I was horrified to learn that the left lever on a bike does not engage the rear brake but instead the clutch. Scooters and bicycles always had the rear brake lever at the left handle.
So why exactly do we have a clutch in a bike? A bike has fixed gears for transmission, and in the process of connecting the engine with these different sets of gears, we would need to disengage the connection between the engine and the gears. Great, derailleurs do the job on cycles, right? But often we don't notice that, unlike us, engines can't dynamically adjust to the change in rotational speeds of the crank. Hence, the clutch.
The clutch is probably the most important part of the transmission, so when the first bike I get to learn on doesn't have one (more like the lever), it just became a matter of adjusting to the new position of the rear brake (at my left leg) and the consistent gear changes. Why do we need the clutch, I'd ask myself. Until, a junior of mine (who calls me his favorite senior) teaches me how to ride a bike with an actual clutch (lever), do I understand how much degree of control the clutch gives.
So if the clutch is absolutely necessary, how was the clutch lever removed in the T Matic system?
The transmission on the TVS Jive had 2 clutches, making it one of the first mass produced bikes to have such a system. So the first clutch is a centrifugal clutch, which engages when the engine RPM crosses a certain threshold. This is the clutch that engages when the bike is in motion.
The second clutch is a hydraulic clutch, which engages when the rider shifts gears. This hydraulic clutch, however is actuated by the gear shift lever, so the first bit of travel disengages the clutch, and then the gear is shifted. Really smart in my opinion, but as someone (post edit: It was Charles Kettering) had once said, "The world hates change, yet it is the only thing that has brought progress", a lot of people hated it because the gear shifter didnt feel as precise, and it felt pretty long. Some people also wanted the rear brake to be at the left handle instead at the right foot, but it's all nitpickings imo.
What about Quickshifters?¶
I began wondering how quickshifters worked. Do they also utilise a dual system?
No.
Quickshifters utilise a totally different part of the bike: the ECU (Engine Control Unit). When a gear shift is triggered, the ECU cuts the ignition for a few milliseconds. Doing that triggers a loss of torque, which is somewhat similar to what happens when the clutch is disengaged (the gearbox has no torque applied), letting the gear shift happen.
But this is only when you're shifting up the gears. When you're shifting down the gears, it is a totally different ballgame. When you shift gears down, the engine speed increases due to the gear ratios. So to match the engine speed with the gearbox speed, the ECU would trigger a blip, i.e. increase the engine's RPM by opening and closing the throttle by a few milliseconds.
But in order for the quickshifter to work reliably, we'd need the engine and transmission spinning fast enough that the momentary loss of torque, or the momentary increase in engine RPM doesn't cause the bike to jerk. So naturally, quickshifters are reccomended to be used after a certain rpm (usually above 2700-4000 rpm). THe quickshifter still gives you the feel of the gearbox, but it also eliminates the time to engage and disengage the clutch.
Tech has come a long way¶
The ECU has been increasingly becoming more and more complex, measuring a host lot of things, and also controlling various parts of the vehicle based on that information. Cutting ignition by turning off spark plugs and/or fuel injection is just one of the many things ECUs can do, and from an engineering standpoint, both the T-Matic System (the dual clutch) and the quickshifter are awesome innovations that aim to solve the same problem, but wildly differently.