Proportional Length Cranks illustrated (on one bike)

I’ve got a bike in my garage that illustrates the proportional length crank philosophy that is one of the cornerstones of the design philosophy of Zinn Cycles.  It’s not a Zinn bike – but even so – it’s still pretty cool…

It’s fairly new and very specialised in that it’s a tandem that my wife and I ride with our special needs son Ted…

The bike is a Hase Pino tandem where the pilot is at the rear and the stoker is on the front in a recumbent position.  And Ted isn’t tall enough yet to reach the pedals on the adjustable boom at the front – so he uses “Kiddie cranks” that are temporary.

As you can see from the photo the kiddie cranks interrupt the regular chain line and are clamped in place.  So there are 2 sets of cranks of the front – eventually he’ll use the longer cranks on the front (which are on a sliding boom) but for now he uses the much shorter kiddie cranks.  Proportional length cranks on display!  Short cranks while you’re short – and longer cranks when you are taller.  Makes perfect sense.  Only problem being – that for the vast majority of bikes – it’s only proportional up to adulthood – when the range of crank lengths becomes very small – yet the difference in size of adults is vast…

Here’s Ted and I and the whole bike (so you can make sense of the above photo)…

So what else have I been up to?

Well – Ted and I rode the tandem in a 6 hr relay – so I’ve been doing a bit of riding on the tandem – but still on my Zinn at every opportunity.  It’s interesting going between the tandem and the Zinn – going from 175mm cranks to 210mm cranks.  You immediately notice the difference when gettting on the Zinn – but within a few hundred meters it the noticeablity goes away and it you are back into the world of comfort and increased ability.  When riding the tandem – the noticeabilty doesn’t go away – and as it’s a big heavy bike (and because Ted isn’t able to contribute much) I’m constantly wishing it had longer cranks – especially when we get to a hill..

I did get a lesson in “being prepared” the other morning.  I set off on a ride to work – with 2 mates.  Early start – riding in the dark – and as it was so early – I decided to skip breakfast.  Mistake!  The guys I was with were faster than me – so that put me under a bit of pressure (which is normally fine – and benificial).  But when we got to a good sized hill about 10km into the ride – I started feeling dizzy and struggled big time.  Halfway up I decided that I’d had enough and said my farewells to my companions and rode home again.  Combination of late night and no food I think was the problem.    Completely underprepared!

Heading off on an early morning commute

Other than that – I’m still riding – not as often as I’d like in the last couple of weeks – but still riding.

Cheers

Adrian