I see lots of info about Sparx alternators and new Triumphs (units ) but not much written about classic preunit applications.
I just received a Sparx, model spx003, 3phase alternator. Before I bought it, I emailed Sparx (Tricore in England) about the correct part for my 6T. Here is the reply:
“the spx003 will fit if you use the alloy adapter ring as used on later p/u models we dont have the alloy ring in stock at the moment”
So….armed with this info…I bought a spx003 (not from Tricore) figuring that I’ll need an adapter ring. When I received the alternator, I see what the adapter ring should look like. It needs to reduce the bolt circle by repositioning the mounting studs. One other problem is the retention nut and keyway. It appears that the nut shoulder dia will have to be turned and the keyway opened up on the new rotor (or modify a key).
The OD of the new coil will fit within the stock bolt circle.
The nut shoulder is about .030” larger diameter than the bore in the rotor.
I have done this conversion. I filed the keyway in the rotor. I also used a rotor nut that fits the rotor and crankshaft ( you will need to order a nut from the 1960-1962 models and possibly up to 1969 will work as well or whenever the thread pitch changed ). Very straightforward operation. Those adapter rings come up on eBay and you can check a few suppliers. Expect to pay between $30 & $80.00 for one.
I’m not shocked (nyuk! nyuk!) that a bit of modification is needed.
I will order the correct rotor nut and keep my eyes peeled for an adapter. What do you think about modifying the key instead of filing the rotor keyway? I don’t have the dimensions here right now, but if memory serves, I think it was around .030” difference. I would end up with a stepped key which I think would be strong enough to drive the rotor. What do you think?
RFW’s comment about ordering an adapter plate from the 1962 Tricore manual was an informative clue that actually helped. The clue, cryptic in nature, implied that the Sparx unit was actually designed to fit an existing Triumph model. This triggered a memory about the different alternators offered by Triumph over the years along with it being a popular upgrade to retrofit a later model alternator in place of an early model.
A quick lookup in my Woolridge Tbird Bible offered this 6T preunit info:
1954 first year for the alternator (RM14) 1959 change to RM15 1962 change to RM19
So my guess is that the Sparx directly replaces the RM15 or RM19
I would file the rotor keyway. It didn't take that much filing and you are filing softer metal than the key...which in my opinion would be a little sloppy in the keyway if filed.
The Sparx replaces the RM19's and up. I run an RM21 in the 6T. As a side note, you will have to order the three bolts that fit into the adapter as they are a one of a kind. I will post a list of part numbers for you later...have to get the parts manual for the 1960-1962 models out of the library.
I have a stepped adapter plate / spacer for an alternator, I will find my camera and post a couple of fotos, might be what you need. I believe it's from a tiger cub, not sure. (shown here with alternator on top, it seems to space the stator about 1/2" higher. ID of the rim where the stator sits is 127mm I would go with RF's suggestion and have the rotor machined to fit the nut. If you are going to do a fair bit of mechanical work in the future why not invest in a Sears/Harbour frieght 7 X 12 minilathe. I don't know how I got along without mine.
Here is a parts list of what you will need to accomplish this upgrade. There are two variations of the adaptor I have seen. The most common which is made of aluminum and the rare steel ones. Get steel if you can, but don't hesitate to grab the aluminum one when it presents itself.
I will duplicate your technique of filing the keyway.
The part numbers are MUCH appreciated . I have two parts lists, a 1955 and a 1957 which do not help in this case.
Would you be so kind as to also post the rotor retention nut (and washer if used) part #’s? I think I could get away with machining mine but I want to keep the original parts in tact when possible (even though they sit on my shelf).
I will include all of this info when I get to the alternator install in the WVK 345 resto post.
A small machine shop in my basement would be great! Fortunately, I have the use of a decent machine shop. I usually go in early and make chips (and clean ‘em up) on my time.
I just looked on eBay and just missed this one…it is clear to me now what they look like.
I meant to post those part numbers...must have been sidetracked !!
Tab Washer - E3975 Nut - E3977
Same parts and numbers from both my 1960-1962 and 1967 parts books. Crankshaft stud is E3114. Check your 1955 parts book or measure to verify that they are the same length ( thread pitch will definitley be ). The length is 1 3/16" O.A.