part 2 - second alton starter failure - the fix

joe czech

joe czech

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incorporating the "yves norton seeley" fix into my Mk2. my friend knocked out the spacer part in short order from 4140 tool steel. next step, machining the flats on the sprag clutch assembly, and finalizing the fix by transferring drive pins from the engine sprocket to the spacer. will post photos as progress continues...

part 2 - second alton starter failure - the fix


hope to put an end to this "alton starter-sheared woodruff key' issue once and for all.
 
I have only seen my original chain drive and then the subsequent replacement with a CNW starter, but if the Alton drive is from the stator woodruff key, could it not be additionally bolted through the 2 bolt holes in the drive sprocket?
 
Landspeedracer said:
I have only seen my original chain drive and then the subsequent replacement with a CNW starter, but if the Alton drive is from the stator woodruff key, could it not be additionally bolted through the 2 bolt holes in the drive sprocket?
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that is one of the features of Yves' mod.
 
Landspeedracer said:
I have only seen my original chain drive and then the subsequent replacement with a CNW starter, but if the Alton drive is from the stator woodruff key, could it not be additionally bolted through the 2 bolt holes in the drive sprocket?
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if i understand what you are saying, the answer is yes. although not bolted, but two pins are threaded into the engine sprocket, and slip fit into mating holes in the newly designed spacer. kind of a neat design. from yves original design, two temporary threaded pins are fab'd to locate the mating holes in the spacer. when complete, the whole assembly is held together with the retaining nut. reference - https://www.accessnorton.com/Norton...-solution-for-broken-woodruff-key-2017.24163/
 
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This is an interesting thread and thanks for sharing your project.
Is the steel the woodruff key is composed of too soft/weak/brittle allowing it to shear? I'm asking because is seems that it would take a lot of pressure or torque or force or whatever to snap the top of the key across its groove into two or more pieces.
I have seen woodruff keys sheared in a variety of applications but there always was a reason for it...have you pinned down what was causing it to shear in your Alton installation?
 
Lineslinger said:
This is an interesting thread and thanks for sharing your project.
Is the steel the woodruff key is composed of too soft/weak/brittle allowing it to shear? I'm asking because is seems that it would take a lot of pressure or torque or force or whatever to snap the top of the key across its groove into two or more pieces.
I have seen woodruff keys sheared in a variety of applications but there always was a reason for it...have you pinned down what was causing it to shear in your Alton installation?
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The woodruff key is the correct material for its designed load, ie to locate the rotor so the timing mark is in a consistent position. Its not the keys fault Alton took it upon themselves to design a setup where if the mainshaft nut loosens off the starter drive goes through the key.
 
kommando said:
The woodruff key is the correct material for its designed load, ie to locate the rotor so the timing mark is in a consistent position. Its not the keys fault Alton took it upon themselves to design a setup where if the mainshaft nut loosens off the starter drive goes through the key.
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bingo. very correct - the whole alton design relies on the clamping force of a single, low profile, 5/8-20 nut. OK in a perfect world, but in a real world, as you said, "if the mainshaft nut loosens...", the force of everything falls on the key. not the key's purpose, and not designed to take those kind of loads. the question is, why do some folks experience this failure, and some don't? the alton folks rely on the nut's torque being sufficient, but IMO, and experience, sounds like it's hit or miss. the design might need something as simple as adding a belleville washer and upping the torque value, seems, the yves design provides a "solid" fix to whatever is the core problem.
 
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kommando said:
The woodruff key is the correct material for its designed load, ie to locate the rotor so the timing mark is in a consistent position. Its not the keys fault Alton took it upon themselves to design a setup where if the mainshaft nut loosens off the starter drive goes through the key.
Click to expand...

The modifications made look like a good solution...too bad one needs to develop all those fixes, especially when considering the costs involved in the upgrade.
 
It seems the "hit and miss" property in the Alton failures is down to proper assembly by the installer, using all correctly matched/spec bits; which SHOULD result in a properly torqued nut, maintaining a proper morse taper friction fit, supported by a proper woodruff key.

