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Alternator Left or Right Handed ?


Alan de Enfield

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28 minutes ago, ivan&alice said:

I did also read this thread:
 

 

And I was still unsure. I think that the fact that I commented on a 6 year old thread should show that I tried to find the information before asking!

 

Yes, I did indeed think that the fan blows rather than sucks! Thanks for the clarification - that helps a lot. I'm surprised though, sucking seems like an altogether less efficient way of moving air, but I must be wrong about that! So, the "buckets" move "backwards" (i.e. convex end first). That makes me understand a lot better - so clockwise rotation (facing the pulley end) is correct for a fan like these:

 

image.png.979a384994cc40cede7d3e8c02f90ac2.png
  

I'm sorry that it took so long to hammer into my skull but I do appreciate your patience and I think what some might not fully appreciate is that it's not always clear to a novice things like which is the "front" and which is the "back" of an alternator. Similarly which is the left and right of an engine? If you are looking at the "front" then the "left" of the engine is actually the "right" of the boat. And yes, I assumed that fans blow rather than suck.

 

 

This seems eminently sensible, thank you Nick! Happily the cheap one that I want to buy has a handed fan and I'm planning on blowing some extra ducted air at it as well for good measure - glad I now know to blow it at the coils rather than the fan! To be honest I give this alternator a 50/50 chance of surviving my meddling so I just really wanted to not spend too much money. 

 

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So for the benefit of any future searchers, what I've learned is:

* Clockwise rotation is usual for alternators (I suppose that if you have an engine that rotates anticlockwise you must buy a bi-directional fan?)
* Handedness of an alternator refers to the side that the mounting points are on. Left hand means that the alternator mounts on the left side of the engine if you are facing the pulley end (this is probably the right (starboard) side of the boat).

* Both left hand and right hand alternators will usually have clockwise-rotating fans

* Fans suck, not blow, air through the alternator and, with centrifugal type fans, you want the concave side to be the trailing side to the direction of rotation.

 

and many, if not all handed alternates with THREE through bolts holding he body together can be altered to the other hand at the expense of drilling out a thread and buying a nut and bolt for the adjuster.

 

If, and its a big if, as long as the designers got it right and you drive the alternator fast enough in theory it should be impossible to burn it out, even with a dead short. This is because the maximum CURRENT is inherent within the design. The higher the current the lower the voltage it can produce (hence a low voltage soon after the first start of the day). However seeing Lucas designed the one you are looking at I would not be so sure that is correct. I had a similar but not identical one shorting out for about 10 minutes in traffic with smoke for the wiring coming from under the bonnet yet the alternator survives. more than I can say about the loom.

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