Lock Washers

[Duccout]

I have today watched a video by Brook Henry of VeeTwo Australia, where he strips a 900 Bevel engine. During the strip he says that the main engine nuts are almost always loose because of the tab washers, which had me initially shaking my head until he explained that because the washers are soft, they are prone to wear, leaving the components on the shaft loose. I must admit that I once found the flywheel nut on my 900 quite loose and put it down to the flywheel having settled on to its taper, and the clutch centre nut also tends to lose tension over time, so perhaps he is right?

I remember Anthony Ainslie telling me that he never uses tab washers, and I know that the Ducati factory has not used them for years, but what is the opinion on here? Nigel? Eldert?


Cheers,

Colin

[blethermaskite]

Colin, I have always used 'new' tab washers on my singles (never owned a V twin ) but I have always used loctite thread lock as well and have never experienced anything getting even remotely slack.....in fact sometimes I wish I hadn't put the loctite on.
Cheers, George

[themoudie]

Aye Colin,

I "lunched" the alternator taper on the 450 early on in my ownership, inspite of nut locking and a lock washer applied to the nut. Never used nut lock on the rotor taper, thank goodness! The problem I found back in 1977 was that the Clymer manual gave no torque values for any of the internal engine nuts and neither did the Haynes manual, when it was published. Hence "tight" was not tight enough, in my case! With a little play, the rotor became slack on the taper that familiar "Clunk, clunk!", the woodruff key locating the crank primary drive gear sheared and the rotor span like a chattering wheel against the taper and the stator! What was tight, without stripping the thread? Having used scaffolding poles to tighten the drive shaft nut on VW Beetles to ~136ft/lbs, I wasn't unfamiliar with torque.

Having been told by race bike owners and other knowledgeable engineers "Just make sure it's tight!"; to the rescue came Nigel, who when I enquired, provided torque values for all the internal engine nuts and the reasons"Why!". As I had feared, applying too much torque can cause as much damage, as insufficient. Since then, whenever re-assembling an engine, or part of, I have used a small amount of nut lock liquid and a new lock washer, having first cleaned all threads, using brake cleaner, then tightened in two stages the nut to the torque recommended by Nigel and turned a tab over against the nut flat, making sure that it was flat and tight against the flat of the nut. To date no further slack nuts, or spinning rotors!

A lock washer, isn't a tab washer and it isn't a sprung washer either! The latter having been advocated by some Ducati spares suppliers, for use rather than lock washers. My limited understanding is that a lock washer is a washer of large diameter than the distance across the nut flats that is malleable and bent against the flat/flats of the nut, it has no extended tabs from its circumference and neither is it dished, as is a sprung washer.

Was it obvious in the video that Brook Henry was refering to "tab washers" or "lock washers"? Semantics, maybe, but ........

I have also stopped using the conventional lock washer on the clutch hub centre nut, as I have found the tabbed lock washer that also fits over one of the clutch hub spring pillars, a more secure fitting.

Inspite of the dry and dusty conditions/salt granules in heaps down the middle of the carriageway, the 450 has been getting aired this past week.

Good health and wear them out, Bill

[Jordan]

If only the alternator rotor did have a Woodruff key. It could have prevented many damaged tapers.
Scored tapers were commonly found on Ducatis that had been worked on by amateurs and backyarders. When I saw a keen d.i.y mechanic attempt to assemble one with no thought to cleaning the tapers, I realised what the main problem was.

Locking tab washers might not be perfect at preventing a nut becoming loose, but they can prevent a possibly catastrophic failure if the nut were to become unthreaded enough.

A spring washer of the usual type that has an angled split cannot be relied upon if up against hardened steel parts. They need to be able to dig in to a softer metal to work. Ideally they should not be used with a plain washer, but that's not always possible.
They are worse than useless with reverse threads unless the angle at the split goes the other way. Those exist but are hard to find.

Loctite is good stuff.

[themoudie]

Aye Jordan, thank you for the "spot", I missed that semantic! Now amended.

Good health, Bill

[Duccout]

Hi Bill,

Brook is talking about lock washers. I remember now also finding the nut loose on the rear camshaft of my 900 the last time that I worked on it. I can see the theory that the engine components can fret against the lock washer and work loose, although this is more likely in racing. My guess is that Eldert and Nigel rely on Loctite, although whether this is due to technical reasons rather than convenience we will have to wait and see.

Colin

[Ventodue]

Fit them if you like authenticity, Colin, but don't rely on them.

Old technology and not efficient.

[LaceyDucati]

I always use tab washers and I've almost never had a nut come loose, including 1000's of miles around the Isle Man TT circuit (done by customers). So as far as I'm concerned they are not the culprit. The only case I recall was early on I had some issues with one engine's clutch center nut. That was quickly identified as poor/incorrect spacers. There are many other issues which can cause nuts to undo:

Incorrect Torque (over and under)
Worn and poor faces
Incorrect spacers
Extra shims
Mismatched tapers
Poor cleanliness
Undersize threads
Damaged or poor thread forms
Incorrect nut material

I also use 243 loctite on threads for extra security, but I don't think it is essential. Thirty five plus years on, I won't be experimenting to solve issues I've not experienced

Regards Nigel

[Duccout]

Thanks Nigel, it is always good to get info from the sharp end! I shall continue to use my lock washers.



Cheers,

Colin