Lightweight Flywheels

[petawawarace]

Any advice on lightweight flywheels and clutches for endurance racing? Aluminum or Chrome-moly? Which ones not to use? Etc?

 

I have to replace mine anyway, so might as well save that rotating mass. But I don’t want to sacrifice reliability. 

Edited October 19, 2020 by petawawarace

[wvumtnbkr]

One with an sfi rating is always a good choice (edit:) if you like your ankles...

 

Yes, I've seen a lightened flywheel explode and take out the floor /break a guys leg in lemons.

Edited October 19, 2020 by wvumtnbkr

[wd6681]

I too am interested in people's experience with a lightweight steel vs aluminum flywheel. A clutch expert told me that they have found several aluminum flywheels that flex (cup) from the pressure plate. In chasing down clutch issues in an E30 (m20) one of the things we did was change from an alloy flywheel to a stock iron one, the pedal felt approximately 10-20% firmer. This did not resolve our clutch issues however as it was related to oiling.

I do notice that all the high end stuff is steel rather than aluminum.

Experience everyone?

[Bremsen]

I work with a mechanical engineer that spent years designing racing clutches and flywheels for a major manufacturer.  One of the issues he brought up with aluminum flywheels in a racing environment is the higher material expansion of aluminum over steel, which can lead to the flywheel bolts wanting to back out.  He suggested using a steel flywheel shim under the bolt heads to help distribute the load on the flywheel.

[RandomTask]

1 hour ago, Bremsen said:

I work with a mechanical engineer that spent years designing racing clutches and flywheels for a major manufacturer.  One of the issues he brought up with aluminum flywheels in a racing environment is the higher material expansion of aluminum over steel, which can lead to the flywheel bolts wanting to back out.  He suggested using a steel flywheel shim under the bolt heads to help distribute the load on the flywheel.

 

Any FW worth anything will use deformed nuts (NOT nylocks!) Also, all the FWs im familiar with, use flat heats... impossible to use a washer.

[Bremsen]

19 minutes ago, RandomTask said:

 

Any FW worth anything will use deformed nuts (NOT nylocks!) Also, all the FWs im familiar with, use flat heats... impossible to use a washer.

 

I'm totally confused by your post.  I never reference nylocks, or even nuts at all.   I was referring to the fasteners that hold the flywheel to the crank.  I've only done a few different clutch jobs in my life but I can honestly say I've never seen a nut used in any of them (flywheel or PP).  But maybe its just been the makes I've worked on.

 

Anyway, for clarity, something like this is what was recommended under the bolt heads that hold the flywheel to the crank:

[petawawarace]

21 minutes ago, Bremsen said:

 

I'm totally confused by your post.  I never reference nylocks, or even nuts at all.   I was referring to the fasteners that hold the flywheel to the crank.  I've only done a few different clutch jobs in my life but I can honestly say I've never seen a nut used in any of them (flywheel or PP).  But maybe its just been the makes I've worked on.

 

Anyway, for clarity, something like this is what was recommended under the bolt heads that hold the flywheel to the crank:

Perhaps he was talking about the nuts (and accompanying bolts) that usually hold the steel wear disc to the aluminum flywheel.

[petawawarace]

I have this laying around collecting dust. A new set of discs and I can likely make it work for cheaper than a stock clutch.  18lbs lighter too. 

[Bremsen]

I have some fun stuff laying around too

 

[TiredBirds]

On 10/19/2020 at 6:08 PM, wvumtnbkr said:

One with an sfi rating is always a good choice (edit:) if you like your ankles...

 

Yes, I've seen a lightened flywheel explode and take out the floor /break a guys leg in lemons.

I wouldn't consider anything but an SFI rated aftermarket unit for racing. The forces aren't as drastic as drag racing with a clutch, but the flywheel and clutch would likely see a lot more heat. 

[MMiskoe]

Call my a cynic but I've not had good luck with such things.  Long ago we put a lightweight PP and aluminum FW into a miata.  Worked great until the car got warmed up then would not disengage.  That lasted about 30 minutes before we replaced it with a stock set up.  I don't know what brand it was, wasn't my purchase.

