Alternator Rotor Machining

C

commandofastback

Joined
Nov 29, 2004
Messages
51
Country flag
Hi All;

So it finally happened to me: burned out a stator.
The 3 phase stator i had been using in the past never had a problem clearance wise but the wires started to crack.
Got a new one from Andover, checked the clearance all round...but obviously not thorough enough...burned out

Anyway: After reading all the other threads about stator / rotor clearance and exploding 2006 rotors (i have one of these) i think the safest way is to get a new rotor and machine it down.

How much you think can be machined off without affecting the charge ?

Thanks in advance
 
commandofastback said:
Hi All;

So it finally happened to me: burned out a stator.
The 3 phase stator i had been using in the past never had a problem clearance wise but the wires started to crack.
Got a new one from Andover, checked the clearance all round...but obviously not thorough enough...burned out

Anyway: After reading all the other threads about stator / rotor clearance and exploding 2006 rotors (i have one of these) i think the safest way is to get a new rotor and machine it down.

How much you think can be machined off without affecting the charge ?

Thanks in advance
Click to expand...
@Fast Eddie posted this a few days back. Incidentally are you running LED’s?

Post in thread 'What Did You Do With Your Commando Today?'
https://www.accessnorton.com/Norton...do-with-your-commando-today.33718/post-709977
 
Nope.
All good old fashioned bulbs.
Boyer Power Box as regulator since 1998.

The new melted one was a 3 Phase 14,5 Amp.
Is there a way to distinguish the 10,5 Amp stator from the 14,5 ?
The old stator doesnt have any markings on it, but the insulator is brown instead of green.
Greg Marsh favours the 10,5 because the 14,5 just produces excess heat if you dont have to many consumers attached.

I recognized that idle was perfect with the new 14,5 while with the old one it was quite unreliable.
Better power output at low revs ?
 
commandofastback said:
Nope.
All good old fashioned bulbs.
Boyer Power Box as regulator since 1998.

The new melted one was a 3 Phase 14,5 Amp.
Is there a way to distinguish the 10,5 Amp stator from the 14,5 ?
The old stator doesnt have any markings on it, but the insulator is brown instead of green.
Greg Marsh favours the 10,5 because the 14,5 just produces excess heat if you dont have to many consumers attached.

I recognized that idle was perfect with the new 14,5 while with the old one it was quite unreliable.
Better power output at low revs ?
Click to expand...

The outside of the stator will have white markings showing either 10.5 or 14.5, hopefully it will still be there.
I just installed another 14.5 with about 80 miles on it, but seriously considering replacing it with the 10.5 one
I have here based on Greg's recommendation and my history of stator issues. For sure use a machined rotor....
I have LED's everywhere...
 
Yes the 3 phase produces a higher output at lower rpm. Thats why I fitted one, I’m running an e start and a Shoria battery and wanted to ensure things were tip top. I also thought 14.5 amp was good as I kinda fell into the mistaken belief that more is better!

So, I have a new (at the time) 14.5 amp stator and a new (at the time) rotor.

BUT…

I had the rotor turned down to be 0.040” smaller that the the stator ID (giving 0.020” clearance)
And
I fitted a Shindengen rectifier as recommended by Grant Tiller.

So in theory at least, I’ve countermeasured both of the potential mechanical and electrical failure modes.

All this was done several years ago now and (touch wood) I’ve had zero issues. When I first rebuilt the bike in 2013, I had 0.010” rotor clearance as used by many, but I still had rubbing witness marks and a overheated stator (whether that overheating was caused by electrical issues, or rubbing, or a combination of both, I don’t know).

So when I fitted the excellent cNw e start in 2019, I did the changes mentioned above. I have all LEDs, and the bike has done many track days (think about that, max rpm, max electrical load, zero draw from any lights etc) and it has been perfectly fine.

So, I stand by the 0.020” clearance / 0.040” under sizing of the rotor, and I can also only conclude that the Shindengen unit works exactly as intended.

The only downsides to the Shindengen are its cost (but that’s negated by avoiding failures and replacement of stators) and its physical size which means it’s not the easiest thing to find space to mount.
 