Sure seems to me that all of this nicely machined "fix" can still result in a sheared key if the clamping nut isn't properly torqued, or if some other malady results in the slightest misfit which will allow the assembled parts to eventually give the nut a double decimal fraction of space to loosen up with. It all relies on the maintained morse taper friction fit, or the key will STILL do it's job...
 
If you do the mod the way I did it you are using the original Alton setup IE the clamping force of the nut against the rotor/woodruff key plus the Yves conversion
 
grandpaul said:
It seems the "hit and miss" property in the Alton failures is down to proper assembly by the installer, using all correctly matched/spec bits; which SHOULD result in a properly torqued nut, maintaining a proper morse taper friction fit, supported by a proper woodruff key.
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as to the "hit or miss failure" and the "proper assembly by the installer" comment. i may not be the best mechanic in rhe world, but i can tell you that, in reference to my second failure, it "was" done by the book. my gut feeling is the root problem lies in the retaining nut and the small step flange. there could be issues with the manufacturing tolerance of the spacer, and tolerance stack-up of the components. throw in norton's piece/part tolerance and stack-up, and the whole design may just be on the ragged edge. without access to norton and alton's design drawings, it is impossible to pin point the problem. i think my issues lie in the retaining nut's step flange, and the mating step on the crankshaft. if those surfaces engage, ever so slightly, and before the retaining nut's full and proper torque is achieved, there may be insufficient clamping force by the retaining nut on the assembly. i'm thinking i could solve the problem by installing a belleville washer, but if i have a third woodruff failure, it might screw up my crankshaft beyond the point of on-bike repair. i'm relying on the yves fix to solve the problem.
 
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I think GPs point was that even with the Yves fix, you still need to ensure you have full and proper clamping force on the components. If not, your taper might not seat correctly and it might then be that woodruff key that goes, and if it does, your crank taper is f*ucked.

So, even with the Yves fix, you gotta get to the bottom of your stepped nut / thread depth theory and fix it.
 
Hi
I've been following this thread with interest although I am now 2 years in with my Alton and well pleased with it. Looking at the machined spacer would it not be equally effective to make it in one piece and just slot the end to engage / lock on the back of the spag assembly? All other details could remain as shown


Please go easy on me, I am not an engineer but an accountant and we all know they were responsible for the down fall on the British motorcycle industry
 
nortonmews said:
Hi
I've been following this thread with interest although I am now 2 years in with my Alton and well pleased with it. Looking at the machined spacer would it not be equally effective to make it in one piece and just slot the end to engage / lock on the back of the spag assembly? All other details could remain as shown


Please go easy on me, I am not an engineer but an accountant and we all know they were responsible for the down fall on the British motorcycle industry
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Not quite sure what you mean? The Yves type spacer does lock on the back of the sprag
 
Fast Eddie said:
I think GPs point was that even with the Yves fix, you still need to ensure you have full and proper clamping force on the components. If not, your taper might not seat correctly and it might then be that woodruff key that goes, and if it does, your crank taper is f*ucked.

So, even with the Yves fix, you gotta get to the bottom of your stepped nut / thread depth theory and fix it.
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i agree, the yves design may not be a 100% solution fix to the problem, but IMO, an improvement to the original alton design. i'm thinking a washer will address my retaining nut's step flange concern. i know someone had issues with using a serrated belleville washer, but that's tha route i'm taking. either way, if i have one more failure, my crank may be toast. i have do everything and anything, and whatever it takes to get this right.
 
joe czech said:
i agree, the yves design may not be a 100% solution fix to the problem, but IMO, an improvement to the original alton design. i'm thinking a washer will address my retaining nut's step flange concern. i know someone had issues with using a serrated belleville washer, but that's tha route i'm taking. either way, if i have one more failure, my crank may be toast. i have do everything and anything, and whatever it takes to get this right.
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I use a plain washer and 648 loctite
 
baz said:
Not quite sure what you mean? The Yves type spacer does lock on the back of the sprag
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once the two flats are machined on the back of the sprag clutck assembly, it locks onto the corresponding flats on the spacer. once the whole assembly is bolted together, it distributed any load that the woodruff key may see and distributes it to the two spacer flats and two engine sprocket pins. with the double locking feature of the serrated belleville washer and thread locker, well if this thing fails again, then i give up. as they say, sometimes the dragon wins!
 
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