MECH5125 Electric and Hybrid Drivetrain Engineering Academic Year 2023-24

Title: Single gear transmission for Formula E vehicle

Coursework Assignment: Detailed design of the shaft and spur gear pair

Weight: 40% of module mark.

Work type: Individual Assignment.

Deadline: 21 March 2023 at 12 noon.

Submission method: Individual report - Paperless via Minerva (Turnitin)

(report must include 2 detailed engineering drawings:

first of a shaft and second of a gear).

Feedback: Written via Minerva and in class feedback session.

( for illustration only, you need to choose your own configuration )

Many modern electric vehicles have a single stage transmission fitted including Formula E cars. This is possible due to high torque at low revs and wide range of rotational speed delivered by electric motors. In this assignment, you will look in details at design process of simplified version of such transmission components.

The aim of the assignment

The aim of this work is to reinforce your understanding of the theory and design principles that underpin the detail design of a power transmission shaft and gears. This is achieved by getting you to design such a shaft and spur gear pair that meets your individual specification. You will first produce a concept design on the assumption of static loading and then go on to develop a detail design that takes into consideration the ability of the shaft to sustain cyclical loading which impacts on the fatigue life of the component.

You will each have ownership of a unique transmission specification, defined by a set of parameters. This data will be augmented by generic data that is common to all. These parameters will be fixed and you will not be able to alter their values.

Design Specification Parameters

You will receive individual design specification parameters from the table below. Full list of parameters is available in Assessment section on Minerva website of the MECH5125 module.

Generic information

There are several generic pieces of information, that are required to enable you to complete the assignment and these are defined in the table below. This generic data applies to all the individual power transmission shaft configurations.

If you find the General Data too restricting for your design you can change them, however please justify the change made.

Please include in your report any other assumptions or constrains you have made during the design process.

Assignment Report Part 1: Concept design of the gearbox shaft and spur gear pair

Using the data contained in the power transmission shaft specification, you will determine:

•   Overall gear ratio of the driveline,

•   Gear ratio of the transmission,

•    Diameters of the spur gear pair,

•    Minimum face width of the gears,

•   The location of the critical shaft cross section,

•   The minimum allowable diameter for the shaft,

•   The equivalent dynamic bearing load at each bearing,

•   Type of the geometry (keyway/spline) located at the critical cross section of the shaft.

The shaft is the output shaft within a single stage reduction unit and supports a straddle mounted spur gear, G1, between two bearings, B1 and B2, whose locations are as indicated in the section Design Specification Parameters. The torque leaves the shaft through a standard keyway or spline (that will connect the shaft to a co-axial coupling) at the right-hand end of the shaft. A lip seal is to be placed between the right-hand bearing B2 and the keyway to prevent ingress of any contaminants to the unit. The bearings are located on the shaft using either conventional bearing nuts and lock washers or external circlips. The spur gear is to be radially located on the shaft using a standard key or spline whose length does not exceed the axial dimension of the gear. The gear must also be axially located. Assume steady state operation.

Assignment Report Part 2: Detailed design of the shaft and spur gear pair

Detailed Design

Using the outcome of part 1 (that made use of a static load case), you will develop a detailed design for your power transmission shaft and demonstrate, how it will meet  the design specification under dynamic loads.

Include the table or list with all assumptions made during the design process. Include one or two sentences justifying each assumption.

The designed spur gear should be optimised for lightweight design. Design and optimisation process could be done for example using Generative Design method in Autocad Fusion 360 software available in the department or other suitable methods.