what was the cause of most clutch explosions back in the day?

faulty flywheels? or clutches? whats the best way to prevent an incident if theres not any scattershields currently available for the motor your working on? how well does a cast iron bellhousing hold up to an explosion?

 

Probably the flywheel scatters from too much RPM,but the pressure plate and disc can blow up also.Dumping the clutch at maximum revs doesn't help matters.Maybe the cast iron is better than aluminum.Back before store bought scattershield you could make something reasonable from welded steel plate.

 

how about a kevlar blanket.

 

what kind of car is this? also wearing a cup while driving never hurts.

 

I've heard of old timers welding fairly thick plate to the underside, or topside of the transmission tunnel, and toe area of the floorboards. That would probably do the trick if you can't find a store bought scatter shield, or don't want to make one to fit to your bell housing.

 

Be aware that anything you fabricate may not pass local dragstrip tech, let alone a sanctioning body's inspection. If this isn't an issue, then fabricate away.

It may be quite possible to use an aftermarket clutch disc & pressure plate, with a thorough reading of the McLeod/Ram/Zoom/Hays etc. catalogs, and adapt an aftermarket flywheel, even if there is no scattershield offered. My personal view is that you are better off trying to keep everything from breaking in the first place, rather than trying to contain things once it happens.

 

Cast iron just shatters when it gets hit with pieces of steel flywheel traveling at 150-200MPH.

 

An unbalanced assembly(Flywheel,Pres plate and disc)is a very good way to increase your odds on failure..Balance the complete unit...very good insurance to start with.
NEW parts would be my next choice.If you want to run a steel scattershield,protect
the inside of your vehicle,leave it open on the bottom so the crap will blow downward
Dont use rebuilt parts! Just be sure to BALANCE THE UNIT

 

Everytime I read about clutch explosions, this picture always comes to mind.

 

rice is not immune to the problem either.


regards,Rod

 

Re: what was the cause of most clutch explosions back in the day?

Stock motors turned less than 3700 rpm with battery/points ignition and oem valve train. Limiting the rpm was a combination of valve float and spark breakdown because the faster a motor turns with battery ignition the weaker the spark gets.

Innovations in hopping motors up made higher rpms possible, clutches and flywheels weren't up to the stress.

Further, over-rev by failure of axle or breaking of traction, especially on a blown motor can go a couple of grand above redline.

 

Centripetal force.

 

That's a gruesome little pic. It's probably well known by now... but was that car raced by someone famous, and do you know the specs on that car? Ya got me curious. I wonder if the driver got out of that alive, or if he bled out.

 

That's the picture I was thinking of. I have it in an old mag but can't remeber the date. Graphic ain't it?

 

Guys, I can't help you with the particulars on that clutch explosion. I remember seeing the article and reading about it in Hot Rod Magazine, but as far as the drivers fate, I can't help.
Years ago a fellow who had a Austin-Healy with a SBC in it lost part of his right foot and some toes on his other foot when the flywheel came apart. This happened at Pittsburgh International Dragway in probably the mid '60's. I think one of the rules at that time was you needed special flywheel bolts along with a scattershield. He had the shield, but not the bolts and the interior of the car looked just like the posted picture. They had to hold up racing naturally to treat him, plus dig out chunks of the flywheel from the track surface. Cars parked near the fence were hit by parts and luckily nobody except for the driver were hurt.

 

Make sure there is no heat checking on the flywheel or pressure plate surface. If there is , have it re surfaced. Do a search and you will find a thread with alot of great stories.

 

friend of my dad's cut the frame in half [passenger side luckily] on a 55 chevy ...street racing a small journal 327 ...over rev..maybe ten grand

 

In the old days the NHRA rules stated 1/4 inch plate around the bell housing area, top and bottom.

