Insight and data driven design, rapid simulation, cutting-edge production techniques, and countless hours of hard work – all within the space of a few months. No, it’s not the latest iteration of front wing for the MCL33, but rather the bespoke rickshaw for the BBC Children in Need 2018 Rickshaw Challenge.
As a Senior Systems Engineer at McLaren Applied; combining the finest hardware, software and mechanical design is nothing new to me, but doing it to build a rickshaw certainly was.
A superb design from the McLaren design team meant the build phase went very smoothly. Yet as is the case with any build, we encountered a couple of bumps in the road which we made sure we were prepared for when readying the rickshaw for its gruelling journey of over 400 miles from Calais to Salford on 9 November, 2018.
A reconfigurable seat and crank assembly necessitated the development of an innovative drivetrain concept. It saw us elect to make the rickshaw belt-driven, with drive transferred from a belt to a regular chain drive and cassette on the rear axle.
To achieve this, we determined the geometries needed for the rider positions based on three ‘hot swappable’ seat and pedal assemblies. We tuned them to be compatible with standard belt lengths, which could therefore be used interchangeably to meet the needs of multiple riders.
A slotted section in the frame was required to allow for tension adjustment and straightforward changeover of belts. However, we found that the initial slot was too small.
In response, we increased the length of the slot to ensure compatibility with differing belt sizes, improving performance, reliability and ease of changeover.
During initial discussions with the BBC Children in Need team, it became apparent that having auxiliary brakes on the rear of the rickshaw - which could be used by the support riders - would be a huge safety improvement compared to past rickshaws.
Previously, if one of the riders lost control while going downhill, the only option available to the support riders to slow the Rickshaw down was to hold on to the bodywork and pull the Rickshaw to a stop while they used the brakes on their own bikes – a hair-raising experience!
The design team came up with a concept to include an ergonomic handrail running around the top of the rickshaw for brakes to be incorporated.
As all the brakes on the new rickshaw are hydraulic, we initially attempted to integrate three separate master cylinders (one on the handlebar used by the rider and one on each side of the handrail at the rear to be used by the support riders) to a common pair of calipers on the rear wheels. This option required a complex spool valve arrangement and did not give a separate means of slowing the rickshaw down in the unlikely event of a hydraulic failure.
The final solution was to fit a third cable actuated caliper, operating on a disc brake mounted directly to the differential on the rear axle, and use a cable splitter that would allow each brake lever to independently actuate the caliper of the central disc.
We also designed bespoke levers for both brakes on the handlebars. These were longer than the standard levers should a support rider want to use the brakes while riding at the front of the rickshaw.
It’s all been worthwhile
This has been the most rewarding project I’ve worked on at McLaren Applied. To see the faces of those who will be riding the rickshaw light up when they jump on the saddle, makes the thousands of hours of hard work put in by everyone worth it.
We’ve succeeded in designing and building a rickshaw from the ground up, which boasts a host of elegant solutions to overcome an array of complex challenges and puts the rider’s needs first. It represents a huge leap forward in terms of accessibility and safety, and will significantly contribute to the continued success of the BBC Children in Need Rickshaw Challenge which has raised over £21 million in the last six years.
Keep up to date with Team Rickshaw’s progress each day on BBC’s The One Show. The full route – including a real-time update of the rickshaw’s progress – is available here.
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