Clutch/flywheel explosions...let's hear some stories.

This photo is from norbsplace.com. This is his twin fuel flathead.

 

I witnessed a flywheel explosion on a street car at the old 1/8 mile drag strip near Darlington, SC in the mid-1970's. Spectators could stand (and park) just a few feet from the side of the track. We were standing about mid-way down the track when a late 60's mid-size Buick (Skylark IIRC) missed a 1-2 shift RIGHT in front of us. BLAM!!! and we all saw stuff spray out from under the car, hit the track and bounce in the air to shower down everywhere. Everybody thought WTF? and simultaneously turned around and high-tailed it. That flywheel must have fragged into ~1/8" pieces because none of the spectators or adjacent vehicles were hurt. AFAIK the driver wasn't hurt either, but it made for a 10 on the pucker-factor meter that night!

 

That's some scary shit there boys! I guess I'm fortunate that I'v never seen one up close.... But I'll most definately be taking all this into account when constructing my next rod!!!!!!!!!!!

 

Ever see a flywheel explosion in a heavy truck? A 50's gas engine dump truck,the novice driver missed a down shift with a compound gearbox,actually managed to get a way lower gear than expected.Blew the shit out of the massive clutch housing,the driver got out with just some minor lacerations.

 

The guys running a late model Chev or Ford have it easy, the swap meets are full of pressed steel blow resistant bell housings. What do I use on my Y block?

 

Every time I look in the seat of an old dragster, I think of my balls practiclly resting on the rear end housing and it makes me respect the drivers that much more!! Do they make an explosion proof cup??!!

 

I have my ol 58' chev truck. I got it home, and got it running again, and took it for a drive. Got half way back up the hill, and somthing in the motor gave. I let it rest for a while, got it fired back up, and just hammered the thing home in 1st gear. Got it parked, and went inside. Came back out, fired it up ( running like shit ) and dropped it in gear. It damn near wouldnt move, so i revved it, and BANG! shut it down, and yanked it in the shop. AFter gettin the motor out, and ripping the tranny off it, i saw that the pressure plate had come apart at the rivits, and let loose. Took a chunk outta the bellhousing, and nothing more.


This reminded me of that, so now im gonna go make a plate outta 3/8ths plate to keep it under me

 

Also, a flywheel explosion killed the driver of the socal speedster back in the 50's didnt it?

 

Here are the details from a street race in late 1968. My '58 Ford 2-dr post had a 427 low-riser, a 4-speed, and a stock nodular iron flywheel. I power-shifted to 3rd gear at 6500 and all hell broke loose. The exploding flywheel took the rear off the block, something cut the bowl on the rear Holley setting it on fire, and another something blew out the right front tire. Luckily I still had brakes and got the car stopped.

The only thing that saved me was a RC blowproof bellhousing. The reason I had a blowproof bellhousing on the car was because I also raced my '58 at the dragstrip in B/MP. It was a NHRA track and they enforced the rules. The bellhousing with sections of the broken block still bolted to it shoved the firewall back but not a single piece came inside the car. All the shrapnel was deflected forward (and towards the Chevelle I was street racing against).

While the older style blowproof bellhousings will save the driver, they will allow the exploding parts to scatter everywhere else. Only the newer style stamped steel bellhousings with the accompanying block plate bolted properly in place will contain all the shrapnel. Also make sure you use either a steel billet or an aluminum flywheel and a blowproof pressure plate to be safe.

 

One year at Englishtown lots of racers were failing tech for not having blockplates. It was common to leave them out because it was so much more work to change engines or clutches with them in, plus some oil pans didn't fit the blockplates, and the inspectors routinely let it go. At the previous race a flywheel let go on a car without a block plate and pieces of it got out into the stands and caused heavy injury. Rumor was that the starter motor had even gotten into the stands. NHRA could not warn the racers that they would be checking for blockplates before the race without acknowleging that they were aware of the situation and exposing themselves to additional liability, so many racers were scrambling to find blockplates and put them in the car. I was working on a Modified eliminator car that required that a cage bar be modified to allow the scattershield to go back the thickness of the blockplate so we were down at exit 7 of the NJ Tpk. trying to get the gas station next to the motel to fire up his torch and cut either the scattershield or the bar so we could get it together, made it easy to remember the occasion. Around '78 or so, IIRC, first gasoline powered flywheel injury in a while for NHRA.

 

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Don't know how well this will post up as it isn't the best pic anyway. If you look under the car in the second picture you can see the flywheel, pistons, & crank. I think that is the pan by the rear wheel.

