Alternator stator explosion

pierodn · May 26, 2016

I was going to Cesenatico NOC European Rally.
After 250 km, the triplex was broken and the inner carter destroyed.
A lot of smoke of oil and dirty fired plastic.
When i opened the primary carter the stator was completely fused and the rotor did not existed anymore.
The stator was a new Lucas 3 phases and the rotor a new Lucas.
The bike has a Boyer Brandsen 3 phases powerbox in place of rectifier.
I have understood that the triplex chain was broken because the stator was fused and a part of steel was gone to the internal side against the primary chain.
I cannot understand why it happened: from stator and rotor there was clearance enough.
But when i have removed the rotor i have seen that the cranckshaft has a assial play about 1 mm and i can hear the noice of this play.
The crankshaft has two FAG superblend and has a shim on the timing side side.
I cannot post picture now because i am writing with my IPhone driving back at home with autostop on a truck!
I will take my car and trailer, all the new parts, and will go to keep the bike and will try to start again.
Please, let me know, pleace.
Ciao
Piero

grandpaul · May 26, 2016

Crankshaft runout is critical to co-exist with proper rotor-to-stator clearance.

With good clearance and excessive runout, just as bad or worse than no clearance.

pete.v · May 26, 2016

Clearance! Tough to prove now, though.

grandpaul · May 26, 2016

pete.v said:
Clearance! Tough to prove now, though.

From original post:

"I cannot understand why it happened: from stator and rotor there was clearance enough."

pete.v · May 26, 2016

grandpaul said:
pete.v said:

Clearance! Tough to prove now, though.

Click to expand...

From original post:

"I cannot understand why it happened: from stator and rotor there was clearance enough."

Yes, well, seemingly so, at one point in the rotation anyways.

toppy · May 26, 2016

It could be that when tightening the outer primary fixing nut that if the inner primary was not supported correctly by the stud and its shimes the clearance of the rotor may be lost. This is not an uncommon acurance unfortunately don't ask me how i know or what a wrecked Alton Ekit looks like

pete.v · May 26, 2016

pierodn said:
I cannot understand why it happened: from stator and rotor there was clearance enough.

But when i have removed the rotor i have seen that the cranckshaft has a assial play about 1 mm and i can hear the noice of this play.
The crankshaft has two FAG superblend and has a shim on the drive side.

Ciao
Piero

Axial movement of 1mm is not so bad. If it was radial movement, then that would be an issue.

I would loose sleep trying to think of what went wrong for their are a maybe 5 0r so possibilities and no way to validate any of them now. Just do your due diligence when applying you new parts.
One thing you might do is to add threaded inserts to the crank case where the inner primary mounts. This will give you much more available torque to secure your primary and greatly increase its integrity.

kerinorton · May 26, 2016

Piero. What a bummer. 1 mm end play in the crank wont cause the problem you have i would not have thought. I did see you mention you have shimmed the drive side bearing on the crank shaft. i have heard that because the drive side bearing is not held positively to the shaft, it might move and cause the shim to fly apart.[ only the timing side bearing is held to the shaft by the timing gear and oil pump drive. ] That would not cause the problem you have though.
I suggest you check the ability of that Boyer power unit. It may have caused the stator to fry. Who Knows?
Looks like you wont have a chance to meet Mark.

Dereck

pierodn · May 26, 2016

Hi.
Shimming on the timng side, sorry.
I fear that the drive side bearing play into the case.
Before there eas not such assial play.
I can think or the bearing was broken so the longitudinal play
made touch the rotor against the stator or (i dont think) the crankshaft is not stright.
The rotor and 3 phases stator was Lucas new and the Power box 3 phases too.
I would like to open the engine and see into.
Ciao
Piero

gortnipper · May 26, 2016

Ouch. On your new blue SS?

pierodn · May 26, 2016

gortnipper said:
Ouch. On your new blue SS?

Hi.
My SS is tangerine.
My S is fireflake blu.
No, the accident happened to my black fastback.
Ciao
Piero

rivera · May 27, 2016

Sorry to hear that, Piero!
Makes me wonder about the quality of these FAG bearings.

Chris · May 27, 2016

Hi Piero

Sorry to hear your news.
Riverais is correct, plenty of wrong spec superblends out there at the moment!!!!!!!
Have a look at the clutch circlip & spacer washer but I think it will be play at the crank shaft once the engine is bedded in.

Chris

Towner · May 27, 2016

pierodn said:
Before there eas not such assial play

Crankshaft end play of at least 2mm is essential. Maybe the reason.

Ralf

Bernhard · May 27, 2016

Re; “After 250 km, the triplex was broken and the inner carter destroyed.”

Whoa, you actually broke a TRIPLEX chain :?:

This doesn’t sound good at all, I have broken the single chain on my Atlas when I lost the oil, it happened 3 time that weekend, but lucky me, the broken bits didn’t get to the alternator.
Any metal debris getting there will not be good, even if the chain cuts the output wire.

mschmitz57 · May 27, 2016

Sounds like the Lucas rotor cracked and expanded. Even new rotors can fail.
Breaking a triplex primary chain is an impressive feat. Of course if all the swarf from the rotor and stator got into the chain it could have sped-up the failure.

kommando · May 27, 2016

But what type of Lucas was it, an NOS, LAP or a Wassell one boxed Lucas.

mschmitz57 · May 27, 2016

A friend of mine had this happen on a MK3 (primary didn't break though) and the forces were so great that the rotor sheared the woodruff key on the crank end
and proceeded to spin so we were never able to find the woodruff slot in the crankshaft. It was really ugly inside the primary case. Especially with goofy the E-start contraption covered in burned/melted stator swarf. Ugh. What a mess. He ended up having to replace the left side crank half.

I _think_ he forgot to fill the primary with oil so it was bone dry inside. I know they run these things dry with belt conversion but I still think the oil splashing pulls heat away from the rotor+stator. Game-over once it starts rubbing.

pierodn · May 27, 2016

Chris said:
Hi Piero

Sorry to hear your news.
Riverais is correct, plenty of wrong spec superblends out there at the moment!!!!!!!
Have a look at the clutch circlip & spacer washer but I think it will be play at the crank shaft once the engine is bedded in.

Chris

Hi.
The aligment from sprocket and clutch was correct.
I fear is the crankshsft FAG bearing but i eill understand only opened the engine!.
Ciao
Piero

pierodn · May 27, 2016

Bernhard said:
Re; “After 250 km, the triplex was broken and the inner carter destroyed.”

Whoa, you actually broke a TRIPLEX chain :?:

This doesn’t sound good at all, I have broken the single chain on my Atlas when I lost the oil, it happened 3 time that weekend, but lucky me, the broken bits didn’t get to the alternator.
Any metal debris getting there will not be good, even if the chain cuts the output wire.

Hi.
The alternator fused and went into the chain that broken.
Ciao
Piero

Alternator stator explosion

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