Forum: HoseHeads Sprint Car General Forum (go)
Moderators: dirtonly  /  dmantx  /  hosehead

    Sounds kind of like the reasoning behind Offy engines going away 50 or so years ago.

Hey Kelly, Do you believe Gravel's crankshaft broke because he was running too hard, as some have insinuated, and it was even mentioned in this thread, because I don't!

If the driver can't run has hard as he can without parts breaking, he needs better parts! lol!

Brad Doty

This is one theory,  it could or could not be accurare

  Cranks do break at times for no known reason.  We broke one on our car and we sure were not over rev. it.  We sort of thought from sounds from cars of Gravel and Schartz that they had high speed rev limiters that kicked in at max rev. at end of straights to a 2 degree or 4 degree retard on corners.  I could be full of bull,  but that is  what I thought just from sound of cars.

I've  been around racing along time. Ive raced a ump modified for 16-17 years. I've seen this happen a lot. Cranks and parts connected to it break frequently on rough tracks. I wouldn't call the track rough that night but it was choppy in places and Schatz stated in his interview he saw gravels tires leaving the surface and what he was basically saying was he snapped the crank because of it. Its possible thats not why it happened and theres no way of knowing. But id put my $ on it.

Who really knows why that Crank broke. But, I would bet it was turning over 9500 at times maybe even 10k, high compression and bouncing around over the cushion. I would bet all of that played a factor. You know what else played a part? Knowing Schatz was behind him... My GUESS is Gravel was flat on the floor all the time and I cannot blame him for 1 second. You may never get that chance in that race again.

DA

Gravels crankshaft issue.

What would have been harder on the crank when bouncing thru the ruts? The high revs being in the air or the sudden pull down when it lands again? Even if its not going all the way in the air just the suspension unloading and loading on landing would cause alot of RPM variation in a short time period.

Also how much will a drive shaft flex/twist to absorb some of the hit on landing? Not sure you can ever pin it down to him driving thru the ruts as a cause but rough tracks are hard on equipment.

Only thing I can relate this to is dirt bikes and bouncing thru rough terrain or whoops. You don't really hear of cranks breaking because of that but there is also a chain and clutch to possibly take out some of the hit.

 Brad, I sent you an email on here.

   Any chance you could share some of that info with us out here on the main forum?

-Thanks

    Can you explain the concept of rev limiters to a non-mechanical mind?

-Thanks

Chip that plugs into side of MSD box to limit RPM so you don't float valve train. You can pick whatever limit you need.

Comes in handy when car is flying through the air upside down with drivers foot on the throttle wide open.

https://www.msdperformance.com/products/rpm_and_timing_controls/modules/parts/87481

 
 
 
They don't even know how to spell sprint car 
much less chromoly...http://www.ycmco.com

     Thanks for the explanation. Question- I understand the idea of setting the RPM's at- I'm just picking a number- 8,000 to save the motor from running too high during a crash or something. Could the same technology be used as someone up above mentioned to set the RPM's at, say 7,000, and save wear and tear on every engine on the track?

Remember one thing. The motor some guys show up with at Knoxville have every lite weight part you can get into the rotating assembly. The huge advantage in today's motors is the craddle the crank sits in and they are cross bolted today. Gravel's bouncing around in the corners may have had something to do with his crank breaking. That's the price you pay. I will also make comment on that's what makes DS so good. The guy is good on keeping his equipment under him. Yea Gravel understood who was behind him and he just didn't get it done. A lot of guys in his position would have done the same thing. He may never get that chance again. It's what makes King KInser and Ds accomplishments at Knoxville so impressive. Brad, you've never broke a crank ??? 

The way I understand it, you say put a 8900 rpm rev limiter in red spark box.  You can have your spark box custom made by MSD  on how rev limiter works.  You can build a say 4 degree retard in ignition  when engine goes over 8900 rpm.  This kills H.P..  Then you could get every cy to retard all at once or alternate thru fire order.  You kill HP and car might handle thru slick corners better.  I think this sort of a new developement.

  That's a crank trigger.  Not new, we started using them on our engines about 7-8 years ago.

  MSD made them but we didn't really like the way they were built.  My dad contacted a guy he drag raced with back in the 70's, Steve Leach who owns RCD Engineering and he designed one for us.  Now pretty much all the engine builders use the RCD crank trigger on all their engines.

     If the powers that be wanted to make sprint car racing less astronomically priced, wouldn't some sort of a compression rule be worth looking into?

Powers to be????

There is other sprint car racing:

360 cid ( with its set of rules)

360 cid ( unlimited rules is certain parts of country)

358 cid ( central pa 10.75 cr and all cast iron engines )

305 cid ( racesaver rules and 10.25 cr )

305 cid ( non race saver rules)

midgets,micros, etc... all other classes to race.

History: people complained about no weight limit... Weight rule instituted ( it is currently in the USA 1400 lbs w/driver) and the winners are still the winners consistantly. A rule on the wing started with a paragraph, after 2007 = lots of paragraphs. Basic rules are always needed.. remember the more rules: the more cheating.

All of you are chatting about the quickest/fastest race vehicles racing on tracks 1/2 mile or shorter on dirt and suggesting limiting them... The word OUTLAW has been cut up and cut up(  by implementing more rules and more and more .

Enjoy this Class of racing as long as you can... it is one of the last true forms of racing today... why? no computers/technology..( except what is ALLOWED currently). Driver has no aids to enhance driving, Crews have no data except the tach to make adjustments.

     My concern is that the cost of sprint car racing is escalating so fast that the fan base may not be able to support the purses.

unlimitedcubes: can you explain what the 10.75 cr means when talking about 358 cid PA sprints? Talk simple please, I'm not mechanicaly minded. -Thanks

Lol that's funny. To the average fan that makes complete sense, but the purses are staying stagnant (or actually going down) while the costs are increasing 10-15% every year. I'm not sure where that extra money that you're paying to watch the races is going each year, but it sure as hell isn't going to the racers.

CR is compression ratio.  It refers to air compression basically.  If you take 2 cubic feet of air and compress it into a 1 foot space, you have a 2:1 ratio.  So conceptually (not actual numbers) a 10.75:1 engine would be taking 10.75 cubic feet of air and compressing it into a 1 cubic foot space.  Again, these aren't actual sprint car numbers.  The higher the compression ratio means a more violent explosion and more stress on engine parts.  But more violent explosions can mean more HP as well.  Limiting the compression ratio should limit the stress on engine parts and increase longevity while theoretically leveling the playing field.   

.  

That's what I gathered, but it seemed a little odd. So, further back in this thread it was said that a 360 runs about a 14 to 1 compression ratio and a 410 somewhat higher. Yet there are some groups or tracks running engines limited to 10.75 to 1 ratio? Am I following that correctly?