Tic

 

Many clutch explosions begin with sub-standard pressure plate-to-flywheel bolts. It never pays to re-use used bolts. The bolts MUST have the requisite shoulder of the correct length and be at least grade 8. Torque to clutch manufacturer's specs.
Resurfaced cast flywheels only hide the stress cracks but give you a good looking clutch surface. The same goes for re-man'd pressure plate assemblies.
A cast iron pressure plate will crack on its own just sitting in your driveway in these northern winter climates. Very cold - then - warm - then cold temperature cycling over the days of winter will fracture an already hidden cracked cast pressure plate. I know of two particular cases: both SBC. Parked the car, ran fine, left it for a couple months, nice winter day, started fine, engine vibration, could not get into gear. broken pressure plate. Other one a 327 COE 5ton truck, flywheel fine, disc fine, pressure plate broken, not exploded.
Stood within inches of a clutch explosion at aproximately 3000rpm in the dirt pit area of a stock car track. Driver complained of a vibration so he pulled in. From under the hood I slowly brought the RPM up. Then BANG. The top half homemade scattershield contained the explosion upwards but not downwards. No one hurt. Diagnosis revealed two of the six pressure plate bolts had failed - they had been used too many times over. Fabbed a "button" (in conjunction with a flexplate) and ran direct drive to the tranny the very next day.

 

I fear clutch explosions.

 

What do you suppose he's saying in the second picture. Hands in the air, looking down between his legs...........

 

When / Who made/ did the first scatter shields come out ??

 

Saw 2 clutches and flywheels let go. 1 in the 60's and another in the 70's. Both were '67 Camaros. When I built my Biscayne, I used a Lakewood scattershield with the block saver plate. My race car, '62 Nova, had a trans blanket.

There was a dual engined "T" running around the So Bay. I use to see it at the Long Beach Swap Meet. The coupler connecting the engines let go. Now it has a shield for the coupler.

 

Coupe i belive, cut the gas tank on it

 

Dangerous stuff. In high school, about 1966-67, a friend had the flywheel come straight up through the floor and then through the dash of his 56 chev. It is an awesome sight to behold.

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My grandfather kicked a clutch out of his top gas dragster in 66 or 67....cut the end of his steel toe workboot off and left shrapnel in the soles...still has one of the boots....keeps me in line when i feel like gettin the clutch hot in my Cdan doin holeshots with no scattershield....

T. Hilton

 

my 55 chevy just lost the clutch and pressure plate...cut the headers in half ...and threw bolt heads everywhere..bad day

 

fuuuuuuuuuuuuuuuuuuuuuuck!!!

 

okay gotta add my own story.

years ago while making a pass at el mirage i had a kong flywheel explode on me. it was the 2nd to 3rd upshift at about 6000 rpm and all of a sudden the car jumped. i hear the sound of parts falling out from under the car and turn off to the right (signals a problem to the course patrols).

after i get stopped and get out of the car i can see where chunks of flywheel and clutch tried to pierce through the aluminum hood in a few spots. we take the hood off to asses the damage and that's when i realized how lucky i really was.

four banger fords have a cast iron upper bellhousing piece that bolts to the back of the block. the chunks of exploding flywheel completely disintegrated this bellhousing and the force of the explosion blew the motor forward enough to break the front motor mount plate (1/4" aluminum plate). the only thing that held the motor in the car after the cast bellhousing piece blew up was a big chunk of flywheel that was wedged between the back of the block and the firewall.

if that chunk hadn't have wedged in there i'm very confident that the motor would have pretty much fallen out of the bottom of the car at about 100 mph right onto the lake bed. that would have been very very bad.

i've got all 10 toes thanks to a super heavy duty hydroformed steel scatter shield. even though the sedan i'm building will only making 350-400hp i'm going to run a scatter shield.

 

i'm wondering this myself, please no one flame me for this,this is a serious question. My project is an 86 accord,it has the larger 2.0 motor in it, these things redline at 6500 rpm, i've exploded a clutch once before, they have a very thick aluminum bellhousing on the transaxle, the pressure plate actually broke the bell housing into chunks, and threw crap everywhere. they have a very heavy steel flywheel , flywheel is actually balanced to the rotating assembly factory. does anyone know of any kind of scatter blanket for cars with transaxles? i'm adding a lot of power to this at the moment, the engine will be fine,but after the pressure plate explosion, i am concerned. if you know anyone who drag races these imports, legitimate drag racing not street racing crap, this might be a real concern. my wifr rides in the passenger seat,thats the side the transaxle is on, and rotating crap would go straight into the car. are there ballistic shields you can put on the inside of the firewall? friend of mine drag races these, he's running in the tens at the moment at over 136 ,he read this and is very concerned also. he's grenaded entire transmissions,and been lucky so far.

