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Re: [ST] Re: Possible bad Triumph valve design



There are several methods possible.  Some engines use double and triple 
spring sets; each spring has a different rate so the whole doesn't 
resonate.  Another way is to select a spring rate and preload that 
doesn't resonate in the rpm range of the engine.  This last method, 
while not "damping" is actually the most common method of resonance 
control.

I have not seen it happen, but I read that valve float, aka that 
"resonance" stuff, sends the springs into such a tizzy that they exceed 
their yield strength and are forevermore weakened.  That makes them more 
suseptible to further float.  Mike Benzon's Triumph with the cupped 
valves had a bunch of miles, as I remember.  That sort of sets the stage 
for weak springs from heat and fatigue.

Engine designer always want to use the lightest springs they can to 
limit wear and friction.  If Mike's springs were on the light end of 
tolerance, he might have slowly worked into the cupping over time.

Mike, be sure to keep the springs, retainers and keepers for Triumph to 
test.

Philip Las Gourgues wrote:
> John wrote:
> 
>>The most common method is to put a spiral wound piece of flat steel on
>>the inside of the spring the rubs its I.D. and kills resonance.
> 
> 
> Ah, thanks for that. Is some form of damping used in most motorcycle
> engines? I don't remember seeing any in my TT250 which is the only engine
> I've stripped down that far but I could have just missed seeing it.
> 
> Phil


- -- 
John Albright
'02 RS
Chattanooga
C-RATs Pack Leader


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