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Sparx 3 phase alternator and regulator

Submitted by robert_evans on Thu, 29/07/2010
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Commando

I have purchased a Sparx 3 phase alternator and regulator to replace the Lucas RM 23, rectifier and zenner diodes on my 1975 Mk III E/s Commando.

1. There are 3 wires from the alternator that go to the regulator. 2 wires come out of the regulator. These will be connected to the battery and earth. On the Mk III there is the black 'square' assimilator for the ignition warning light which is connected to the alternator. Does anyone have any experience of how to wire in the ignition warning light assimilator with the Sparx system?

2. The rotor does not push on like the original one. The supplier says that it should be a tight fit and drifted on with a hammer. I am reticent to do this. Has anyone experience of fitting one of these rotors?

Rob Evans

Submitted by jack_blakemore on Mon, 23/08/2010

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Rob - I am just in the throes of doing a very similar thing using a Wassell regulator/rectifier.

I was looking a the circuit diagrams yesterday, and I believe that the warning light assimilator "senses" the alternator output. So for the Wassell unit at least, I suspect that you can take a feed off any two of the coil taps from the new 3 phase stator and use those to replace the feeds from the old 2 phase stator - originally supplied by the green and yellow and white and green wires from the old stator to the assimilator (and rectifier of course) - I think (check the wiring schedule).

I am also replacing the capacitor, as it is definitely tired and shagged out after a long 35 year squawk! They do dry up after a while and should be replaced occasionally.

I used one of these:

Specifications

Capacitance Value4700Î?FConstructionCanEquivalent Series Resistance0.036Î?Leakage Current6000Î?AMaximum Operating Temperature85?CMinimum Operating Temperature-40?CMountingScrew TerminalProduct Diameter36mmProduct Height52mmRipple Current6700mATolerance20%TypeElectrolyticVoltage63Vdc

Which may be found at:

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=3819087P&x=31&y=14

Better spec than the original, a bit cheaper and screw in terminals are far more preferable in my opinion.

Can't help with the rotor I'm afraid - except to suggest that you could use a can of freezer sray on the end of the shaft and a hide mallet!

However it goes on it will probably be a total b****r to get the required air gap of 8 thou all around to allow for expansion.

Good Luck

Jack B

Submitted by david_henshaw on Mon, 06/09/2010

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Hi Rob

I`ve fitted the same to my 750, it was a snug fit but NO problem.

The end of my crank had a few score marks so used some 320grit tape to clean it up so it prob went on a little easier.

With regards to the assimilator !!! my research leads me to believe its better left off which I have done, because if it fails it 's like to take out the regulator with it!!

I think I read a good article on pro's and con's on the oldbrit's site.

Regards

Steve

i

Submitted by robert_evans on Sun, 19/09/2010

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Thank you for the welcome advice. I have now fitted the alternator after finding a local engineer who honed the correct amount off the rotor to allow an interference fit. I provided him with the dimensions of the main shaft.

After consulting Al Osborne and studying the Owner's Manual, I connected 2 of the alternator wires to the ignition warning light assimilator. There is a slight flickering of the warning light at tickover but at normal speeds it operates as normal.

The alternator is a great improvement on the old one. I can now ride with lights on all the time at low speeds around town and so far the battery has not gone flat as previously happened after less than a week. If someone threatens to pull out in front of me I can rely on the horn working!

Rob Evans

 


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