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Bike Review - Posted 4th October 2010
Home -> Bikes -> Road Tests and Profiles -> 'Ha ha. Look at the poor fool on the Tiger Cub!'

123cc BSA Bantam D1

Have you ever wondered what a classic bike might look like if it was recreated in today's virtual world? Team Bantam at the University of Limerick wanted to find out...

Last year, the University of Limerick in Ireland set their engineering students an interesting challenge. Using Pro-Engineer, a CAD software package, the teams of five were given the opportunity to virtually ‘build’ the motorcycle of their choice. Team Bantam – as you might have gathered from the name – chose a D1 Beesa.

The original D1 BSA Bantam was built in 1948. Its three-speed, unit construction engine was a mirror-image of the DKW RT125 motor, 'Now get your trousers back on unless you want another clout with this tennis racquet...'adapted to suit BSA’s non-metric machine tools and the British inclination towards big flywheels from the designs handed over as war reparations.

The 52mm bore by 58mm stroke motor gave a capacity of 123cc – later and bigger Bantams used the same stroke even as capacity rose to 175cc. The D1 was initially equipped with simple, undamped telescopic front forks and a rigid rear end, although plunger suspension was an option from 1950. The D1 was built until 1955 but the much-loved Bantam lived on for another full 15 years until 1970, giving it a production lifespan of over two decades.

As Roy Bacon once explained; ‘The Bantam was everyone’s learner model in the 1950s and few riders from that era did not own or at least try one. Later it grew up and lost its cheeky air, but it never fell from favour.’

So why did the modern designers choose a Bantam? ‘We had an actual D1 bike which was partially restored’, explains team member Diarmaid Sheehan. ‘One of the group members suggested this bike because of its history and popularity. This, along with its basic but elegant looks, directed us towards the BSA Bantam D1.

Even better than the real thing? 2008 BSA Bantam D1

‘The partially restored bike also had a service manual which had most of the information we needed such as ride heights and stroke and bore. We also had a scrapped gearbox which helped with the intricate internal dimensions of the gearbox. All other dimensions were taken from the bike itself.’  

Some details - the engine cover castings - are great, others - the brake pedal - a little clunky. 2008 BSA Bantam D1 engine.

Even with this information, it’s not exactly straightforward to model a motorcycle from scratch, as Diarmaid explains. ‘There were several difficult parts of the design to get right, like the spokes, the tank, the exhaust, the gearbox, engine, chain assembly, plus the rendering (colour, light, shade etc). In the end the rendering of the bike was very realistic. It added to the appearance and overall aesthetics of the bike. We also felt that the bike was very accurately modelled.’


Click this play button twice to start the video...

Not bad, considering that none of Team Bantam actually ride bikes! ‘We all have a general interest in mechanics and there are a few petrolheads in the team.’  

Ready for a bimble in the sun... 2008 BSA Bantam D1

They certainly needed to be enthusiastic. The project took five weeks to complete, and Team Bantam worked for somewhere between 400 and 500 man hours on their version of the D1.

So even 60 years after it was originally built, the BSA Bantam can still inspire considerable dedication…

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More about BSA Bantams: www.mistgreen.com

2007 BSA Bantam D1 2007 BSA Bantam D1
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