Metal Fatigue

[Walshy]

There was an incident at Anglesey at the weekend, when a perfectly well prepared and maintained RF'85 was tanking along the pit straight when the the front rocker pivot bar ear on the chassis, broke it's weld and collapsed. Luckily, this was in qualifying and the incident was contained to the one car. If this had of been in the race with several cars around, it could have been a seriously big accident.

With this in mind, a conversation ensued along the lines of chassis fatigue. This car was one of the best maintained ones and this happened. Was it isolated to this particular design as I know the same configuration on the early Swifts used a bolt on ear.

Some of these cars are upto 20 years old now (and beyond) and not being an engineer, maybe someone will answer this for me. What degree of metal fatigue would these chassis be subjected to? Should we really be stripping down to a bare chassis every few years to have it crack tested or would this be extreme?

I know one of the other lads from the NW has had his chassis redone as it was found once shot blasted, that several of the tubes and crossmembers had fractures and in some cases, complete splits in them......

Any thoughts?

[heel'n'toe-no]

Chris, you make a good point. I suppose it depends on how much use the car has had and what if any shunts it has been involved in in it's lifetime. In a perfect world I guess the only way to record this would be in a race car log book. Something I am sure the MSA must have considered in the passed.

The thing is with log books is busy cars would be de-valued which would render the log books as useless as it would not be in the car owners interest to record accurate information. The only way this would work is if the MSA took an active role and only MSA scrutineers were allowed to enter the details. This would be fairly easy to manage I think.

You would need to present your log book along with the car at scrutineering. The Scrutineers could be given a list of cars that were present for testing the previous day by the circuit and enter that too. If the car is involved in an accident then the scrutineers could detail what the accident was and where the damage to the vehicle was sustained.

It's far from perfect but as you rightly point out Chris the cars are up to 20 years old (and I would say even more).

I'd be interested to hear others thoughts on this. Is it up to us as drivers to make the sport as safe as possible. F1 have drivers consulted in safety matters - Why not FF1600 where I think given the age of some cars there is, in my opinion, a greater need for such.

[Ian Sowman]

An interesting - if potentially expensive - idea Lee. But what about accidents when the car races overseas? Or if the car has been bought from or sold to another country? Or only ever has big accidents in general testing?

And surely you could only really implement the system for new cars.

[JNWRF01]

My old Rf01 had a French FFSA log book for the 1 race it had done in the French FF champs...so I assume log books are complusory over there? Seems a sensible idea to keep an eye on owners, damage etc etc. Certainly will provide invaluable if a car is stolen etc etc. When one considers the value of cars on your typical clubbie grid (av FF race of 20 cars must be £150k worth of kit) then its a good way for us all to protect our cherished toys. A sensible one off charge of £20-30 for each chassis would help things...

Would be interesting to see how many log books claim they are works Van Diemens or Ayrton Sennas RT3!

[Walshy]

I mean.

The same applies to Carbon Fibre tubs. Does anyone 'really' know the long term effects of fatigue to carbon fibre. There are F3 cars out there now etc that are over 10 years old. Does the Carbon go brittle, or crack?????

One other thing that isn't really policed is the work to chassis's. We are really lucky with the Formula Fords as we do have some expert welders etc and you can always get a great job done, but how many "have a go" lads are out there, welding new bits to their cars, that learnt to wled after a few nights at night school. Potentially dangerous stuff. If your daft enough to do it.

It could be an idea to ticket a damaged chassis and only certain reputable engineers can remove the ticket as proof that the chassis has been attended to by someone that knows what they are doing.

[carsten.meurer]

we have compulsory log books in germany, and i work around them, baseing
my cars abroad, so i save the money on them !
its 140 quid every two years per car for nothing !

they are useless to say the least, just make your asn a lot of money...
( bet you get them once someone from msa reads this... )

if every mile on the car was recoreded, you might have a point !

as it is not, i personally saw cars beinng crashed with bend rollhubs and the
like in testing, obviously without any scrut on the logbook, and sold on accident free down to logbook !

each driver or team chef should have the responsibility to repair accident damage and keep the car within the rules and safe ! no reason for a log book there...

but we too had a case where a rf 88 broke the chassis open during a small shunt in monza in 02. the inside of the frame did not look good at all !

problem is : how do you find out, and what to do against rust and ageing metall ? seems its out of question that 20 plus year old cars trashed hard over cerbs are well past theire fall by date...