When i checked the clearance after fitting the new stator it was about 0.010" all round, but i didnt turn the engine over to check in all positions.
My mistake.
So i guess turning the rotor down by an additional 0.020" in diameter should be ok
 
I installed a new Andover rotor and struggled to get 8 thou all around.

A machinist friend mounted the rotor on a close fitting shaft and clocked it up on the lath to check it was perfectly round and centred on the shaft.

He found it took 4 to 5 thou cut to clean it up around and front to back.

He then took another around 5 thou off and when I mounted it I had 12 thou clearance all around and at different crankshaft positions.

He said he has gone uo to 15 thou clearance and not had any charging issues. He has good electrical and mechanical experience so I think I trust him.
 
Fast Eddie said:
Yes the 3 phase produces a higher output at lower rpm. Thats why I fitted one, I’m running an e start and a Shoria battery and wanted to ensure things were tip top. I also thought 14.5 amp was good as I kinda fell into the mistaken belief that more is better!

So, I have a new (at the time) 14.5 amp stator and a new (at the time) rotor.

BUT…

I had the rotor turned down to be 0.040” smaller that the the stator ID (giving 0.020” clearance)
And
I fitted a Shindengen rectifier as recommended by Grant Tiller.

So in theory at least, I’ve countermeasured both of the potential mechanical and electrical failure modes.

All this was done several years ago now and (touch wood) I’ve had zero issues. When I first rebuilt the bike in 2013, I had 0.010” rotor clearance as used by many, but I still had rubbing witness marks and a overheated stator (whether that overheating was caused by electrical issues, or rubbing, or a combination of both, I don’t know).

So when I fitted the excellent cNw e start in 2019, I did the changes mentioned above. I have all LEDs, and the bike has done many track days (think about that, max rpm, max electrical load, zero draw from any lights etc) and it has been perfectly fine.

So, I stand by the 0.020” clearance / 0.040” under sizing of the rotor, and I can also only conclude that the Shindengen unit works exactly as intended.

The only downsides to the Shindengen are its cost (but that’s negated by avoiding failures and replacement of stators) and its physical size which means it’s not the easiest thing to find space to mount.
Click to expand...
Nigel,
Could you tell us where you mounted the Shindengen unit. I have one in my stash and after 2 stators this week with turned rotors I am sick of this problem. I have the same components as you and want to keep them all. I also went with the thought that bigger was better.Apparently not the case.
Thanks,Mike
 
commandofastback said:
Nope.
All good old fashioned bulbs.
Boyer Power Box as regulator since 1998.

The new melted one was a 3 Phase 14,5 Amp.
Is there a way to distinguish the 10,5 Amp stator from the 14,5 ?
The old stator doesnt have any markings on it, but the insulator is brown instead of green.
Greg Marsh favours the 10,5 because the 14,5 just produces excess heat if you dont have to many consumers attached.

I recognized that idle was perfect with the new 14,5 while with the old one it was quite unreliable.
Better power output at low revs ?
Click to expand...
Are we seeing a pattern failure here?
 
YING said:
Nigel,
Could you tell us where you mounted the Shindengen unit. I have one in my stash and after 2 stators this week with turned rotors I am sick of this problem. I have the same components as you and want to keep them all. I also went with the thought that bigger was better.Apparently not the case.
Thanks,Mike
Click to expand...
Alternator Rotor Machining
 
I looked closely at both my rotor and stator. I've come to conclude it was an electrical problem and not interference that overheated the stator so installed a Shindengen. The only one I could find that shut off the AC is quite big and ended up installed on the down tubes. Aesthetics aside it seems to be working fine. i did not machine the rotor. I wanted power available for heated clothing. I pulled the primary to replace all the seals this winter and there was no sign of overheating on the stator. I think the one I used is the SH847, way overkill as rated for 50 amps. I could not find a smaller open type. Grant Tiller cautions not to buy on Ebay.
 
