iank
|
| posted on 25/9/09 at 12:54 PM |
|
|
quote:
Originally posted by twybrow
quote:
Originally posted by iiyama
^^^ No!
Kevlar will probably do the trick in stopping any shrapnel but it wouldnt stop a prop. Carbon definatly wouldnt stop anything, in fact it would
shatter sending even more shrapnel your way........
That failiure looks well dodgy......
Where do people get this opinion from, that carbon fibre laminates are as brittle as a sheet of glass!? I make/develop primary aerospace CF parts,
including test firing 8lb birds, travelling at several hundred miles an hour into the parts - you would be amazed at what a well designed composite
part can withstand.
Well I suspect people get that idea from watching every f1 crash which leaves splinters and shards of cf all over the track, it is certainly more
brittle than a mild steel hoop.
I suspect a flailing steel tube at 7000rpm and an 8lb bird at 100's of miles an hour are going to cause any test piece to fail in completely
different ways.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
|
|
|
|
|
NS Dev
|
| posted on 26/9/09 at 02:29 PM |
|
|
quote:
Originally posted by MikeRJ
I read this in PPC last night, and he mentions that there was a lot of vibration from an "unbalanced wheel" during mapping, and that the
welds on the prop held up ok.
I suspect the vibration was far more likely the prop was already bent/unbalanced, and you can see the prop has failed right next to a weld in the
pictures.
Prop failures are almost unheard of in road cars, the only reason they can be failing in kit cars is faulty manufacture (unlikely if professionally
done) or incorrect installation e.g. not enough of the sliding joint in the gearbox, incorrect flanges, loose bolts etc.
Completely correct!
Read the article myself the other night, and yep, it would have been prop inbalance that he was feeling.
Whether it was just out of balance, bent, or welded up out of alignment is now a matter for debate, but, in answer to the "reinforced
tunnel" brigade, what about side impact on the road, object through an ally floor, the list goes on, if you want something safe sell your locost
and buy a VW Golf.
Fact is, if you make it right it won't fail.
There have been a few prop failures on Caterhams in our race series (R400 superlights) but these have either been on crashed cars that have been
repaired (suspect bent prop) or on cars that have had big spins at 130mph or wheel to wheel contact, all of which severely stress the
transmission.
The balance thing is REALLY critical on most sevens, as the prop is smaller diameter that you would normally choose to use, so while its perfectly
strong enough,its not very resistant to whip created by imbalance, which then makes it lose nearly all its torsional strength. Its loading becomes
partially bending, which on a rotating shaft tries to twist it up, just like in the pics from PPC.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
|
|
|
livelee
|
| posted on 26/9/09 at 03:26 PM |
|
|
Do we know what make of car the shaft was on?
|
|
|
rusty nuts
|
| posted on 26/9/09 at 06:36 PM |
|
|
Makes you wonder about the quality of the steel used? Cheap Chinese? Glad I had mine made by Bailey Morris , at least it should be decent
|
|
|
jacko
|
| posted on 26/9/09 at 07:06 PM |
|
|
If the gearbox seized and the drive wheels kept turning would this happen?
|
|
|
rusty nuts
|
| posted on 26/9/09 at 07:08 PM |
|
|
quote:
Originally posted by jacko
If the gearbox seized and the drive wheels kept turning would this happen?
Unlikely IMHO . Can't say I've ever known a gearbox to sieze especially without warning
|
|
|
Liam
|
| posted on 26/9/09 at 07:50 PM |
|
|
Eek - makes me more concerned about the one I'll have running down me leg to the front. As I'm a paranoid bugger, I've been
considering for a while retaining rings I've seen in drag racers etc. Seem to be popular stateside.
|
|
|
bartonp
|
| posted on 25/2/13 at 01:09 PM |
|
|
quote:
Originally posted by rusty nuts
quote:
Originally posted by jacko
If the gearbox seized and the drive wheels kept turning would this happen?
Unlikely IMHO . Can't say I've ever known a gearbox to sieze especially without warning
Selector failure can sieze a 'box, usually only while changing gear tho.
|
|
|
Padstar
|
| posted on 25/2/13 at 01:47 PM |
|
|
Very unpleasant.
I dont plan to use a DIY prop, but given that i am just completing my chassis and it is yet to eb painted, is there any mileage in adding a few more
stell tubes into the tunnel wall? Would this prevent it entering the seating area if it failed?
|
|
|
loggyboy
|
| posted on 25/2/13 at 01:53 PM |
|
|
Simplest, cheapest, lightest and most effective way is to add a catcher or 2.
I made mine up mid build:
http://locostbuilders.co.uk/viewthread.php?tid=165585
Mistral Motorsport
|
|
|
britishtrident
|
| posted on 25/2/13 at 03:03 PM |
|
|
quote:
Originally posted by twybrow
quote:
Originally posted by iiyama
^^^ No!
Kevlar will probably do the trick in stopping any shrapnel but it wouldnt stop a prop. Carbon definatly wouldnt stop anything, in fact it would
shatter sending even more shrapnel your way........
That failiure looks well dodgy......
Where do people get this opinion from, that carbon fibre laminates are as brittle as a sheet of glass!? I make/develop primary aerospace CF parts,
including test firing 8lb birds, travelling at several hundred miles an hour into the parts - you would be amazed at what a well designed composite
part can withstand.
With laminates something as minor as dropping a screw driver on to an aircraft composite panel can cause major damage, often unseen because it is
on the reverse side from the impact.
