dynamics of a motorbike has always fascinated me.
When I was a little kid I loved my Lego Technic, I built everything
with it, but mostly cars and motorbikes. Thanks to the fact
that “back in the good old days” the Lego Technic
range wasn’t that elaborate at all, in fact, it was
quite bulky and cumbersome. This of course was the design
obstacle, you could not build exactly what you wanted, simply
because the materials weren’t flexible enough. But this
was a good thing for me. You see, I had to overcome that problem
and design my vehicles with what I had. Sure I cheated sometimes
by drilling a hole or bending the plastic by heating it with
a lighter, but that wasn’t really helping that much.
One of the biggest problems I had was actually
designing a car with the combination of four wheel drive,
front steering and suspension. One of them was not a problem,
two became cumbersome, but all three was either a very ugly
design decision or simply, not feasible. Motorbikes, on the
other hand, were much easier to design. Sadly there were no
such things as motorbike tyres, let alone in any size that
I wanted. I remember it quite clearly when my dad took me
to watch trials. Where we lived there was a creek-stage, and
these bikes went in, out and around this little creek of an
old mill. It was very fascinating for a small boy.
all the times we went to watch the races, I can clearly remember
one thing, This huge trail bike, it really looked massive,
but the thing I remember mostly about it, was it’s single
sided swing arm. This piece of engineering was truly amazing,
so amazing that I adopted it for my Lego-bikes. It wasn’t
that stable, but it looked good. And remembering back, the
Lego wheels looked a bit like the hub of, you guessed it,
the BMW GS!
The BMW GS range is now a living classic
range. When it was launched it did something that nobody really
thought that would work – a huge and heavy off road
bike – can’t be done..! Oh how wrong – the
GS is now the best selling BMW model, simply amazing. I remember
“riding” my Lego GS models over anything that
I could find in the house; pillows, old chocolate boxes, thresholds,
anything with some sort of surface. The surface could not
be even, because what would the point of front and rear suspension
be on a flat surface?! I used rubber bands to act as the shock;
more rubber bands – stiffer suspension. Some of them
even had brakes; I used a little lever to push onto a smaller
wheel attached to the rear axle spindle, worked like a treat.
Unfortunately, for me, my mechanical engineering
career never took off, there were simply no schools around
for that sort of jobs, and I didn’t like crunching the
numbers – “Anyone can do that”, so I ventured
onto other areas, but I never forgot the simplicity of the
Lego’s and what they could do.
Luckily this came in handy not to far ago. My beloved girlfriend
had a job interview with a motorcycle manufacturer and to
prepare for it we sat down and discussed the technical aspects
of bikes. We spoke about engine layouts, we spoke about centre
of gravity, brakes, handling, tyre sizes, you name it, we
talked about it. At some point I picked up the latest BMW
R1200GS brochure. One of the pictures is a stripped down GS,
with no panels, no extras, just the frames, swinging arm,
wheels, gearbox, engine and complete front suspension. We
were talking about how the individual parts of the GS bike
make no sense and that there are better compromises.
Shaft drive is, heavy and expensive, but
it is maintenance free – “heavy” is bad
on an off-road bike. The flat twin engine is self balancing,
but the layout is wide and produces sideways engine inertia.
And so forth – there are better individual parts, but
if you bolt them together like BMW has done, it all starts
to make sense. And on top of that all big “Beemers”
have got the wonderful Telelever front suspension. When you
see the naked GS you see that it really is an engineering
masterpiece. To me it is more elegant than anything that has
come out of the Ducati factory.
As a graduate engineer with limited hands
on experience with spanners and, above all, Lego, my girlfriend
struggled to see exactly how the Telelever suspension really
worked without resorting to drawing on the diagram and jot
on the beautiful picture. To me, this was completely absurd,
nobody, never ever will be allowed to draw on this Mona Lisa
of engineering. To me, the only solution was to show her that
there are other ways of understanding this. Ways that don’t
require powerful CAD programs, pens, paper and calculator!
