Head Fin Ringing

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Tornado

Tornado

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Has anyone heard of using some kind of inserts between head fins to eliminate vibrational ringing? I"ve seen this on other aircooled bikes in the past. Is this ringing a thing on Commando heads?
 
My 900 Ducati has little rubber disks stuffed between the fins, but the clutch is so loud, I doubt if the vibrating fins add anything to the overall noise level.
-George
 
Between the valves and exhaust note I've never noticed any ringing. I suspect the roughness of the Norton head castings as opposed to the smoother thinner fins on other makes may have something to do with it as well.
 
Seems RE and Triumphs of certain era's had these. Even came across a fairly modern dirt bike forum discussing them.

One point, perhaps makers added them to help pass the noise level requirements. Plus, there is a known phenomenon that we lose higher frequency hearing as we age. So perhaps all us oldies just cannot hear the ringing (masked by our tinnitus problems!).
 
Never really worried about the ringing from a commando engine because they are relatively quiet
But I did once do this to a big bore BSA b25/T25 engine , now they really do ring and clatter !!
I used a sheet of hard rubber that I punched out discs of rubber with a wad punch about 20mm diameter and 5mm thick from memory
The problem is getting them into the fins ! You can't just push them in with a screwdriver
I had to make a tool from a piece of flat bar that would fit into the fins and fitted the diameter of the discs
Even then it's fiddly
I fitted them in all four corners of the barrel and head
It did make a difference to the engine noise , with the valve clearance set to zero and the discs fitted it was almost as quiet as an air cooled Japanese bike
 
So is it a real ringing noise you would hear or just an amplification of valve train clatter? Do they need to be fitted between every fin? Just curious because my hearing has never been that acute even when I was in my 20s.
 
Found an actual research study on fin resonance dampers:



Head Fin Ringing
 
Triumph did it differently.

They joined the front of the fins together with the casting. At the rear they drilled through vertically and inserted a cylindrical rubber damper through all the fins.

They must have done this cos they felt the need, the casting was added early, but the rubber ‘peg’ was on later bikes when they were chasing noise regs and had fitted quieter silencers.

Personally, I’d be surprised if it made any difference on a Norton running peashooters, but I’d be very interested in your findings if you do experiment with this. Just don’t let it lead to broken fins !!

Some pics of the a late Triumph, zoom in and you can see the casting linking the fins at the front and the cylindrical ‘peg’ at the rear…

A4F96C5A-F547-4613-8D38-7AE7F4A8440A.jpeg
C7751359-68FE-428B-A15E-792AB81D6E27.jpeg
 
A bit of Johnnie Walker Green for me--Glenlivet in a pinch. An Arturo Fuente if the task requires lots of thinking! Nice hammer/mallet.
 
A shot of Four Roses, a can of PBR and a 14 ounce ball peen.......oh wait....thought I was working on a Chevy
 
I hate to change the subject here but- I never noticed any ringing from the head on my bike until I added an extra inch of fin for more cooling. Then you could hear it from a block away. Silicone rubber blocks fixed it -now I just need to find some silicone that is a better color.....
Head Fin Ringing
 
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