Stator Failure

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Bodger

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This is the second Wassell stator to self destruct on my Atlas. (I've posted here because there are more viewers). Never had this problem before. Always used milk container plastic to check clearance. I don't know how it was done with the Wassell since I didn't do the install. What's the diagnosis, inadequate clearance?
 

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I am not sure what I am seeing in your pics, Bodge. Can you describe damage?

If clearance problem, there should be lots of evidence of scuffing on the stator poles and the rotor, plus metal swarf in the primary oil.

Slick
 
Sorry pictures aren't great. They show the inside face of the stator. There is a crack perpendicular across the inner diameter and also cracks/break up across the outer circumference. I don't see any really obvious rubbing/wear marks, but maybe it doesn't take much to cause a problem.
 
I see! Said the blind man!

First thing comes to mind is the dreaded vibration induced fractures attributed to the rightfully or wrongfully excessive Atlas vibration. In my experience, the Atlas shakes are over exagerated.

I have suffered many vibration induced fractures in 85K miles, but never in a stator, except for my original stator that was not epoxy encapsulated. That stator had vibration rub the windings bare until they fried.

Obviously, your alternator output power failed, or else you would not be poking about in the primary. Power would fail if the wires which interconnect the coils were broken, or if the laminated steel plates were to crack. The latter failure would cause the magnetic flux to diminish.

You can ohm out the lead wires for continuity to rule out (or rule in) coil interconnection failure.

I would look for any reason that might enhance vibration such as a loose stator mount. Without more investigation, I am going with vibration as the cause.

Next, I would ask the Forum members if their Wassel stators have been trouble free. With or without favorable replies, I would look for and consider alternate stators.

Keep us informed. Hope you worth it out.

Slick
 
The pictures you sent don't seem to show that the stator/rotor have been cooked or significantly melted or charred, I could be wrong.

I'm a firm believer that checking rotor/stator clearance is best done after establishing the initial, pre-run proper primary chain/belt tension; I like to check clearance every 90 degrees of stator while turning the crank through at least one complete revolution. I also suggest that the primary chain/belt tension be checked again after a good run when hot, especially the belt drive primaries.

If your chain/belt is excessively loose there will be period of time when accelerating when the chain/belt stores the energy, but does not transmit it. When the chain/belt does transmit the power it does so with a spike which may pull the rotor and stator into an intimate relationship. Too tight can present similar symptoms, but hard shifting is usually part of that party and the stator/rotor contact tends to near constant creating melting/charring of the stator.

Be interesting to hear the numbers if you measured the clearance before you removed the alternator components. Are the bosses where the 3 stator support studs mount allowing proper torque on the studs? Are the 3, 1/4-20 bolts that mount the inner primary cover to the engine similarly taking requisite torque? The split in your stator core, depending on depth, could easily change the geometry.

Best wishes.
 
RoadScholar said:
The pictures you sent don't seem to show that the stator/rotor have been cooked or significantly melted or charred, I could be wrong.

I'm a firm believer that checking rotor/stator clearance is best done after establishing the initial, pre-run proper primary chain/belt tension; I like to check clearance every 90 degrees of stator while turning the crank through at least one complete revolution. I also suggest that the primary chain/belt tension be checked again after a good run when hot, especially the belt drive primaries.

If your chain/belt is excessively loose there will be period of time when accelerating when the chain/belt stores the energy, but does not transmit it. When the chain/belt does transmit the power it does so with a spike which may pull the rotor and stator into an intimate relationship. Too tight can present similar symptoms, but hard shifting is usually part of that party and the stator/rotor contact tends to near constant creating melting/charring of the stator.

Be interesting to hear the numbers if you measured the clearance before you removed the alternator components. Are the bosses where the 3 stator support studs mount allowing proper torque on the studs? Are the 3, 1/4-20 bolts that mount the inner primary cover to the engine similarly taking requisite torque? The split in your stator core, depending on depth, could easily change the geometry.

