We have “special” clutches that allow drivers to keep engine revs at 1100rpm even at the sharpest turns
In the end the intricacy of the new KF engines is starting to give the expected results. With the usual evolution of ports, transfers and exhausts blocked by homologation form and regulations, which get more and more limited, the fantasy of designers has had to move on to other things. And, in fact, there are a number of alternatives, considering that the number of elements on today’s engines have doubled compared to the direct drive 100cc engines used for karting in the early days. For example, take ignition; rev limiter, balancing countershafts and centrifugal clutch. It is, in fact, the latter which have been the protagonists of some exploitation, having undergone changes that enable drivers to gain 5 tenths per lap, even one second, depending on the track.
The latest situation sees few and simple parameters that have to be respected for the following components; diameter, established by regulations minimum 80mm; weight given on each technical form for each engine; ability to move kart at not more than 5000 engine revs. The thing is that also on testing, the commissioners check with digital rev counter while pressing down on gas pedal to make sure that the kart starts moving forward before 5000 revs. However, starting to move doesn’t necessarily mean, that the centrifugal clutch has “geared up” 100%, on the contrary. Besides, that drive torque speed is really not enough, and above all, it increases to its highest peak around 1100 revs making automatic clutch skid as easy as possible. Setting it thus, (machining angle, springs and centrifuged masses) you can let the clutch go on skidding over the 5000-rev mark.
What’s the advantage? As the present 125 KF engines are practically “dead” below the 8000 revs, letting them work at that speed before the clutch engages completely enables you to get a different thrust on drive wheels. But, this isn’t all, allowing the clutch to skid until over 1100 revs, it has also been assessed that also at 9000 revs there is relative skidding between drive shaft and pinion, 10% - you get best drive torque and with it thrust is stronger too. To give you an idea, also the dragster clutch works along this same principle: here we’re talking of V8 engines with over 8 litre displacement, including volumetric and nearly 6000 horsepower, coupled with direct transmission, no gears. Well, Top Fuel and Funny Car fed on nitro-methane that go over 400 metres, when not moving, in 4 seconds and a half, going over 500 km/h, they are direct drive, in fact, because any skid is controlled by the clutch! Besides in karting, this enables you to mount a final gear with one or two teeth less, making the most of this technical device.
Rest assured, there’s nothing irregular in all this, you simply use a part of the international karting regulations that we can call “shadow zone”. But we can’t help noticing how we’ve managed to get to a situation that hasn’t been established by a legislator, and a font of evident discrepancies: in fact, usually these clutches aren’t readily available for everyone on request. So you have situations that are evident differences between some official drivers (whether they pay or not) and normal private drivers. With “doped” results, which don’t often give a true picture of the actual skill on the field, and it doesn’t only concern driving but chassis too. We’ll wait and see if and how the technical-sports commission manages to deal with this evolution (or involution) of a class that is respecting its basic rules least of all.
Report: M. Voltini
Photos: Vroom Archive