[jimbomit]

As the owner of that chassis Chris mentions I can certainly tell you it opened my eyes.

The history of my car is well known having raced in the UK for several years, since myself and the previous owner (total of about 9 years I think) the car has had no big accident. Prior to that it is known to have rolled and been repaired by a highly skilled engineer.

Having seen my chassis, the quality of the repairs was not in question. However, 9 extra years of pounding around tracks had taken one heck of a toll.

Several welds were cracked at major junctions, one lower cross beam was crushed (but damage was hidden by the floor) and the front lower had become detached.

The effect of this has been to allow the chasiss to move far more than it was designed to do and as a consequence more stresses will have passed through the structure.

When we put the chassis on a jig, we found it was twisted, compressed and pushed up so that there was distortion over all three dimensions.

The repair I've undertaken has been massive and due to the need for the job doing properly, the chassis has only just been completed.

We had to build a jig around the car to secure it ridgid while all the bad tubes were systematically removed and replaced one by one (you can't replace them all at once). Then we had to hydraulically pull it straight and flat, secured to a substantial steel bed. It was then sent to an autoclave where it is gradually heated in cycles up to about 400 deg C (I think!) then slowly cooled. This takes all the stress out of the chassis and when released from the jig it has been stove enamelled.

Now mine has taken a long time, partly due to the pick-ups needing replacing for the front suspension as well as the brake cylinder locators.

After all this work the chassis is A1, over the whole length it doesn't deviate from the horizontal by more than 1mm, in fact it is probably better than when it left the factory.

BUT, if I take it out, hit a few curbs hard will it still be straight? Could I damage a weld so badly that it disintegrates at it's second outing? Well the answer is yes, they are only perfect when they haven't been used.

That said, the degree of wear shocked me, I hate to think what would have happened if I'd copied Mr Minshaw at the Moose Trophy two years ago. . .

Now I don't suppose everyone needs to go and bear chassis rebuild their chassis but I bought a good straight car with a known history that had been very well maintained and I mean that, I know the former owner and engineer and neither would cut corners and both have the utermost integrity.

It wasn't until the chassis was shot blasted that we found half of the damage.

It does worry me as to how many other well worn chassis's are out there.

[Alan Raine]

We drag our old 79 PRS out for the odd Track day every other year or so. Most of the bolts are original unless they have been changed through accident damage or obvious wear an tear. Last time the car was used the bolt holding the radius arm to lower rear wishbone sheared, 2/3rds the way down the main straight at Aintree. Fortunately the car went off on the inside missing the fences, but it could have very nasty. I know the nut wasn't loose as I checked it before the car was used (does continuous spanner checks overtighten the nuts?). Every nut and bolt is being replaced before it's used again! - It's not only the chassis that need looking at.

Apart from the normal engine and gearbox breaks this is the first structural failure we have had (in over 25 years).

The chassis on our car has been patched up in places after various bumps, but being outboard suspension perhaps it doesn't suffer the same loads as the inboard cars.

[heel'n'toe-no]

Originally Posted by Ian Sowman

An interesting - if potentially expensive - idea Lee. But what about accidents when the car races overseas? Or if the car has been bought from or sold to another country? Or only ever has big accidents in general testing?

And surely you could only really implement the system for new cars.

Exactly, I believe this is true Ian. I t would be a step in the right direction and looking at the responses from overseas it would appear already common practice. I think in order to regulate this a little bit better the , track administrators should be duty bound to sign log books before allowing cars on to tracks for testing and also before allowing them to leave the circuit for a sign off signature, which would confirm the test session was incident free or record whether the car was involved in a crash of some sort.......Comment column could allow for a brief description of where the damage occured.

Surely this could be implemented quite easilly to the circuits and all racing formulae from now on. Some or partial information has got to be better than none.

WALSHY.......>See what you've started.....This could ACTUALLY happen!!!!!

MSA - call us to discuss if you feel, like we do, there is a need for such controls. (What do you think Chris? - Want to form a committee????)

[Marshal]

Interesting topic.