Best wishes.
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Thank all for your comments. Primary cover was off to check timing. I took the opportunity to check stator clearance (unscientifically) with plastic strips and saw that there was clearance but it was not equal. While investigating I observed cracking on inner face of stator and removed it to find the perpendicular cracking shown in the photos. There was no melting or charing. Perhaps that would be the next step if I did not see the cracking? Will now check torque of all fasteners. Also considering relieving the inner circumference of the replacement stator to permit slightly excessive clearance. I'm willing to give up electrical output on a magneto bike in exchange for reliability.
 
There is some wiggle room for the inner cover between the center fixing stud and the 3 bolts that hold the inner cover to the engine. New stator studs may give you more consistent clearance; moving the studs you have to different positions may achieve similar results. Some forum members have had luck with bending the stud(s), but not a good idea to do this with the studs mounted to the inner cover.

If you hone the stator you may be creating more problems than you solve; I've never done this, so I can't say with any certainty.

Additionally, and in my experience, I haven't had many good experiences with Wassell products, although I expect that the majority of stator/rotor sets come from the same manufacturer. I have a couple of OE Lucas rotors that will need to be re-magnetized and you are welcome to one for postage; if that appeals to you PM me and I'll get the ball rolling.
 
I spoke to a British restoration shop once and he said that he had ordered a rotor and a stator for a customer who was being cheap from a supplier of oriental knock offs. They came marked as Wassell. Kind of makes you wonder where and who makes them for Wassell.
 
TMS Motorcycles sell UK made alternatives made on Lucas tooling but not Lucas marked, LAP make them who used to be part of Lucas. It's a strange world when the pattern part is genuine and the genuine part is pattern.
 
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The crack is only in the epoxy. I don't think there is any loss of mechanical integrity. The core is made up of thin iron laminations and they wouldn't crack all the way through.
You really should not hone or file the pole pieces to get clearance because they should not have much of a connection between lams. The filing or honing smears them together and defeats the purpose of a laminated core. I'm not a transformer engineer but was taught a lot by an old master at it in a job long ago.
 
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batrider said:
The crack is only in the epoxy. I don't think there is any loss of mechanical integrity. The core is made up of thin iron laminations and they wouldn't crack all the way through.
You really should not hone or file the pole pieces to get clearance because they should not have much of a connection between lams. The filing or honing smears them together and defeats the purpose of a laminated core. I'm not a transformer engineer but was taught a lot by an old master in a job long ago.
Click to expand...

I agree with your points. I was doubtful the cracks propagated all the way thru the laminated iron plates, but assumed that something had killed the electrical output, causing the OP to open the primary case. He now informs us such is not the case.

Most likely explanation is simple shrinkage in the epoxy. Why not then, if there is no loss of mechanical integrity, or electrical power, to simply close up the primary and run it?

Slick
 
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RoadScholar said:
There is some wiggle room for the inner cover between the center fixing stud and the 3 bolts that hold the inner cover to the engine. New stator studs may give you more consistent clearance; moving the studs you have to different positions may achieve similar results. Some forum members have had luck with bending the stud(s), but not a good idea to do this with the studs mounted to the inner cover.

If you hone the stator you may be creating more problems than you solve; I've never done this, so I can't say with any certainty.

Additionally, and in my experience, I haven't had many good experiences with Wassell products, although I expect that the majority of stator/rotor sets come from the same manufacturer. I have a couple of OE Lucas rotors that will need to be re-magnetized and you are welcome to one for postage; if that appeals to you PM me and I'll get the ball rolling.
Click to expand...
A safer way to bend the 3 studs is to remove them from the 3 fragile inner primary casting points and then thread them into the Z plate where the footrest attaches , then put a nut on and tap at the nut until you can see a little bending starting, then stop. Crude but effective if you choose this method of adjusting clearance between rotor and stator.
 
