Alternator stator.

[Jordan]

No keyway could be so different flywheel magnet positions could be used WRT the bigend. Factory manuals listed what the angle should be for various models, mostly of importance on "energy transfer" type systems without batteries.
It is indeed surprising how the Ducati taper system doesn't seem up to the relatively light duty of retaining a flywheel against its own inertia. I have a 600cc single that relies on just a taper for its transmission powerline - never a problem.

Jordan

[DewCatTea-Bob]

" Here is a picture I put on another post. As you can see the taper is well and truly spun. "

____ I'm sorry I hadn't yet taken time to open your other thread-post on this crankshaft-issue of yours.
Your concern about the damage to it is natural, and such has (unnecessarily) put many Duke-motors out of continued-use (due to the expected expense of full-repair).
And while your particular amount of loose-rotor damage is indeed significant, it's still quite less than the worse I've seen (which could STILL possibly be put-back into use pretty-much as is) !
__ Because many Duke-owners in the past would've otherwise had to junk-out their Duke (rather than try to afford the extensive repair-work of replacing the crankshaft), a number of them instead chose to get-by with the 'spun' damage by simply ignoring it ! - Cuz it was considered to be the cheaper way-to-go.
And somewhat surprisingly, it MOST-often turned-out to have been a non-issue, as the rotor still stayed-put (despite having been spun, to whatever degree).
There's theory to support that the roughened-surfaces become locked-together even more-so than the original smooth-surfaces.
__ What I've most-always done to address the issue (of the spun-surfaces), is to use hard-type emery-tape against the damaged surface (of a spinning crank) just long enough to remove all the peaks (of the damaged-surface),, and also with emery-tape attached to the end of a hand-drill, smooth-away the peaks of the damage within the rotor-hub.
Then press the rotor back-onto the crankshaft as normal (with or without Lock-Tight adhesive).
I've gotten-away with this type of simple/cheap repair-procedure of spun crank & rotor jobs which had become considerably WORSE than yours ! _ And most all the jobs I (and others) have done, did not come loose again any more readily than if those parts had never been 'spun' before ! _ (Although I must admit that over-torquing of the shaft-nut was always practiced, just to help make-sure that the rotor would stay-put !)
So there's really no greatly important reason to be much concerned with that kind of damage (unless you're rich enough to want to have EVERYthing looking pretty, even if ya can't see it after it's all-assembled back-together).


" The eng. shop which is splitting the crank is going to try spiral welding it and then regrinding.
The problem I have is that the rotor is just as bad, so it seemed pointless to put it on a repaired shaft, "

____ INDEED ! - All that work (on the c.shaft) seems to be a waste (of effort & funds) !


" Do you know why there is no woodruff key on the tapered shaft? "

____ Not for certain but, I'm sure it has to do with getting the magnets of the rotor into properly timed position with the crankshaft. _ And (for some unknown reason to me), Ducati didn't consistently place their timing-marks on the rotor-face with consistent respect to magnet-location,, so apparently, they wanted/needed the rotor to be able to be dialed-in, (and that kind of rotor-adjustment can't be done when a keyed-location won't allow it).


Dukaddy-DUKEs,
-Bob

[DewCatTea-Bob]

" I have a 600cc single that relies on just a taper for its transmission powerline - never a problem. "

____ Impressive.
Do you know the size of the associated crank-nut and what pressure it's supposed to be torqued-down to ?


Enlightened-Cheers,
-Bob

[Single duck]

Crankshaft drawing attached. Should be able to figure taper accurately instead of trial and error.

Key & keyway is counterproductive. Clamping force is a function of the degree of taper and the force holding them together. Having a good finish between the two faces certainly helps; lumpy & scored surfaces will NOT clamp to the same degree of efficiency that pristine tapers will.

[Jordan]

What do you see is the minor diameter of the taper?
I'm not sure what is counter-productive about a key?
It could be that the tapers don't hold, only after they've been separated after initial factory assembly. Then maybe reassembled without careful cleaning, and not enough torque on the nut? Anyone know for sure of a flywheel that broke its taper on a factory assembled motor?
Wow, that's 4 questions. Still hungry for knowledge, after decades of owning singles!

