Engine relocation, clutch explosions and leg safety

I am planning to move the S52 in my race car rearward about a foot to get it behind the axle and make room for UEL control arms. Technically there is no issue with this whatsoever but - I am a little concerned that there is going to be a flywheel even with my knees concealed behind about 1/4" of aluminum bell housing and 22 gage sheet metal.

I don't want to over-think this - I've never seen a clutch/flywheel explode on a road racing car (esp one w less than 300 hp) and see it only as a very remote possibility. I'm not really sure if I should even be concerned but I HAVE seen one blow apart on a dragster with a blow proof bell housing and it was berkeleying spectacular enough for me to pay attention to what my stubs would look like if that were to happen.

So... what reasonable precautions can I take without being ridiculous? The ZF trans has an integral bell housing so I expect I'd be limited to adding plate to the tunnel - I really don't want to do any unnecessary adding of weigh so how much is enough? 3/16? How wide? Would 6" in both directions from the rotational plane be enough? Too much?

Add a layer or two of tire rubber maybe 6" in both directions? Not too heavy but should keep the shrapnel down. Maybe some kevlar too?

Can you not just wrap it.

I don't know a whole lot, but on DSMs, for example, they are pretty serious. 1/4" stainless, 4-5" over the center of the rotational plane.

GameboyRMH wrote: Add a layer or two of tire rubber maybe 6" in both directions? Not too heavy but should keep the shrapnel down. Maybe some kevlar too?

It is a fairly destructive thing when it happens - I thing it is primarily a job for steel... not sure tire rubber is enough but kevlar is an interesting idea.

wearymicrobe wrote: Can you not just wrap it.

I would have never thought to google 'flywheel blanket'. Thanks. Brilliant idea.

Found some here:

http://www.streetperformance.com/m/cats/204-transmission-drivetrain/4957-transmission-blanket.html

For once an off-the-shelf solution!

GameboyRMH wrote: Found some here: http://www.streetperformance.com/m/cats/204-transmission-drivetrain/4957-transmission-blanket.html For once an off-the-shelf solution!

And light weight too! I was none too happy with the idea of having to weld 20lbs of plate in there.

Kevlar is not made to stop metal at such a force. Yes, they are used in flack jackets, but I don't think its your answer. I have a thick Kevlar vest on and know someone could slide a sharp blade right on through there.

N Sperlo wrote: Kevlar is not made to stop metal at such a force. Yes, they are used in flack jackets, but I don't think its your answer. I have a thick Kevlar vest on and know someone could slide a sharp blade right on through there.

That's what I was thinking, I know blades can tear kevlar, the ones cops use to resist knives have chain mail in them as well. I was thinking the tire rubber might be harder to pierce.

So the blankets are typically rated pretty decently for holding in a exploding clutch. They are made in a composite construction technique so they will hold a lot of force in

Mind you if the flywheel goes it needs to make it through the transmission case. Around the drive splines and will almost always go out the path of least resistance. But it will make it out

It takes a metric ton of force to rip apart a clutch or flywheel and if they are installed right the chances are slim that it will go. But in a track car and one that rev's with a lightweight flywheel you would be crazy not to run something stronger. Normal car placement says that when one goes you loose your feet. If I am reading your post right your going to loose your life if it goes due to placement.

It seems the "nays" have it. I used a little google-fu to find that those are used on automatics and are to stop a flex plate and internal bits but are NOT flywheel safe. Those guys are required to have 360˚ 1/4" steel plate or approved blow-proof bell housing for real flywheels according to conjecture on several forums by people with serious looking cars that passed tech.

4" wide 48" long strip of 1/4" steel only weighs ~ 14lbs. Seems like a small price to pay for protection.

Really you only need to reinfoce the area on yourside if you don't have a passenger seat.

Also are you saying your only worried if it takes out your knees? Sounds like today it would take out your Ankles. still Ouch!

Not sure how much room you have, but it might be possible to put the liner on the inside of the bell. Just a rolled ring of steel around the id, and of course something to keep the transmission from falling on the track if the bell does fail.

I made my own bell from steel, could have used any thickness i wanted, went with 3/16" for the rolled ring, 1/8" to close in the rest of the bell. I have a 15lb flywheel, not a 60lb unit like the aftermarket bells were designed to contain. My complete bell, block plate, and midplate w/ hardware only weighs 26.2lbs...

bellhousing fabrication page

nocones wrote: 4" wide 48" long strip of 1/4" steel only weighs ~ 14lbs. Seems like a small price to pay for protection. Really you only need to reinfoce the area on yourside if you don't have a passenger seat. Also are you saying your only worried if it takes out your knees? Sounds like today it would take out your Ankles. still Ouch!

