>speaking of starter ring gears, why is there 2 types, what are the advantages
>and disadvantages of the 2, i need to know soon as i may purchase an engine
>tommorrow.
>>There are (at least) two ring castings for the lycomming (the casting is
about
>>the size of a dinner plate and dished shaped). The difference is the
casted-in
>>pulley diameter, The other variable in the mix is the steel tooth ring
that is
>>fitted (interference) onto the casting ...one being 144 tooth the other
being
>>122 tooth. It really makes no major difference which your engine has
other than
>>the starter drive gear needs to match your tooth-ed ring. Starters come in 2
>>options 144 & 122 tooth
Early 60's everything 122 teeth. 149 tooth gears came along
later on some engines to get a better cranking ratio.
Current production O-235 and IO-720 have 122 tooth gears
stock. All other engines leave factory with 149 tooth
gears.
Pinion gear on all starters have 9 teeth.
When this info was repeated to the Lycoming rep at OSH last
year, the rep was unaware of the 122 tooth gear on the
larger engine. He went to the parts catalog for the
IO-720 and confirmed Bill's observation.
B&C recommends that every engine be fitted with 122 tooth
ring gear. The tooth engagement is better and the system
runs smoother. Be aware of the fact that either casting
can be fitted with any ring gear . . . the mating diameters
are the same. If you put a 122 tooth gear on a casting
designed for 149 tooth, the gear moves 0.060" too close
to the starter.
>>........ My last post just mentioned a vendor who has a
>>inexpensive pulley for the alternator of slightly larger diameter that
reduces
>>the rpm's of the starter a little ( 10 to 12 % if I recall) no mater what
>>casting you have on your ring gear......
B&C has offered the small pulley on their ND alternators since
day one. IF the rotor is balanced well then the positives
for running the alternator faster outweigh the negatives.
You get better output from the alternator at ground operating
RPMs and better cowl clearances. The exemplary demonstrated
service life of these alternators shows there are no life
issues to be addressed by running the alternator slower.
Bob . . .
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( Knowing about a thing is different than )
( understanding it. One can know a lot )
( and still understand nothing. )
( C.F. Kettering )
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http://www.aeroelectric.com
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