 

When the 55 chevys came out

 

http://www.jalopyjournal.com/forum/showthread.php?t=185297&highlight=clutch

and mine...

http://www.jalopyjournal.com/forum/showthread.php?t=36919&highlight=clutch

 

Another reason was most factory flywheels were made of cast iron. After they had been resufaced to many times they became awful thin. I had one for a BB Ford motor that I had to grind the heads of the flywheel bolts to clear the clutch springs. Steel flywheels are much less prone to come apart. Pressure plates can also come apart and that can lead to catasrophic failure. When the plate separates from the cover. Like Homespun said keep everything from breaking from the start. Use a steel flywheel and quality parts Your feet will thankYou. FEDER

 

well it just seemed that way, thats when i first started to go to the drags and I,m sure the 'really old' timers have seen them blow before that, I saw a chrysler powered coupe blow the back off of the engine and it was showering sparks from the block dragging on the ground. Afterwards at the drive in my buddy noticed a dent in his fender[we used to be able to parkalongthe strip]. [Colton Ca.] them hi winding chevys blew a lot of clutch/flywheels back then..

 

STOCK CAST IRON flywheels, COMBINED with heat cracks/stress risers, and an RPM they were'nt designed for lead to most "clutch explosions". The flywheel goes and takes EVERYTHING with it, although the disc and cover can come apart separately. I've tossed the lining off discs, but never had a blow up, yet. Seen a Chevelle and a Camaro that looked similar to that 55 posted earlier. Both drivers had minor injuries.The cars were heavily damaged; dash ripped apart, broken windshield, floor torn up, headers literally cut off. SEMA/SFI parts for any high RPM/racing use, and a scattershield, will keep you walking without a limp.

 

guy in town did it to his 67' Chevelle. Tore the hell out of the firewall floor dash, and windshield. he was not injured

 

And yet look how many people like to watch the drags - standing right at the starting line...

 

As a kid my dad always told me not to stand inline with a car at the drags at the startind my son is coming with me on the weekend when I race and he'll be told the same and have ear plugs, they didn't know about that in dads day. My car has a Hurst scattersheild, steel flywheel and new clutch and it the only thing a fear blowing up, especially after seeeing that picture of the 55

 

The cut-line on the caption of that '55 dash is simply "driver kept his feet."
It's in the '63 Hot Rod YearBook.

I know a guy who had a '53 or '54 Chevy with a 283 back in the day, and the throttle stuck open while he was racing a friend. Being young and dumb, he figured the best way to get the car slowed down was to push in the clutch. He ended up with a lot of stitches in his right foot. The thing that amazed him most was that when the flywheel came apart, it straightened the ring gear out--said it was almost perfectly flat.

I'm curious about this whole thing too--I'm thinking I'd like to build a Carrera Pan Americana '54 Buick, and I'd like a little security. The aluminum bellhousing I have doesn't give me a lot of confidence. I hadn't thought about getting an SFI flywheel, but there's probably something that can be made to work...same with the clutch.
I have a friend who raced a Shelby Mustang clone in the Targa Newfoundland race the last three years. Last year, the clutch disc blew up, and the can caught it all. They swapped in a new clutch and were back in the race. This year, the 289 broke the crank into 4 pieces.

Nobody makes a blowproof bellhousing for a 322 Nailhead--or most any other vintage engine that isn't a 354/392 Hemi. I wonder if a stock or aluminum bellhousing could be wrapped in carbon fiber? I've seen carbon fiber shields for auto transmissions.

-Brad

 

actually half of his foot is missing to the arch

heres a video of "superman" nicol popping in indy 70'
http://www.youtube.com/watch?v=aSAuf8mE_k4

 

Didn't Scheifer claim to have guaranteed explosion-proof flywheels? I thought I read somewhere that nobody has ever blown up one of their composite (alum/steel) flywheels.

I had one with an overheated, heavily checked surface that I threw away years ago. But every other one I saw seemed bulletproof.

Factory cast iron is stupid for any high rpm use.

 

Didn't Scheifer claim to have guaranteed explosion-proof flywheels? I thought I read somewhere that nobody has ever blown up one of their composite (alum/steel) flywheels.

I had one with an overheated, heavily checked surface that I threw away years ago. But every other one I saw seemed bulletproof.

Factory cast iron is stupid for any high rpm use.