 

More recently in a BMW there was some toggle switch for a clutch installed, the guy doing the prep commented it was a small diameter, un-sprung affair.  It did one 12 hour race before it was replaced.  It would stick when you put the pedal down, making a really hard section of pedal travel.  I don't know what it was doing but I was told it was a PP and slave cylinder issue.  Again, worked fine for the first hour of the race, then gave the occasional trouble, I'm sure it worked fine in a sprint race.

[EngEtan]

Aluminum has a much higher coefficient of thermal expansion than steel, so a sticking clutch isn't all that hard to believe. For this reason, I'd always use a chromoly or keep the oem steel flywheel for endurance racing.

[CBraden]

I really wish I had seen the info in this thread before I put in an aluminum flywheel this summer.

 

FWIW, we ran one in our 4 cyl Mustang for years without any issue. 

 

 

[mhr650]

On 10/20/2020 at 2:45 PM, Bremsen said:

 

I'm totally confused by your post.  I never reference nylocks, or even nuts at all.   I was referring to the fasteners that hold the flywheel to the crank.  I've only done a few different clutch jobs in my life but I can honestly say I've never seen a nut used in any of them (flywheel or PP).  But maybe its just been the makes I've worked on.

 

Anyway, for clarity, something like this is what was recommended under the bolt heads that hold the flywheel to the crank:

 

 

As if everything else wasn’t strange enough, rotary’s use a nut to hold on the flywheel, 54mm nut 350 ft/lbs torque.

 

 

[Black Magic]

On 10/20/2020 at 3:20 PM, petawawarace said:

I have this laying around collecting dust. A new set of discs and I can likely make it work for cheaper than a stock clutch.  18lbs lighter too. 

 

Does the 18 lbs weight reduction include any trans parts escaping through the case  

 

I haven't seen high success rates with stiff solid hub clutches attached to passenger car OE transmission in endurance racing. Almost like the springs were there for a reason.....

 

The most spectacular was a FWD team I helped that broke the trans case in half from a clutch and trans failure. "Stage 4 solid hub" clutch. They run an OE appearing clutch now and have kept the trans cases in one piece. Don't forget the shock loading that occurs in the system from throttle lift\stab events many times a lap for hours on end when picking your clutch design type....

[petawawarace]

1 hour ago, Black Magic said:

 

Does the 18 lbs weight reduction include any trans parts escaping through the case  

 

I haven't seen high success rates with stiff solid hub clutches attached to passenger car OE transmission in endurance racing. Almost like the springs were there for a reason.....

 

The most spectacular was a FWD team I helped that broke the trans case in half from a clutch and trans failure. "Stage 4 solid hub" clutch. They run an OE appearing clutch now and have kept the trans cases in one piece. Don't forget the shock loading that occurs in the system from throttle lift\stab events many times a lap for hours on end when picking your clutch design type....

Do you know something specific to the quartermaster clutches?  They use this exact style on a lot higher horsepower engines in lots of endurance races.  

[Ray Franck]

Hey guys please hold off on those fancy clutches and flywheels, the rule is under review. 

[petawawarace]

55 minutes ago, Ray Franck said:

Hey guys please hold off on those fancy clutches and flywheels, the rule is under review. 

Please tell me you are kidding.  

[Black Magic]

2 hours ago, petawawarace said:

Do you know something specific to the quartermaster clutches?  They use this exact style on a lot higher horsepower engines in lots of endurance races.  

 

Specific to high clamp load clutches with little to no rotational compliance. Not a quartermaster clutch issue. 

 

The lack of compliance during shifts and load reversals will put extra stress on the trans. Higher HP race cars typically address this issue by running a different trans, treating the gears, and using better materials in the trans. They also sometimes have fluid pumps to pressure feed the oil to give a cushion. Compared to the torque rating of most OEM trans, they are much stronger. Looking at the Subaru WRX world, the 5mt cars had a restrictor in the clutch line to slow the release because the OE sprung hub clutch had enough stiffness and clamp load to break the trans. True off the line production stuff can be really weak, and the OE clutch design helps to hide these sins. 

