Flywheel Weight

[CWilcox]

Could someone please expand on my flywheel weight confusion. What happened between 1997, when the Jake Lamont book was published and the 2007 SCCA rules regarding flywheel weights?

To my best understanding the Jake Lamont book quotes 19.9# whereas the 2007 SCCA rules quote 15.5#. That is a big difference and I would like to know what is the current requirement being used. Possibly the rule book doesn't include the clutch bits. Maybe there was a rule change.

Thanks in advance,
Chris

[Stan Clayton]

Chris,

The minimum flywheel weight was 17.4 lbs for the original engine, and 19.4 lbs for the uprated engine up through December 31st, 2003. Since January 1st, 2004 the minimum weight has been 15.5 lbs for both engines. IIRC, the primary motivation was increased gearbox life. The nice engine response boost was a freebie...

Stan

[Larry]

I didn't know there was a problem with gearbox life. I thought the reason was improved crankshaft life and reliability.

Larry Oliver
International Racing Products

[Stan Clayton]

You could be right, Larry. I was new on the F/SRAC at the time and may be mis-remembering.

Stan

[DaveW]

I didn't know there was a problem with gearbox life. I thought the reason was improved crankshaft life and reliability.

Larry Oliver
International Racing Products

Correct - the heavier FW set up harmonic vibrations (IIRC) that caused crankshaft cracks at the rear next to the FW flange.

[TimW]

I'm pretty sure 15.5 was legal in 2003 as well. It was a new rule added at the end of 2002 for 2003 if I recall correctly.

[TIM CLOWATER]

Chris all the flywheels I have for the car you have are machined to legal wieght and the reason was for what Dave said ( the crankshaft)

Tim

[Joshharvey]

All this talk about flywheel weight is interesting. Formula ford rules were the same for quite a while, which is one of the defining properties of it being an entry level racing class. More and more rule changes that seem to benefit some kind of vendor have crept in. As for flywheel weight, the lighter you go, the better shifter you better be, because the engine speed can change faster than you can shift gears. A lightweight flywheel is hard on both on the engine and gearbox due to the rapid acceleration/decelaration of the roating assy. Fast guy is fast, no matter what. The cream rises to the top. Through all of the rule changes (cylinder head, flywheel, ect.), times have not changed, just the cost of the class. I would like to see it again where there are 30+ FF's/CF's on the field rather than go 0.10 faster.

[Tom Tipsword]

While I agree with you about 'rules creep', the flywheel weight issue was brought about by the late Jake Lamont-crankshaft grinder extraordinaire, and the author of the book almost everyone uses to keep their FF engine alive. Through lengthy research he discovered that the weight of the flywheel-at the RPM's we turn- was causing cracks in the crankshafts which of course led to ventilated blocks. He fought for years for the change but it wasn't until blocks and cranks started to become scarce that the Comp Board agreed. They didn't want to change 'stable rules' unless they were sure the only advantage was engine life. Sure, you could continue to use the heavier flywheel, but you risked the engine every time out, and crankshaft replacement was a routine maintenance item. This is one item that was a good idea. Cheap, available to everyone and it kept you on track.

[se7en]

Just dipping my toe into the swirling maelstrom of the "scarcity of blocks" discussion. IMVHO, there should be plenty of used (not used up) Kent blocks/engines in the UK. Has anyone (or any entity) investigated the possibility of having a contact in the UK checking out some of the "breaker yards" there and inquiring as to the availability of said Kent blocks/engines? With the UK FF series having gone over to the "dark side" by running the Zetec 1.6, one could surmise that the demand for the Kent engine has decreased quite profoundly in those circles.
Just my tuppence (two pence),
Ken Wiseman

[Stan Clayton]

Ken, all the major FF engine shops scour the UK, Oz, etc., in their search for FF and FC engines. The stumbling block isn't really blocks, so much as usable iron heads. Stan

[Dave Hopple]

Could someone please expand on my flywheel weight confusion. What happened between 1997, when the Jake Lamont book was published and the 2007 SCCA rules regarding flywheel weights?

To my best understanding the Jake Lamont book quotes 19.9# whereas the 2007 SCCA rules quote 15.5#. That is a big difference and I would like to know what is the current requirement being used. Possibly the rule book doesn't include the clutch bits. Maybe there was a rule change.

Thanks in advance,
Chris

Chris, we put out an update to Jakes book about 2 years ago in this thread http://www.apexspeed.com/forums/showthread.php?t=11467 (all the books printed since Feb 05 have this update, feel free to print them out.)

The current SCCA gcr is available for download here:

http://www.scca.com/Club/Index.asp?reference=gcr

Stan, increased gearbox life? -Dave

[Stan Clayton]

Stan, increased gearbox life? -Dave

I think I had that crossed up with the flywheel lightening we did on the F-SCCA. Stan

[Stan Clayton]

I did a little checking on lightening the flywheel for the FE/SR-SCCA cars, and here is what I found out. With the original 18 lbs flywheel that comes with the Duratec 2.3L engine as used in those cars, some harmonic was pounding out and breaking the Elite gearbox. The fix was to replace that pickup-truck flywheel with a flexplate from the automatic and a billet aluminum adapter to accept a (IIRC) 5.5" racing clutch. Total weight? 2.6 pounds.

Happy faces all around the FE camp...

So, how you FF guys liking your 15 pound flywheels?

Stan

[mblanc]

So, how you FF guys liking your 15 pound flywheels?

Stan

Great,

if 15#'s is great, then 3# would be better just kidding, kind of.


What I see is just a long term, slow, gradual creep down in this figure, once everybody's ran right at this min for a while, flywheel availability could be in a little question again, as they get resurfaced, and could fall below the minimum, so,
lose another 1/2# every few years, (like every 5 or so) and it's all good.

[akilcoyne]

I agree with Marc, but in a much more aggressive manner. How many F500's have you qualified ahead of to get blown away on the start? How hard have you worked to pass a F500 in a handling part of the track to get repassed on the straightaway? (in the middle of your race for position) A 5# flywheel would sure address acceleration differences.

[Jon Jeffords]

Stan, the FF drivers who fatigue cracked their 10-hour crankshafts thru the rear web due to flywheel whirl will love the 15.5 lb flywheel.

By lowering the flywheel weight these few pounds, the fatigue stresses put into the rear web at redline were reduced significantly. Crankshaft fatigue life was the main objective with Jake's rule proposal, not gearbox life nor setting track records.

[Eric Cruz]

Stan,
As you mentioned, love the lightened (seriously - when you consinder MOI, which is what matters) flywheel and clutch in FE.

Just wanted to let you know that what you post always seems to me to be balanced, logical and coming from a well informed foundation (imagine that). Please keep it up.

Best regards,
Eric

[Stan Clayton]

You're right, Jon. Last month I got the reason for cutting the FF's flywheel weight crossed up with why we did the same thing for the FE. I was just poking a little fun at the idea of using a 15 pound flywheel in a purpose-built race car.

I thank you for the words of encouragement, Eric, even though I'm confident not everyone agrees with your assessment...

Stan