Today it would tear apart the area in front of the pedals and the firewall has extra material at the tunnel flange. No other BMW race cars do anything about it in the factory location and AFAIK there has never been an issue. I might just be paranoid but I don't have the fighting spirit of Alex Zanardi for overcoming physical disabilities. I'll add material just so it isn't always in the back of my mind.

In reply to weedburner:

That is sexy - not just for safety reasons but for mating all of the incompatible combos that haunt my dreams. Bookmarked!

FWIW, the flywheel isn't the only thing that can be fatal. A friend of mine almost lost his life when the output shaft link failed (guibo on the Alfa)- it flailed around and cut his leg open really well. Really good corner workers + another Dr friend of mine saved his life and limb.

I'm glad you are looking into this.

alfadriver wrote: FWIW, the flywheel isn't the only thing that can be fatal. A friend of mine almost lost his life when the output shaft link failed (guibo on the Alfa)- it flailed around and cut his leg open really well. Really good corner workers + another Dr friend of mine saved his life and limb. I'm glad you are looking into this.

I do have a driveshaft loop on it already - the result of having not had one when a BMW guibo let go at the Glen on me (my own fault - used a 325 one behind an S52 to try to cut rotational mass, DOH). As luck would have it - the BMW folks were smart enough to add a nipple to the front of the DS so it doesn't fall right out or I could have had the first pole-vaulting E30. It destroyed the gearbox.

N Sperlo wrote: Kevlar is not made to stop metal at such a force. Yes, they are used in flack jackets, but I don't think its your answer. I have a thick Kevlar vest on and know someone could slide a sharp blade right on through there.

Kevlar is used for exactly that purpose. That's why way back in history when the stuff came out we started wrapping our engine rooms in the stuff. It's about the best there is for containing exploding steel. Kevlar is far stronger than steel, pound for pound.

And you're right, as a fiber, if it's just laid there, a blade will slip right through it. That's why you use layers of the stuff, including woven layers.

Giant Purple Snorklewacker wrote: It seems the "nays" have it. I used a little google-fu to find that those are used on automatics and are to stop a flex plate and internal bits but are NOT flywheel safe. Those guys are required to have 360˚ 1/4" steel plate or approved blow-proof bell housing for real flywheels according to conjecture on several forums by people with serious looking cars that passed tech.

I just spent an hour online and quickly take back my thoughts on using a blanket to catch a flywheel/pressure plate/clutch. You and N Sperlo are right.

I read one of the SFI tests for a transmission blanket was to shoot it with a .22 bullet and if it catches the bullet it passes. I would think there are bigger forces with a flywheel/parts.

PENETRATION RESISTANCE – FLEXIBLE BLANKET Section 5.2

http://www.sfifoundation.com/Spec_4.1_071907.pdf

Since this is for a racecar, I would assume you already have a lightweight steel or aluminum flywheel. This works to your advantage in two ways. First is that they are considerably less likely to get a case of the comeaparts than an iron flywheel. Second is that in the unlikely event that one does, the pieces will be carrying considerably less energy that needs to be absorbed. That's not to say a shrapnel collection device wouldn't also be an advisable precaution, just that the structural requirements will technically be appreciably less than for systems designed to contain an unmodified stock V8 flywheel...Which is OK, since this is the type of thing where it's better to over do it than under do it.

I seem to recall a story about the Pentagon coating their walls with Herculiner to reduce shrapnel in the event of future attacks, so that might be a nice light-weight improvement as well.

foxtrapper wrote:

N Sperlo wrote: Kevlar is not made to stop metal at such a force. Yes, they are used in flack jackets, but I don't think its your answer. I have a thick Kevlar vest on and know someone could slide a sharp blade right on through there.

Kevlar is used for exactly that purpose. That's why way back in history when the stuff came out we started wrapping our engine rooms in the stuff. It's about the best there is for containing exploding steel. Kevlar is far stronger than steel, pound for pound. And you're right, as a fiber, if it's just laid there, a blade will slip right through it. That's why you use layers of the stuff, including woven layers.

I'm just thinking back to how not-so-great the Vietnam flack jackets were, so if you guys wrap the rooms in them... Right on. I've got up to 42 layers across my chest. Pointy things bad. Blunt, not so bad....

N Sperlo wrote: I'm just thinking back to how not-so-great the Vietnam flack jackets were, so if you guys wrap the rooms in them... Right on. I've got up to 42 layers across my chest. Pointy things bad. Blunt, not so bad....

I bet a 6lb, blunt hunk of flywheel going 900 m/s would sting like a bee even with that jacket. You might even have to pause from speaking so the other men in the room didn't notice the faint hint of strain in your voice.

Really? Because I had this idea of that dull knife from the infomercial that squashes the tomato before the sharp one cuts it...