This CVT for karts
test has to be one of the most unique, and interesting tests
I have ever done. From the outset the CVT does weird things
with your brain
Your foot is to the floor, and you can feel the kart accelerate
(and does it accelerate hard), but the engine is keeping
a constant note at 11,500rpm (as you can hear on the video).
You definitely need a few laps to get your head in order.
The CVT is such a unique product to karting, and the way
it works on a kart is magical. The guys from CV Racing have
really done a great job with creating this product. Check
the video to see the system working with the kart on the
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How it works for Dummies
Ok, I'm not technically astute, but I'll give a
brief explanation of how this thing works. Right the main benefit
is that the CVT makes sure that the kart is always running at the
right gear ratio. So, it eliminates the problem of needing a large
rear sprcket on a twisty circuit, or needing a small rear sprocket
on a fast circuit... the CVT automatically adjusts itself to what
you need!!
It defeats the problem of conventional karts where
you need to fit a sprocket to give the overall best performance.
So for example you would fit a small rear sprocket at shennington
to take advantage of the long straights, but because shenny also
has hairpins the kart will struggle to accelerate out of the hairpins.
The CVT defeats this problem because when accelerating from a hairpin
it acts like it has a huge rear sprocket, and when you get on the
straight it acts like it has a tiny rear sprocket....perfect!
How does it do it.
The CVT has conical shafts on the axle and crank
which squeeze the belt drive and continuously change the gear ratio
to match the situation you are driving in, thats as much as I dare
say, my advice is to look at the video and see for yourself!
Driving the CVT for Karts
The first session out was definitely a feeler session.
What got me most was the pull out of the corners. The bottom end
of a Rotax Max is famous for being non existent, but with the Continuously
Variable Transmission it's a whole different kettle of fish. The
accelerator is like an on/off switch. You put your foot
down, and bam POWER! That’s the idea of a CVT, it
can utilize the full power of an engine at all times, from 0mph
upwards.
Once you get used to it, you start to realise how
much more inherently quicker it is that your standard chain and
sprocket drive. Out of the corners it’s clearly quicker
than a standard Rotax Max. Unfortunately there
weren’t many other Rotax karts out there on the circuit to
tag along to compare speeds. But when I did have a drag up the hill
at Whilton against a standard Rotax Max there was no comparison
- the CVT was quicker. That is backed up by the times of the CVT
karts at the Open Endurance Championship at Dayton Milton Keynes
UK where the CVT teams where about 1 second quicker than the standard
Rotax Max karts on Kartline tyres.
The CVT did require me to change my throttle control,
and it’s all about faith. Once I had got settled into driving
the kart I started to get my braking sorted, I could then concentrate
on throttle control. The general
idea with 2 stroke karts is to blend the throttle in as you come
of the brakes nice and progressively! But the Continuously Variable
Transmission does something very special. It acts as a traction
control system. So as the wheels spin, the Constinuously Variable
Transmission changes its ratio and stops the wheel spin. This is
where the faith part comes in. You can actually bury the
throttle 6 feet under and prey and it will stick, well, hopefully,
and it does! I only managed to master this once or twice,
but it worked! Obviously the CVT in the wet would be even more rapid
with the system working like that!
As I had a few more sessions with the kart I started
to get used to how the system worked, and how it felt, and I really
started to enjoy myself. I think Steve (CV Racing) was a little
worried after the first session when I
pulled in looking bemused, and bewildered. But I can assure
him that was through amazement.
As I progressed through my last laps my neck started
to go. The sticky new Vega’s had finally caught up with me.
And it was the pull out of corners that got me also. I was trying
to put my head looking down so I looked good for the camera, but
as I came out of the corner I could feel my head pulling back. So
maybe that didn’t looked to good on my part. That just shows
the pull of the Continuously Variable Transmission system on a Rotax
Max kart.
Driving a CVT is a totally unique experience. It’s
like it’s from another universe. And one of the greatest things
about the CVT is – its makes your kart go faster,
and increases the life of your motor. Imagine how many hours on
your Rotax engine you’re saving if it is only revving to 11,500rpm?
It is an engineering marvel.
So if your looking for some serious speed, and
don’t want to have to rebuild your engine every 5 minutes
the CVT is well worth a look!
Continuously
Variable transmission explained
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