Bare metal rebuilds, with crack detection? Well, I guess it depends on your budget, but I wouldn't have thought that a FFord racer (any racer) was designed with a 20 year life in mind, so there's obviously an increased risk as the car gets older. So the risk is yours, but at least you shoud think about it.

The one that worries me more is the one which Walshy mentioned, which is ageing Carbon chassis. Damage on metal is at least visible, and metal is ductile and relatively forgiving. Serious damage on composites isn't necessarily visible, and failure tends to be more catastrophic. Something to think about isn't it?

Marshal (Materials engineer during the week)

[carsten.meurer]

and its not just the cheap crap carbon on bmw and renault cars !

remember the f1 ferrari that 'exploded' without impact ( guess in donnington )
leaving the driver sit in the open, strapped to the remaining part of the 99 or so tub ?

frightning, and a good reason i won't buy a carbon car, at least not with the
intention of useing it for long !

[heel'n'toe-no]

Wow, is it possible to get this can of worms back in the can? ....Don't think so.

I think you might have opened pandoras box here Walshy....TOP MAN.

The carbon fibre is a very interesting topic, Chris (Walshy) I would be keen to here Gaz's input on this. He's got invested interest in this field I believe and we have briefly discussed same at the track.

I hope he is a 10-10ths contributor.....If not send him round to mine I'll soon have him signed up

[Eddy V]

Originally Posted by Alan Raine

...does continuous spanner checks overtighten the nuts?

Yes it does. We had a similar problem with some rose joints, checked them too often it seemed!?
Only a few weeks ago (a brand new car with brand new rose joints) had a big off, because (without hitting anything) a rose joint sheared.

Can of worms? Even worse, methinks.

[Mark Mitchell]

Just a thought!
I don't know anything about engineering or race prep etc, nor do I know anything about the driver of the car in question, but.......

If he is a regular competitor/tester at Anglesey, could the "Elements" have a small part to play?
By that I mean damp, salt air from the sea on those days that are less-kind to us all.
I'm assuming that you don't all chasis-wash your motors after a race, so just wondered if this is a possibility?

[heel'n'toe-no]

After the first race of the season at Anglesey, I washed my car completely. You have to if you don't want it rotting from the sea salt. I would imagine most do this. To completely wash and dry the cars is a relatively simple job when you get the body work off.

At least it is simple with mine, there may be more difficult makes and models but I'm sure they are of a similar principal.....aren't they?

[StephenRae]

The chassis in question is as good an example of an RF86 as you can get, maintained to the highest standard,no amount of 'expert' inspection would have found the fault. The braze which let go was clean and bright for the whole of it's length and there was no internal corrosion.
There seems to be some confusion between the terms brazing and bronze welding. In my opinion there was not enough nickel bronze in this weld which subsequently let go.
To be fair, Ralph Firman couldn't have been expected to have his cars designed to last forever but I can think of a few other examples of chassis just strong enough to last till the cheque clears.

[Alan Raine]

Originally Posted by Walshy

I mean.

The same applies to Carbon Fibre tubs. Does anyone 'really' know the long term effects of fatigue to carbon fibre. There are F3 cars out there now etc that are over 10 years old. Does the Carbon go brittle, or crack?????

This was one of Schueys old Ferraris that crashed at Laguna Seca. Although it was quite a biggy the chassis shouldn't have broken the way it did. Fortunately the driver was ok!

[Walshy]

Originally Posted by Eddy V

Yes it does. We had a similar problem with some rose joints, checked them too often it seemed!?
Only a few weeks ago (a brand new car with brand new rose joints) had a big off, because (without hitting anything) a rose joint sheared.

Can of worms? Even worse, methinks.

Simple check for the rose joints eddy without the need for a spanner.

Get a permanent marker and mark the thread on the rose joint, the locknut and the end of the wishbone. All in a straight line. Instead of getting the spanners out, just look at it. You will notice any movement by a shift in the line. Hey presto.

With a nut and bolt check, there is no need to keep "nipping up". Your only checking if it's still tight. Nothing more. I used to overtighten all the time, till I got this little tip from someone.

[Walshy]

Originally Posted by heel'n'toe-no

Wow, is it possible to get this can of worms back in the can? ....Don't think so.

I think you might have opened pandoras box here Walshy....TOP MAN.