This is an interesting thread. I bought my 3 phase stator, podtronics r/r and trispark EE all at the same time as a kit. Rotor said 14.5 on the side, ran fine for about 300 miles and then smoked one day at the gas station after I filled up! I put the original stator from 1971 back on and no problem for like 6500 miles now… both showed the same clearance through several engine rotations after the ol ‘pop bottle shim’ method. Now I wonder if I got a dud… 🤔
 
tompkins said:
This is an interesting thread. I bought my 3 phase stator, podtronics r/r and trispark EE all at the same time as a kit. Rotor said 14.5 on the side, ran fine for about 300 miles and then smoked one day at the gas station after I filled up! I put the original stator from 1971 back on and no problem for like 6500 miles now… both showed the same clearance through several engine rotations after the ol ‘pop bottle shim’ method. Now I wonder if I got a dud… 🤔
Click to expand...
I just measured an original against new Lucas 2 & 3 phase stators, and the new Lucas ones have an inside diameter 0.010" smaller than the original.
I haven't checked a rotor yet.
@Fast Eddie reported seeing evidence of physical contact on his before having the rotor skimmed, so my plan is to ensure a running clearance of at least 0.025" on future builds.
I doubt if a greater clearance would materially impact performance, given the new ones are already over-rated for the job...
 
B+Bogus said:
I just measured an original against new Lucas 2 & 3 phase stators, and the new Lucas ones have an inside diameter 0.010" smaller than the original.
I haven't checked a rotor yet.
@Fast Eddie reported seeing evidence of physical contact on his before having the rotor skimmed, so my plan is to ensure a running clearance of at least 0.025" on future builds.
I doubt if a greater clearance would materially impact performance, given the new ones are already over-rated for the job...
Click to expand...
Further... New and original rotors both measure the same 2.912", or a bug's pube under 74mm.
I get the mathematical running clearance to be .024" originally, .019" with the new rotor.
 
I could be miles out here… but I have a theory that the sizing issue is not the normal quality control we might assume.

I wonder if the manufacturers don’t understand old bikes and are more used to modern bikes tight clearances, and they actually think they’ve improved upon the sloppy originals?
 
B+Bogus said:
I just measured an original against new Lucas 2 & 3 phase stators, and the new Lucas ones have an inside diameter 0.010" smaller than the original.
I haven't checked a rotor yet.
@Fast Eddie reported seeing evidence of physical contact on his before having the rotor skimmed, so my plan is to ensure a running clearance of at least 0.025" on future builds.
I doubt if a greater clearance would materially impact performance, given the new ones are already over-rated for the job...
Click to expand...

Fast Eddie said:
I could be miles out here… but I have a theory that the sizing issue is not the normal quality control we might assume.

I wonder if the manufacturers don’t understand old bikes and are more used to modern bikes tight clearances, and they actually think they’ve improved upon the sloppy originals?
Click to expand...
Parts are manufactured to drawings, with dimensions, and tolerances.

Without know that data, and also what used to be produced (dimensions) then you'd be pondering: "how long is a piece of string?"
 
B+Bogus said:
Further... New and original rotors both measure the same 2.912", or a bug's pube under 74mm.
I get the mathematical running clearance to be .024" originally, .019" with the new rotor.
Click to expand...
I just figured I’d screwed it up somehow. Nortoneering is a mystical craft to the uninitiated… also I cheaped out and reused the factory rotor so I figured maybe parts mismatch? Guess that wasnt the case 😵‍💫
 

Similar threads

WEM
  • Locked
Replace Alternator Rotor??
2 3
Replies
51
Views
10,671
ntst8
ntst8
joe czech
  • Locked
whac-a-mole problems and alton e-start (alternator rotor) timing marks.
2 3
Replies
56
Views
8,384
Carl H
C
maylar
  • Locked
How much difference does the alternator rotor make?
Replies
12
Views
2,955
comnoz
comnoz
jimbo
  • Locked
What is the best Alternator Rotor available today (2019)
2 3 4
Replies
62
Views
15,035
Fanfan26
Fanfan26
powerdoc
  • Locked
Testing alternator rotor (2011)
2
Replies
28
Views
7,095
Mr. Rick
Mr. Rick
Back
Top