Lucas Alternator

Likely to be an RM 19, I don't think thats your problem ,the switch and wiring is complex with lots of places where bad connections could give problems. Start with checking the earth ---- positive by the way!, If the rectifier has not been changed its likely to be dud by now, if it HAS been changed it may be the wrong type ,a new one is very cheap and has to be pos earth type. If you have the big PRS8 switch it could be bad inside or poor connections . What are you looking to do? stick with 6v or switch to 12,?. Time to decide if you want a combined rec/voltage control or the old zener or stick with 6v and switched output. If you switch to 12 then the PSR8 can be rewired to do just ignition and lights.

Hi Brian, see you there!, If you see a red /dove Deluxe with red Panniers thats mine (with my son riding) .I will be close by on something else.

Previously brian_weightman wrote:

I was hoping some one could identify the alternator fitted to my 1960 model 88 Its a Lucas 47199 A 360 3 wire stator and has a 70mm rotor the bike is running 6v battery and coils/bulbs but does not appear to be charging I have disconnected the wires and am getting 10vAC between GB and WG and up to 20vAC between GY and WG the rectifier has been tested okbut will be replaced any way . Any guidance would be appreciated thanks.

NORTON ALTERNATORS

RM 15 -

47127

6V 3 wire 60Watts

RM 18 -

?

6V 3 wire 80Watts

RM 19 -

47204

6 or 12V 3 Wire 110Watts

RM 20 -

47209

6 or 12V 3 Wire 90Watts

RM 21 -

47205

12V 2 Wire 110Watts

RM 22 -

N/A

RM 23 -

47194

Single Phase 180Watts

RM 24 -

47252

3 Phase 180Watts

PNH's Alternator numbers is a good list but some more information does not go amiss. Robert Tuck's information is also mostly good except the comment re rectifier 'it may be the wrong type'. From the late 50's and maybe the early 60's we had SELENIUM rectifiers, these were often duck egg green, 3" diameter or even grey 2"square. Throw them away. The black 1 1/4 round fined Lucas item is Silicon and due to it having a bolt down the middle which is for fixing AND earthing which pins you down as Positive earth. (although there is Negative earth versions) The modern 1 1'4" square rectifiers which have 4 Luca terminals sticking up need bolting down for heat removal only and they need an earth wire connecting (either + or - ).

Now the above voltages quoted from reading an alternator are usable but not reliable as the meter you will be using will be calibrated for mains 50c/s and a sine wave. neither of which come out of a Lucas alternator. Also the tests did not check earth connection which the alternator does NOT have. If there is any earth connection, then half or more of the output is lost.

To confirm full testing please refer to the pdf on my web site www.aoservices.co.uk. The orange 'information ' icon will lead you to the pdf.

Above alt. info. all numbers prior to RM19 are 70mm rotor, RM19 and later are all 74mm rotor. There is no 70mm new products so a failed 70mm rotor or stator means changing both parts to 74mm. All cranks on Nortons are 19mm except the lightweights which had a 1" crank (mixed measurements....) Wipac and good they still are.

The later 3 phase had the same 3 colour wires as the earlier RM19 but the later was switched 6V NOT 3 phase. (Seems Lucas had cornered the worlds supply of GRN/BLK GRN/YLW and WHT/GRN. Very early alternators had plain colours-see my web site.

Identifying the precise number, especially on the early ones is quite academic as there is no parts, if you use an old part then as long as it fits and works you are in business. RM19 is the only alternator for 6V (or 12V).

Have fun

AL O

Oh dear! , I'm old enough now to be able to blame fading memory, but I was just too lazy to check!, most unlikely to be an RM 19 ,probably rm15. And the new rectifiers can be wired for either polarity ( but there are some poor quality ones around.) . I'm convinced my RM15 is putting out more than 60 watts at 12v probably 90 ? ,as with all on the ampmeter will chase well across the dial. It explodes the myth that old alternators can't do the job .( perhaps an unfortunate choise of words with my luck).However AL's post has illuminated why my last rec failed, No heat sink. The old ones had their own built in sinks, mine is mounted on a nice insulating rubber block. Thats all I need ,another job to do! , thanks a bunch Al.!!.

Sorry Rick , I can't help  as I don't do belts.  I have fitted a high output  single phase Alt  which  needed  some work  to adapt to the 60 99.   I would use a combined rectifier /regulator for 12v , Al Oz can supply.   PSR8  can then be  used for just ignition and lights  with much simplified wiring . You could use one of the redundant wires  as an earth  for the  headlamp  shell.  (sleeve ends red)

The thinnest stator I could find was the 3 phase 10.5A stator, not the 14A version which is a wide as the other Lucas single phase offerings. On the rotor there is a special thin 27mm wide rotor used on the Tiger Cub part number 54212284, not available new so expect to use Al Osborne remagnetising service if you find one.