alternator

TonyBaxter
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Re: alternator

Postby TonyBaxter » Tue Jan 09, 2018 9:16 am

If replacing just the stator, make sure it's the same size as the rotor. I know Triumph changed from the smaller diameter in the early Sixties, I'm guessing most Brit manufacturers did the same as the larger one became available from Lucas. The larger size is approximately 4mm bigger in diameter than the early one. I have just looked at the factory workshop manual and see that both RM15 and RM18 were fitted to the Ariels, I assume from Brian's post that these were both the larger diameter ?
According to the Lucas bulletin which can be viewed as a pdf on the 'British Only' website, the RM18 superseded the RM13 for smaller capacity machines and the RM15 was for larger bikes.
The Lucas 12volt ones currently (terrible pun !) available from most stockists are the RM21 and 23 models, (plus the three phase 24). Personally I wouldn't bother going for a new 6 volt job, might as well go for 12 volt if you are spending money.
Can anyone give a definitive answer as to which RM model is best ?
When I get around to mine I will probably fit a new alternator, so would be very interested to know which model is best.

Just re-read above posts and see that Brian has the RM18. According to that pdf it was meant for smaller capacity bikes with low ratio top gears.
I guess the big danger nowadays is to fit the supposedly best performing alternator and then finding the bike doesn't rev fast enough to charge the battery, or it produces so much power (with high watt bulbs, heated grips etc) that it saps engine power.

ken-drink
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Re: alternator

Postby ken-drink » Tue Jan 09, 2018 12:55 pm

Brian, so you need both parts, rotor and stator?

Ken

TonyBaxter
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Re: alternator

Postby TonyBaxter » Tue Jan 09, 2018 1:35 pm

The RM15 and RM18 are a different thickness, I would guess that miss matching the rotors would not give the best output. I don't know which one is the same thickness as the later types.
I updated my Triumph by buying a new encapsulated stator to replace the old open type, and kept the original rotor, it worked Fine.

bh.sprint
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Re: alternator

Postby bh.sprint » Tue Jan 09, 2018 6:04 pm

Hi Ken,

I've attached a picture of the two rotors used on the Leader/Arrow engines.The left is the smaller diameter, the right the larger diameter but thinner rotor used with a spacer. My 1965 Leader has a RM 18 alternator from what I remember, it is said gave a bit more power, 55 watts. It has the larger rotor of 2.915'' diameter which is thinner approx 1.100'', a spacer is used with this set-up.

The smaller diameter rotors are 2.750'' dia and approx 1.700'' thick . As far as I can find out these were RM 13 or RM 13/15 ( the 13/15 was said to give a slightly bigger output)

I've used the larger rotor on the Leader with a stator from Paul Goff , I 'm not sure what its number( RM ?) was but it powers a 60 watt head light bulb OK and other items .

Brian H.

PS I will be taking some orders for spares in the next week or so.
Attachments
IMG_0416 (2).JPG

ken-drink
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Re: alternator

Postby ken-drink » Mon Jan 29, 2018 12:49 pm

just fitted this to my Leader at the weekend, https://www.feked.com/alternator-stator ... e-12v.html and this rotor
https://www.feked.com/alternator-rotor.html, works a treat, only mod was to fit allen screws to the door as one bolt fouled the new stator, i now have good lights and can charge the battery at the same time with the ampmeteter showing a charge even at low revs, so more than happy so far. i now have a very original alternator, rotor and stator that i don't need so if any one wants it they can have it cheap.
Ken


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