Mark Sanders is an engineer and industrial designer
who's best known for his creative design of folding bikes.
His first bike originated as a postgraduate design project.
I'd gone back to college
to study industrial design engineering as a postgraduate
and I needed a project.
I also commuted from Windsor into London,
and so something that combined cycling
with other forms of transport seemed ideal.
To get started, he drew up a specification
of how he wanted his bike to perform
and then made a detailed review
of the state of the art in folding bikes.
There are lots of folding bikes but they all try and be as small as possible.
Seeking a new and simpler concept,
he was inspired by another folding transport device, the baby buggy.
The key thing about the Maclaren baby buggy is when it's folded up,
it's not actually as small as possible but it's long and thin
and it's like a walking stick with wheels on the end.
I thought, "Why not apply that concept to a folding bike?"
Instead of trying to fold it really small, make it long and thin
with the wheels together at one end.
Sketching played the crucial role
in Mark's exploration of how to turn his basic idea into a concept design.
Like the process before,
I immersed myself in the problem
and really tried to think of every possible way
of making a structure that could fold into a long, thin shape.
This is why I used the sketching,
as a sort of dialogue with myself
to try and have an idea and then sketch it,
then refine it between my head and the sketchbook.
I didn't really worry about which ideas were good and which ideas were bad,
I just got down as many ideas as possible at this stage
to really try and cover the whole of the area.
To decide which of his many concepts might work,
he needed to categorise them and narrow them down
using the criteria in his specification.
It boiled down to basically two shapes,
the triangular shape and an X-type configuration,
and so what I did here was to put the different drive arrangements
along the different frame arrangements
and check back that they all must fold into a long, thin shape.
There were also practical and engineering factors to consider.
For example, we can't have a chain which crosses a joint
or a belt which crosses the joint,
and so some ideas were automatically thrown out
due to these practical considerations.
The next step was to make some very simple models.
Sketches for something very three-dimensional like a bicycle
have their limitations
and the only way to really explore
how, for example, three tubes might be realigned into a long, thin stick
is to make models,
and so the little wire models were an ideal way
of exploring, very quickly, these three-dimensional shapes.
Mark decided that the triangular frame was the way to go.
I really wanted to have something which hadn't been done before
because one of the ideas was to patent the design
and try and put it into production myself,
and so I didn't want to infringe anybody else's patent.
It had technical advantages too.
A triangle is inherently stiff
and it's basically just three tubes and three joints
and so it really stood head and shoulders above the rest.
Getting from sketches and wire models to the real thing
involved some engineering science.
He started doing very rough calculations
on bending moments and weight distribution on the triangle
just to see that it was feasible.
As the project progressed
the calculations became more and more sophisticated,
looking at the actual materials proposed
and wall thicknesses and other details.
A key element of the original specification
was that folding and unfolding the bike was as easy as possible.
This required creative ideas for components like the front joint.
The front joint is the first thing that disconnects on the bike,
and so I tried to think of other things in the world
which disconnect and are obvious to use
so that people wouldn't have to have a long learning time on using the bike.
And then it struck me that a car seat belt joint
is just the sort of mechanism I would like for the joint on the bike.
And in fact, more than that, I thought maybe I could actually use
an existing car seat belt mechanism.
When I could find one the right size
and one that fitted in with the action of lifting up the front tube,
I used a car seat belt for the first prototype.
To make sure that the bike was actually going to be rideable,
the next stage was to make a full-size mock-up,
cobbled together out of bits of old bicycle.
The fully adjustable joints and fittings
helped Mark to come up with a final design,
the first triangular-frame folding bike.
Eventually he found someone prepared to set up a company
and manufacture a commercial version of the bike called the Strida.
Its great strength was the simplicity of its folding mechanism.
It was a considerable commercial success,
with some 25,000 sold worldwide.
As a folding bicycle design, it won on simplicity
but it didn't win on long-distance ability
and I think that was the main criticism of it.