Bodger said:
This is the second Wassell stator to self destruct on my Atlas. (I've posted here because there are more viewers). Never had this problem before. Always used milk container plastic to check clearance. I don't know how it was done with the Wassell since I didn't do the install. What's the diagnosis, inadequate clearance?
Click to expand...
Bodger said:
This is the second Wassell stator to self destruct on my Atlas. (I've posted here because there are more viewers). Never had this problem before. Always used milk container plastic to check clearance. I don't know how it was done with the Wassell since I didn't do the install. What's the diagnosis, inadequate clearance?
Click to expand...
Hi just seen exactly the same failure on a Wassell stator on a Triumph Daytona 500. Bike is new to me and on a recent Scottish tour I lost most but not quite all of the charge. Inspection showed multiple and serious splitting of the epoxy encapsulant. No obvious signs of rotor to stator contact and I had checked the clearances as part of getting to know the bike.

Failure looks like is down to the epoxy resin not the stator and right now I am wondering if the encapsulant does not have the required chemical resistance and has been affected by the warm to hottish oil. I am using a good quality semi-synthetic oil and this could be more aggressive than a straight mineral oil.?

Right now I am fitting a Sparx stator and rotor once I have that done and run the checks I will section the old stator looking for clues. Maybe I will do a hot oil soak test on some of the epoxy resin.

Looking for a new alternator left me feeling uncomfortable with the options ---- if I need another stator at some point I would try the TMS /LAP route as I had to work at getting the Sparx unit to accept the stator fasteners and the output wire look a little light gauge.

Wassell and green box Lucas did not appeal having read posts from others.
 
Henrynorton said:
Hi just seen exactly the same failure on a Wassell stator on a Triumph Daytona 500. Bike is new to me and on a recent Scottish tour I lost most but not quite all of the charge. Inspection showed multiple and serious splitting of the epoxy encapsulant. No obvious signs of rotor to stator contact and I had checked the clearances as part of getting to know the bike.

Failure looks like is down to the epoxy resin not the stator and right now I am wondering if the encapsulant does not have the required chemical resistance and has been affected by the warm to hottish oil. I am using a good quality semi-synthetic oil and this could be more aggressive than a straight mineral oil.?

Right now I am fitting a Sparx stator and rotor once I have that done and run the checks I will section the old stator looking for clues. Maybe I will do a hot oil soak test on some of the epoxy resin.

Looking for a new alternator left me feeling uncomfortable with the options ---- if I need another stator at some point I would try the TMS /LAP route as I had to work at getting the Sparx unit to accept the stator fasteners and the output wire look a little light gauge.

Wassell and green box Lucas did not appeal having read posts from others.
Click to expand...
Please keep us posted with the results of your investigation. I have decided to go with a green box Lucas. I have been told that the green box Lucas are probably made in Taiwan by an Emgo supplier. At this point I would rather risk Emgo quality than Wassell.
 
Green box = Wassell as they bought the rights to use the name, could be made in Taiwan sourced but maybe not. Sparx have not got a good reputation either.
 
good luck with that. the sparks has probley the worst reputation for quality. i have seen all three parts of there charging system fail. rotor magnets coming out, stator failures with wires burning off at the encapsulation. and regulators fail. JUNK IMHO

Henrynorton said:
Right now I am fitting a Sparx stator and rotor
Click to expand...
 
Are some of the Sparx and other failures caused by overheating due to dry primaries (belt drives)?
Is the epoxy coating on these stators too thin, or chemically inferior to what the factory originally used?
I'm thinking about upgrading my charging system to something like the Sparx 3 phase 220 watt unit, but these failures have put me off.
 
on the sparks i have sen them fail in both dry and wet primary's. the 220 watt rating is also NOT a fair comparison as they rate the output at a higher voltage than the others. also wet or dry has no effect on the rotor slinging the magnets out or the reg. rect. failing. like i stated IMHO the stuff is cheep JUNK.

BritTwit said:
Are some of the Sparx and other failures caused by overheating due to dry primaries (belt drives)?
Is the epoxy coating on these stators too thin, or chemically inferior to what the factory originally used?
I'm thinking about upgrading my charging system to something like the Sparx 3 phase 220 watt unit, but these failures have put me off.
Click to expand...
 
I have had a similar failure with a Wassel stator. As I use similar stators on several of my bikes I had .005 machined off the rotors, it fixed my problem.
 
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