Friction Brake Project – HYPED (Hyperloop Edinburgh)

HYPED - Friction Brakes Project

Overview

HYPED is delighted to be a recipient of this year's RS Grassroots’ Student Project Fund! This fund will play a key role in completing one of HYPED’s projects – the Friction Brakes.

HYPED (Hyperloop Edinburgh) is a student-led society which designs and builds prototypes and participates in the annual EHW (European Hyperloop Week) competition to accelerate the development of the Hyperloop concept. This year’s pod is called Poddington and, for the first time, the aim is for the pod to be capable of a fully levitating pod run. In the process, HYPED strives to provide an innovation-centred ecosystem for university students to develop the necessary skills for their professional careers and generate value towards Hyperloop development. Through engaging with the public about HYPED’s initiatives, the society aims to inspire future generations about STEM and expand the Hyperloop and high-speed transportation community.

The Friction Brakes project is undertaken by the Dynamics sub-team, within the Technical Team in HYPED and the aim is to design the secondary and emergency fail-safe braking mechanism of the pod. The brakes are operated by applying frictional forces to the Hyperloop test track via the normal force exerted by compression springs for a failsafe design and a pneumatic actuator retracts the brakes but can also provide additional braking force using the pneumatic system also designed by Dynamics. This failsafe functionality is essential for meeting safety standards and ensuring a reliable transportation experience.

The CAD (Computer-Aided Design) renders show the Friction Brakes modules and HYPED’s subsystems mounted on the chassis and track profiles:

Objectives

The Friction Brakes Project is the secondary and emergency fail-safe braking mechanism of HYPED’s pod and operates by applying frictional forces to the Hyperloop test track via the normal force exerted by compression springs. This functionality is essential for meeting safety standards and ensuring a reliable transportation experience. Safety is of primary concern, therefore the braking force has been calculated for a worst-case scenario of decelerating a 250kg pod from 5m/s inside a 5m braking distance, with a friction coefficient of 0.3. As sustainability is core to the concept of Hyperloop, cost and efficiency must be considered so the performance and weight have also been optimised. Consequently, although the design requirement is a maximum braking distance of 5m, the brakes have the potential to stop the pod in 1m by utilising a double-acting pneumatic actuator, which retracts the brake pads to allow for a pod run, but also has the additional functionality of providing additional braking force.

In a more general sense, HYPED is hoping to research, develop and produce the future of Hyperloop technology. This will undoubtedly revolutionise the transport industry and provide efficient and high-speed transport to the masses. This means that one can be less limited by the place that they live in providing more equal career opportunities to all. This is a very ambitious goal but HYPED believes that Hyperloop technology is very much the future of transport.

HYPED announced a significant development in technology related to the Hyperloop concept, a proposed network of near-vacuum steel tubes to transport humans and cargo in magnetically levitating pods. Such innovations bring the distant Hyperloop dream, as well as the often-quoted 50-minute Edinburgh to London journey time a step closer. The team, comprising of STEM students from the University of Edinburgh, work hard each year to design and manufacture cutting-edge technology and this year announced three novel and innovative designs, each of which has been the centrepiece of a master’s thesis. Furthermore, the new designs for linear induction motors, lightweight chassis, electromagnetic levitation, and power redundant brakes are all bringing HYPED a step closer towards developing a full-scale Hyperloop system.

HYPED’s 2023/24 pod further improves on its predecessors and paves a path for future technical development for the HYPED Technical Team. HYPED hopes to find a feasible, cost-effective and efficient solution to bring the Hyperloop concept to reality. The Friction Brakes project also works under this philosophy, by providing a simple, fail-safe design which has been optimised for performance and efficiency.

Sustainability is at the forefront of this technology and Hyperloop transportation has the potential to significantly reduce carbon emissions and contribute to a more sustainable future by using electromagnetic propulsion systems. It offers an energy-efficient, all-electric alternative with the potential to be easily powered by renewable energy sources. Hyperloop systems will be highly efficient due to the limited friction they generate, which is prevalent in all current forms of transport, as the systems are designed to levitate using electromagnetics, whilst travelling in very low-pressure (near-vacuum) tubes. This means that less energy is wasted, and therefore less electricity will be used. As electricity is such a valuable resource, lowering the amount needed to get from A to B is essential, especially in today's climate-conscious times. This means that less fossil fuels will be used to cope with the increasing energy demand.

The friction brakes are essential for this concept as the electromagnetic braking is not power redundant (hence it is not a failsafe). Furthermore, the friction brakes have been designed with efficiency and cost-effectiveness in mind. Naturally, SolidWorks FEA has been used extensively to optimise strength-to-weight ratios so the pod can be made as light as possible and to reduce the raw material required to manufacture the friction brakes.

Methodology

The timeline for Dynamics is largely based on the academic year, as HYPED is an extra-curricular society and university exams and holidays need to be taken into account. In general, the vast majority of the design work is carried out in Semester 1 (September-December), whilst the finalisation of designs, ordering parts, manufacture, testing and integration with other teams occurs in Semester 2 (January-June).

