6.9 transmissions Flashcards
what are spur gears
straight cut
parallel to shafts axis
pro and con of spur gear
cheap/simple
noisy
what is the larger and smaller gears called when 2 spur gears of different size are put together
larger wheel is a spur
smaller is a pinion
when are external spur gears used
when a change in speed is required and the shafts are parallel to eachother
when are internal gears used
when a change in speed is required whilst maintaining overall minimum diameter
what are helical cut gears
parallel shafts but teeth are cut at an angle
what are the pros of helical cut gears
quiet
larger contact area
transmit more power than straight cut gears of the same axial width
where are bevel gears used
intersecting shafts
engine to gearbox
pros of spiral bevel gears
quiter than spur or straight bevel
carry greater loads
smooth
pros of worm gears
quiet
can carry heavy loads
cons of worm gears
inefficient
where can worm gears be found
aircraft flap control systems
where can rack and pinion be found on aircraft
leading edge flaps for extension and retraction
what is mechanical advantage
no of teeth on driven gear divided by no of teeth on drive gear
what is speed ratio
ratio between two gears opposite to the ratio of number of teeth
whats the purpose of idler gears
make the output gear rotate in the same direction as the input gear
link gears when there is a distance betweeen them
does an idler gear change the ratio of speed
no
what are epicyclic (planetary) gears used for
reduction gears
whats difference between friction drive belt and positive drive belt `
friction belt relies on friction between belt and pulley
positive drive belt rely on teeth
what can v belt pulleys solely be used for
transmitting power between two parallel axles
what style is the majority of chains
roller type
what are downsides of leaf chain
must be lubricated regularly
only used for low speed applications
how are chains classified
by their pitch
what
