So it's been a bit since I posted an update on my GIANT ENEMY CRAB 2 project (Part One and Part Two), and that's because I have both run into some difficult questions about how I want to design its weapon system, and also because I got some brand new waterjet-cut metal parts from SendCutSend! Now with titanium armor and an AR500 steel weapon, my other bot-in-progress JACKALOPE is just a set of wheels (and maybe a new lid) away from being a fully-functioning combat robot. This is definitely the most dangerous thing I have ever designed and I'm a little nervous about the weapon test once I get these last parts on.
Anyways, to help keep myself active while I decide what I'm doing with GEC2's weapon, I've decided I am going to start on another project - a simple Wedgebot. Wedgebots are the simplest form of combat robot - an armored wedge or plow being pushed around by a robust drive system. Examples include the original La Machine from old-school BattleBots, Storm 2 from Robot Wars, Original Sin and Crash n' Burn from Robogames, and arguably certain iterations of Duck! from the BattleBots reboot. It's a surprisingly effective strategy, breaking your opponents with your face. In fact, many attribute the fall of classic Comedy Central era BattleBots to there being way too many wedge-vs-wedge matches, which usually aren't very fun to watch. In lower weight classes however, Wedgebots are very common and new builders are encouraged to start with them since they are much safer than a bot with an active weapon. They are also very common for beginner kits like the Fingertech Viper, and the Botkits 1lb Candy Wasp and 3lb D2.
My bot will be very much in line with the Botkits bots - 4 wheel drive using 4 motors, with a separate wedge up front. It will be 1lb like the Candy Wasp, but with a 3d printed TPU chassis (flexible and strong) and aluminum motor mounts, instead of being all billet aluminum. I also have a different wedge design in mind that I think should allow it to function upside-down, unlike the Candy Wasp.
Anyways, to start on this design, I open up Fusion 360 and start pulling parts from my saved parts library of common bot parts that I have been collecting, and arrange them on the workspace. I don't need to worry about any pulleys or weapons or anything so it's pretty simple.
For this bot I will be using:
- 4 Fingertech Silver Spark Gearmotors
- 2 5A Brushed ESCs (1 for front drive, one for rear)
- 1 Fingertech Mini Switch
- 1 FS2A 4 channel receiver (each drive ESC takes 2 channels, so this is perfect)
- 1 3S 450Mah Lipo battery
- 4 Fingertech bearing blocks to mount the motors
- 4 Fingertech 3mmx.75" wheel hubs to mount the wheels
- 1 pair of terminal blocks (not pictured)
Arranged on the workspace they look like this.
Next step is to build a quick little chassis around these components and give it some wheels. 3mm walls and floor, 1.5"x.75" wheels, a couple more adjustments to add mounting holes for the bearing blocks, and pop a lid on top, and it turns into something like this.
Now on its own, this is a fully-functional boxbot. Defenseless and underweight, no obvious way to tell which side is the front, but it will drive. My next step will be to design the wedge mounting system, and maybe some internal walls to hold all the electronic components in place. My next post will likely be about that, and maybe getting some wheels on JACKALOPE so I can take a video of how it works. Or maybe I'll have a breakthrough on the crab again, who knows?
Right now I use an Ender 3 S1 Pro, stock except for a glass bed. So direct drive and all-metal hotend. Before that I ran an Ender 3 with a buncha upgrades including a MicroSwiss direct drive. I've never tried it with a bowden extruder, but with the direct drive it prints basically as easy as anything else, aside from a occasionally feeding into the extruder wrong when starting a print. It's an easy fix.
Oh wait, it actually adheres to glass? :isaac-pog: I tried doing PLA on glass once just to see what would happen and it was a complete disaster. I should give that a try.
Yeah, the bowden setup is not ideal. Basically a CNC rope pushing machine. It does work fairly well for convex shapes though, but requires a lot of patience. A lot of trade-offs need to be made in the slicer settings, and what works in one situation can be very detrimental in another. The filament has a tendency to knot itself up between the extruder drive gear and the tube opening, killing prints instantly. To counter this, I crank up the temperature to limit the backpressure on the filament, but I gain no speed out of this and it makes the oozing worse. To counter the oozing, and the fact that the filament is stretchy, larger retraction distances are needed, but this feeds back into the knotting problem. I haven't gotten a chance to see if Marlin's linear advance feature would help at all yet.
If I end up dumping any more money into this thing, I guess I'll be getting a direct drive setup.
I love my glass bed. It's the Creality one, but I run it upside down. Makes for a slick smooth surface on the bottom. I use hairspray with it, or white glue when I'm doing the CF-Nylon.
Definitely recommend the Direct Drive. There are even some printable ones I've seen that look pretty decent.
Yeah, I could just print out a bracket and strap the current extruder to the top of the hot end, but I think I'd prefer to get something that weighs a little bit less.