Catastrophic racing failure

So we had a pretty spectacular failure this weekend at Mid-Ohio, with Marnie behind the wheel of the red car.

At the last event the aluminum hub on our Tilton clutch set-up was lost, and were forced to swap in a stock flywheel and clutch set-up to get her through the weekend. A stock clutch will do just fine, but a stock flywheel is pretty heavy for 8,000 RPM work.

We returned to Mid-Ohio this weekend with that stock flywheel set-up,
knowing it wasn't optimal but assuming that we'd make it through the event. Nope.

After a couple of offs, and a slam on the brakes 60-0 dead stop effort to avoid a car on track, a few laps later the stock flywheel decided to escape on a hard 5th to 3rd downshift.

The carnage was just that. Carnage.

flywheel-damage-b.jpg


flywheel-damage.jpg


All 6 bolts were sheared on the crank, along with the crank alignment dowel. The input shaft of the trans is sheared clean at the flange. Bell-housing in 20 pieces, starter wiped, and worst of all, it broke the forward mounting ear on the block.

A number of factors contributed to this, including as stated above, several harsh stops of the engine which likely compromised the bolts, and repeated hard downshifting without heel-toe rev matching....

Racers, let this be a lesson. You really need to use lightened rotating mass components, and learn how to rev match on downshifts!
-M
 
So we had a pretty spectacular failure this weekend at Mid-Ohio, with Marnie behind the wheel of the red car.

At the last event the aluminum hub on our Tilton clutch set-up was lost, and were forced to swap in a stock flywheel and clutch set-up to get her through the weekend. A stock clutch will do just fine, but a stock flywheel is pretty heavy for 8,000 RPM work.

We returned to Mid-Ohio this weekend with that stock flywheel set-up,
knowing it wasn't optimal but assuming that we'd make it through the event. Nope.

After a couple of offs, and a slam on the brakes 60-0 dead stop effort to avoid a car on track, a few laps later the stock flywheel decided to escape on a hard 5th to 3rd downshift.

The carnage was just that. Carnage.

flywheel-damage-b.jpg


flywheel-damage.jpg


All 6 bolts were sheared on the crank, along with the crank alignment dowel. The input shaft of the trans is sheared clean at the flange. Bell-housing in 20 pieces, starter wiped, and worst of all, it broke the forward mounting ear on the block.

A number of factors contributed to this, including as stated above, several harsh stops of the engine which likely compromised the bolts, and repeated hard downshifting without heel-toe rev matching....

Racers, let this be a lesson. You really need to use lightened rotating mass components, and learn how to rev match on downshifts!
-M

I have never seen (an Xs) bell housing break away like that before. That is carnage! Glad it didn't result in an injury.

Mixing components; performance with non always has it's risks. But none more serious than drivetrain parts.

Lesson learned...
 
Glad to hear nobody was hurt. What a terrible thing to happen to your poor X! Did anything get damaged besides the transmission when it all grenaded? For us racing types, are there other components of an X that are likely to fail in competition if they aren't replaced with something superior? I have a lightened flywheel. Maybe wheel bolts or something?
 
Wow! And a question,

I've heard of so many similar incidents but this is the first time I've seen it documented (with pictures) so well. Incredible forces at work. Luckily, the driver was safely residing about two feet or so ahead of the carnage.

Matt, are you updating racing results in general in a blog or something?
 
Holy Cats! That is impressive.

With the way it looks you are lucky you didn't have any shrapnel come through the firewall. When you do the forensic analysis keep us posted on what you find, class (grade) of bolts etc. That is s a good one.

I had seen something similar but probably less severe many years back in a big money x that was at Overseas motors (it had a tv in it). It was from a guy that kept sidestepping the clutch drag racing. I guess it was fast for a short time there.

BTW thanks for posting this. It is great information for reference.
 
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I have never seen (an Xs) bell housing break away like that before. That is carnage! Glad it didn't result in an injury.

I seem to recall Steve Hoelscher describing a flywheel failure in apocalyptic terms somewhere back in the old n54 forum... and I know of an Audi station wagon (R200, 5-cylnder turbo) that lost its flywheel when a parking lot attendant couldn't resist the temptation to try a burnout.

