Early design decisions

11 Mar

Design is a process of understanding the requirements, developing and assessing the options and making design decisions.

Some of the design decisions we have made so far include:

  • The vehicle will almost certainly have four wheels, to be able to traverse potholes.
  • The horizontal spacing between the wheels will be 1350mm, so we can ride in the existing road ruts created by ox carts.
  • The total vehicle weight should be as close as possible to 100kg, so the overall loaded weight will be approximately 400kg. This will minimise the energy requirements, which will therefore minimise the size and cost of the motors, batteries and energy storage infrastructure.
  • We will not initially incorporate human power, and will instead rely on electric motors powered by onboard batteries. Human power is insignificant compared to the power required to drive the vehicle at the required speeds, and ┬áthe extra drivetrain would add weight and complexity. (This is despite a pro-cycling bias in the team, and despite some redundancy and range extension benefits from hybrid electric-human power. We may revisit this in the future.)
  • We will mount the wheels on a frame that sits beneath a structural chassis. The frame will locate the wheels, handle the horizontal forces between the wheels, and support a structural tub. The tub, which will contain the seats, will be fastened to the frame with suitable mechanical isolation. The tub will handle its own bending and torsional stiffness requirements.
  • We will use trailing arm suspension on the rear, with a motor mounted near the pivot point of each rear wheel.

The team is meeting again this Wednesday evening to work towards a decision about wheels and tyres, and to progress the thinking about suspension and chassis design.

Here is one of the early design concepts:

Designconcept

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