Alternator rotation?

[seaesta]

I am fitting an alternator to my MD1. I plan to womble one from a scrappie. How do I know whether it should turn clockwise or anticlockwise ? Will it work either way?

Advice appreciated

 

[VMALLOWS]

It'll work either way, but it will be better to keep it going the way it's used to or you may wreck the carbon brushes. The vast majority turn clockwise when viewed from the 'front' (the end with the fan on). To this day I don't understand why people pay hundreds for a 'marine' alternator. Last one I got from a scrap yard(Hampshire) was £20........quite a bit up on £10 a couple of years ago, but it was
catalogued, tested.........and still working great.

 

[halcyon]

It's the fan that can be effected, there are ant-clockwise fans, but rare.


Brian

 

[VMALLOWS]

Brian,

Agree. Always had trouble trying to make sense of those fans. In reality, the biggest problem in most boat installations is whether there is anywhere for the air to go to. IMHO.

 

[Avocet]

The fans are nearly all designed to send the air from centre to the outside. They effectively "centrifuge" the air out rather than gather it and try to force it into the alternator. If you imagine the direction of rotation as being the one that would try to "spray" air outwards, this should give a good clue.

 

[VMALLOWS]

So am I correct that a clockwise alternator looked at from the front would have its 'blades' angled backwards at about 320 degrees, with a bit of rake as well?

Never liked fluid dynamics.

 

[halcyon]

Thats about right, any way anti-clockwise alternators are very rare.


Brian

 

[VMALLOWS]

Thanks, Vic

 

[alanporter]

Fitting a car alternator is fine on a power boat, but probably not so good on a sailboat, if you need to keep batteries charged. Car alternators are high rev-ing low output, whereas marine alternators are lower rev-ing with high output. Just a thought.

Alan Porter

 

[oldharry]

I beleive the 'only' difference beteween marine and auto alternators is that the marine one is theoretically more corrosion proof - i.e. brass contacts and springs rather than steel.

However I have always used car type alternators, and never had any problems with them. Anyway, most modern boat engine compartments are a whole lot better protected from the elements than any car engine bay that I know of - open to everything that is thrown up off the road, and often hitting the alt head on at 70mph + You wont find that in the engine compartment of your boat!

 

[VMALLOWS]

Obviously the alternator speed will depend on the pulley ratio, but in practice (BUKH 20) I get maximum output (50A) at just over tickover revs with car alternators. (The BUKH does have a fairly large flywheel pulley, about 6 inch diameter)

Ref Oldharry: The only alternator I have had fail purely through corrosion was the original (Paris-Rhone) one (presumably 'marine') fitted to the BUKH.!

 

[frilaens]

Perhaps you pay more for the little arrow on "marine" ones to tell you the direction of rotation Mine has an arrow, by the way!

Andy

 

[Johnjo]

I fitted a car alternator several years ago to my M D 2 B no problems at all.
You can buy a lot of used ones for the price of a new marine one.
mike

 

[Joe_Cole]

I found that Lucas were very helpful. They have detailed information on all the popular alternaors, output, rotation direction, maximum revs etc etc. You'll nedd to give them a reference number to work with.

Joe Cole

 

[Peter_Shipley]

Fitted a car alternator to my MD1B several years ago. Worked very well.

There seemed to be two ways to fit the alternator drive belt. Either get the flywheel machined with a third groove or try to source the Volvo original pully that fits to the centre of the flywheel with four bolts.

I opted for the second option and also sourced a second hand cast alternator mount. Was then able to buy the curved bar enabling me to tension the alternator from Volvo. The alternator was from a car, which I simply modified to fit the mounting.

You then get the dynastart to charge a engine battery and the alternator to charge the domestic battery. Since then I have had no problems with flat batteries.

I have since sold the boat however I may be able to dig out some further details if you wish.

Good lock with the modification.

 

[Guest]

hi where did you get the smaller pulley wheel, this sounds a great idea

 

[Peter_Shipley]

I got the parts from Challenger Marine, Penryn, Cornwall Tel:01326 377222. Also try John Hawkins Marine, Halling Kent. Tel:01634 242256

Parts needed as follows (Volvo part numbers):

Part Number Qty Description
833425 1 Pulley
833309 1 Mounting Bracket
833311 1 Tensioning Arm
959241 1 Screw
941908 8 Washer
941744 3 Washer
940132 1 Screw
941907 2 Washer
955782 1 Nut
980336 1 Stud
970950 4 Screw
955296 1 Screw
191172 1 Washer

Sorry I do not have the records to show which car the alternator was off, however I seem to remember that it was a common car. The alternator mounting boss needed to be drilled out to take the larger diameter mounting screw and also reduced in length to fit the volvo mounting bracket. Drive belt from Halfords.

A new alternator connector can be purchased at www.vehicleproducts.co.uk.

I hope the info helps and that you manage to fit the alternator sucessfully.