Still, pretty amazing to see the damage... It would be very interesting to see what the fracture surfaces of the sheared bolts looks like.
 
Glad Marnie is OK

Wow, that looks like quite an explosion of bits. I am relieved there were no injuries. You can replace the parts, but odds of finding another Marnie are not good. ;)

BTW... I know of a good parts vendor if you need some stuff!! :grin::dance2::devil:
 
Shifter...

...As the flywheel was leaving out the bottom of the car (which wasn't found, BTW) it grabbed the shifter linkage with enough force to do this:

flywheel-damage-c.jpg


Yes, we were very lucky on this one...

I've only had one other flywheel issue, with an aluminum unit a few years back whose hub was manufactured too thin, and it broke the hub out. It broke on a 4th to 3rd downshift but managed to stay inside of the bell-housing leaving only a couple of cracks, which were repaired and we still use that trans today.
 
OUCH !!!

Good to hear no one was injured as this could have been far more serious than just broken bits. Serious to fatal bodily injuries could have resulted from a flywheel explosion.

The amount of energy stored in a flywheel spinning at higher speed is great. The amount of damage illustrates as an example of the amount of energy stored in these rotating devices.

The failure could have been due to a small stress riser, small crack, void in the material, mechanical damage to the flywheel some time during it's life time or ??? Difficult to really know without most all of the failed bits for analysis.

There are steps that can be take to significantly reduce the risk from part failures like this. These steps apply to both stock and racer parts. Failure prevention is far more significant for a race car due to the types and amount of stress parts are subjected to and results of part failures can result in far more than just a DNF.


*No sharp edge or rough surfaces, these can propagate cracks or stress risers. There appears to be a tendency for machinist and parts fab folks to make parts with nice sharp edges, bends at direct 90 degrees-no radii, no debarring and such. Every sharp edge is a potential failure risk as that sharp edge can harbor cracks which grow into a failure.

Same applies to surface finishes where cutting or machine cutting tool marks are allowed to remain on the finished part. These can also grow into cracks which can propagate into a part failure.

Rust and corrosion can also produce stress risers. It is quite possible rust or corrosion has caused sharp edge pitting or material degradation beneath the surface causing stress risers and those failure producing cracks again.

Very generally, higher strength materials can be far more prone to stress crack failures then softer and more complaint materials.


*On all parts fab, break all sharp edges and include a radii (large as reasonable) as often as possible.

*Smooth out machine cutting tool marks when possible or strive for a smoother finish during the part fab process.

*Protect parts from rust and corrosion when possible.

*Test and check for cracks via magna flux or fluro crack inspection on all highly stressed parts. Replace them if a problem is found.

*Replace used hardware with proper new hardware when possible. This is often neglected yet a very easy and simply disaster preventive measure that is easy to do.

*Never take for granted that what worked fine race after race will be fine for the next race. Murphy will assure the chances of that part will fail when least expected.



Bernice
 
*Never take for granted that what worked fine race after race will be fine for the next race. Murphy will assure the chances of that part will fail when least expected.

That is the most true of all statements.

It's a real son-of-a-gun, effort and $$ wise to preventatively replace perfectly functional things like wheel studs, carriers/uprights, CVs, and clutches but that is in-fact what needs to be done on a regular basis on highly stressed race cars.

I have been extremely proud of our record regarding DNS/DNF (did not start / did not finish) on the race track.

I can count less than 5 occurrences in almost 100 starts, and interestingly two of those were flywheel related.

-M
 
I can only add my good wishes... Glad everyone is OK...

I guess I grew up in an age when drag racing required scatter-shields on all clutch operated cars... I only remember seeing one foto back in the day where a clutch/flywheel let go and the interior of the car looked like it was peppered with shrapnel from a grenade.

No arguments after seeing that... if you are gonna race a manual trans, you'd be a fool not to. But who would have expected something like that from this little engine?

My guess would be that its primary cause was fatigue and the your ability to get more ponies out of that engine than was ever imagined.

