CASE STUDY - MICROCAB CHASSIS

Microcab Chassis - Lotus Lightweight StructuresDESCRIPTION
Microcab Industries are focused on the development of an efficient, inner City, Hydrogen fuel-celled Taxi. The drive is to move beyond the inefficiencies of the electrical grid and generate electricity in situ for the drive motors.  The concept also allows for greater range from a single charge.  More hydrogen charging points are now becoming vailable in the major conurbations around Europe.

CHALLENGE
The primary challenge for the design is lightweight as available torque and energy from current generation of fuel cells requires that vehicle mass is reduced as far as possible.  The all up target for the vehicle is 750 kg and the mass of the frame 85 kg, but with the functionality and flexibility to provide a platform for a taxi, including wheelchair capability and a small commercial vehicle e.g. for parcel deliveries. 

Further, as the technology, and hence the product, is evolving the Customer wanted a frame solution that offered low initial investment costs but with the option to scale production up to 10,000 units p.a. and to accommodate change in a cost-effective way.

Lotus Lightweight Structures MicrocabSOLUTION
Developing a design based on sheet parts allowed LLS to optimise the gauge of material throughout the chassis and achieve the lowest mass, and the use of structural bonding ensures that the final product has high durability.

As the Customer had no paint plant the anodised finish on the frame was specified as the final finish and we know that this provides many years durability, with products on the road for twenty years with no adverse corrosion effects.

Additionally, as there was no formalised assembly line in the early stages of the prototype, the accuracy of the frame assembly, as built, was a key element in the vehicle build process.

In order to provide high volume flexibility, with very limited investment, the process for the sheet components is specified as laser and fold.  This also underpins the ability to evolve the design quickly and cost effectively.
Component types with any significant investment such as castings and extrusions were specifically excluded from the design brief with the Customer.

All assembly, at lower volumes, is completed in a single assembly fixture. This type of design and process will operate effectively up to approximately a thousand units per annum, and beyond this the process for each of the sheet components is reviewed to establish the most effective options for upgrade tooling to reduce the piece price.  By this stage the business plan for the product is better understood and payback calculations can be constructed with confidence.

Assembly of the frame can be extended to ten thousand per annum using an additional main assembly fixture, some sub assemblies and further operators to reduce the cycle time to thirty minutes.

Lotus Lightweight Structures MicrocabPROOF OF SOLUTION
Microcab are now running and developing a small fleet of 8 vehicles from their location in Coventry.  The vehicles are involved in all the Hydrogen Fuel Cell research activities within Europe and are performing well. Fossil equivalent fuel economies over 120 MPG are being achieved.  The all up weight of the vehicle is 743 kg and the frame is on target at
85 kg.

Plans are in development for the next build phases, with LLS fully in support.

CUSTOMER REFERENCE

We are pleased to have been able to support Microcab Industries and their Managing Director, John Jostins, with this project. www.microcab.co.uk