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ENGINE HARMONY

 

 

What's the most misunderstood and ignored engine part under the hood of your of your machine?  The harmonic damper or balancer.

 

 

I suspected that the harmonic damper could be the cause of an annoying harshness that was part noise and part vibration and which seemed to be in everything from the ash tray to the tyres in my 38 Packard straight 8.  

 

 

Problem is you can't call a part defective when you have no idea how it works or what it does.  I served my mechanic apprenticeship some years ago at South Auckland Motors (Ford) where this engine part was never mentioned on the floor or in any training material - if it's not giving a problem you don't get told about it.  

 

 

Having had no luck in trying to find the information I needed within the trade, I then Googled it on the internet and hey presto.  If you are looking for something you never expect to find it on your own door step but the solution was!  

 

 

Harmonic Damper Rebuilds Ltd 07 863 3350 (John Mallett) is in Waihi and he overhauls and services harmonic dampers.  After talking to John about my 38Packard straight 8 damper – all my questions were answered. 

 

 

John explained the damper's job as follows: 

 

 


'All objects have a natural frequency that they resonate or vibrate at when struck. An everyday example of this is a tuning fork. The sound that a particular fork makes is directly related to the frequency that it is vibrating at.

 

 

Crankshafts twist back and forth a small amount every time a cylinder has a power stroke. This motion is complicated because the amplitude of the vibration varies along the shaft. Eg. the combustion process bending the con rod is one of the complications. The crankshaft will experience torsional vibrations of the greatest amplitude at the point furtherest from the flywheel or load.'

 

 

 

 

 

These forces are absorbed and neutralized by the damper.  

 

 

If the damper is seized as it was on my Packard 8 not only is driving it a little unpleasant but I was risking bearing and or crankshaft failure.

 

 

 

 

 

Consider these points:

 

 

1) The more con rods an engine has, the more capacity the damper needs to have.

 

 

2) If a manual trans is replaced with an auto trans the damper spec could well be different.

 

 

3) The length and number of main bearings a crankshaft has determines the dampers capacity.

 

 

4) Horizontally opposed 4 cylinder engines although small rely on dampers due to con rod layout and distance between main bearings. 

 

 


‘By the way the Packard delivered the bride very smoothly!’

 

 

 

Cheers

 

Nigel