Originally Posted by
Martin-Hadland
I'm torn between taking the simple route of using a one piece propshaft and using a split prop on my Firenza, anyone have any useful input to make on this bearing in mind I'm using a live axle and the prop will be 45" overal length?
My concerns are vibration and noise transmission.
I did originally try a one piece prop on my Escort but I swapped it for a split one because I was getting a vibration, this disapeared when the second prop was fitted.
Critical speed is the most important thing you need to consider when deciding 1 or 2 piece ( and overall strength I guess )
A long shaft can only be spun so fast before it reaches it's critical speed and will explode due to resonance.
Just picture trying to spin a flag pole and you'll understand. The vibrations and resonances may not be visible on a prop, but they will be felt ( and when you feel it, it is horrific )
Long shaft = bad
Thin shaft = bad
Alloy or composite shafts will have a higher critical speed for any given length or diameter
2 piece shafts are effectively 2 x short shafts so their critical speed will be much higher.
So you need to determine the shaft length you require, and the maximum shaft speed you will ever see. Then you can decide which is most suitable.
And either way, due to the live axle there will need to be a slip mechanism on the shaft somewhere ( although T56 has this already if you're using it )