cad – Near Chaos Research

Building a Compact, Portable Test Box

Fabrication files

The above .zip file contains the .dxf’s for the flange, side plate, polycarb holddown polycarb panel (if you want to route it out or similar) and the .step file for the polycarb pull handle. The steel for this build was all laser cut by SendCutSend.

While it’s certainly possible to build a bot, show up to an event, and run it without taking the time to test it’s not the best idea. Similarly, if you’ve got a weapon capable of damaging your opponent, you’ve got a weapon capable of doing real, lasting damage to a person. If you want to test it, you need somewhere safe to do it, and a test box is a great way to protect yourself, protect the other people around you, and test your bot.

With that in mind, I wanted to replace my old bulky test box with something that hit a nice balance of usable space and portability.

The core goals of this design are:

Small enough to easily go through a door
Able to be mounted to a wheeled platform
Big enough for almost any 3lb robot to be tested safely
Easy to build
Easy to repair

Goal 1: Small enough to go through a door.
The main structure of the test box is a 26.5″ square frame that can be built to effectively any height. It’s rare to see a door narrower than 30″ so this should fit with room to spare.

Goal 2: Able to be mounted to a wheeled platform.
The hole patterns on the exterior of the flanges will allow the test box to be securely bolted to a frame using a simple hole pattern and #10 hardware.

Goal 3: Big enough for almost any 3lb robot to be tested safely.
With 1/2″ plywood walls the internal usable floorspace is just over 23″ square. Only the largest of the large in the 3lb class can’t fit that footprint.

Goal 4: Easy to build.
The main frame design uses two main parts, a flange and a side plate at qty. 8 each, made from laser cut mild steel. These components key together to aid in fixturing for welding and provide easy attachment points for wall and floor panels. Additionally, the top polycarbonate panel is retained by bolt on flanges and a pin lock to allow a simple rectangle of polycarb to used without any drilling required. The dimensions also allow for 2′ square 15/32″ thick plywood project panels from any local hardware store to be used for the walls and floor with little to no modification required. Similarly, the polycarbonate retainer height can be easily adjusted via 5/16″ OD spacers sized for #10 bolts. For mine I added adhesive backed felt pads to help with sliding the panel in and out. With sufficiently stiff polycarb panels you likely can slide the panel straight back with no issue. If you notice sagging then a small bonded tab that lifts the edge of the panel as it slides in will make closing the test box easy.

Goal 5: Easy to repair
The mild steel frame, easy to swap hardware, and use of commercially available plywood panels means that there’s typically a quick, easy repair option for almost any kind of damage.

Fresh cut parts slotted together
Clamped for welding
Off the shelf walls and floor
Welded and ground
Welded and ground

For my build I opted to paint much of the plywood, while it’s not necessary it does add a nice finishing touch to the whole thing.

Floor fitting
Checking alignment
Walls going in
Mostly assembled
Polycarb retainers and felt installed

So, what’s left to do? At this point the test box is fully usable. Most of the box is held together using some fairly short #10 wood screws and the pin to lock the polycarb panel in place is McMaster #98320A125 if you want to track down the same part.

RadioMaster MT12 Joystick Mod

For a long time, I’ve wanted a ground style transmitter with a third channel that wasn’t a basic switch or slow scroll through an input range. Not long ago RadioMaster released the MT12 which is a ground style radio running EdgeTX.

Before I get too deep into what I did, here’s the finished mod:

Finished mod being bonded to the removable base plate
Finished mod being bonded to the removable base plate

Here are the STL’s you’ll need to print your own:

Joystick Housing Body

Joystick Back Cover

With that out of the way, here’s how this was made:

After the MT12 was delivered and RadioMaster told me there wasn’t a CAD file available I looked into free 3D scanning apps, eventually settling on Polycam. I took the MT12, set it on a flat metal plate, scanned it, then exported the scan, used a converter to get it into STL format, imported it into Solidworks, then made the first version of the main housing.

3D scan of the MT12 done with Polycam
Raw STL imported to Solidworks
Raw STL being used to mock up first draft of the joystick mod
First draft mod being used to validate scan geometry

Overall, it was ok, but a bit bulky. It also meant that I couldn’t grip the transmitter the way I wanted to. Enter the realm of near impossible to machine parts that are effectively trivial thanks to 3D printing. The second version of the housing dramatically changed the shape and added mounting features. It also made it clear that I’d need at least a short cable extension. V3 quickly followed with fine tuned mounting and a cover for the back of the joystick.

V3 geometry to determine fits/location and cable length
V3 geometry with rear cover installed
V3 with a test for a removable mounting strap

I didn’t happen to have the right connectors on hand, so a quick Amazon order later and I was ready to build an extension cable. For this step the big thing is making sure you don’t swap around the order of the wires from cable to cable since that could cause input issues or damage a board.

