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Another propshaft failure
40inches - 24/9/09 at 08:27 PM

Not mine,on a Seven that Dave Walker had on his rollers, went through the side panels and hit his leg at 120mph On page 98 in this months PPC.
That does it for me, definitely going to reinforce the tunnel.


liam.mccaffrey - 24/9/09 at 08:28 PM

saw that have n't read thearticle yet though


tomgregory2000 - 24/9/09 at 08:34 PM

its quite mad that it split in three and twisted to feck


scudderfish - 24/9/09 at 08:39 PM

Looked like it was made out of toffee.


40inches - 24/9/09 at 08:47 PM

What the feck causes them to do that? never heard of one twisting on a 1.5 ton Sierra! Scary? I think so


blakep82 - 24/9/09 at 09:00 PM

anyone know where i can see it?


twybrow - 24/9/09 at 09:09 PM

I've just finished wrapping my prop up to send back to D&F to have the front section replaced after my fun at Coombe. Sounds like I got off very lucky compared to Mr Walker...!


YQUSTA - 24/9/09 at 09:25 PM

I think I will do some thing with mine when I change the engine over the winter
this talk of props going is getting to often on the forum.


Dangle_kt - 24/9/09 at 09:37 PM

I don't read that mag, is his leg ok?


A1 - 24/9/09 at 09:40 PM

blimey...hope his legs ok...
i always give my prop a wee check these days after hearing the stories.


coozer - 24/9/09 at 10:35 PM

Another lesson in NOT making your own prop, best left to the professionals. Not that I'm saying it was homemade mind you...

Dave reckoned if there'd been a passenger they would have got it!


A1 - 25/9/09 at 01:19 AM

bit dodgy what hes saying about the compensation... yet another reason to take out the passenger seat


livelee - 25/9/09 at 07:00 AM

The propshaft on my Mac was a disaster waiting to happen.

As I understand it the "knuckles" on the UJ at each end of the shaft should line up with the other. Well mine were fixed so that they were offset from each other for some reason.


speedyxjs - 25/9/09 at 07:26 AM

I have welded two upright bars on either side at the front and back on my transmision tunnel to hopefully take most of the force should my prop break. I am also getting mine done professionally (when i have some money).


40inches - 25/9/09 at 07:37 AM

Would a panel of Kevlar/Carbon instead of ally offer protection I wonder?


iiyama - 25/9/09 at 07:47 AM

^^^ 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......


motorcycle_mayhem - 25/9/09 at 07:58 AM

Propshaft failure scares me enough to take the tunnel top off and check after every weekend.
I had the rear section go (just on the output of the reverse gearbox), when (yet) another spindle snapped on the gearbox end of last year (whether the spindle went first and then the UJ or vice-versa don't know). Fortunately on the downchange, entering Quarry, so slower than a lot of opportunities, but the mess took a chunk out of my thigh nonetheless.

Only thing that really worries me now (having dumped the gearbox) is that the electric reverse assembly is now the obvious danger area. But don't get me started on the MSA's insistence that I have such an assembly....


pif - 25/9/09 at 08:19 AM

those pictures look bad, makes me glad now that mine stayed in the engine bay when it let go.


MikeRJ - 25/9/09 at 09:03 AM

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.


livelee - 25/9/09 at 10:24 AM

Probably the same issue as mine would have had. With the UJs not lined up properly it causes the shaft to be unbalanced. Definately an "engineering" error on behalf of the builders.


twybrow - 25/9/09 at 11:01 AM

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.


MikeRJ - 25/9/09 at 11:17 AM

quote:
Originally posted by livelee
Probably the same issue as mine would have had. With the UJs not lined up properly it causes the shaft to be unbalanced. Definately an "engineering" error on behalf of the builders.


I agree that is a very fundamental aspect of universal joints. A decent, professional propshaft manufacturer simply wouldn't make that kind of mistake.


cd.thomson - 25/9/09 at 11:30 AM

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.


I'm not doubting your knowledge and experience but playing devils advocate iiyama did make most of his car in CF himself - he's not just trolling


Gergely - 25/9/09 at 11:30 AM

Is there any info on the car that was tested in the article? How much power / torque does the engine have? BEC or CEC? Home made propshaft or bought from the kit manufacturer or a specialist?

Our prop worries me, too. We have a two piece propshaft, having a Quaife reverse. The front prop is short, but is angled quite sharply. The second prop is the longer one to the diff. We did have loose bolts in the past, but noticed the vibrations and tightened with stronger Loctite. It seems fine now, but I check every week...
Gergely


livelee - 25/9/09 at 12:16 PM

quote:
Originally posted by MikeRJ
quote:
Originally posted by livelee
Probably the same issue as mine would have had. With the UJs not lined up properly it causes the shaft to be unbalanced. Definately an "engineering" error on behalf of the builders.


I agree that is a very fundamental aspect of universal joints. A decent, professional propshaft manufacturer simply wouldn't make that kind of mistake.


Yes, you'd hope so.

My car was a factory car from Mac. Maybe they were buying them in and didn't check the shaft before assembley, or maybe they had a YTS lad in building them when my car was built. Who knows. If they are all like mine was then i'd be very concerned. If I was an owner of a Mac now i'd definately be under it to check the shaft has been built correctly.

For my new build I've got a shaft from Dunning and Fairbank. HD tube, circlipped uj's and grease nipples on the uj's for proper maintenance. All new parts, no cut and shut from a donor.

[Edited on 25/9/09 by livelee]


iank - 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.


NS Dev - 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.


livelee - 26/9/09 at 03:26 PM

Do we know what make of car the shaft was on?


rusty nuts - 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 - 26/9/09 at 07:06 PM

If the gearbox seized and the drive wheels kept turning would this happen?


rusty nuts - 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 - 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 - 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 - 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 - 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


britishtrident - 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.


britishtrident - 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.


Furyous - 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 - 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 - 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]


Not Anumber - 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 - 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 - 27/2/13 at 11:55 AM

wot with a pinto ????


loggyboy - 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]


NS Dev - 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]


mcerd1 - 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 - 12/3/13 at 04:08 PM

looking through my workshop last week , ive got a couple of prop catchers spare....


gavin174 - 12/3/13 at 04:09 PM

here's a pic of a prop failure I had..




[Edited on 12/3/13 by gavin174]


rick q - 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.