Pneumatic System

Abstract

This study investigates the creation of a custom pneumatic tank for a VEX Robotics “Over and Under” competition robot, with a focus on using Acrylonitrile Butadiene Styrene (ABS) for its durability in high-pressure situations. Recognizing the limitations of standard tanks in space-restricted settings, the research details the design and fabrication processes that leverage advanced modeling to ensure the tank's fit within the robot's compact build. Testing across various pressures confirms that the tailored ABS tank not only meets spatial requirements but also outperforms traditional tanks in durability and efficiency. The findings emphasize the importance of targeted material choice and custom design in producing pneumatic components for robots where space is at a premium, without sacrificing performance.

Problem

The major problem included the limited movement of the catapult when the air tank was placed hori-zontally. The drivetrain model shown in figure 2 gives an accurate visualization of restricted area to place a pneumatic tank.

Pressure Ratings for ABS Pipes

The pressure rating for different ABS pipe models are shown in table 1. Temperature increase of robots is common due to collisions and overheating robots. For 1½ inch pipe we are using, pressure rating for ABS 2112 is required for 200 psi rating. Since water pressure is stronger than air pressure, the theoretical yield should be higher than 200.

Materials

In addressing the challenge of constructing a compact pneumatic tank for our robot, our team employed specific materials and methods tailored to meet the stringent size requirements. The primary material used was Acrylonitrile Butadiene Styrene (ABS), chosen for its durability and compatibility with our design objectives. The main component of the tank was a segment of ABS pipe with a 1.5-inch radius, selected as the smallest viable op-tion that could feasibly be integrated into the robot's structure without exceeding the 18-inch dimensional limit.

Methods

To construct the tank, we first cut the ABS pipe to the required length of 8 inches, ensuring that it would fit within the robot's spatial constraints. Each end of the pipe was then sealed with a specially designed cap to create an airtight enclosure. The caps were carefully chosen to match the diameter of the pipe and were secured in place using an appropriate ABS adhesive to ensure a robust and leak-proof seal. For the air inlet, we installed a Schrader-compatible valve, a standard recognized for its reliability and ease of use. This valve was integrated into one of the end caps, allowing for straightforward pressurization and de-pressurization of the tank. To ensure airtightness around the valve, we applied thread sealing tape meticulously around its threads before screwing it into a pre-drilled hole in the cap. The use of thread sealing tape was crucial in preventing air leaks, thereby maintaining the efficiency and safety of the pneumatic system.

Obstacles and Finished Product

This process required precision as a slight angle will cause leakage in gas. Furthermore, threading becomes harder as screws are meant to thread-in vertically. Our team used TTB75 1½ Industrial Thread Sealing Tape. This prevents leakage as well as providing more stability during the construction of the robot. We used ABS cement to glue the cap to the body of the tube. Reading a journal on cement-based pizeoelectric sensors helped in finalizing out decision. Static currents are frequently encountered in robotics, especially when there are over 20 active ports for sen-sors, motors, and pistons. The use of polycarbonate in robot construction further elevates the likelihood of static buildup, particularly when foam tiles are present in the competition arena. Consequently, incorporating materials like cement and ABS is essential to reduce the robot's conductivity.

Testing Process

Instead of employing the typical "Drilling and Tapping" method, which involves using oil and various drill sizes to create a smooth hole and then tapping it with a lathe in the UW Machine Shop, we opted for manual threading. "Drilling and tapping" are two fundamental processes often used in machining and manufacturing to create threaded holes in a material. Here's a breakdown of each: The manual method demanded excessive force because of the friction from the non-threaded holes. A sim-pler analogy would be the difficulty of threading a flat surface screw, as opposed to a sharp wood screw, into a flat plastic piece. Figures 3 (a) and (b) show the bottom and top caps, respectively, of the completed pneu-matic model. Using an automatic air pump and pressure gauge, the tank was able to withstand 100+ psi.

Conclusion

As shown, using different brand for model M3 pipe cap may lead to different results. The summary indicates that Ruthex inserts are consistently stable across all tested loads, eBay inserts can han-dle up to 80 kg before becoming unstable, and Aliexpress inserts show significant performance issues at 40 kg and above. Therefore, it is important to check which brand of pipe inserts are being used.

In conclusion, the study successfully demonstrates that through innovative design and material selec-tion from construction ABS pipes to cement, a custom ABS pneumatic tank can be integrated into a robot constrained by size without any degrade in performance. The tank’s ability to withstand significant opera-tional pressures and reliable durability compared to original model overall shows the enhanced system for the Waterloo VEXU robotics team. The research also illustrates the importance of choosing appropriate components, as brand variability can have a profound impact on the reliability of the tank, which is a crucial aspect in competitive robotics.

Abstract

Problem

Pressure Ratings for ABS Pipes

Materials

Methods

Obstacles and Finished Product

Testing Process

Conclusion

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