Build – 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.

High Steaks Deep Dive

Have you ever thought of a terrible pun? Has that terrible pun resulted in dozens of hours of work to transform it into a tangible object?

Big wheeled bots aren’t new. Bots like Huge, Gabriel, Starchild, and plenty of others have been out there fighting for years and are inspiring new designs all the time. While thinking about the pros and cons of this style of bot the thought came up: What would happen if Team Food Fight built a big wheel style bot? While I can’t say what the bot would look like, a name immediately came to mind.

With that pun, the CAD effort began and Hotkoin was contacted for the logo you see above.

So, what are the goals of High Steaks?

Re-use the hubmotor and electronics from M-80
Test viability of PLA+ for semi-protected structural elements in a 3lb bot
Test segmented cleats as a means of increasing grip and adding structural stability to UHMW wheels
Lean hard into the theme

With those goals the parts list and profile started taking shape. High Steaks would recycle the drive and weapon esc’s from M-80 along with the hubmotor. Some left over FingerTech Mega Sparks would be the drive solution with an extra 2:1 reduction to the wheels.

If you’re gonna go all in on a steak theme, you can’t be generic on your weapon disk. This lead to the question of just how steak-like a disk can be made to look. After some digging around I settled on two base colors and the Montana Cans white marble effect paint.

With the electronics pulled mostly from an existing bot the wiring process was fast with the main challenge being routing wires between the two halves of the chassis. The rear channel was snug, but it wasn’t too difficult to pull the wires through with the assistance of some forceps and a bit of patience.

Electronics Overview
Power Switch with TPU Mounting Spacer

Thanks go out to SendCutSend for making the weapon disks, steel chassis components, and spring steel cleats. The UHMW wheels and carbon fiber armor panels were made by CNCMadness.

Top View
Bottom View
I Swear It’s Not On Fire
Weapon Lock On Theme

With all the pre-event goals met that leaves the final question: How did it do?

Overall I’m very happy with the performance. The one serious design issue that popped up didn’t really impact the results, but with the width of the tips on the side forks it would require the axle to be removed to replace a wheel, which isn’t ideal if there’s a time crunch. Because of that some new side forks have been designed that keep the aesthetic while allowing the hex bore on the wheels to slip over them for easy replacement. Beyond that, some extra UHMW wheels and cleats have been made to ensure enough spares are on hand and that there’s a heavier duty wheel option for bots where wheel damage is particularly likely.

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

Introducing High Steaks

https://www.youtube.com/watch?v=o4-EwGFc1cQ

Introducing Outlier

What’s the current meta in the Antweight class? Compact verts? Probably. Big horizontals? Fair chance. Wedges? Certainly a contender. Whatever it is, it certainly isn’t… Outlier.

Some brief specs:
Drive motors, weapon motors, and esc’s from Repeat Robotics.
2x 250mah 2s LiPo from Palm Beach Bots wired in series.
Welded 4130 chassis with a printed weapon module and carbon fiber baseplate.

2D Profile Gearmaking

Gears can be expensive. Custom gears with weight relief can be even more expensive. 2D fabrication processes can be used to significantly cut these costs if you’re willing to put in the time and deal with a bit of extra prep/cleanup.

There are plenty of vendors out there that’ll sell you a gear, but more often than not the gear you can buy isn’t exactly what you’re after. Similarly, places like https://www.rushgears.com/ will make custom gears to order, but at a steep price, particularly at the low quantities most projects will need. Maybe if the loads are light you could 3D print the gears. Given the choice between “not right”, “too expensive”, and “wrong material” there’s got to be another option, right?

This is the spot I was in when looking to do a custom gearbox for a 30lb combat robot. I was able to source a few gears that were “right” but to get the full reduction at the strength, weight, and footprint required I would need to go custom.

Using 2D fabrication (waterjet and laser cutting) I was able to get gears cut to spec at a much more affordable price via https://www.bigbluesaw.com/.

For my gears I opted for laser cutting from AR500 plate. I also opted to go with a stacked gear approach to minimize the impacts of taper and HAZ due to the cutting process.