They pointed out that it wasn't good for tall people,
that it wasn't as stiff as some of the mountain bikes they're used to riding
and that its handling wasn't as secure as a mountain bike.
The feedback we got from users from the Mark 1
was that people wanted a bike which they could use for longer distances,
more like a conventional bike.
They wanted something that was stiffer,
handled more like a conventional bike
and also had more knee room.
And so the changes between the Mark 1 and the Mark 2
are basically an increase in frame length,
which gives the knee clearance,
and at the same time the steering geometry was altered
to make the handling a bit more predictable, like a conventional bike.
The other feedback we got from users
was they wanted a much flatter package
which could fit into the overhead lockers on trains and buses,
particularly on trains.
And so we had some folding handlebars added,
which makes the whole thing very narrow in this plane.
After a spell away from the company that made his bikes,
Mark was invited back to help design the next generation of Stridas.
Moving from the Mark 2 to the Mark 3 was a fantastic opportunity
because the production was going to be moved from the UK to Taiwan
and they asked me to see if I could redesign it
and take out all the user feedback problems that they'd been having.
At the top of the list were making the bike handle like a regular bike
and also making it as stiff as a regular bike.
The move to Taiwan
has made lighter and stiffer all-metal construction economically viable.
A major thing, I think, was moving a lot of the parts
which were previously plastic
to aluminium and welded construction,
which is actually as cost-effective in Taiwan
as plastic construction is in the UK.
Mark still uses sketching to create and develop his basic ideas and concepts.
Sketching is still my main way of generating ideas.
I still fill loads of pieces of paper with sketching.
I can't refine an idea unless I've sketched it down
and thought it through and added.
He now makes much greater use of computer-aided design.
I use CAD in a big way now
and after the initial stage of sketching I find it's a way
of refining down to which prototypes to make.
Rather than having to make ten prototypes,
the CAD system helps me decide which ones are worth making
and then maybe just make one.
I also like to make physical models,
and that can either be hand-made models out of wood,
just to check how things feel and how you hold them, for example,
or also parts made out of solid aluminium, for example,
which need to take loads.
These parts are made directly from the CAD data
using a computer numerically controlled machine
to actually mill them out of solid aluminium,
and then they can be tested with real live loads.
That technology has been hugely helpful in this development process.
Even with CAD, there's still a need for physical test rigs.
The full-size test rigs are absolutely vital
because handling is such a subjective thing.
There's no way a computer could simulate
what a bicycle feels like to ride, no way.
It may be able to work out the stiffness
but it doesn't give you the feel of a bicycle.
So the only way is to make a test rig.
I particularly like fully adjustable test rigs
where things can be subtly changed to see the effect on the handling.
This is the adjustable test rig
that was used to optimise the frame geometry
to make the handling really good for the Mark 3.
Every aspect of the frame is completely adjustable,
from the steering axis to the length of the tubes
and also the height of the handlebars.
Using this, and lots and lots of hours of testing
using riders who hadn't ridden the Strida before,
we found the optimum steering geometry.
In fact it was quite different from what all the theory suggested.
The production version of the Mark 3
incorporates all the optimum features from the test rig.
As far as the ride goes, it feels much more like a non-folding bike.
It's still really fast to fold
and now a magnet has been added
to pull the wheels firmly together when the bike is being wheeled along.
But the Mark 3 is far from the end of the line for the Strida.
There are several improvements that are still in the pipeline for the Strida
and that includes gears, electric power versions,
even lighter versions, maybe even different materials.
My personal ultimate goal is not actually to make it more complicated,
but to keep it as simple as possible
and ideally make it as light as possible.
One of my driving philosophies is to make design affordable,
in other words design within reach,
and so one ideal thing for the Strida would be to keep the costs down
so that it is an affordable, useful product
that a lot of people can get benefit from.
I obviously totally believe in it
and believe in its advantages of being able to link other forms of transport,
but I'd like to be able to offer that to as many people as possible.