The carbon fibre is a very interesting topic, Chris (Walshy) I would be keen to here Gaz's input on this. He's got invested interest in this field I believe and we have briefly discussed same at the track.

I hope he is a 10-10ths contributor.....If not send him round to mine I'll soon have him signed up

Hi Lee.

Gaz is signed up as far as I'm aware, but he hasn't posted yet. Bust preapring course work I think for his studies. I'll get him to get his finger out. He was talking about ringing you for a pint when he was done anyway.

I like the sound of the book idea. Instead of handing out tickets in scrutineering, they could sign your book. That way, a potential buyer would also know how much racing the car had done also. I don't think it would affect the price of a car as we all know, the better cars are the ones that are raced. Race cars don't sit well in a garage doing nothing. At least a car that has been raced, is maintained.......

[Tim 27]

I see many (mainly ex GP) cars advertised in Autosport as being 'crack tested'. Is this an expensive process? And how many companies in the UK can do it?
The subject of carbon delaminating is indeed scary, as I know of no process to detect it.

[heel'n'toe-no]

Originally Posted by Walshy

I mean.

The same applies to Carbon Fibre tubs. Does anyone 'really' know the long term effects of fatigue to carbon fibre. There are F3 cars out there now etc that are over 10 years old. Does the Carbon go brittle, or crack?????

Chris....The things I do for you.....Been reading some right rubbish on the web about this and found that tests have been done by some clever people it would appear: (Don't read on unless you are having trouble sleeping)


"Abstract. Changes in electrical resistance during static and fatigue loading of unidirectional and cross ply carbon fibre reinforced polymer composites have been studied. The carbon fibres in the study were T300 and the matrix resins were Hexcel 914 and 920. It was found that changes in resistance during static tensile testing were about three per cent of the original resistance of the samples, while fatigue testing caused resistance changes of up to 10% of the original resistance, immediately prior to final failure. The initial linear portion of the resistance increase on static testing was reversible and could be attributed to reversible elastic strains in the fibres; later non-linear changes were a consequence of fibre fracture and were irreversible. Changes in resistance during fatigue also contained both reversible and non-reversible components. It was found that during fatigue testing the initial changes in resistance caused by the first few thousand cycles could be correlated with the eventual life. Samples with large initial resistance change had reduced lives compared with those with small changes in resistance. Fatigue lives of composite laminates may thus be predicted from monitoring of initial resistance changes. Many of the results could be explained via the parallel resistance model of conduction in composite laminates."


........Now then - It's all as clear as mud to me now.

Question - Does this mean I will have to change my Carbon Fibre Rain light bracket?????

[FranksWilde]

Would it not be preferable to have the chasis tig wilded rather than brazed?
Isn't tig more reliable and stronger or is there no real difference.

[Walshy]

Originally Posted by heel'n'toe-no

Chris....The things I do for you.....Been reading some right rubbish on the web about this and found that tests have been done by some clever people it would appear: (Don't read on unless you are having trouble sleeping)


"Abstract. Changes in electrical resistance during static and fatigue loading of unidirectional and cross ply carbon fibre reinforced polymer composites have been studied. The carbon fibres in the study were T300 and the matrix resins were Hexcel 914 and 920. It was found that changes in resistance during static tensile testing were about three per cent of the original resistance of the samples, while fatigue testing caused resistance changes of up to 10% of the original resistance, immediately prior to final failure. The initial linear portion of the resistance increase on static testing was reversible and could be attributed to reversible elastic strains in the fibres; later non-linear changes were a consequence of fibre fracture and were irreversible. Changes in resistance during fatigue also contained both reversible and non-reversible components. It was found that during fatigue testing the initial changes in resistance caused by the first few thousand cycles could be correlated with the eventual life. Samples with large initial resistance change had reduced lives compared with those with small changes in resistance. Fatigue lives of composite laminates may thus be predicted from monitoring of initial resistance changes. Many of the results could be explained via the parallel resistance model of conduction in composite laminates."


........Now then - It's all as clear as mud to me now.

Question - Does this mean I will have to change my Carbon Fibre Rain light bracket?????

You need to get out more mate.

[heel'n'toe-no]

Originally Posted by Walshy

You need to get out more mate.

Your started it!

[Walshy]

I mentioned this Thread to Gary yesterday, but as yet, no movement eh...........

It can take a while sometimes..............