Jordan

[Jordan]

" I have a 600cc single that relies on just a taper for its transmission powerline - never a problem. "

____ Impressive.
Do you know the size of the associated crank-nut and what pressure it's supposed to be torqued-down to ?


Enlightened-Cheers,
-Bob

Nut has 7/8" (22mm) thread. It's 5/8" (16mm) thick, and the flats are 33mm across. No specs exist for tightening torque - "bloody tight" seems to be the accepted standard. This is for a Panther M100, a bike usually used with a sidecar.

Jordan

[ducwiz]

Hi Chris,

I have two comments:

- welding the taper might result in micro-cracklings (and deformation as well), as the precise alloy of the shaft is unknown. Metal spraying is thus preferable. >20 years ago the famous german company "Hoeckle" did a similar repair job for me, using this processing. The crankshaft in question is still performing well. Unfortunately, Hoeckle stopped all services on roller/ball bearing crankshafts.
The corners of the key's groove in the shaft are places of stress concentration, i. e. start points of cracks, finally leading to shaft failure. That's why engineers avoid woodruff keys on heavily loaded machine elements.
- the guy in the eng. shop is obviously not an engineer, has no knowledge about shaft-hub joints. A woodruff key is solely intended to fix the angular position between shaft and hub, it shall never carry any shear stress. The engine's torque is carried through the tapered joint, which on the DUCATI flywheel is a bit undersized in my view.

rgds Hans

[DewCatTea-Bob]

____ First I should note that I-myself don't actually have any disagreement with anything stated within Hans's post.
Just have comments which came to mind when reading his post/words.


" The corners of the key's groove in the shaft are places of stress concentration, i. e. start points of cracks, finally leading to shaft failure. That's why engineers avoid woodruff keys on heavily loaded machine elements. "

____ Unlike the crankshaft's primary/drive-gear, the alt.rotor ITSELF is really not solely directly under any forces of power-drive transmission-stress, all on it's very-own,, only directly-under forces of inertia (of it's OWN mass).
Now it may SEEM that Hans's statement is at odds against DUCATI'S "engineers" since Ducati employs a slot/key between the crankshaft & it's drive-gear,, however that key-way is not depended-on to support all the drive-force/torque (from the crankshaft to the primary-gears),, rather, the tight-grip afforded by the friction-pressure between the crankshaft-nut & the pinion-gear & the rotor-hub's rivot-heads (& of-course the tapper-fit as well), is what actually is MOST depended-upon to transmit the drive-force (provided by the engine). _ The key's thickness of steel, itself, no-doubt also comes into play for helping to transmit the power-torque but, it alone, could not be expected to last long under the stress of performing the power-transmission work all by itself.


" A woodruff key is solely intended to fix the angular position between shaft and hub, it shall never carry any shear stress. "

____ As many-others who've removed the primary pinion/drive-gear have found & noted, that steel-key very often does indeed show quite obvious signs of having been under stress !
And that's due to the crankshaft-nut having either come-loose or not having been torqued-down strong enough.
__ In fact, I've seen one or two instances (after the nut had come well loosened), where the key was completely sheered-through (in halves), (in a 450-motor, if not also a 350). _ So rather high torquing-down of the crank-nut is of certain importance !


" The engine's torque is carried through the tapered joint, "

____ Again, while that may SEEM to be false, (as it's rather quite more obvious that it's the drive-gear which directly transmits the torque, rather than the alt.rotor itself), the rotor's tapered-fit against the shaft does indeed HELP transmit the crankshaft-torque (which ends-up powering the rear-wheel),, however the power-transmission though that fitment-connection can't be accomplished without the shaft-nut's equal contribution ! ...
__ (And now if ya understand all this stuff well-enough, this now leads to my belief that the perfection of the mating-surfaces between the shaft & rotor-hub tappers is-NOT so very important. _ Which I'll get back-to covering in my next post here.)


Enlightened-Cheers,
-Bob