All that was needed was an adventurous mind, materials and
a good laugh.
was 11 o’clock in the evening when I pulled out my trusty
hot-glue gun, and ran around the house looking for materials.
I found old CDs, old pens, old drink bottles and cans and
other such things. I also got some tools like knife and scissors
out. I then started thinking, and I started out with gluing
an empty can of pop onto an old CD-ROM, this was the base,
this was the body of the Beemer. I then proceeded to cut out
a bottle neck to use as the fixing point for the Telelever’s
forward facing swinging arm and the front frame that holds
the shock and the top triple clamps of the forks. I manufactured
the forks out of two similar pens that I slaughtered –
the ink-reservoir tube was used as the top and the outer “pen-part”
as the bottom. These inner-outer tubes slide nicely –
just like BMW’s construction. I then took the inner-ink-tubes
out of two other pens and manufactured the swinging-arm. I
used a pen and a part of a pen-cap to make the pivot point,
the top sub frame was just an outer-piece of a pen. I used
a bit of cardboard to create the point where the top frame
pivots with the forks. I used needles as the pivot points.
To finish it off I got a spring from a pen that can act as
the WP-shock unit (note that the WP unit fitted to the real
GS model is much more expensive than the one used on the model).
End result is a model that works exactly like the BMW Telelever
The beauty with the Telelever system is that
it retains the looks and functionality of a normal fork-setup,
but it gives the engineers much more precision when engineering
the characteristics of the bikes handling.
A traditional fork-setup has got two big disadvantages –
the first one is the length of the forks – they are
very long, and aren’t braced in anyway. This means that
they have to be very sturdy to take the longitudinal forces.
The Telelever on the other hand has got the swinging arm fastened
as close to the wheel as possible.
The biggest advance, though, is the Telelever system combines
the advantages of both the forks and a swinging arm –
well, it’s got both, doesn’t it. ? A normal front
fork-setup has got fixed geometry, now this is very good,
apart from the fact, that the bike changes its geometry. When
you apply the brakes, the centre of gravity moves forward
on the bike thus increasing the pressure on the front springs.
This means that the forks compress (d’Oh!), all normal
so far. However, the bad thing is that geometry changes when
the forks compress (and the rear doesn’t), the rake
of the front has suddenly decreased – you get the same
effect as if you would drop your fork legs through the yokes.
While this isn’t really a big problem, the big problem
is the dive and the weight shift under braking.
you have ever seen a pooch slide on a newly waxed floor, you’ll
notice that he’ll extend his front legs, not bend them.
He does that to get more pressure on the front legs to stop
quicker and to stop him from tumbling over. Your traditionally-equipped-bike
does exactly that – wants to tumble over.
Thanks to having a swinging arm, the lower pivoting point
of the forks can be engineered to move. The swinging arm,
after all, has got a radius just like any arm attached to
a pivot point.
By adjusting the length of the arm, and the position relative
to the lower pivoting point on the fork-legs the rake of the
fork legs can be engineered to either increase, decrease,
or, surprise, surprise stay the same. Technically the Telelever
can be engineered to give zero dive under braking. Amazing.
Der Engineeren have engineered in a bit of dive, for us mortal
humans, so that we can feel that we are stopping.
You also get a lot of other advantages, such as only one shock-spring-unit.
However, there are also disadvantages, mainly which are due
to the swinging arm. The construction isn’t really suitable
for all sorts of bikes, mainly depending on engine-layout.
It would be very hard to engineer a bike with both an inline
four and the Telelever suspension. I also suspect that it’s
quite an expensive construction.
You also might wonder why other manufacturers
don’t use the Telelever construction, well… it’s
patented – Natürlich!
All in all, the new BMW GS is a piece of
engineering art – to check it out, go down to your local
BMW garage, and try one out – you’ll see what
The Telelever suspension is “über
alles” when it comes to front suspension. In fact the
whole BMW package, flat twin, Telelever, separate gearbox,
Paralever shaft drive, is an incredible package. It’s
well thought out, I might even go as far as saying that the
BMW engineers have engineered out anything that’s not
desired from the original flat-twin-shaft-drive construction.
Hats off to engineers!