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#861694 10/26/21 7:56 am
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What year was the first Alternator released on a Brit bike ?
Im guessing Lucas ?

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friday1 #861705 10/26/21 3:23 pm
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I'd venture a guess around 1960/61

(for the common 60s/70s style that we all know and love)

Last edited by GrandPaul; 10/26/21 9:22 pm.

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friday1 #861714 10/26/21 4:37 pm
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the history of Lucas motorcycle alternators , or just the first alternator ?

the first Lucas alternators would (have been early to mid 50s ( 1953 ? ) for 70mm rotor pattern , with RM13
the 70 mm stators were ... RM 13/14/15
and 5F ( flywheel cast alternator rotor) used on the Triumph Tigress ( 1959~64)

the early 1960s began a change to the 74 mm rotor pattern ... starting with maybe RM 18 .

but as to the earliest Lucas fitment I don't know , 1953 ?
... and the change to 74 mm wasn't done all at once , certain models got them before others ,
Probably as older stocks are used up .

Last edited by quinten; 10/26/21 5:06 pm.
friday1 #861741 10/26/21 7:20 pm
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Triumph TRW flat head was supposed to be a WW2 model

friday1 #861759 10/26/21 8:49 pm
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Looks like the 1950 TRW had an alternator.


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friday1 #861773 10/26/21 10:07 pm
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Perhaps try locating Lucas catalogs from the past. I have owned a couple of reprints from the mid 1950s, these catalogs would show fitment of a particular switch etc. on a large range of makes and models. Also delving into parts books of various motorcycle manufacturers prior to 1953 may show an earlier use of the alternator than the 1953 Triumph 650 and ?500?
Many parts books available for viewing free online, not so sure if Lucas catalogs the same.

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I have a 55 6T with alternator

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i see bunch of uses by 1953
the 53 Thunderbird had a RM12 alternator
the 53 Triumph Terrier T150 , precursor to the tiger cub , used and alternator

and the parts books ive seen indicate that the TRW ( pointed out by T. Thrasher )
used an RM14 alternator from the beginning ... 1948 .

The change from generator for alternator would have been made possible by selenium rectifiers .
Invented in 1933
But probably not a generally publicly available until after the end of WW2

friday1 #861813 10/27/21 5:06 pm
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Triumph Service Bulletin #93, dated June 23, 1952, states the change to "new positive-ground electrics" began with Speed Twin serial number 18706 NA.

I think this was to accommodate the newly introduced alternators.
(and selenium rectifiers as well?)

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the Wico-Pacy
Direct AC lighting coils used on the
D1 bsa bantam from 1948 is
An alternator ... but direct AC lighting coils bends the category of inclusion for " alternators"

friday1 #861818 10/27/21 7:00 pm
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Didnt even think about Bantam.
Its the TRW that got me thinking, they had the Alt cover on the primary but then surely the first model was the same as the last. so it looks like 1948 it is. Im going to dig into Wico-Pacy see what turns up ....

quinten #861822 10/27/21 8:18 pm
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Originally Posted by quinten
the Wico-Pacy
Direct AC lighting coils used on the
D1 bsa bantam from 1948 is
An alternator ... but direct AC lighting coils bends the category of inclusion for " alternators"

A flywheel magneto with a direct lighting coil is technically an alternator and must have been used long before WW2, but is it what we’re arguing about?

Last edited by triton thrasher; 10/27/21 8:21 pm.

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friday1 #861824 10/27/21 8:50 pm
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The Bantam had its origins in an earlier German design, the DKW RT 125, I don't know if these bikes had an alternator or not, but maybe worth researching this bike and also other pre-war designs.

There was also apparently a Watsonian-JAP designed around 1948, it used an all-light-alloy JAP 50-degree side-valve twin of 998cc, producing around 35 bhp. and was possibly the first motorcycle engine to dispense with a Magdyno and, instead, incorporate an alternator unit. The alternator was housed in an extension to the timing chest, and from the rear of the chest there projec­ted a car-type distributor. There was a rec­tifier and battery and, coil ignition. See This Link for details, the bike is apparently housed at the National Motorcycle Museum.

Lord knows who made the alternator & distributor, though Lucas/WIPAC etc are likely suspects.


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gunner #861846 10/28/21 7:13 am
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here's another contender , the TRWs older stillborn sibling , the 3TW
[Linked Image from nationalmotormuseum.org.uk]
Originally Posted by the National Motorcycle Museum
Developed in 1938–39 to meet military specification, the 3TW never went into service because the first 50 machines were destroyed during the devastating aerial raid on Coventry in November 1940. Military requirements had changed when Triumph’s new factory, at Meriden, opened in May 1942.

The 3TW, however, is a fine example of a lightweight machine (264lb) with a nippy performance for road and cross-country work. It was also the first British motorcycle to be equipped with an alternator.


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