Aim : Study of freewheel mechanism

Introduction:A freewheel is a device in a transmission that disengages the driveshaft from the driven shaft when the driven shaft rotates faster than the driveshaft.

Mechanics

Device consists of two saw-toothed, spring-loaded discs pressing against each other with the toothed sides together.

Rotating in one direction, the saw teeth of the drive disc lock with the teeth of the driven disc, making it rotate at the same speed. If the drive disc slows down or stops rotating, the teeth of the driven disc slip over the drive disc teeth and continue rotating.

Freewheel1-freewheel mechanism2-sprocket3-teeth4-central bore5-free wheel body6-cylindrical shoulder8-side plate9-bolts10-pawl means11-pawl spring means12-pawl teeth13-internal thread14-external thread15-pawl seats16-bicycle hub17-clearance hole18-threaded hole20-pawl spring groove21-bias surface22-pawl tips

Side view

Benefits:

Acts as an automatic clutch, making it possible to change gears in a manual gearbox, without depressing the clutch pedal, limiting the use of the manual clutch to starting from standstill or stopping.

Also produces slightly better fuel economy on carburetted engines without fuel turn-off on engine brake and less wear on the manual clutch.

Applications: In agricultural equipment it is typically used on hay

balers and other equipment with a high inertial load, when used in conjunction with a tractor without a live power take off (PTO).

Many unpowered 'push' cylinder lawnmowers use it to drive the blades. these are geared or chain-driven to rotate at high speed and the it prevents their momentum being transferred in the reverse direction through the drive when the machine is halted.

Widely used on engine starters as a kind of protective device.

The freewheel controlled drive from the gearbox to the front axle, which disengaged on the overrun. This allowed the vehicle to have a permanent 4 wheel drive system by avoiding 'wind-up' forces in the transmission.