In this instructable, we will look into the basics of robot design (and mostly how it SHOULDN'T be done)
firstly you may notice that it uses a fully 3D printed chassis again this is NOT recommended for serious combat but all things considered, it is a viable choice for small weight class (Ant or Beetle). I have however hit a snag that my robot is way too heavy (max for ant is 150g in the UK). mine is currently close to 300g and it doesn't even have top or front armour. this is probably due to me making the walls of the frame half a centimetre thick and printing with 8 perimeters, however, because of this, it is incredibly strong.
if for some absurd reason you want the STL files for this you can find them here: https://www.thingiverse.com/thing:2374705
Step 1: Electronics (transmitter Choice)
the transmitter that I choose is the flysky fsi6x due to the fact that it has fully programmable mixes that are very important for use in robotics due to the fact that you need the elevator control on the remote to effect both drive sides (channel 1 & 2 in my case). in order to do this properly, I went into the TX's functions menu and selected mixes and made 2 new mixes.
mix 1 was channel 1 (typically pitch) mixed with channel 2 (typically roll) by +100% this means that there is now a positive correlation between channel 1 and channel 2 with identical power levels (full power on both sides) this means that up on the left stick results in both drive sides moving straight ahead.
mix 2 was channel 2 (roll) mixed with channel 1 (pitch) by -100% this again means that the drive sides had identical power levels but this time channel 1 was opposed so that when channel 2 was moved up (right on the left stick) the drive sides would move in opposite directions thus creating the turning movement.
the benefit of this is that if you move the stick diagonally you get a movement that is forward with a slight turn thus allowing for more accurate manoeuvres.
Step 2: Electronics Drive (motor and ECU Choice)
The motors and ECUs that I chose are very cheap and inexpensive.
The motors are 12v 600rpm n20 motors on eBay each time I look there is a different price under a different seller so I haven't posted a link here but if you google the three things above I can guaranty you will find some.
The ESCs are yet another china special and although rated for 20 amps I would be hesitant to even put 10 amps through them for more than 5 minutes but as my motors have a stall current of 1.2A the worst case for these controllers would be no more than 3 amps for 3 minutes (that is the full length of a match).
the only downside to these ESCs is that they can only handle 2s (2 cell lipo) this means that the most I can run these motors at the moment is 8.4v, the motors would be happy up to 14v and possibly 16.8v or 4s (might only last 2 matches at that though, but they would be very very speedy matches)
one way around that is to get motors that run at a lower voltage but my bot can do about 1.1 M/s anyway so it would be ok to just run them as is. this being what it is though I was thinking about getting some beetletwo ESCs as they can do 45amps for 3 minutes and are capable of 4s
Step 3: CAD Work
I used SolidEdge 9 to make all of the models.
I can't say much about this as the designs will be different for all of yours (hopefully as its the randomness of robot combat that makes it interesting), but what I will say is that you WILL NEED multiple revisions in order to get to a good final robot (as with most things you will find that it is rarely actually finished).
in terms of print settings, the standard profile is probably fine for most of the parts the flexibles took a bit of tweaking.
for a more detailed print setup and STL files check out the thingiverse page: https://www.thingiverse.com/thing:2374705
Step 4: Assembly
I'm assuming that if you made it this far then you are seriously considering building a robot and probably have some vague form of soldering experience. it is quite simple to build, just join each drive sides motors in parallel with wire and then connect the ESCs to each drive side after this plug the ESCs into the receiver and the built-in BEC (battery elimination circuit) will provide the receiver with power so there is no need to run two batteries. once you have done this solder the 2 ESCs power leads to one connector and then place the robot so none of the wheels can touch the ground and plug it in.
If you are lucky it will work perfectly first time but most likely you will need to modify the mixes and directions of the connected motors to make it move properly.
Step 5: Super Janky Battery
not much to say about this other then don't do it. it's too heavy to be useful in lightweight robot combat and the output is two small to be useful in heavyweight combat (it can only put out like 8 amps continuous).
a much better option would be to just get a generic lipo unless like me you just want to see it move. (I will be getting a lipo before I go to any events)
another important point is that you should have armour for the battery as lipo's can explode very violently if damaged