Going Clutchless
There are many things that a gas car needs which an electric vehicle does not. Besides the obvious things like gas tank, muffler, oil changes, etc. a manual transmission Electric Vehicle conversion doesn’t even need a CLUTCH!
What?! How is that possible!? Doesn’t that break the laws of physics?
No. It has to do with how gas engines and electric motors are different.
WHAT DOES A CLUTCH REALLY DO?
To start with, a clutch in a manual transmission fulfills several different purposes. The main ones being to disconnect the engine from the wheels to stop the vehicle without stalling the engine and to more easily shift from one gear to another.
On a gas vehicle, the engine must always be rotating. If it’s stopped during normal operating, we call that “killing it” or “stalling the engine”. In the course of normal driving, when the car is stopped, the engine must be disconnected from the wheels so that it can continue it idle. On a manual transmission car, that’s typically done by pushing in the clutch pedal while coming up to a stop sign or red light.
On the other hand, it doesn’t matter if an electric motor stops or not. An electric motor can simply stop spinning, and then be brought to spinning again in a moments notice. There’s no need for a starter or idling the way a gas engine requires. The electric motor can be essentially attached directly to the drive train. In some cases, electric motors are bolted straight to a driveshaft (not uncommon in pickup truck conversions,) or the motor can be built right into the wheel itself (hub motors are popular on electric bikes!)
A clutch is generally required while “going through the gears” accelerating a gas vehicle. Gas engines only produce their peak power at a certain range of RPMs. The various gears allow the driver to match that power band with the speed of the tires on the road and the torque required to accelerate. Electric motors produce high torque over a wider range of RPM. DIY EV conversion drivers often drive using fewer gears, sometimes simply leaving the vehicle in a single gear at all times. Commercially produced EVs commonly only use single-speed gear reduction. In essence, they are permanently left in a single gear!
ACTUALLY SHIFTING
But how DOES a DIY EV conversion driver shift without crunching the gears?
Modern manual transmission have “syncros” in between each gear. Their job is to properly mesh together before the gears do. As they come together, they match speeds and in doing so bring the gears to the correct speed for “crunch”-free meshing before the gears come into contact. The rotating mass of an engine and flywheel would be too great for the syncros. Pushing in the clutch disconnects the rotating mass of the engine and flywheel, and allows the syncros to do their job, quickly meshing the gears.
In a clutch-less EV conversion, the electric motor is directly coupled to the transmission WITHOUT flywheel, clutch, or any of the other typical components. This is often done with a Lovejoy-type coupler, or even a solid coupler made from the hub of a clutch plate to match the transmission input. The spinning mass of the electric motor is SIGNIFICANTLY less than that of an engine and flywheel. The syncros can still do their job of meshing the gears, although it takes a moment longer.
Typically, the EV driver lets off the accelerator for a moment, gently pushes the gear selector into the next gear, and a moment later it drops right in. No need for a clutch, and no grinding gears. It does take a little longer to shift than it would with a clutch.
Keep in mind that a driver doesn’t have to shift out of gear at a stop or shift into a gear before pulling away from a stop. On our DIY 1996 Geo Metro clutch-less conversion, this driver typically just drove in 2nd gear in town and 3rd gear out on faster roads, shifting just once while leaving town. Imagine that! Shift just once on an entire drive!
IT’S YOUR CHOICE
Clutch vs. Clutch-less on an EV conversion is just a personal choice.
Having a clutch allows for faster shifting and a mechanical disconnect between the motor and wheels, but also requires more complexity, more machining and skill to build, and more weight in the car. Going clutch-less means shifting is slightly slower, but also allows for a simpler build and saves weight and rotating mass.
The most common questions about clutch-less shifting come from drivers of manual transmissions who have a lifetime of GAS engine driving behind them. Electric motors and gas engines simply work different, and have different characteristics, but it’s sometimes hard to get misconceptions out when a person only ever has experience with one technology.
In building your own Electric Vehicle conversion, it’s your choice to go clutched or clutch-less, but keep in mind that clutch-less can be a great simple and effective way to go!
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