Aluminum Flywheel ???

[DRCustom]

I'm going to be installing one on my car, but there are a few things I'm wondering about. I've heard of bolts sinking into the aluminum, and the expansion/contraction from the heat causing the flywheel to become loose. Should I have a thin plate (something like a large steel washer with holes for the bolts drilled in it.) made for it to protect from this problem?

Also, how necessary is a scatter shield?

[The Dude]

Why do you even want an aluminum flywheel. Do you own like a honda or something. hahah. Anyway a scatter shield helps keep you legs in tact. When you run high rpm and your fly wheel breakes it keeps pieces of metal from flying into your feet.

[DRCustom]

Do flywheels really break that often? Any idea where I could get a SS, or could someone just make it for me?
Thanks for the info

[CraigFL]

I would think that if you had a good steel washer under the head of each bolt and had the bolts torqued and safety wired you would be ok.

[enginerd]

If you do any racing, a scatter shield is a wise investment. I've seen flywheels and transmissions fly apart and the damage they can do. A friend of mine was out of commission for 6 months when his trans let go. A very hot piece of nodular iron shattered his femur. Racing can be a very safe sport, so do not skimp on safety equipment.

[BeEfCaKe]

DRCustom: You say hondas are for losers, but u seem to have a CRX urself correct? soooo...ummm...

enginerd is right with the scatter shield...

[texan]

He's right with the scatter shield, but there's no reason to assume an aluminum flywheel won't be as safe as a moly or steel unit, assuming proper design. It's just a helluva lot easier to make the things really light using aluminum, plus you do have the added benefit of easily mating ring teeth metallurgy to the starter gear. Moly units not very well thought out tend to eat starter gears for lunch.

[DRCustom]

sarcasm - NOUN
1. A cutting, often ironic remark intended to wound. 2. A form of wit that is marked by the use of sarcastic language and is intended to make its victim the butt of contempt or ridicule. 3. The use of sarcasm. See wit.

Well, regardless of what type of material it's made of, I don't think I very much like the idea of molten metal becoming part of my anatomy.

Thanks for all the input, but where can I find a scatter shield, and how much can I expect to pay for one?

[texan]

I don't believe anyone makes an off-the-shelf scatter shield for that car. STR and B&M are the leading manufacturers for Honda scattershields.

[enginerd]

Plus the lighweight flywheel can cause a harmonic imbalance to the engine. Often an aftermarket harmonic balancer is required.

[texan]

Originally posted by enginerd
Plus the lighweight flywheel can cause a harmonic imbalance to the engine. Often an aftermarket harmonic balancer is required.

Show me when a flywheel is used to balance a motor. I can't even conceive of how a perfrectly round, relatively flat disc is going to counter first or second order vibration on the bottom end.

[ivymike1031]

I think that by "harmonic vibration" what he really meant was "harmonic" torsional vibration, which can be affected by the flywheel. Most notably, the vibratory mode shapes will be altered when a lighter flywheel is introduced, with the first-mode node moving farther from the tail end of the crank, etc. There will, of course, be an increase in the zero-order vibration as well (crank rolling motion), which is not such a concern for engine durability as it is for accessory durability and NVH.

That said, as long as the engine will idle (or at least stay running when you need it to) I don't think that changing the flywheel will result in big reliability problems in a 4-banger. With a longer crank I might be more concerned. The biggest troubles will arise if the vehicle is used as a daily driver, as the idle speed fluctuation of the engine may be unacceptably high (for accessory durability, timing drive durability in some cases, and general noise/vibration/harshness).

This topic brings me back to one that I've touched on in the past... "harmonic balancer" is quite a misnomer. The devices typically called "harmonic balancers" are more accurately described as torsional vibration dampers. They aren't intended to balance any kind of imbalance within the engine, rather they attenuate torsional vibrations.

[texan]

I agree, most notable is the reduction in engine smoothness and NVH. The flywheel effect helps smooth out the power pulse delivery from the engine, which does reduce shock loading to the rest of the drivetrain. This is especially important in larger displacement, low cylinder count motors. Once you break the .5 liter per cylinder point, if the engine is a 4 cylinder this becomes an important constituent of overall feel.

[The Dude]

You guys got it all wrong. Think of a flywheel as something that uses mechanical energy. It makes torque as it spins and this can keep an engine moving, lets say up a hill. The more weight the flywheel has the more "energy it harnessess" So if you got a heavy load going up a hill the GIANT flywheel can keep the engine moving under enormoous load.

The flywheel does keep the engine running smooth but no the same way a vibration damper does. A vibration damper twists to help relieve crankshaft torque.

The flywheel turns fast ok? Engines cylinders fire Independitly and on a big diplaced engine at idle you can really feel this? Now the flywheel takes its mechanical energy and in fact turns the engine. So the flywheel is turning the engine between and during firing of the cylinders which results in a smoother ride. Do you understand?
ITS ALL ABOUT PHYSICS MAN

[The Dude]

So the lighter the flywheel the more acceleration you will have but not as good of a ride than a standard one.