.

=

Not an inane question at all. Although there are undoubtedly far more technical reasons involved, here's my two cents. Believe the rule of thumb is to use a flat washer next to soft aluminum between the split ring lock washer and bolt head to avoid gouging the soft part. With that said, however, the handlebar parts diagrams seem to show only an 8mm "spring washer" used with the hold down clamp bolts (presume this means a split lock washer). Nevertheless, adding a flat washer (go first class with stainless steel) would seem okay to me. My primitive understanding about lock washer function is not based on their bite into the material, but for the purpose of causing and maintaining thread tension decreasing the tendency to spontaneously loosen over time due to vibration, etc., so this function would continue application regardless of flat washer use also (I could be wrong here). In any event, regardless of washer or combination of washers or even without any washer, I believe you would notice an undue loosening of the handlebar long before it became a dangerous condition. Leaving the bars just barely loose enough for slight rotation while riding may help you find the "perfect" position and thereafter snugged down more tightly (with re-adjustment of the rearview mirrors). I like using stainless steel fasteners whenever their use is permissible because they don't rust and look really cool. So go ahead, use the flat stainless steel washers and use stainless steel lock washers too. Happy Trails.

On critical parts like handlebars, I'm going with bite versus spring tension. Once you compress the washer the spring tension is gone and you only have the bolt torque and the lock washer.

David

Here you go. 9.8 megabytes of fastener know how assembled for your reading pleasure as the...

NASA Fastener Design Manual

Post edited by: Duck, at: 2006/10/31 16:38

Thanks for the NASA link. After some donking around on the net I marvel at the plethora of theories and opinions on split lock washers which range from being a totally worthless item designed by the devil (closest to the NASA view) to the proper remedy for keeping a Rambler starter from loosening and falling off (see following link somewhat questioning the NASA view).



www.straightdope.com/mailbag/mwasher.html



Wonder what those Kawasaki engineers had in mind, what with all those lock washers on the bolts for triple clamps, brake calipers, handlebar holders, etc.? :laugh:


As to experience regarding washers on handlebar holders, have for many years and miles on the 900LTD used both stainless lock and flat washers and only flat washers on the Z1, with never a hint of any spontaneous loosening, and with no digging into the soft aluminum holder caps. Certainly can't presume to question NASA, but am not yet quite prepared to ditch all the OEM lock washers.


Whatdaya say we keep on riding and testing for another 33 years or so and then have a few drinks reviewing the matter??

My nutshell interpretation of the NASA paper.

I read the NASA split lockwasher as reverting to a flat washer when flat. It no longer bites. It's still a washer.

Friction on the threads is what holds the fastener in place but the friction goes away if the threads are unloaded from flex or thermal cycling.

For washers...

If the fastener is hard and the surface is soft or irregular, use a flat washer to prevent unloading as the soft/irregular material deforms.

If the material is subject to enough dimensional change from flexing or temperature changes to unload the threads, use a spring washer to keep the them loaded. If the bearing surface is soft, use a flat washer under the spring washer.

If it will do the job and you need a lock, a washer that will bite into the fastener and the bearing surface is an option.

Otherwise...

If you need something that is subject to loosening from thermal or mechanical action locked, one of the other methods described in the NASA paper may be more prudent than a washer.

-Duck





That's what I got out of the NASA stuff.

Post edited by: Duck, at: 2006/11/01 13:47