 

With a syncro trans this also assumed you can get the drag low enough to keep the syncros alive, which can be a challenge on some. 

 

I would do the math and verify the "HP equivalent gain" for that rotational weight reduction, looking at a reasonable champcar RPM ramp rate and RPM window. I think you will be really disappointed, our slow ramp rates and low RPMs really hurt the gains. A lighter flywheel using a sprung single disk sized for your power might get your more than half of the way to your weight goal with 10x less issues. 

Edited November 12, 2020 by Black Magic

[petawawarace]

42 minutes ago, Black Magic said:

 

Specific to high clamp load clutches with little to no rotational compliance. Not a quartermaster clutch issue. 

 

The lack of compliance during shifts and load reversals will put extra stress on the trans. Higher HP race cars typically address this issue by running a different trans, treating the gears, and using better materials in the trans. They also sometimes have fluid pumps to pressure feed the oil to give a cushion. Compared to the torque rating of most OEM trans, they are much stronger. Looking at the Subaru WRX world, the 5mt cars had a restrictor in the clutch line to slow the release because the OE sprung hub clutch had enough stiffness and clamp load to break the trans. True off the line production stuff can be really weak, and the OE clutch design helps to hide these sins. 

 

With a syncro trans this also assumed you can get the drag low enough to keep the syncros alive, which can be a challenge on some. 

 

I would do the math and verify the "HP equivalent gain" for that rotational weight reduction, looking at a reasonable champcar RPM ramp rate and RPM window. I think you will be really disappointed, our slow ramp rates and low RPMs really hurt the gains. A lighter flywheel using a sprung single disk sized for your power might get your more than half of the way to your weight goal with 10x less issues. 

Thank you for that.  Unfortunately it doesn’t look like running it will be an option now anyway.  

[Team Infiniti]

4 hours ago, Ray Franck said:

Hey guys please hold off on those fancy clutches and flywheels, the rule is under review. 

Edited before posting... Where is common sense or progressively building up to potential?

 

Only rule/go fast updates we do are upon failure of the previous component, not the day a rule changes...Surprise, we have never been surprised/disappointed or had to backtrack. Best advice would be to err on the side of "lesser racy" ,but that should go for any rule, new or old.

 

Rather then the latest widget, strategy/clean race/sticky tires, play more into good finish position than anything else.

[WTFover]

On 11/12/2020 at 2:31 PM, Ray Franck said:

Hey guys please hold off on those fancy clutches and flywheels, the rule is under review. 

4FS!  Could the 2021 BCCR rollout have gone any worse?

[Ray Franck]

4 hours ago, WTFover said:

4FS!  Could the 2021 BCCR rollout have gone any worse?

  I doubt it, but trust me the pre rollout was much worse. 

  As I have stated earlier I am sure some lessons have been learned and the process will be handled differently in the future. 

Edited November 14, 2020 by Ray Franck

[hotrod]

[Bill Strong]

On 10/20/2020 at 2:45 PM, Bremsen said:

 

I'm totally confused by your post.  I never reference nylocks, or even nuts at all.   I was referring to the fasteners that hold the flywheel to the crank.  I've only done a few different clutch jobs in my life but I can honestly say I've never seen a nut used in any of them (flywheel or PP).  But maybe its just been the makes I've worked on.

 

Anyway, for clarity, something like this is what was recommended under the bolt heads that hold the flywheel to the crank:

 

 

that's what I use with a Fidanza SFI tagged aluminum flywheel with ARP bolts. The SFI rated ACT clutch and SFI rated ACT pressure plate is held to the flywheel using ARP bolts too. After seeing a cars clutch explode on overshifts coming out of oak tree during a VIR South 12-hour. we went the full SFI treatment as the clutch sits right behind the driver. The seat is also kevlar with a kevlar blanket hanging on the firewall behind the driver.