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Alternator cooling

mikeholl

Member
Hi all, we are about to upgrade our alternator with a B&C 20/40 amp unit mounted on the accessory case (vac pump pad) of our Lyc 0-320. Would appreciate any comments on cooling. Do we need a blast tube?
All comments will be appreciated.
Thanks, and Cheers from OZ.
Mike
 
Yes. Put a blast tube towards the aft end electronics. A large wire tie holds it in place nicely. :)
 
Neither my B&C L-60 nor SD-20 have needed it in 1350 hours. Standard RV-7 cowling/baffles, O-360.
 
I called B&C when I was installing mine. They said it is not required but will not hurt. I installed one for my own piece of mind.
 
my main alternator had a blast tube installed in first place but i removed it. i figured that the charging current (with a not completely drained battery) is high only within the first minutes when you're still taxiing, but then there shouldn't be enough incoming air anyway.

at the time the airplane takes off the charging current should be so low that the regulator/rectifier shouldn't have any problems to deal with the thermal losses. so for me the entire cooling blast tube thing on alternators doesn't make sense... as long you don't have an airliners cockpit installed in your RV.

any blast tube will take away cooling air from your engine which is much more important i think. and if the manufacturer of the alternator says cooling air is not needed, than a blast tube has really no point.
 
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So what happens if you cool the alternator with a separate tiny naca duct?

you add building time and weight to increase the drag of your aircraft.

i think the best approach is to estimate the electrical power consumption of your system. if that continuous load is well within the limit of the alternator's rated output... don't install a blast tube.
 
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What's the airflow direction from the internal fan of the alternator?

Thru the rear then alternator and out or vice versa?

Is there a study somewhere that took temperatures from various places under the cowl?

Could you just have the internal fan of the alternator pull air from the coolest spot?
 
Hi again,
Just to follow up, I asked B&C for their recommendation and, as stated above, this alternator has internal cooling fans which they believe will keep it cool, and therefore don't recommend a blast tube.
Thanks again for the discussion.
Cheers
Mike
 
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