Formula Student Fundamentals - Part 2

Formula Student Team

Part 2 of this series of short articles aimed primarily at supporting new Formula Student teams and competitors, written by Head Design Judge and competition veteran Neill Anderson.

If you missed part one, make sure you start there and catch up with the details!

Part 2

Breaking Down how to Design the Answers

It’s probably too much work for one person to design the whole vehicle. So, accepting that there will be more than one “designer” means accepting that communication between those involved is required. For a small team that can happen quite naturally if everyone is on board and conscientious: indeed, it is one advantage that the small team has. If you have more than say 8 team members then you will need to start to formalise management of those people. Project management is a skill in its own right, you might be able to get some Business Studies types involved. A love of cars/engineering/motorsport is not restricted solely to engineering students!

Given your restricted resources it is vital that time is not wasted in duplication of duties. The opposite applies equally as well: don’t have two people trying to place different things in the same physical space. This happens a lot when trying to package the driver’s legs, the steering system, the suspension system and the pedals into the front chassis area!

Takeaway 8: territorialism must be avoided: it’s a group effort!

Whilst it is tempting to (classically) split the vehicle into functional project areas I would advise against following such an approach too precisely. For example, the steering system as a whole is influenced by:

  • Rules (cockpit templates, mandated structural members etc.)
  • Tyre parameters
  • Front suspension geometry
  • Overall mass and mass distribution
  • Any aero forces
  • Rear differential characteristics
  • Internal space and ergonomics
  • Chassis structure
  • Brake system parameters (pedal space inevitably fights for steering space)
  • Potential influence of frontal impact structure forces
  • Available money (a factor in all design decisions)
  • Mass (a factor in all design decisions)

As you can see it is hard to decide into which of the major sub-systems the steering system naturally fits. It doesn’t need to be a collaborative design but requires a respect for all the other influences. A conscientious team member can, and will, ensure that what they are doing doesn’t negatively impact on anyone else. This will work well enough in a small team and will often be quicker and more efficient than formal structures in a much larger team.

Project/Time Management

There are lots of fancy ways to brand the basic planning of time and money but in its simplest form it means thinking ahead and trying to knit together the sequence of what happens and when. It’s usually intrinsically linked to available money and people resources.

As with the vehicle design, the planning ahead requires you to know where you currently are, where you want to get to and by when. It also requires you to know what is involved in completing each stage/milestone of the project.

By definition, as a first-year team, you won’t really know what is involved in detail and hence any timing schedule will be a first best guesstimate only. However, all good plans are active and dynamic things and should be continually updated as you gain information and experience. You don’t need a sophisticated computer package to do this: a simple calendar and diary will suffice.

Takeaway 9: the clever, sustainable way to reduce the overall timescale is to move away from thinking sequentially (i.e. we finish Part A then we start Part B etc.) and start to think simultaneously (i.e. we can do Parts A and B side by side as they have similar operations/requirements).

The only way to do the above is to ensure that at least one individual is capable of what I call the “big picture view”. Sometimes they get called “project/programme managers” but basically, they need to be able to understand, in some but not all detail, how everything fits in with everything else. It’s not as hard as it seems but for it to work, they need to earn the respect of others so that any changes are updated to them. This can be as simple as the small team acting respectfully and conscientiously or as complex as steering groups, project chairs etc.

For example, if you are having to outsource the fabrication say of an upright because you don’t have a milling machine perhaps, then it makes sense to try and determine (and then design/draw) all other parts that require a milling machine and then to organise one firm to take on all of that work. This in turn may then require that the steering system is completed at the same time as the suspension uprights and the differential carrier etc. And from this a basic plan/timeline starts to emerge so that the correct parts overlap rather than conflict. I hope that makes sense!

Most of (first time) “design” is conceptual, packaging and stiffness, not detailed stress analysis FS cars are small, light and nimble things. There isn’t much room to fit everything in so your main first challenge will always be packaging. Luckily the Rules will (conceptually) drive a lot of this for you. There is a minimum wheelbase and there were previously minimum track widths. There are front and rear roll hoop requirements which also relate to the helmet clearance required above the driver. There is a driver template (“Percy”) and cockpit space templates.

Within the wheelbase you will be hoping to include all the major masses (you do want a low polar moment of inertia, don’t you?). You’ll probably opt for rear wheel drive so that implies an engine and gearbox assembly just ahead of the rear axle centreline. Some space for the driver will then most likely place the pedal box ahead of the front axle centreline and fighting for space with the inboard front suspension mounts.

The cockpit templates will limit how far inboard you can locate those inboard front suspension mounts and the chosen front track dimension, combined with chosen tyre/wheel dimensions and with due consideration of caliper and disc will dictate the outboard front suspension points.

In reality the length of your wishbones will therefore be fairly limited.

Of course, nothing states categorically that a classic double wishbone set up is the best or is required. There are very good arguments, especially for cross ply tyres, for an “old fashioned” style of axle, e.g. De Dion. It’s easier to do at the rear than the front and I personally am convinced that a fresh look at a genuine “live axle” arrangement at the rear could both save significant weight as well as cost.

Takeaway 10: at the front the biggest design challenge is fitting the driver within the structure whilst meeting the cockpit template rules and having a friction free, precise steering system.

It follows then that the front suspension/chassis structure/footwell ergonomics/pedal box should be your key priority. After physically cramming everything into 3D space you should consider stiffness next.

Remember that you will of necessity iterate back and forth between the smaller details and the bigger picture concept as you discover what helps structurally and what is required ergonomically. Start with the Rules mandated structures.

Strength versus stiffness

For almost all your components, small (e.g. uprights) or large (e.g. chassis) you will be designing for stiffness rather than for strength. In general, once you have adequate stiffness you will have an excess of strength. You are assisted here by the Rules in that if using compliant steel tube in the major structure then strength won’t be an issue and partly by the fact that once the structural elements (tubes and shear panels) are in efficient locations for stiffness then again adequate strength will likely be guaranteed.

Remember always to minimise mass and to consider the cost/ease of manufacture, including any tooling fixtures.

Takeaway 11: almost unanimously the wise placement of material creates the stiffness, not the material (properties) itself nor the amount of material.

How do I know what is stiff enough I hear you cry? You don’t! the best you can do is try and find some figures elsewhere for a similar style of vehicle. Chassis stiffness is readily available, figures for local corner stiffness such as toe and camber control are perhaps harder to unearth but consider the likely grip levels (maybe 1.5g maximum) and estimated unwanted wheel deflection (most likely less than 1mm at the rim maximum) to arrive at possible values.


Professional Engineering magazine

Professional Engineering app

  • Industry features and content
  • Engineering and Institution news
  • News and features exclusive to app users

Download our Professional Engineering app

Professional Engineering newsletter

A weekly round-up of the most popular and topical stories featured on our website, so you won't miss anything

Subscribe to Professional Engineering newsletter

Opt into your industry sector newsletter

Related articles