Two stages in this gearbox would be done via stacked, laser cut gears. The smaller gears were cut from ⅛” plate and the larger gears were cut from 3/16” plate. For each stage of gear you stack three small gears and align them with two large gears. The reason for doing this is to ensure that there isn’t a situation where a single stacked plate is only engaged with another single stacked plate. This minimizes the risk of one of the stacked gears taking on the entire load passing through that stage of the gearbox and reduces the chances of the binding that could result from one gear wearing faster than the others. I also opted for hex shafting as it would better spread the forces out than a single keyway, reduces sharp corners (the cutouts in the gears have rounded features at each corner) and avoids creating a thin section near the keyway that would be a likely failure point.

The first step in gearbox assembly was match marking the gears so I could easily assemble each stage without having to determine which of the 12 possible orientations was the correct one for installation. For this I set each plate on a common shaft and used a green paint pen to mark the teeth.

As you can see looking at the above image, some of the teeth look a bit rough. This is illustrative of one of the downsides to this fabrication method – As features get more detailed and plate thickness goes up the surface quality of the cut will tend to go down. Luckily, this is a case of things looking worse than they are.

With the gears marked it was time to make the shafts and spacers for the gearbox. (Along with a few other shafts used for the build)

With the shafts made it’s test fit time.

Here you can see how the differing plate thicknesses force all gears to be engaged instead of allowing for the possibility of only one gear being engaged during use. The gaps you see between the plates can be closed up with additional shims if necessary.

At this point the gearbox was ready for run-in using valve grinding compound to smooth out the rough surfaces on the gear teeth.

Grinding the Gears

Once the gears were running smoothly the gearbox was disassembled and cleaned to remove the valve grinding compound.

After a full cleaning it was time to reassemble and lubricate the gearbox.

With that all done a quick hand check showed that things were running smoothly and were ready for use.

Hand Test

Notes and Lessons Learned

At 16p, 3/16” thick plate resulted in aesthetically poor teeth, but a bit of finishing work got them running well
Taper could quickly become an issue at higher plate thicknesses
Using low taper waterjet cutting may allow for full thickness gears with no HAZ and should be considered if the project budget allows it
Using hex shafting required some additional work on the front end but should simplify maintenance
The ability to design weight relief into the gear profiles is a massive benefit when dealing with tight weight limits
Good gear tooth profiles are important, as is modifying the profiles to accommodate the fabrication method. Kerfs and beam/jet radius need to be accounted for in your profiles and should be designed into the part so you’ve got better control of it.
There are plenty of sources out there for gear tooth profiles that you can use as a baseline, https://geargenerator.com/, https://evolventdesign.com/pages/spur-gear-generator, and https://www.engineersedge.com/calculators/spur_gear_calculator_and_generator_15506.htm are just some of them

2 x 72 Grinder File Release

With testing complete, drawings updated, and the launch video uploaded it’s now time to release the full design.

GnH-NCR_Grinder_Files Download

The link above contains a STEP file of the full assembly along with the PDF assembly drawing and the DXF you’d need to have the flat cut parts fabricated by a waterjet or laser shop. (SendCutSend) With the DXF I’ve left a border on the drawing with the overall sheet dimensions needed. For fabrication shops with automatic quoting you may need to delete this to not get an inverted version of the parts.

This project was a collaboration with Goat n Hammer. The files above are being provided at no cost for anyone that would like to build their own version.

If you’ve got any specific questions feel free to reach out via any of the social media accounts linked on this page.

Motor
Tracking Adjustment
Face Mounting
Tooling Arm Sockets
Ratcheting Tension Adjust
T-Nut/Slot & Tab Construction

Build Progress: Custom 2×72 Belt Grinder

A while back I began work on a project with the fantastic folks at Goat n Hammer and it hit a major milestone today, the laser cut (thanks Big Blue Saw) frame was built up enough that the motor could be mounted and the tilt functionality tested.

Once the grinder build is done the drawings will be updated to reflect any changes I want to make after building the prototype and the drawings along with some build documentation will posted and made freely available.