quack.

This post covers the progression of my signature 30lb combat robot "quack." This robot expands upon the concept and technologies from my 1lb combat robot "Bioluminescent." Similar to that robot, this design features modular weapons which can be configured to gain an advantage over any potential opponent. A highly optimized frame which leverages the unique properties of over 6 different materials allows the robot to be larger, stronger, and lighter than any other competitor. Custom sensor boards wirelessly monitor the condition of the robot and relay it to a custom phone app to provide the driver with live information. Cryogenically cooled sensored brushless motors power the rotary weapons to over 430mph, over double of most standard competitors. These features, tempered through years of experience, have resulted in what many people deem "the most ambitious combat robot of all time"

Combat robotics is inherently an optimization problem. With limited weight, money, and repair times, each bot must be designed to win against as many opponents as possible. With these limitations in mind the following objectives were set:

• Design a weapon and attachment system capable of winning a head-on engagement with any other robot currently on the field

• Adhere as closely to the 30lb weight limit as possible.

• Build two entire copies of the robot within the designated $2200 budget.

• Optimize performance for 3 minute runtime

• Withstand typical impacts with minimal damage to performance.

To address the first design objective, I implemented an innovative modular design previously developed for my 1lb combat robot Bioluminescent. The core principle lies the "rock, paper, scissors" aspect of dominant combat robot designs. A majority of combat robots use high-velocity rotary weapons to store kinetic energy and deliver impacts to opponents. While the each robot can vary in form and function, they tend to be sorted into 3 primary categories.

By having modular weapons that adhere to each of the primary archetype, the function of the robot can be altered to most effectively counter every opponent. The beater bar uses a wire edm weapon made from 4340 steel, hardened to 48hrc to maximize toughness above the 46hrc hardness threshold necessary to reduce tip dulling. Powered by a sensored outrunner, the weapon reaches a velocity of 430mph and energy equivalent to a 50bmg bullet. The reach vert uses an internal gearbox capable of taking 60000 input rpm to power a colossal 11 inch balanced disk. The module is designed to place the weapon as far forward as feasible, accounting for COG, handling, and load transfer paths. The small vert module is designed to maximize durability and velocity. Both verts use the same hub which features large tapered roller bearings preloaded using spring washers to withstand extreme impact loads. By using a single stage reduction from an inrunner, the weapon spins up to a maximum velocity of 450mph, allowing it to break opponent weapons in half. The horizontal spinner uses a high-speed spiral bevel gearbox to transmit power at 90 degrees to the large live shaft. The shaft rolls on massive needle roller bearings and is pretentioned throught the pulley and bottom flange. A spline retains the weapon disk and transfers torque while reducing features and cost.

Weapon Modules: Beater (top left), Reach Vert (top right), Small Vert (bottom left), Horizontal (bottom right)

Beater module showing the bent g5 ti fronts, welded AR500 attachments, 30mm hollow 62100 steel hardened shaft, wire emd 4340 hardened weapon, aluminum uprights with keying geometry, and carbon fiber top and bottom plates for load transfer.

Vertical spinner hub comprised of a single piece of aluminum machined on 4-axis live tooling with custom jaws. Weapon blade sits on a spline pattern to transfer torque and is retained via aluminum plate. Spacers can be added or removed to accomodate different weapon sizes. Integrated pulley is compatible with 15mm width timing belts for maximum power transfer but smooth to allow slipping on impact. Oversize tapered roller bearings accommodate radial, axial, and bending loads far better than standard needle roller bearings to ensure reliability. 62100 hollow shaft resists bending by 300% as compared to a 3/4" solid shaft. Belleville disk washers maintain adjustable preload against uprights to ensure proper bearing function.

Reach vert module showing the sensored outrunner for faster spinup, reduced thermal loading, and the ability to self right. Can support stops faceplate of motor from shearing and extends impact tolerance range. Integrated gearbox reduces the rpm of the motor to increase engagement while increasing torque for spinup and self righting. Vertical and horizontal reinforcements increase bending stiffness and allow the structure to be reduced in mass. UHMW front armor with a double-beveled profile absorbs impacts and prevents shock transfer to internal components. Compliant mounting structures reduce shock loads to cf components reducing the risk of failure.

Solid 1/4 in aluminum baseplate to prevent punctures from opposing vertical spinners. 3/4" in disk to mitigate bending and dulling in direct weapon to weapon interactions. 1:1.7 gear reduction for maximum velocity while allowing self righting. Counterbored motor support to reduce loading on can.

Undercutter module using a waterjet clamp mount to hold and adjust inrunner motor. Spiral bevel gear for decreased friction and noise at high speed. Live shaft enables lower total stack height for form factor. Bumper system limits total deflection to protect chassis from self impacts.

Undercutter Hub with live shaft. Hardened shaft has a lip to interface with tapered roller bearings and retain weapon. Spline transfers load with minimal cross section. A countersunk plate retains weapon while minimizing stack height. Top pulley uses hex interface to transfer torque and a m20 countersunk bolt to tension and retain stack.

To augment the effectiveness of the design, different front attachments can be added to alter the characteristics of the robot. A wedge made from welded AR600 ballistic steel deflects impacts from opposing horizontal spinners into the path of the drum spinner and protects vital components. Articulated forks of varying design get under opponents to control and more effectively deliver the weapon.  

Wedge (left) Forks (Right)

The frame of the robot was designed with multiple key features in mind. The structural frame of the robot comprises of interlocking 2024 aluminum rails, cut using a waterjet. This style of construction was selected as 2024 represents the optimal balance of strength and ductility required in combat robotics. Components cut from large sheets have excellent material properties while requiring minimal post-processing. A large bay sits in the front of the robot to accept all weapon modules. The center rail has slots for each weapon module to key into and transfer force to the frame. 

Aluminum subframe with big vert structure and UHMW armor

Welded sheet metal gussets sit in every corner, reinforcing the frame and providing mounting points for hardware and weapon modules. Ar500 was chosen as the material for the gussets due to its combination of high availability, weldability, and strength. In addition, welded AR front brackets provide structural support and allow the mounting of attachments. 

Aluminum Subframe with welded brackets and attachments.

Carbon fiber top and bottom plates span the frame, maintaining alignment, providing strength, and protecting internal components from impacts. Carbon fiber was initially selected for its extreme specific strength and stiffness, but is now being replaced by srpp sheets for reduced weight and additional impact resistance following damage sustained from a fight.