I have a 2-piece prop in my Se7en BEC conversion (no reverser) and something I want to make sure is that there is enough protection in the event of a
prop failure.
Where the front prop mates to the adapter on the gearbox output, there is plenty of steel tubing around the footwells.
Where the rear prop mates to the diff flange (live axle) I have had a steel 'hoop' made, which goes over the prop and would stop it flying
into the cockpit!
How about the joints with the centre-bearing though? Is it possible for one of the props to become unattached here (not really sure what the internals
of the CB are)?
Cheers!
I guess anything is possible but Ive not heard of a BEC style prop failing in the middle, in fact Im not sure Ive ever actually heard of one failing
at all, only bolts coming loose or the flanges themselves breaking the retaining bolt and coming loose.
If you do want to put in something I would be inclined to concentrate on the area behind the centre bearing rather than in front, because if you have
a failure where the front half of the prop flails around whilst attached to the engine, it will not have as much energy going through it and will stop
flailing as soon as you kill the engine, whereas if the joint on the rear half fails, the whole car is forcing the flailing prop to rotate until you
either lock the wheels up, it digs into the road, or you stop the car totally.
At the rear of the tunnel though, where it attaches to the live axle I would think about a bar across the tunnel to stop the prop coming upwards in
the event of the rear bolts coming loose or the flange failing. I had exactly this happen at about 95mph down the back straight at LLandow and
although the tunnel retained the prop fine, the prop flange put a 1/2" high dent in the ally tunnel cover and just tapped my elbow enough to make
a bruise 
Also think about the positioning of your brake / fuel lines through the tunnel so as not to be in the firing line if one does let go. You can tuck
them as tightly into the corners as possible and maybe putting some kind of shroud over them in line with the ends of the prop, because the last thing
you want as well as a prop bashing the car to bits, is no brakes to stop it and fuel p1ssing out about 6" from your arse!
We are all DOOMED. DON'T PANIC.
WOMEN AND CHILDREN FIRST
I will too frightened to use my car if any more comments like the above are made.
How often do these things happen? 
Not very often hence my opening comment, as long as you're religious at checking the bolts etc and use the proper grade and type of nuts / bolts
(e.g K-nuts) with a liberal dose of threadlock, there's little chance of anything going wrong.
Having said that, you wouldnt want to be in the way if a prop did decide to let go, so it makes sense to take a few simple precautions to minimise the
risk.
heres what can happen though........
Rescued attachment prop.jpg
this was the seat.......... lucky ?
Rescued attachment prop2.jpg
quote:
Originally posted by ChrisGamlin
I guess anything is possible but Ive not heard of a BEC style prop failing in the middle, in fact Im not sure Ive ever actually heard of one failing at all, only bolts coming loose or the flanges themselves breaking the retaining bolt and coming loose.
Yep, sorry should have qualified that comment by saying that Id not seen any 2 piece props fail in the middle, I remember Pete's single piece one in the early days that failed.