Alternator Rotor Machining

[jimbo]

But is it perfectly central to the shaft.

As I said above mine clocked uo on a lath showed it needed a 5 thou skim to centralise.

That seems to be alot, it might even cause some vibration?

 

[concours]

...yet all this stuff was originally designed mass produced, to be slapped together & WORK.

My stator has .008 on the tightest side. Clearance enough. Charges fine. Doesn't rub. Doesn't go on fire

 

[Fast Eddie]

...yet all this stuff was originally designed mass produced, to be slapped together & WORK.

My stator has .008 on the tightest side. Clearance enough. Charges fine. Doesn't rub. Doesn't go on fire

So what’s your theory as to why modern pattern ones have such a high failure rate ?

 

[concours]

So what’s your theory as to why modern pattern ones have such a high failure rate ?

I would think that poorly coated wire is being wound, and or poor procedures used. Even using stamping dies that are no longer sharp produces greater burr size, which can penetrate wire insulation during the winding process.
If I was needing to fit a new one, I would test it with my megohmmeter before fitting it.

Given the failures observed, THEY ALL should be megged, batches on the shelf, all of it. The maker should have already done this. But, due to the cascading chain of "not my job man" on down through the supply chain, here we are.

https://www.amazon.com/dp/B004OMAWIA/ref=sspa_mw_detail_3?ie=UTF8&psc=1&sp_csd=d2lkZ2V0TmFtZT1zcF9waG9uZV9kZXRhaWw

This IS a reasonably priced tool that works as intended. You can spend A LOT MORE for continuous use equipment, but I have found this most accurate diagnosing shorted cables, connectors and servo/spindle motors on CNC machinery.
Make sure it says "Supco" if you want the original quality piece. (I see half-price knock offs missing the trademark name).

 

[johnm]

That seems to be alot, it might even cause some vibration?

It was out side to side but also front to back.

 

[YING]

While on this subject of charging issues,is there anything wrong with wiring the regulator/rectifer directly (fused) to the battery?
If wrong,why?
Thanks,Mike

 

[kommando]

If they were too small wouldn’t they smoke up as soon as you start the bike?

The difference is small but enough so over a longer period heat builds up. If I had one, luckily I will never need one with the LAP spares I have, instead of reducing the rotor externally I would increase the ID of the stator internally. As the stator frame is built up from sheet steel then this would not cut well with HSS or a carbide tip and instead it would be better to grind.

 

[JimNH]

While cleaning the shop I came upon a removed stator and rotor. As I've stated before there was NO sign of rubbing yet the whole stator, well away from the center, was blistered and overheated. I truly believe that the problem is electrical in nature. The original zeners dumped DC so all heat was absorbed to a huge aluminum plate. That's not an option with the 14.5 amp 3 phase. The replacement regulator/rectifier shorts the AC windings of the stator leading to its demise. https://granttiller.com/regulator-rectifier

 

[Triton Thrasher]

While on this subject of charging issues,is there anything wrong with wiring the regulator/rectifer directly (fused) to the battery?
If wrong,why?
Thanks,Mike

I think that’s normal.

 

[speirmoor]

Another thing to add to to the mix.
As a bolt up construction, Norton cranks are more flexible than Triumph or BSA cranks (hence the so called superblend main bearings). This could lead to the end of the crank whipping at high rpm. Maybe Nortons require a little more rotor clearance

I always thought this was the case with mine. I replaced two stators already and it was always after flogging the bike. I wonder whats the max gap allowable for the unit to still work ?

 

[DennisMo]

If you shave the magnets on the rotor, this takes them further away from the stator and less current is generated. It will still work but with less output.

However, if you have been through two stators, then perhaps shaving a bit more off to make more gap and having slightly reduced output is
an acceptable tradeoff that saves you replacing stators. My Alton has 13 thou gap from rotor to stator and that has worked fine. But I guess in your case, a lot of flogging induced heat is causing distortions.

 

[concours]

While cleaning the shop I came upon a removed stator and rotor. As I've stated before there was NO sign of rubbing yet the whole stator, well away from the center, was blistered and overheated. I truly believe that the problem is electrical in nature. The original zeners dumped DC so all heat was absorbed to a huge aluminum plate. That's not an option with the 14.5 amp 3 phase. The replacement regulator/rectifier shorts the AC windings of the stator leading to its demise. https://granttiller.com/regulator-rectifier

Jim, can you bring it to the next NENO meeting for testing?

 

[ashman]

To me after reading all these faults from failed ALT seems to be a problem with aftermarket Rota's causing these failures, after coming up to 50 years since I brought my Norton 850 new I am still running my original Rota, my ALT was replace once when the centre keyway bush on my rota failed, that was over 40 years ago, but instead of replacing the rota I got it re bushed but the keyway wasn't cut deep enough and had to file the key down to make if fit on the crank, lucky I had access to a broch set I was able to cut the keyway deeper to fit the key without filing down, but the replacement ALT was a stock Lucas one.
I am still running with that replacement ALT and original rota and I don't pussy my Norton when riding it, I have never machined the rota down and always make sure the clearance is even all the way around, the only problem I had with the replacement ALT is the wires broke just where they come out of the ALT from brittle wiring but was able to dig it out at the ALT and solder new wire leads into it that was done over 35 years ago now and still working fine.
So as I say seem to be the replacement stators are not right, or the end of the cranks not right for even runout, but replacing ALT/Rota's is not cheap was expensive way back when I replace my ALT back 40 years ago, I think it only cost me $20 to re bush my rota at the time.

Ashley

 

[JimNH]

Jim, can you bring it to the next NENO meeting for testing?

I will attempt to make it and if so, will bring the parts.

 

[JimNH]

To me after reading all these faults from failed ALT seems to be a problem with aftermarket Rota's causing these failures, after coming up to 50 years since I brought my Norton 850 new I am still running my original Rota, my ALT was replace once when the centre keyway bush on my rota failed, that was over 40 years ago, but instead of replacing the rota I got it re bushed but the keyway wasn't cut deep enough and had to file the key down to make if fit on the crank, lucky I had access to a broch set I was able to cut the keyway deeper to fit the key without filing down, but the replacement ALT was a stock Lucas one.
I am still running with that replacement ALT and original rota and I don't pussy my Norton when riding it, I have never machined the rota down and always make sure the clearance is even all the way around, the only problem I had with the replacement ALT is the wires broke just where they come out of the ALT from brittle wiring but was able to dig it out at the ALT and solder new wire leads into it that was done over 35 years ago now and still working fine.
So as I say seem to be the replacement stators are not right, or the end of the cranks not right for even runout, but replacing ALT/Rota's is not cheap was expensive way back when I replace my ALT back 40 years ago, I think it only cost me $20 to re bush my rota at the time.

Ashley

I think the problem has appeared with 3 phase and regulators that short the AC windings rather than the original single phase that short the DC through zeners. I could be wrong but remembering and inspecting failed parts it seems the overheating has been electrical rather than mechanical interference. I don't have picture posting.

 

[hybridracer]

For comparison I have measured the stator to rotor radial clearance on the Kokusan 19 Amp alternator fitted to my Commando.
0.030 in.