The Dynamics team conducts every stage of the design process, which involves:

• Determining the design requirements and specifications.
• Creating an initial conceptual design.
• Developing high-level design by conducting research, calculations, and overall design using SolidWorks CAD software.
• Refining the designs by choosing appropriate components and sources, using Finite Element Analysis to ensure that the designs have the required Factor of Safety, and iterating the designs until the requirements are met. Shown below is the C-Bracket Stress Results in the worst-case scenario as an example of an FEA Analysis conducted (note the high deformation scale to understand how the geometry reacts to the applied loads):

• Continuous collaboration with other teams during biweekly meetings and online over Slack, to ensure fully successful integration of designs, which includes mechanical fit and obtaining the required level of sense and control for a safe pod run.
• Creating engineering drawings and sending them off to be manufactured, as well as ordering off-the-shelf components once the designs are finalised.
• Assembling and testing the subsystems before integration testing and assembly with other teams' systems.
• Throughout the process, writing extensive design and safety documentation to demonstrate that the designs are well-engineered, safe for use, and feasible for a full-scale Hyperloop.

The design of the Friction Brakes is a very iterative process. Dynamics needs to adapt to both:

• Internal changes – considering ease of manufacturing, a sufficient factor of safety, and any changes in design requirements all influence components and geometry.
• External changes – other teams’ parameters and dimensions often change throughout the year and Dynamics needs to update the designs accordingly.

Finally, after HYPED’s full pod run testing in Edinburgh, HYPED will take the pod to EHW 2024 in Zurich, Switzerland, where Dynamics will demonstrate the Friction Brakes project in front of other Hyperloop teams and companies from all over the world.

Friction Brakes Design

The Friction Brakes consist of several key components, as shown in the figure attached, and are described below:

• Brake Pads: High friction material to provide the necessary friction for deceleration. These are forced directly into the track surface by the normal force exerted by the springs/actuator.
• C-Bracket: Structural component that supports the shafts, springs and brake pads and ensures stability during braking forces. It is free to slide vertically along the mounting shafts via linear bearings during brake pad retraction and whilst transitioning over track misalignments. This means that after the upper brake pads hit the track, this will drive the module upwards, and the lower brake pads will create a reaction force on the underside of the track, effectively doubling the braking force achieved. It is made of bent-sheet steel, as it is more sustainable and wastes less material compared to milling a block of metal.
• Spring Shafts: Connect the brake pads to the actuator, for controlled application of braking forces.
• Springs: The springs have been chosen so that the pod can still be brought to a stop in the event of a pneumatic failure. To ensure sufficient braking force as the pads wear, the springs are compressed more than necessary.
• Double-acting Compact Actuator: Back-driven in its to release the brake pads from the track by compressing the springs. Also, compressed air will be supplied to extend the actuator (the piston’s default position is extended) to provide additional normal force to increase the braking force.
• Mounting Shafts: Connects the module to the chassis using linear bearings to allow the c-bracket to move vertically as the brakes engage/disengage, and to allow operation for both levitating and non-levitating runs.
• Safety: The actuator’s normal position is in the extended state so that the brake pads will clamp to the track in the event of an electrical or pneumatic failure to ensure a fail-safe system. The double-acting nature allows pressurised air to increase the normal force to the brake pads in the default position.

Product

An integral part of the Friction Brakes is the c-bracket’s ability to freely slide vertically during braking so that the module can move relative to the chassis as it moves vertically when travelling over track misalignments (during non-levitating runs), transitioning between non-levitation and levitation (a several mm vertical displacement) and during the occurrence of oscillations due to the Hybrid Electromagnetic Suspension system.

Most importantly, this freedom of vertical movement also allows the friction brakes to operate in the same way when during the demonstration of both non-levitating and levitating pod runs. The only way this can be achieved is by using linear bearings, which require a high load capacity – this is due to the reaction force to counteract the braking force which will want to produce a moment on the pod. Furthermore, to ensure the pod is safe, a safety factor of two is required on the calculated load capacity, as per EHW’s rules and regulations. After extensive research, the team have found that the Bosch Rexroth Bearing Unit R102722544, supplied by RS Online, is the best choice and these can be seen in the photos of the braking modules in the previous section.

Next Steps

For the Friction Brakes project, the engineering drawings were recently completed so manufacturing of custom parts has begun alongside the ordering of off-the-shelf components. Once, all the components arrive, the friction pad material will be tested against the custom track to determine the friction coefficient (in turn determining the maximum braking force) and then the braking modules will be assembled. The modules will then undergo further testing in conjunction with the pneumatics systems, followed by integration with other sub-team subsystems, including mounting the modules onto the chassis. Later in the semester, the braking modules will eventually be tested in a full pod run!

As for HYPED as a society, the rest of the semester will be very busy! As well as preparing for the upcoming AGM where the society will elect next year’s committee, all of HYPED’s members are busy preparing for manufacturing and testing, which always proves to be extremely beneficial in gaining new knowledge, skills and practical experience.

RS Grassroots is enhancing the student experience through workshops which all of HYPED’s members have thoroughly enjoyed and found very insightful and RS’s support in making the Friction Brakes design a reality is greatly appreciated – thank you RS!

Get in Touch

If you would like to hear more about our student-led society you can find out more at HYPED – Hyperloop Edinburgh (hyp-ed.com), on Instagram @hypededinburgh or email us at team@hyp-ed.com.