Generator Pully

[mamoose124]

My Lucus C40 generator went out and I purchased a British Parts Northwest Generator/Alternator conversion which comes without a pully. The pully off my C40 is not straight and is a bit loose on the alternator shaft so I ordered one from BPN. However, my original pully is 3-1/2" in diameter and the one BPN sent is only 2-1/2" in diameter. I hesitate to install the small pully fearing that the small diameter will force the fan to spin too fast. What do you think, fellows? Should I find another 3-1/2 pully? On that point, If any of you have a spare pully, I'm in the market for one.

 

[Barry]

In general, automotive alternators operate at higher RPM than equivalent sized automotive generators. Also in general, automotive alternators operate at a maximum of about 18,000 RPM. Compared to a 3.5" pulley, a 2.5" pulley will result in about 40% greater RPM.

Instead of assuming that the pulley supplied by BPN is too small, I think it would be a good idea to ask BPN about the difference.

 

[Tom H]

Did you really mean it would cause the "FAN" to spin too fast? Not at all, But as Barry noted, it would cause the generator/alternator to spin faster.

 

[hartmandm]

Like Barry said - get some specs from BPN on the alternator. Do some math (engine crank pulley diameter versus alternator pulley diameter ratio) to figure out if there is any concern with how fast the alternator will spin with the smaller pulley. If there is a concern and you need a larger pulley, then I'd check the alternator shaft diameter versus the generator shaft diameter to know whether original generator pulleys are actually a good option.

Mike