second alton starter failure - WTF?

Fast Eddie

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not flaming anyone, but one thing i see in cliffa's photo - the retaining nut, with the flange outward and the belleville washer, appears that the nut does not have a full , 100% thread engagement on the crankshaft. i always try use the minimum 1-1/2 thread showing on the male threads on any fastener.

note, on my Mk2, the retaining nut has full thread engagement w/ some crank thread showing. i also have sufficient clearance to add a bellville washer to the assembly. i would imaging, most likely, no two bikes are the same.

IMG-2724.jpg
If it were mine, I wouldn’t use that serrated bevel washer, removing it a few times will chew up that alloy rotor terribly.
 

cliffa

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What purpose does the lip serve if it's facing outwards?
None, but as I wanted to use a Bellville washer to keep the tension and it would not fit over the lip I reversed the nut. It was 4 years ago and I don't remember if the lip would have fitted between the crank and the sprag anyway.
 

Derek Wilson

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The thought of the clamping load generated on the starter drive being capable of withstanding the starting torque has never sat well in my mind. So I sat down and calculated it this morning. With 70 ft.lb of torque on the nut, the resistive torque before slipping is only about 33 ft.lb, unless all of the clamping surfaces are meticulously cleaned and dried, which may get you up to 100 ft.lb. before slipping. This does not take into account the key.

Depending on the quality of steel in the key, the key can carry between 85-115 ft.lb of torque before starting to fail.

Neither one of these numbers is overly impressive, but it looks to me like the biggest gains would come from assembling the starter drive and spacer completely dry. Somebody had mentioned about retorquing the crankshaft nut, but that would preclude the use of any sort of thread locker on this joint.

The 70 ft.lb torque on this nut is actually less than the Grade 2 recommended bolt torque. As the crankshaft is made of better material than this, it may be more appropriate to use a higher bolt torque. The Grade 8 recommended bolt torque is 93 ft.lb. I would tend to split the difference and go to at a minimum 80 ft.lb. Under ideal conditions (joint clean and dry, nut thread lubricated), this could yield a resistive torque of 150 ft.lb.

Add a good quality key, and you could generate a joint capable of resisting about 260 ft.lb of torque before slipping.

Whether or not this is enough depends on the state of tune of your engine....

Edit: Research into the rules of thumb for starter design shows that our engines need a minimum of 115 ft.lb just to overcome static friction and spin up to 100 RPM. Most starters are designed to output at least 3-4 times this. This means that the starter at stall (or engine kickback) could easily overcome the resistive force at this bolted/keyed joint, even under the best of conditions.

I think I am going to continue with my design.

FWIW.
 
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cliffa

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" i would imaging, most likely, no two bikes are the same ".

IMG-2724.jpg
They may have been when they left the factory, but who knows what has been changed in the intervening years. For example mine has a Norvil belt drive and a Maney outrigger within the primary.
 

Fast Eddie

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They may have been when they left the factory, but who knows what has been changed in the intervening years. For example mine has a Norvil belt drive and a Maney outrigger within the primary.
Does that mean you run the primary dry Cliffa?
 

baz

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Did a little more work this morning - this looks easier to make:
View attachment 80302

Two changes:
1. Hex replaced by 2 drive tangs (5/8" wide, ~1/2" of engagement) - easier to produce
2. Countersunk screws holding drive member to main engine sprocket replaced by low head socket head screws - can loosen tolerances,

FWIW
With the greatest of respect I think you are over thinking this drive unit
I own Yves old system and it works perfectly
I had to modify it a bit more because he was running a chain primary
And I'm running a belt drive
I remade the adaptor plate plate out of an old handrail bracket (the bit with 3 woodscrew holes) I already had the sprag clutch that Yves had ground two flats on
 

Derek Wilson

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With the greatest of respect I think you are over thinking this drive unit
I own Yves old system and it works perfectly
I had to modify it a bit more because he was running a chain primary
And I'm running a belt drive
I remade the adaptor plate plate out of an old handrail bracket (the bit with 3 woodscrew holes) I already had the sprag clutch that Yves had ground two flats on
As I like to say, anything worth doing is worth over doing - LOL!!

I just do not ever want to experience the failures that I have had ever again. And my bike, my money, my shop, my time, my steel - so my rules :cool:

Good to know that the Yves fix is still serving well - gives me confidence that the work that I am doing will be successful.

Cheers!
 
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cliffa

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As I like to say, anything worth doing is worth over doing - LOL!!

I just do not ever want to experience the failures that I have had ever again. And my bike, my money, my shop, my time, my steel - so my rules :cool:

Good to know that the Yves fix is till serving well - gives me confidence that the work that I am doing will be successful.

Cheers!
Maybe you could be persuaded to do a run of them ? ;)
 

baz

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As I like to say, anything worth doing is worth over doing - LOL!!

I just do not ever want to experience the failures that I have had ever again. And my bike, my money, my shop, my time, my steel - so my rules :cool:

Good to know that the Yves fix is till serving well - gives me confidence that the work that I am doing will be successful.

Cheers!
I was lucky to have Yves setup to copy ,as I said in an earlier post I also incorporated the alternator Woodruff key
I'll post some photos
 

baz

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As I like to say, anything worth doing is worth over doing - LOL!!

I just do not ever want to experience the failures that I have had ever again. And my bike, my money, my shop, my time, my steel - so my rules :cool:

Good to know that the Yves fix is till serving well - gives me confidence that the work that I am doing will be successful.

Cheers!
Real engineers should avert their eyes, all you are making is a big washer with 2 driving flats
It's a couple of hours work
I made the disc big enough to act as the belt guide on the engine pulley
I've been running it for over two years with many many starts and no problems as yet
I took it apart recently when I changed the gearbox sprocket
It was good to see everything working perfectly
I also have the iwis big pin chain from the chain man fitted
 

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Derek Wilson

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Maybe you could be persuaded to do a run of them ? ;)
I think I want to try it out first, but if it works, I might entertain it. I really don't want to run these in volume, so I would be looking for a machine shop to make them. I will keep folks posted.

I sent my models to Paul at Alton a couple of months ago for his review, and apparently they are under consideration. That would be best course of action - Alton incorporating them into the design. I really have no desire to make money off of this or take any credit for it - I just want to see some product improvements.
 
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got an email back from alton -

Hello Joe,

Step flange inboard (toward the engine)
Make sure the nut is fully backed against the « rotor » flange when tightened. Normally it goes without washer.

Kind regards

Maxime
 
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