The diagram below shows the major parts of the crankshaft:
|NotTaR of small Gasoline Engines and Rotary Lawn Mowers : Crankshaft anatomy
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- Main bearings support both ends and whatever is driven by the engine.
- The crank pin journal is the surface upon which the piston's connecting
rod bearing acts to rotate the crankshaft.
- The crank gear drives the camgear/camshaft assembly which operates the
valve lifters/valves and possibly the oil pump as well.
- The flywheel is actually mounted on a machined taper (not shown) held on
by a large nut. The starter engages a clutch mechanism which may also
be mounted with the flywheel. For point-type ignition systems, a cam
to operate the contact points is usually located on the crankshaft under
- The blade or other driven equipment is mounted on the other end with an
adapter (not shown) held on by another large nut.
- Auxiliary equipment like front wheel drive may be powered from a worm
gear which is part of the PTO end of the crankshaft (not shown).
- The counterbalance weights help to smooth the operation of the engine.
__ | __
| | | | |
Threads for | |<-+->| | Threads for
Flywheel nut | | | | blade adapter nut
| | | | | __ |
V _________---| | | |-|__|_______ V
...---/ | | | | | |__| ----+...
||| | | | | | | |__| | ||||
'''---\_________| | | | | |__|_______----+'''
^ ---| |_____| |-|__| ^
| |--| |--| ^ |
Main bearing | | | | | Main bearing
(Flywheel end) | |_____| | | (PTO/blade end)
|__| ^ |__| |
| +--- Crank gear (meshes
with cam gear)
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