Flywheel - how much is too much?

[arizonazcar]

The sharp corner is irrelevant, engaging the starter while running might take the teeth

off the ring gear but I dont see how it can damage the land it's mounted to. The land

does not see stress unless you'd like to take the ring gear off and break it off with a pliers! Again my flywheel is exactly as thick as the HKS/Trust/Greddy units of which thousands have been sold. There is no stress riser unless you put it in a press and bend it in half. I Reiterate : " I know of no failures in the 8 years or so we’ve been making them."

A lot of posts on these forums about theoretical possibilties that just dont occur.

Dave

[Drax240z]

A lot of posts on these forums about theoretical possibilties that just dont occur.

 

The discussion on these forums is both a) to further peoples knowledge, and to make sure problems don't occur. Granted we've had our share of mental masturbation type posts here in our 5 years, but I think even those that aren't directly discussing a problem that has occured, do have value all the same. I like to think that our little community here is well educated, and will always take in more information than is needed to make a decision just to be sure that they are well informed about the topic at hand.

 

"I know of no failures in the 8 years we've been making them" is fine and grand, and I'm happy you haven't had to deal with any issues evolving from those failures. I don't doubt that the thickness you've copied from HKS/etc. all has been very well researched and documented by them before they made it, and using that R&D to your advantage by copying what they made is intelligent.

 

However, I can see in the picture that Clifton has posted that the Greddy/Trust unit has a radius in the place in question. Your thickness might be identical, but there is more to the equation than thickness.

 

I'm not suggesting that it's going to fail. I'm simply suggesting that in engineering terms, any chance you have to eliminate a stress riser, you take. Especially when it is so simple in this case to do so.

[JMortensen]

It looks to me as if the ENTIRE back of the Greddy flywheel is radiused. I'd be willing to bet that the front is too. Every time this issue has come up I've stated that I have checked my flywheel for cracks repeatedly and found none. Bottom line for me is that if the corners were radiused and the bolt holes weren't cut through I wouldn't have even bothered to check and the machinists wouldn't have made a big deal out of it. As it is I will check EVERY time that flywheel comes out regardless of Dave's experience.

[arizonazcar]

The HKS/Greddy flywheel needs a generous radius as the ring gear is cut into the flywheel , it is not a seperate part and is subject to a centrifugal load, the land on the AZC flywheel has the ging gear interference fit onto it , cant go anywhere. There is a huge difference in this that your are not understanding. All racing components should receive regular inspection regardless of manufacture anyhow.

John, please tell us how long has the flywheel been on your car and what RPM has it been subject to?

By the way look at the recent post by Jason84NA-T titled "flywheel went boom" Stock flywheel, no modifications made to it.

[Guest bastaad525]

I took my stock turbo flywheel to a machine shop that lightens flywheels all the time, and had them lighten mine and they got it down to around 17-18lbs, I was assured this was about the lightest you could safely take the stock unit, and also, this involved shaving the flywheel surface down enough that the flywheel would not be able to be resurfaceable/reusable... found this out the hard way when my ACT six puck clutch wore a groove into the flywheel and the springs of the clutch started rubbing against the bolts holding the flywheel to the crankshaft!!!!!!

 

So I figure if I ever do another one I'll skip on the surfacing on the face of it and maybe end up with a sub 19lb flywheel?

[Cody 82 ZXT]

I took my stock turbo flywheel to a machine shop that lightens flywheels all the time' date=' and had them lighten mine and they got it down to around 17-18lbs, I was assured this was about the lightest you could safely take the stock unit, and also, this involved shaving the flywheel surface down enough that the flywheel would not be able to be resurfaceable/reusable... found this out the hard way when my ACT six puck clutch wore a groove into the flywheel and the springs of the clutch started rubbing against the bolts holding the flywheel to the crankshaft!!!!!!

 

So I figure if I ever do another one I'll skip on the surfacing on the face of it and maybe end up with a sub 19lb flywheel?[/quote']

 

 

I had mine lightened and it's int he same condition as your. I think next time if I don't go with the AZC flywheel I'll buy a new one and just have the back done.

[JMortensen]

The HKS/Greddy flywheel needs a generous radius as the ring gear is cut into the flywheel , it is not a seperate part and is subject to a centrifugal load, the land on the AZC flywheel has the ging gear interference fit onto it , cant go anywhere. There is a huge difference in this that your are not understanding.

I'm not a machinist. I'm not a mechanical engineer. The people who warned me were. The Exedy website says that their flywheel is STRONGER because the ring gear is integrated into the design. They also say that the land where the ring gear is pressed on is THE source of failure in aluminum flywheels:

The ring gear teeth are milled onto the flywheel unlike an aluminum flywheel where the ring gear is pressed onto the flywheel which has the possibilities of separating from the flywheel. This could cause the flywheel to explode due to two different expansion coefficients (aluminum flywheel pressed on steel ring gear).

Again, I'm not an expert, but I don't see why having that part pressed on makes any beneficial difference in the stress riser situation. If anything you've got a now stressed land (because the ring gear is an interference fit) and it has a giant stress riser all the way round with 6 threaded holes cut right through it. I would be shocked if the expansion coefficient of the steel in the ring gear and the flywheel were exactly the same.

 

To answer your other question though, my flywheel has seen 40K miles, 6 seasons of autox and quite a few track days. On a couple occasions it saw 7400 rpm or so, I can't say for sure, I wasn't watching the tach at the time. It has performed FLAWLESSLY to date, which again is something I've said repeatedly.

 

One last thing, of course I inspect the flywheel every time it comes off - visually. Since the repeated warnings I've been using a chemical inspection process that I can't recall the name of, but you clean the flywheel then put a dye all over it, then clean it again, and put another chemical on it that will pull the dye out of any crack. One of the machinists told me about it and showed me how to use it. Next time I'm going to magnaflux the flywheel. I don't know of anyone that inspects their flywheel to this degree every time it comes out.

 

I'm not well versed enough in this crap to make a very good argument, so I'll leave it to the engineers on this site to continue arguing. I'm done.

[arizonazcar]

The aluminum flywheels are a whole different story.

Too bad I cant show you in person what I'm talking about, you'd see in a second.

Anyhow I appreciate your comments and glad to see you've had excellent service

from some of my products.

 

" my flywheel has seen 40K miles, 6 seasons of autox and quite a few track days. On a couple occasions it saw 7400 rpm or so, I can't say for sure, I wasn't watching the tach at the time. It has performed FLAWLESSLY to date, which again is something I've said repeatedly."

[Guest bastaad525]

BTW lightening the flywheel down to 17-18lbs made a HUGE difference, I LOVED it. Not only in how it revved up/down but also it was just easier to shift, and even shifting w/o the clutch was very smooth when I could get the revs right, used to practice it all the time but now that I'm back to a stock flywheel it's MUCH harder so I dont do it much anymore. I say try a lightened stocker... I've heard it said that you dont want a SUPER light flywheel with a turbo application anyways. Have them just remove all the excess material from the rear... it's cheap, the machine shop I took mine too only charged me $40 to do it, plus the $50 I paid for the flywheel so less than $100... not a bad deal.

[240Z_Master]

I know this is a little off topic...but I am looking for a RB20DET Flywheel from Fidanza part # 143341 if anyone can get a better deal than $379 please let me know. These companies want to charge me way too much.

 

I am looking at $310 max for the Fidanza unit.

 

Thanks