2015 RCR #5

Questions and answers about CMC and NASA rules

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Al Fernandez
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2015 RCR #5

Postby Al Fernandez » Thu Oct 01, 2015 3:50 pm

Another from Tyler...this time about internal balancing:

--1) Tyler Gardner / TX / #013
---2) 7.11.10 (new)
---3) Ford 5.0 cars may use aftermarket internally balanced and forged crankshafts
---4)
---------->a) 4 5.0 catastrophic crankshaft failures in the past few years
---------->b) Will promote series growth because of reliable engines.
---------->c) Rule change is only for durability and there is no performance gain
---------->d) When mine broke the cars behind me lost control, oil and sharp metal on the track is a serious safety issue that could cause loss of equipment or life.

Examples:
Tyler Gardner CMC 013 MSR-H 2015
Michael Mosty CMC 11 2014 and 2012
Wade Zimmer CMC 2015
Al Fernandez
CMC Chief National Director

mach1
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Postby mach1 » Thu Oct 01, 2015 6:37 pm

This may need to go hand and hand with an update to 7.26.1

Current
"Any single disc clutch and pressure plate of OEM stock diameter may be used provided that it is bolted directly to the unmodified OEM stock flywheel and the pressure plate is made of the same material as OEM."

Revised
"Any single disc clutch and pressure plate of OEM stock diameter may be used provided that it is bolted directly to the unmodified OEM stock or unmodified aftermarket flywheel that is made of the same material and is no lighter than the OEM flywheel, additionally the pressure plate must be made of the same material as OEM."

Thanks to Chuck Penney for pointing this out.

DAlgozine
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Postby DAlgozine » Fri Oct 02, 2015 10:24 am

Would the crank upgrade apply to carb'd engines?
If so, I would be concerned that by not having a redline for all carb'd cars this rule would provide an advantage over other engines. You can rev the snot out of them and they would take it.
(related item : rev limits on carb'd engines)
Dave Algozine
CMC #12

mach1
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Postby mach1 » Fri Oct 02, 2015 12:25 pm

DAlgozine wrote:Would the crank upgrade apply to carb'd engines?
If so, I would be concerned that by not having a redline for all carb'd cars this rule would provide an advantage over other engines. You can rev the snot out of them and they would take it.
(related item : rev limits on carb'd engines)


Ironically the broken cranks have all happened on EFI motors, perhaps because of the increased torque? I think having them apply to carb motors would be good to future proof the rule. The cam and valve train seem to be the limiting factor more so than than the rotating assy when it comes to power, if there is concern perhaps we could impose a rev limit on the carb engines?

Supercharged111
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Postby Supercharged111 » Fri Oct 02, 2015 3:30 pm

The carb'd car rev limiter was shot down last year, I believe on the premise that they make less torque than a fuel injected engine though I can't be sure without a search.
Rocky Mountain CMC Director
#45 Camaro Challenge Race Car

mach1
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Postby mach1 » Fri Oct 02, 2015 4:03 pm

I am trying to think of any way that revving higher in a carb car would be an advantage, doesn't the B cam tank at 5k rpm? They could go to 7k and it would be a dog. Either way, a forged crank wouldn't make me feel any better, the block is also very weak.

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BADVENM
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Postby BADVENM » Fri Oct 02, 2015 4:05 pm

Am I correct in saying the broken cranks happened in Texas cars only? I've been running my EFI motor for 5 or 6 years without any problem whatsoever. Did the three of you with broken cranks have your motors built from the same facility by chance? Did the three of you get together and compare notes on what failed...any similarities or were they all different?

Anyone outside of the Texas folks (if the three cars are from Texas) with either a carb'd or EFI Ford motor have any similar issues?

Why the need to revise the allowed clutch? I don't see a reasoning why the change is needed. Again, for me at least, several years on Exedy stock replacement clutch, no issues.
NASA Rocky Mountain - Camaro-Mustang Challenge car #8 Team Incidental Contact
3rd Place CMC - 2010 NASA National Championship
3rd Place CMC - 2015 NASA West Coast Championship PTB

mach1
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Postby mach1 » Fri Oct 02, 2015 4:13 pm

BADVENM wrote:Am I correct in saying the broken cranks happened in Texas cars only? I've been running my EFI motor for 5 or 6 years without any problem whatsoever. Did the three of you with broken cranks have your motors built from the same facility by chance? Did the three of you get together and compare notes on what failed...any similarities or were they all different?

Anyone outside of the Texas folks (if the three cars are from Texas) with either a carb'd or EFI Ford motor have any similar issues?

Why the need to revise the allowed clutch? I don't see a reasoning why the change is needed. Again, for me at least, several years on Exedy stock replacement clutch, no issues.


I looked around online and found others with the same break that we have had, but they are not in CMC. Texas cars only, different builders on the motors, the crank broke between the 1 and 2 main journals on all of our cars. The revision is for the flywheel, we would need to be able to run a neutral balance flywheel with an internal balance crank. The rule change is to allow a stronger crank and internal balancing, the steel crank should be able to handle more cycles than cast, and the internal balance should reduce the stress and the "jump rope" effect of the crank.

Supercharged111
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Postby Supercharged111 » Fri Oct 02, 2015 5:30 pm

I think we should be careful here not to allow knife edged cranks that are lighter than stock too. Maybe spec a crank the way we do oil pans to keep things from getting out of hand.
Rocky Mountain CMC Director
#45 Camaro Challenge Race Car

mach1
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Postby mach1 » Fri Oct 02, 2015 8:05 pm

Supercharged111 wrote:I think we should be careful here not to allow knife edged cranks that are lighter than stock too. Maybe spec a crank the way we do oil pans to keep things from getting out of hand.

Agreed, we can drop in Scat/Eagle part numbers, for example:
Scat:4-302-3000-5090-2123-1
Eagle:430230015090

Both are significantly heavier than stock because of the internal balance.

mach1
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Re: 2015 RCR #5

Postby mach1 » Tue Oct 27, 2015 7:31 pm

I ordered a forged scat crank, I will weigh it vs a stock crank when I have them both in front of me. Everything that I am reading is showing the forged crank to be 9lbs heavier than the stock crank.

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TX#11CMC
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Re: 2015 RCR #5

Postby TX#11CMC » Fri Oct 30, 2015 4:52 am

Remember to weigh "all" the pieces of the stock crank. :wink:
-Michael Mosty
TX region #11
"Fox" driver and lovin it!!!
Texas Region - CMC Director

mach1
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Re: 2015 RCR #5

Postby mach1 » Fri Oct 30, 2015 6:00 am

TX#11CMC wrote:Remember to weigh "all" the pieces of the stock crank. :wink:

Damn, I think some of them are still in Houston :-/
I have a stocker that is in 1 pc somewhere :x

D. Francis
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Re: 2015 RCR #5

Postby D. Francis » Fri Oct 30, 2015 7:09 am

mach1 wrote:I have a stocker that is in 1 pc somewhere :x
It's probably turned 0.030. Add 10lbs to be safe.
David Francis
#39 CMC Camaro
Orange is FAST!

mach1
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Re: 2015 RCR #5

Postby mach1 » Sat Nov 07, 2015 8:39 pm

Scat forged crank is 47.5lbs on my postal scale.
Trying to find a stocker that is in 1pc for stock weight.


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