With the mod tested and the housing painted it was time for the final step, bonding the housing to the removable base plate with one of my favorite adhesives, Shoe Goo.

Finished mod being bonded to the removable base plate
Finished mod being bonded to the removable base plate

The paint’s a bit glossy, so I may give it a matte clearcoat at some point, but beyond that I’m very happy with the final outcome.

Outlier Deep Dive

Outlier prior to competing at Robot Battles 71

Outlier is the teams newest 1lb bot and is the end result of trying out a bunch of new stuff and new ideas.

Going into the design the core goals were:
1. Build a 1lb electric lifter that’s competitive
2. All brushless (this goal came in after initial concepts used some brushed parts)
3. Run 4s lipo effectively
4. Test viability of TPU lifter arms
5. Try new wheel construction methods

Early concept with a brushled lifter motor
Layout is starting to take shape
Design as built for Robot Battles 71

CAD from the early concept stages through the design that was made

Over the course of a few design revisions and a few product releases the bot went from a semi-direct brushless drive, brushed lifter with all of the components integrated into a single chassis to an all brushless lifter with replaceable weapon modules and indirect brushless drive.

Key components in Outlier:
Drive/Lifter: Repeat Robotics Repeat Mini Mk3’s (prototype HR gearbox for the lifter)
ESCs: Repeat Brushless Drive ESC for drive, Repeat AM32 Drive ESC for the lifter
Battery: 2x 2s 250mAh lipos from Palm Beach Bots
Power Switch: FingerTech Mini Power Switch
Weapon Module Structure: Custom Printed by Team Malice
BEC: iFLIGHT 3S to 6S Micro 5V 3A BEC

In addition to the above, the chassis, forks, and plow on outlier were made from 0.050″ laser cut 4130 steel from SendCutSend, the baseplate was 1mm carbon fiber from CNCMadness, and there were a lot of PLA+ and TPU parts printed in house.

Weapon module test fit
Weapon module test fit
Lifter gear and wheel hub
Chassis test fit
Plow test fit
Silicone to TPU bonding test
Completed wheels

Assorted photos from the build including test fits and some adhesive testing

Rolling chassis
Weapon module test fit

Test install of the drive wheels & weapon module

With that done and the event rapidly approaching a lot of things happened off camera with the end result being a working 1lb robot.

First drive and arm wiggles

A bit of lifter testing

Outlier is a pretty dense little bot and was probably one of the more challenging wiring jobs I’ve done.

Outlier (left) along side Firecracker (middle) and Quark, (right) two of our 150g bots.

So, how’d the event go?

The good:
The drive power was insane, even with the fairly grippy silicone it was easy to spin the tires.
The chassis and drive mounting held up great, even with some major hits repairs were easy.
The TPU lifter arms took crazy hits without any trouble.
The PLA+ – TPU – Silicone wheel combo held together well even when taking some nasty hits

The bad:
The D shaft I was using had a very small flat, so between the Delrin gear and printed TPU adapter it was struggling to transfer torque, so the lifter often struggled to lift.
Changing configurations took longer than I’d like which meant I ran a config that wasn’t well suited to my opponent and took some massive damage to the weapon module & plow during the fight
After a few fights in close succession the printed PLA+ motor guards deformed, jamming the drive motors in the final, luckily late enough that it didn’t cost Outlier the match.

Damaged but still usable wheel
Post event teardown showing deformed PLA+ motor guards

So, what’s next?
1. New homemade titanium D shaft for the lifter module
2. Modified, lighter, 1095 steel plow design that will allow weight for wheel guards so changeover time is reduced between configs
3. Explore additional wheel configurations
4. Connectorized weapon motor to allow easy swapping of entire weapon module

Nyx and Algos CAD Files

I’ve seen a few people request cad files of bots in varying weight classes recently and had already published variants of these elsewhere, however between site updates and host migrations the old links aren’t likely active. Beyond that, I wanted to republish these in a neutral format with both bots in their “final” state.

NyxAndAlgos Download

The above link contains .step versions of the forked lifter and hammer configurations of Nyx along with the final design for Algos and a slightly updated weapon design that should make manufacturing easier. In the case of Algos, there was some hand finishing to get it within weight (wedge sharpening, shaving off small non-critical areas, etc) but it is the chassis design as fabricated.

If you don’t already have a cad program that can open step files one great option is getting a maker license for Solidworks. The SDK-IDs that are working at the time of this post are 9SDK2020 and 9MAKER with the former likely updating each year some time in the fall.