Alternator air gap

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MexicoMike

MexicoMike

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I'm putting everything back together and am wondering about the alternator air gap. I didn't check it when I pulled it but reinstalling it the gap is much wider on one side than the other. .010 will fit easily on one side but .006 is quite snug on the other. The book says 8-10 thou all the way around and if it isn't, to correct it by "very careful slight realignment of the studs." How the HECK does one "realign" studs? They screw into to the aluminum inner chaincase, I don't see how one realigns anything... ???
 
I thought of that but a steel stud in an AL case...I'd be afraid that the case would fracture before the studs would bend. It's another "I wonder how the factory did it" thing. ;)
 
Had an "AHA!" moment so I rushed to the garage to try something and it worked! Now I have an 8-10 thou gap all the way around.

It occurred to me that since the stator is bolted to the inner chaincase and the rotor is bolted to the crankcase, if there is any possible adjustment of the chaincase position fore/aft/up/down then it is possible that the gap can be adjusted by shifting the chain case. And the answer is, YES, I was able to adjust the position of the chaincase (slightly up and to the rear) and then tighten the 3 bolts to hold it in that location. There was sufficient "play" to allow the gap to be adjusted to oem specs without bending or otherwise "slightly adjusting" the studs. :) :)
 
Cool. I haven't had any problem with my spacing, but that is good to know.

Thanks
Dave
69S
 
I cut a strip of plastic from a gallon milk carton - long enough to almost wrap around the rotor. Fit it in with the stator on loose, tighten the nuts, pull the plastic out and I've got a nicely centered rotor.
 
Thats a good method if there is sufficient play between the stator/studs to allow some stator shifting on the studs. My stator was tight on the studs and could not be moved at all. I thought about wallowing out the stator mounting holes so there would be some "adjustment" but, as it turned out, there was sufficient play in the chaincase itself to come up with the few thousandths needed.
 
I asked a guy that used to work at the Norton factory how they did it. He told me they used a hammer. He was serious. Jim
 
MexicoMike said:
Thats a good method if there is sufficient play between the stator/studs to allow some stator shifting on the studs. My stator was tight on the studs and could not be moved at all. I thought about wallowing out the stator mounting holes so there would be some "adjustment" but, as it turned out, there was sufficient play in the chaincase itself to come up with the few thousandths needed.
Click to expand...

I have used BillT's method a few times and sometimes have had to open up the stator mounting holes a bit to give me enough slack to move the stator on the mounting studs. You really want to be sure you have 0.010 all the way around. If you have insufficient clearance you WILL lock up your primary and cause all sorts of havoc. Ask me how I know this.
 
I worked at a norton shop one summer.Got my first commando in 71.We always as crude as it might seem used a lead hammer and gently bent the studs a few thousands .It does not take much.Still use that method.
Bruce
 
I guess there's nothing wrong with the hammer method then! I just figured the AL casing would be damaged before the studs would bend. But I guess those guys at the Norton design shop figured out that there had to be some sort of "adjustment" available so in absence of a "real" method of adjustment they had the AL castings made up strong enough to handle "stud bending!" :)
 
Moving the chaincase is a good method, but still did not give sufficient clearance on my MKIII - bit of a trade off between clutch seal alignment at the rear and rotor clearance. Had to bite the bullet, assemble some patience and adjust holes with a swiss file, took ages but worked a treat.
 
Had similar issues with the 3 phase units I put in both the Norton & Triumph, solution for me was to enlarge the stud holes on the stators by a hair, while at the same time use an old forstner bit to enlarge the opening in the epoxy so as to allow a spanner to be fitted properly.
 
I have marked the side of the studs with a felt pen, then unscrewed them from the chaincase. Screwed on a couple nuts and clamped them in a vice. Then I used length of tube over the stud and gently bent it in the direction of the marking. Screw the studs back in the chaincase and check alignment. It doesn't take much.

I have done this only as a last resort. Moving the chaincase and/or the stator will usually provide sufficient clearance.

A Commando is much easier to do than a P11. The stator is mounted in the outer chaincase and the only way to check clearance is to use a strip of plastic or copper over the rotor similar to BillT's method!
 
MexicoMike said:
I guess there's nothing wrong with the hammer method then! I just figured the AL casing would be damaged before the studs would bend. But I guess those guys at the Norton design shop figured out that there had to be some sort of "adjustment" available so in absence of a "real" method of adjustment they had the AL castings made up strong enough to handle "stud bending!" :)
Click to expand...

I would avoid hammering on the studs if you can. Enlarging the holes and/or gently bending the studs would seem a lot less crude and a lot less potentially damaging!!
 
bchessell said:
I worked at a norton shop one summer.Got my first commando in 71.We always as crude as it might seem used a lead hammer and gently bent the studs a few thousands .It does not take much.Still use that method.
Bruce
Click to expand...


I have used the hamer method many times also. Like you say it doesn't take much. I always looked at it like I was straightening things instead of bending things. Sounded better. Jim
 
The best fix in my view is to waist the plain section of the stator studs in a lathe. Then the stator can be tightened up dead even all round
 
I've been running air gaps as low as .003" for perhaps ten years now with no ill effects. The battery almost never needs recharging even though I seldom exceed 3000 rpm around town--and I use Widder gloves in the winter. Smaller gaps mean higher output. Unless you run near the engine blood-line or have worn main bearings I've found that close is good enough.


Tim Kraakevik
kraakevik@voyager.net
Three Commandos
 
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