Congrats on a great racing and SAFETY record otherwise and again, everyone is OK~!
 
Flywheels are a extreme stress part that required extreme care to prevent serious problems.

It is so very common for racers to take for granted that what worked fine for the previous race it will all be fine for the next race.. No, simply NO.

For us, LeMons racing is hard endurance racing. This means the car and all related is pounded and stressed to the limit hour after hour. All that time, in the back of my mind is always wondering what got forgotten, what should have been replaced, checked, tested that did not and will fail. With any failure, what serious consequences will result from that failure. It could be a simple tow in or the cause of wrecking other cars to a fatality.

I take this racing stuff very, very seriously knowing any small error could result in really, really bad stuff. To combat this, I go over the LeMons racer, very, very carefully with meticulous attention to details. Yet, stuff always gets by to cause problems.

Fixing stuff at the track is IMO, a result of forgetting to get what should have been done at the shop before it was loaded on to the trailer.

That two cent part that failed, costed an entire race weekend and a DNF.. this is the kind of stuff I'm not at all tolerant of.

And yes, never, never take anything for granted as it can come back and bit in the worst way.



Bernice



That is the most true of all statements.

It's a real son-of-a-gun, effort and $$ wise to preventatively replace perfectly functional things like wheel studs, carriers/uprights, CVs, and clutches but that is in-fact what needs to be done on a regular basis on highly stressed race cars.

I have been extremely proud of our record regarding DNS/DNF (did not start / did not finish) on the race track.

I can count less than 5 occurrences in almost 100 starts, and interestingly two of those were flywheel related.

-M
 
Wow

Bernice wrote: "I take this racing stuff very, very seriously knowing any small error could result in really, really bad stuff. To combat this, I go over the LeMons racer, very, very carefully with meticulous attention to details. Yet, stuff always gets by to cause problems."

Bernice - Good for you for the meticulous attention to detail. Do you use a checklist when you go over the car? Aviators know the benefits of a checklist and the fallibility of the human memory, especially under clock related stress. Auto racing is almost as unforgiving as aviation. I highly recommend (everyone) developing and using a checklist, if you don't have one already.

Matt - So glad there were no injuries! Thank you for posting this, the story is incredible and the pictures amazing.
 
Wow..

I remember Steve H talking about this. If I remember right, it concerned him so much he put a kevlar blanket where the gas tank goes to protect him from pieces of transmission coming into the cockpit.

I wonder what the cause was from, suppose it was out of round holes for the bolts and the dowl could not keep it secure?
 
Really carnage as you say ... amazing
But most importantly no injuries
A 8000 RPM no forgiveness.

Sorry for Marnie
 
Kevlar blanket...

I was running RedWedgeX at time of SteveH's mishap.
It had 1 layer of 18 gauge aluminum between bellhousing & right kidney,
so I sourced an outdated bulletproof (kevlar) vest from cop friend.
Shortly after, I went back to stock bodied X for track use,
so never installed it as tranny blanket.

I asked my friend what the dept did with outdated vests.
He said they let cadets wear them on patrol!
 
Indeed incredibly lucky.

I saw a Turner blow up its flywheel on an autocross course years ago. The car jumped up 6". Luckily the car had a retention collar (or whatever the correct name is) and it contained it. All that was inside was broken cast iron, springs etc. Considering it was right alongside his leg, he was very lucky to have fitted the proper safety gear.

Hope she is OK. The dent from the gear shift is testament to some of the forces imparted to the rest of the car.
 
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Glad she is Okay

Holy flapping bat droppings Batman, that was a close call.

Thank goodness that you guys are uninjured. The side you guys sit in it could have been far worse.

That IS the first time I have witnessed a Fiat SOHC flywheel 'let go' causing total obliteration of the bell-housing, thanks for posting the images.

ARP or standard bolts ?

Another good point for us non track car users is never reuse old STD flywheel bolts even if only on your daily driver.

To answer John in AZ's question

Flywheel bolts M10 x 1.25 thread size - ARP part # 209-2801, the dowel is very important if you want to spin at these revs.
 
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