 

In 1965 or 66 my friend was racing at Dover Drag strip in New York. A warmed over 327 with 4 speed in a 61 two door Post Chevy with street tires. Right at the start line he launched and blew the whole shebang clutch, pressure plate, flywheel, bellhousing. Went up like a hand grenade and parts went into spectators. The result was one guy seriously injured in his arm with a piece of pressure plate. As usual back in those days no insurance and the driver got sued and lost. Had to pay something like $100,000 back in those days. He didn't have the money so the lawyers had his pay attached. Last talked to him around 1997 and HE WAS STILL PAYING after twenty years and will be still paying for the rest of his working years. Stay safe.

 

<--- Makes a note to send back shiny wheels and get a scatter shield instead.

Makes ya think, really. I put 'em on race cars... I never put a scattershield on my street cars, and I run 'em hard (and they're heavier...). I think I'm gonna from now on. All it takes is once...

Good thread.

 

I have been reading this thread for a while and it brings back some bad memories. Nearly 20 years ago I was racing a Datsun and due to some dodgy wiring had the starter motor engage at 9000 rpm between shifting from 3rd to 4th. The explosion lifted my car and the car I was passing off the track. It actually straightened the ring gear out and when I walked back up the track I thought it was a broken fan belt. The car was an ex US SCCA car and was left hand drive which was lucky for me , for if I had been sitting on the normal side for us Kiwis I would have lost my feet..For the record the flywheel did'nt get damaged I had made it from high strength alloy steel plate and survived without a scratch. See photo below.

 

I think I've posted this before, but this flathead dragster let loose, broke off the bell housing, and a chunk conked a guy's head way up in the stands. I was trackside taking pictures and I had parts whizzing past me. In this case, it was the clutch, not the flywheel.

 

Not really a car but it is a flywheel coming apart. Hey , at least its old lol , Just shows how dumb some folks really are.

Was redoing a a 1949 John deere 70 for a friend of mine. Now for anyone not familair with thes vintage deere tracotrs , They are just a twin cylinder tractor , they really get thier power from the spinning mass of the monstrous flywheels. Its been a year or so since i did the tractor but if memory serves me correct that fly wheel weighed in around 185 pounds and was almost 2 feet tall and 3 - 4 inches thick in the heavy casting around the edges.

Well John deere 70's are really bad about wearing out the splines on these big flywheels from the winding up and winding down , and they would tend to crack and start to knock . Some of the old boys remedeys were to do things like smash a beer can on the splines and beat the wheel on with a sledgehammer to get it tight .

Well when i found this one to be bad and cracked , i simply did the smart thing and ordered a tapr lock flywheel that solves the problem instantly and is an ingenius idea on how it is designed.

Now where this story is going , As i was ordering my taprloc flywheel from the only guy in the country that makes them . He starts telling me some horror stories ,
These flywheels do not sit crossways on the tractor , the sit off to the left side and spin front to back , He was at a show where someone had done the beer can trick and this yahoo had this ole double lunger really poppin to show it off , When that 185 pound piec of cast came apart it litterally sheared the rear axle tube and axle on the left hand side in half , ripped everything off the front of the tractor and knocked the front steering post" tricycle type " out from under the tractor.

 

From the NHRA 2009 Rulebook, General Regulations, 2.10, FLYWHEEL SHIELD.....
All front-wheel drive or transverse-mounted applications using a clutch and running 11.49 or quicker, for which an SFI Spec 6.1, 6.2, 6.3 or 9.1 flywheel shield is not commercially available, must be equipped with a flywheel shield made of 1/4 inch minimum thickness steel plate. Shield must surround the bellhousing completely except for area of bellhousing adjacent to differential and axle shaft. Shield may be multi-piece, with pieces bolted together using minimum 3/8 inch diameter Grade 5 or M10 class 8.8 bolts; may be attached to engine and/or bellhousing.

Someone made a reference in an earlier post to using conveyor belting. I remember that from days gone by and in my opinion, once you get the shield made and mounted, it wouldn't be a real bad idea to mount some belting on the interior of the firewall. I'm talking about the belting that is used to convey rock, sand and gravel from one location to another at sand and gravel operations. I'll bet if you were to ask real nice, one of the companies would give you some for free.

There's a turbocharged Honda that shows up nearly every Friday night at Firebird. The owner has fabricated a shield like that detailed above. He has also added an SFI 4.1 ballistic blanket over the fabricated steel shield. The 4.1 is actually designed for use around an automatic transmission on a RWD car, but he has used it on his transverse application and made it look nice. These 4.1 blankets are dated and must be replaced every two years, so I'll bet if you check around with some of the racers at the local drag strip, you could find someone with an outdated blanket that they would give to you. Just because it's out of date doesn't mean it won't add some degree of additional protection. This car I'm describing is teched to 8.50 in the quarter. It's a real nice car from a tech standpoint and the owner is obviously very safety conscious.