ChrisGamlin
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 posted on 23/9/02 at 12:59 PM |
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Prop problems and Llandow on Saturday
Well, a warning to all, do whatever it takes to ensure your prop bolts cannot possibly escape, ever! At Llandow at the Yahoogroups BEC trackday on
Saturday, my first lap out in anger and down the back straight at around 90mph there is a mighty bang, followed by a small whack on my left elbow and
then total loss of drive. For some reason the diff flange nut had loosened slightly, causing the whole flange to vibrate the four prop bolts clean out
of the flange, even though they were Locktited! The prop smacked against top and bottom of the tunnel, whacking the aluminium transmission tunnel
cover upwards and catching my elbow, but thankfully no injuries and no real damage to the car, just a slightly dented additional vertical tube I put
in the tunnel precisely for the purpose of catching a failed prop, and a scuffed prop tube where it flailed around a bit before I dipped the
clutch.
Anyway, there is a happy ending, we found some spare prop bolts and tightened up the diff flange to take out the slack, and then did over 120 track
miles without any other problem at all, although I am going to rebuild the diff soon as I think there must be something amiss there somewhere.
Chris
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Jasper
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| posted on 23/9/02 at 01:15 PM |
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Scary stuff, gonna be adding some extra tubes in my tranny tunnel this week......
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ChrisGamlin
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| posted on 23/9/02 at 01:27 PM |
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the best thing if you can get it done, rather than weld in additional tubes, is to get lengths of thick aluminium (preferably dural), get them
bent into a U or P shape, then bolt them into the tunnel over each end of the prop so that if it lets go, the prop can only flail around within the
confines of the aluminium.
Although the prop on mine stayed in the tunnel (pretty much), I was still lucky that it didn't damage any of the fuel / brake lines and electrical
gubbins that runs through the tunnel, luckily I routed everything down the edges of the chassis tubes so that pipes were tucked in tight to the
chassis tube and floor, which prevented the flange being able to hit anything too much. If I had run the brake or fuel line on the floor along the
centre of the tunnel it would definitely have severed a pipe.
Chris
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philgregson
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| posted on 23/9/02 at 01:39 PM |
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Scary thing prop failure and not to be under estimated!!
was once in a long wheelbase 12 seat landrover. There were 11 people and the only empty seat was the centre seat in the front.
The next thing we knew there was an almighty bang and the end of a prop shaft apeared through the seat cushion!!!
I've never forgotten this and consequently have been thinking about prop failure protection in my tunnel, as in a locost one sits periously close to
it.
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ChrisGamlin
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| posted on 23/9/02 at 02:52 PM |
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Thats very scary! Luckily mine let go at the "good" end, in that because it went at the back, as soon as I dipped the clutch, it stopped spinning.
If the front prop joint goes, the prop will keep trying to flail around until the car stops, which at 90mph+ is going to take a few seconds at
least.
In mine, I've ensured there is at least one diagonal or vertical tube covering each joint from the driver/passenger compartments, so if any of the
joints fail, in theory it should have to go through at least one steel tube rather than just a bit of 1mm Ali! Having said that, unless you cover your
entire tunnel in thick Dural (unltra tough aluminium) or maybe kevlar sheet of some kind (not exactly low cost!) then its almost impossible to cover
all eventualities.
Chris
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Wadders
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| posted on 23/9/02 at 07:32 PM |
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I have heard of cars actually flipping over
because of the front u.j letting go at speed and the flailing prop digging in to the tarmac, dunno how true this is, but the advice is to fit a
dropwire across the front of the tunnel to keep the prop off the ground.
Alan
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Jon Ison
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| posted on 23/9/02 at 08:33 PM |
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green locktite n snoor washers on mine, hope they do the trick, saw one let go at donnington early this season, messy...... 
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ChrisGamlin
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| posted on 24/9/02 at 08:56 AM |
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quote:
....the advice is to fit a dropwire across the front of the tunnel to keep the prop off the ground.
Alan
Or, if you are building a BEC, simply leave in the tube that goes across the front of the tunnel at the bottom, cant remember what tube its called,
its the one you need to cut out if you're putting in a car engine cos the hooj gearbox would hit it 
Chris
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