutes but it will prevent serious injury. Do not skip this part. Making a weapon is hard task and usually requires a milling machine or other heavy tools to cut through the thick material. Our aluminum beater bar is usually made with 1in. thick aluminum. You could also try using saw blades with a 1/2 arbor so it will fit on bar.
Step 8: Final Step
Once your batteries are charged, and everything is wired up. Use the switch to activate the bot. Drive it around and get a feel for driving, if you have added a weapon be careful of the weapon button on the transmitter. If you are ready to run your weapon put down the transmitter to prevent accidentally turning on the weapon and pull out the safety key you put in the belt. Then proceed back to your transmitter and take cover behind a thick object. Remember these weapons have been known to annihilate metal bots. Take cover behind something you can trust not to break.
Be safe and Happy Making