National Motorsport Academy

Lifing Your Parts

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There is something that I must make clear before we start – when I am talking about Lifing, I am using the engineering use of the word not the Urban Dictionary version. In other words… The amount of time that a part can be safely used for before it becomes susceptible to fatigue or failure. You can look the other versions up yourself. I say this because once upon a time, at a University far away from NMA, I proposed a module that had Lifing in its title and I was not allowed to use the word because it was not becoming….?? It is fair to say however, all of us at the NMA are race engineers and we understand industry language is essential. So ‘Lifing’ is well embedded into the programmes here.

Pointing the Finger

Lewis Pirelli Tyre Lifing

The reason I chose this subject will be obvious to any F1 fan. The tyre failures at Silverstone in the British Grand Prix last week. Although there were many on the idiot’s lantern (again, check the Urban Dictionary) at the time that talked about debris on the racetrack causing the failures but I’m going to call that political bull…t.

We know that carbon fibre shards take no prisoners and will puncture tyres in a heartbeat and, yes, there had been a crash with bits everywhere and Kimi had misplaced a wing, but strangely all the punctures were to the left hand front; the most hard working tyre on the Silverstone circuit.

Massive right hand corner speed chews up a left front tyre and when you add those super long high speed right handers even the hardest of tyres are begging for mercy very quickly.

Add in that these tyres, according to Pirelli, on the television, had a life of 40 laps (I note they are now saying 50 laps to shield themselves from blame, hence the political bit) and the failures were at 37, 38 and 39 laps.

So, What Went Wrong?

What went wrong then? Did the teams play fast and loose with the cambers again like in 2013? Were the tyres under inflated, like 2013? Or were Pirelli, whilst working to the FIA mandate of spicing up the races, wrong in advising 40 laps life? Was the life less than that in reality and the early pace car allowed the teams to drop in a “cheap” (in terms of time) pitstop that became very expensive (in terms of stress as well as ££s and points) later on?

This is where Lifing comes in – it doesn’t matter whether it is our racing cars or bridges, planes or lightbulbs; each part of each machine or structure has an engineered length of usage time where it is considered to be “safe” within certain limits and boundaries (the operating window). Using it after that time or number of cycles increases the probability of failure. In some cases, such as lightbulbs, we use them to failure and the life is actually an expectation of the time it will serve us. Whereas the Porsche engine that I use in the NMA Course content on this subject, most certainly is not used to failure as it is being used in the WEC series and a non finish because you overused your engine is not going to be popular!

Performance Vs Life

“Overengineering” or adding in “safety factor”, will make things last longer but at what cost? An overengineered lightbulb with a filament like a coil of barbed wire might last forever but will use electricity way out of proportion to the usefulness of the light it provides. So, what we can see is a trade-off – performance vs life.

What was the difference between my old BMW M3 race engine and the road going version of the same thing? In reality it was about 100,000 miles. So the additional weight, the reduction in horsepower, the drop in revs all contributed to the engine lasting longer than a 24 hour race before needing a rebuild. A trade-off; Performance vs life.

Is that what happened at Silverstone? Was there a trade-off? I think so, the teams traded certain time lost in the pits for uncertain risk at the end of the race. They rolled the dice (in an engineered kind of way) and Lewis ended up with double 6 whilst Valtteri and Carlos had their dice fall off the playing table! You can see the highs and lows in the video below.

What can we learn from this? Numerous things I think.

Everything has a finite engineered life, whether that is an engine, lightbulb or a tortoise.

………

There is always a “risk versus reward” calculation to do when you engineer something to be lighter, harder, softer, faster or whatever, or as my old Yorkshire grandfather told me and anyone that would listen, “You don’t get owt for nowt”

STOP PRESS!!!

An announcement from Pirelli has indeed now blamed the long stints that the teams did on the tyres on one of the most destructive and high speed tracks on the calendar.

Well, well, well, it is not Pirelli’s fault then. Having learnt from the debacle in 2013 and other events that showed their tyres to be chewing gum under the FIA mandate, they don’t want the bad PR to transfer to road car sales, so they have got in first with the excuses, explanations and evasion of responsibility.

NO, say Pirelli, there will not be any problem with tyres for F1 70th anniversary race. Let’s wait and see what changes to make sure that doesn’t happen.

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