Engineering innovation that leaves modified cars for dead

Posted on February 24th, 2007 in Opinion by Julian Edgar

Click for larger image

I know that this is a car publication – and primarily a modified car publication – but forgive me if I digress.

As we’ve been covering in our series Building a Human Powered Vehicle, I have been making a recumbent trike. That is, a three wheeled, pedal-powered vehicle where the rider lies back at an angle and the pedals are relatively high up in front. My design uses full suspension (front double wishbones, front sway bar, rear trailing arm), is made from aluminium and uses a rear damper. It was inspired by the non-suspension Greenspeed series of trikes, of which I own one – the Greenspeed GTR.

Before building the trike, I knew very little about them – and very little about bicycle design as well. So, you might be thinking – what is there to know about bike design? Well, lots and lots. Things like gearing (crank length, front and rear cog sizes, gear ratios), steering (trail, castor), and of course frame design. With tadpole trikes, you can also add scrub radius, toe and Ackermann, and with a suspended trike, static and dynamic camber, anti-dive and so on.

Home builders of bikes and trikes have an extensive web presence, and while there are some simply horrible designs prominent, there are also some excellent engineering pages devoted to design. In fact, when I compare this scene with modified cars, in terms of uniqueness, engineering innovation and results, recumbent bikes and trikes show far more progressiveness than home builders and modifiers of cars. (The only home-built transport application which I think is even better can be found in experimental class aircraft.) Small, specialist engineering companies are also prominent in recumbent trike building.

Enough of the generalities – let’s look at a specific case.