Lightened Flywheel

[69S4]

Hi Brian,
Where do you expect to see an improvement in your car's performance once you shave six pounds off its gross vehicle weight?

Eric

As I understand it you do get the performance advantage of a car six pounds lighter but you also get an acceleration advantage from the reduced inertia of the lightened flywheel. It should be particularly noticeable in the lower gears where the full rev range is traversed quickly. Downside is said to be a lumpy idle.

I had a small amount taken off the flywheel during the last engine rebuild (10 yrs ago) and I can't say I noticed much difference but the balancing that was done at the same time has made the engine much smoother.

[john.p.clegg]

...similar to fitting alloy wheels.....look up rotational mass.

John

[alaric]

Hi. I've looked up the radius of gyration, and it appears for a uniform disc it's r/sqrt(2). That vizard equation posted above assumes a uniform reduction in mass i.e. that the radius of gyration is not changed, and gives the worst case gain from lightening. If I take 3.777 as final drive and 3:1 for first gear, and the diameter of the flywheel as 8.5", and 10" radius on the wheel, I think - working from memory - that I got 6.8 from the expression. So a reduction of flywheel mass of 5 lb would reduce the weigth of the vehicle seen by the engine by 34lb. In second, with 2:1 ratio, it's not as much - I think I got 3.56, so the benefit is even lower ~18lb. I haven't worked out the gain when most of the mass is taken from the outside of the flywheel, and suspect that'll be very much more effective. It may be as much as the order of 100lb effective weight reduction in first and 50 lb in second. Not huge but noticeable. If I manage to find a general expression that can estimate with a non even mass removal I'll post it.

I want that twinc vizard book - had no idea it existed.

All the best.

Sean.

[dlbutler]

My flywheel looks like the Vizard 'after' shape. Either the PO lightened it or it came that way from the factory - in a Europa Special. The PO changed the engine when he resurrected it after a fire (1970's).

Don

[dlbutler]

Google found a few for sale.

http://www.amazon.co.jp/Tuning-Twin-cam ... 0851130070

http://www.atlanticmotorbooks.co.uk/viewbook.php?id=852

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 0424685925 (on CD)

Good luck,
Don

. . .
I want that twinc vizard book - had no idea it existed.

All the best.
Sean.

[john.p.clegg]

...and the last one is a CD copy....he must have more....for ?4.99....bargain

John

[Lyn7]

Eric/Brian

The improved performance a lighter flywheel gives is not because the gross weight of the car is reduced.
The improvement is because the recipricating weight of the engine components is less,therefore less engine power is used to turn it releasing more power to drive the car.
This is more noticeable in the intermediate gears getting less so as you move up the gearbox.

Lyn

[bcmc33]

...and the last one is a CD copy....he must have more....for ?4.99....bargain

I can't resist a bargain - I hope it's what we expect when it arrives.

[john.p.clegg]

Brian

I've got a hard copy,so if you show me yours I'll show you mine...

John

[msd1107]

This question has come up in the past.

There is a downloadable spreadsheet at elan-f15/updated-spreadsheets-t18445.html that, if you are determined enough, allows you to model the effect of different flywheel weights and diameters and wheel weights and diameters.

The effect of a lighter flywheel is most noticable when blipping the throttle under no load conditions, where you are just accelerating the rotating engine components. It becomes less when accelerating, since you are accelerating the entire vehicle mass. And it has virtually no effect on top speed, only the time to reach top speed.

There is the question as to just how much improvement you will see. Certainly, it will not turn your Elan from a 8 sec machine to a 4 sec machine.

But each incremental improvement adds to the performance envelope so that if you do not go to the effort to improve a factor by a small amount, you will forever not have the benefits of the improvement. And if you are determined, you can make numerous incrementally small improvements that, taken individually, do not make a noticable difference, but when added together, make a noticable change.

Look at the F1 boys. They use a very light flywheel but then add tungsten weights at the periphery to bring the flywheel inertia to an appropriate figure while minimizing the weight of the flywheel. It is not likely we would do that, but they expend large efforts to gain even an infinitesimely small improvement.

David
1968 36/7988

[ceejay]

The David Vizard Book. Tuning Twin Cam Fords.
I bought this book way back in 1981...look at the
orig price $5.85AU.

Another good book to own is: Race Car Braking Systems
By Steve smith.
Lots of valuable info in both of these books, but there is
also info that is not applicable today... but you only need to
use the info you want.

And also shown is a drawing of the fly wheel machining details,
supplied of course within the fair use clause of the copyright act.

These books are probably now lying around in second hand
books shops... perhaps even amazon.

Sorry for the side view but that is the only way they would
load.
Col.

[archigator]

From my post in 2007: "I've had a Fidanza aluminum flywheel installed for several years now, and I'm quite happy with it. It's quite driveable on the street, although I was aprehensive about that before I installed it. (Weighs 8 pounds) I bought mine on eBay from someone who had four or five for sale in a Dutch auction. I see on Fidanza's website too that it is no longer listed; it's a shame, but you can Google it and find several suppliers who have them in stock. (http://www.jazzproparts.com has them for $379.79) I got mine for $250.00, but they typically retailed for $459.00 back in 2003, so around $400 ain't too bad in 2007... "

I'm still happy with my Fidanza flywheel in 2010. No driveability issues whatsoever.

From the Fidanza website: http://www.fidanza.com/Aluminum-Flywheels.aspx

"Our aluminum flywheels are made from the highest quality 6061 T6 aluminum. The material is fantastic for strength, heat dissipation and of course reduction in weight. The friction surface we use is an icredibly strong 1045 steel. The flywheel friction plates are milled to meet our high specifications. A Fidanza aluminum flywheel can mate with any type of clutch material, including organic, kevlar, ceramic, metallic and sintered iron. We attach the replaceable friction surface with military grade aerospace fasteners. With these replaceable friction plates there is no need to replace the entire flywheel when the clutch or flywheel is at the end of it's life, saving time and money. The ring gears we use are also made from 1050 steel and are heat treated for durability. The flywheel ring gears are heated then pressed on and secured with grade 8 button screws. We were the first to utilize a stepped dowel system in most of our flywheel applications. This doweling method ensures that once the pressure plate is installed the dowels cannot be removed because they become locked into place.
No chromemoly can compete with the awesome serviceablity, strength and superior design of Fidanza's aluminum flywheels. If there was a better material out there, we would be using it."

Elan Fidanza aluminum flywheel $400 - http://www.nolimitmotorsport.com/prod/fz-122751

Gary
'71 Elan Sprint
Miami, FL

[teachair]

Bought my Elan back in 1974 and someone had lightened the flywheel following a pattern similiar to the diagram that was shown by Vizard. Weight removed near the outside edge, insidently where it does the most good. Flywheel had a terrible re-occuring problem of always losing its ring gear. The problem was not resolved until the flywheel was replaced. BE CAREFUL.

[memini55]

Gary,

I too have a Fidanza and have no issues with it at all. I have recently been trying to buy another and they are all out of stock even though they show on there websites. Fidanza will make another batch but require five to be ordered to make the run. I would be interested if there are four others out there needing them. Happy to work as a group to buy and I found a site for about $360.

Mark

[SJ Lambert]

Besides 6061 T6 grade aluminium, are there any other grades used in racing flywheels? We're intending to machine up one for a 90 tooth application.