Key word is well designed, pure CF as used in the original 1970's Hyfil is so brittle it is rarely if ever used these days Modern CG
components nearly always use the more elastic Kevlar and Glass in combination with Carbon fibres.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
britishtrident
|
| posted on 25/2/13 at 03:11 PM |
|
|
More than ten years back access to a suitable press I toyed with the idea of making the tunnel out of folded heavy gauge steel to act as a backbone
but the access and weight issues put me off.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
Furyous
|
| posted on 25/2/13 at 10:26 PM |
|
|
quote:
Originally posted by loggyboy
Simplest, cheapest, lightest and most effective way is to add a catcher or 2.
I made mine up mid build:
http://locostbuilders.co.uk/viewthread.php?tid=165585
Prop catchers are a requirement in New Zealand to get kit cars registered for the road. This thread makes me think it's not such a bad idea.
|
|
|
rick q
|
| posted on 26/2/13 at 03:27 AM |
|
|
I've had a prop shaft fail [my mistake - allowed the welds to be too thin] and the damage was significant, thogh fortunately not to me as the
prop catchers did their thing. If you look closely, apart from the scoring around the shaft at the hoops, look at the flattened the steel tube that
holds my fuel and wiring [adjacent the diff nose ] :-
|
|
|
Dick Axtell
|
| posted on 26/2/13 at 09:37 AM |
|
|
quote:
Originally posted by coozer
Another lesson in NOT making your own prop, best left to the professionals. Not that I'm saying it was homemade mind you...
Agreed. Definitely one item best left to the experts. These guys - http://www.davemacprops.com/DMPHOME.html - did mine. they also make some
for Land Rover, and other major customers.
BTW - Have seen 1 p/shaft fail on the road, although it was at low speed, thankfully. "Failure" was due to front flange nuts coming
undone! On a well-used (i.e. never-serviced!!) Transit.
Noticed rick q's post above. That failure, at the rear flange, looks worrying. Not seen that one before.
[Edited on 26/2/13 by Dick Axtell]
Work-in-Progress: Changed to Zetec + T9. Still trying!!
|
|
|
Not Anumber
|
| posted on 26/2/13 at 11:21 AM |
|
|
I had this happen on a Pilgrim Sumo a few years ago on the road. No real damage to the car as the thing went down into the road and just kicked the
back of the car into the air. I could see how that one happenned though as the prop was running at a wild angle as the diff (Mark 2 Granada) was
massively offset to one side, a serious design flaw.
Not expecting the same to happen to my MK ever though as the prop runs in a straight line.
|
|
|
motorcycle_mayhem
|
| posted on 26/2/13 at 12:30 PM |
|
|
....Not expecting the same to happen to my MK ever though as the prop runs in a straight line.
Hmmm... !
|
|
|
Not Anumber
|
| posted on 27/2/13 at 11:55 AM |
|
|
wot with a pinto ????
|
|
|
loggyboy
|
| posted on 27/2/13 at 12:15 PM |
|
|
quote:
Originally posted by Not Anumber
Not expecting the same to happen to my MK ever though as the prop runs in a straight line.
Isnt that a bad thing? I thought it was ideal to have a small degree of change in a prop?
http://locostbuilders.co.uk/viewthread.php?tid=177947
http://jniolon.clubfte.com/drivelinephasing/drivelinephasing.html
[Edited on 27-2-13 by loggyboy]
Mistral Motorsport
|
|
|
NS Dev
|
| posted on 12/3/13 at 10:08 AM |
|
|
prop failures in caterhams used on track are pretty common, at least in the higher power cars.
I have had a fair bit of involvement with an R400 racer and now a CSR, and we had two prop failures in each, with the last one in the CSR sending a
chunk of UJ through the alloy tunnel top and clean through the carbon dash as well, and severed two of the tunnel tubes. Failure occurred at
135-140mph at snetterton, when the flatshifter glitched and caused a transmission shunt on the straight, flat out!!
We've now upgraded to 3" diameter prop tube (by widening the tunnel), and gone for a much deeper insertion (ooh err missus) into the
gearbox that it had originally (well, originally with the Sadev box, that's not to say it wasn't deeper as supplied by caterham)
The combination of flatshift, straight cut sadev sequential gearbox and 290hp duratec seemed to break the stock prop pretty easily. This wasn't
tube failure though, it was shattering the actual UJ's
[Edited on 12/3/13 by NS Dev]
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
|
|
|
mcerd1
|
| posted on 12/3/13 at 11:47 AM |
|
|
quote:
Originally posted by rick q
I've had a prop shaft fail [my mistake - allowed the welds to be too thin] and the damage was significant, thogh fortunately not to me as the
prop catchers did their thing. If you look closely, apart from the scoring around the shaft at the hoops, look at the flattened the steel tube that
holds my fuel and wiring [adjacent the diff nose ] :-
not too bad then - bet your glad you fitted the catchers now 
if you adapt you existing catcher design to have a ~round hole only 10-20mm bigger than the propshaft then it would do even less damage - it should be
possible to have them so that the prop can't touch anything should it fail
-
|
|
|
Volvorsport
|
| posted on 12/3/13 at 04:08 PM |
|
|
looking through my workshop last week , ive got a couple of prop catchers spare....
www.dbsmotorsport.co.uk
getting dirty under a bus
|
|
|
gavin174
|
| posted on 12/3/13 at 04:09 PM |
|
|
here's a pic of a prop failure I had..
[Edited on 12/3/13 by gavin174]
http://www.essexkitcarclub.com
|
|
|
rick q
|
| posted on 13/3/13 at 02:57 AM |
|
|
quote:
Noticed rick q's post above. That failure, at the rear flange, looks worrying. Not seen that one before.
My mistake - after the propshaft was built, we found hadn't allowed enough clearance for the diff pinion nut.
Opened it up a bit on the lathe - but opened it up just a bit too much. The thing sheared under full throttle up a steep bumpy corner with too much
load for the way too thin metal we'd left at the yoke.
|
|
|
.jpg)
