# Flywheel KERS CVT

## Main Question or Discussion Point

I've been reading a lot on the "flybrid" mechanical flywheel based KERS system which was developed for use on F1 cars. I understand the basics of how energy is stored in this system, however, when it is recovered, it is said to provide a constant 60kW of power for 6.67 seconds. I'm confused on how the flywheel is used to provide this constant energy output because to my understanding, as the flywheel slows down, the power that it provides must also decrease. I assume that the CVT is somehow used to maintain this constant power output, but I have no idea how the CVT would change its gear ratios in order to keep the power at 60kW. Could someone please explain?

Related Mechanical Engineering News on Phys.org
berkeman
Mentor
I've been reading a lot on the "flybrid" mechanical flywheel based KERS system which was developed for use on F1 cars. I understand the basics of how energy is stored in this system, however, when it is recovered, it is said to provide a constant 60kW of power for 6.67 seconds. I'm confused on how the flywheel is used to provide this constant energy output because to my understanding, as the flywheel slows down, the power that it provides must also decrease. I assume that the CVT is somehow used to maintain this constant power output, but I have no idea how the CVT would change its gear ratios in order to keep the power at 60kW. Could someone please explain?

http://www.flybridsystems.com/F1System.html
http://www.racecar-engineering.com/articles/f1/flywheel-hybrid-systems-kers/

These are some that I found through Google. There are others but they all contain essentially the same info. I'm on mobile and don't know how to make the links clickable. Sorry

Note that those numbers are based on the regulations set up by F1. 400 kJ per lap at a maximum of 60 kW.
So, in order to achieve a maximum power boost, one can utilize those 400 kJ over a minimum time-frame of 6.67 seconds (400 kJ / 6.67 s = 59.97 kW). They use a CVT on the driveline to control both how the energy goes into the flywheel and how it is discharged.

Exactly how they are used to maintain smooth power output depends on the exact system, but basically the CVT system uses the torque control (or gear-ratio-changer-thingy-mechanism, as I can't come up with a better name) spring to change the output torque, and a high performance slip clutch to vary output rotational speed.

Last edited: