Machining Flywheels

[corolla_nut]

Hey

Putting some thought into my next engine build, was thinking about a lightened flywheel. I'm just after some opinions on this, everybody I've spoken too seems to have their own STRONG opinions about this. Has anyone got a machined flywheel? where do you get them machined, how much did you take off, and how is your car to drive? what other mods have you got as well? There doesn't seem to be much mention on here of people machining flywheels, I know superjamie had a machined flywheel on oke250.

 

I don't want to use an alloy flywheel for two reasons, a) the cost, and b) they wear out as fast as a clutch, makes for an expensive engine. I'm just interested in machining the cast flywheel.

 

The engine i'm building is for a daily driven khanacross/motorkhana and maybe hillclimb/supersprint ke11. I'm putting a tighe 104 cam, electronic distributor, 4-1 extractors, 11:1 compression, and sprinter twin carburettors with a bigport spec cylinder head.

 

Robert.

[parrot]

Once upon a time in a land far far away, actually Melbourne in the mid 80's, EVERYONE who modified their engine had the flywheel machined. No one had ever heard of buying the assorted TODA bling flywheels you can get now.

 

I had my 2T and L20B flywheels machined at my local brake and clutch place as did my club racing mates. I can't remember how much as it was long ago. The thing then was not to get too carried away in case they took to much off. You don't want the flywheel disintegrating at 6500rpm (or even 1000rpm for that matter).

 

I would have no problems doing so again. Perhaps this time I will go along to a specialist brake and clutch place (with a lot of racing car work) such as BGT in Melbourne rather than my current local dodgy joint.

 

B.G.T. Brake Services

 

10 Webster St, Dandenong, VIC 3175

 

p: (03) 97946787, (03) 97922806

 

Unfortunately they have moved from nearby leafy Hawthorn to the sticks of Dandy, but I wouldn't go anywhere else for anything brake or clutch related.

[Xany]

Machined or lightened....theres a difference.

 

I class machining as preparing the flywheel for a new clutch....

 

I would guess you mean lightening, if thats the case then heres a link you may want to give a read.

 

http://www.geocities.com/motorcity/7177/flywheel.html

 

As said in the above post, flywheels can and DO disintergrate....personally i've never heard of a K flywheel doing it, but it doesnt mean it can't.

Edited May 27, 2009 by Xany

[parrot]

Semantics, the flywheel is lightened by machining it.

 

The friction surface is also refaced by machining it.

 

Clearly we are talking about reducing the weight of the flywheel here.

 

Just make sure you get advice from a reputable brake and clutch shop. The difference is very noticeable and you don't need to take off vast amounts of material. Engine pickup will be markedly improved.

 

Realistically, the amount that you would have safely removed from a cast flywheel will be unlikely to adversely affect driveability. I never noticed any problem.

 

Just don't go putting a solid centre clutch plate in a road car. That WILL destroy your driveability and is completely unnecessary.

[corolla_nut]

I've heard that machining cast materials is bad as it takes the rigid external coating off and exposes faults/cracks in the material, thus leading to premature failure. I've also received lectures from tafe teachers and brake and clutch centre staff about this as well.

 

By machined I meant lightening by machining, not resurfacing. Both are machining operations however :P

 

I'm still poking around on the internet reading. Why didn't toyota make a forged steel flywheel for the 4k so it could be lightened? Damn cheap and easy manufacturing methods :P

 

Robert.

 

It just occured to me I'm logged in as Kylie ;)

[Xany]

Firstly, lightening a factory cast iron flywheel can have its dangers and is not recommended. The process of casting iron produces a metal component with a hard, fatigue resistant surface and a particularly soft core. If this hard surface is removed during the lightening process ( which it often is ) then this will seriously weaken the flywheel and could result in the wheel coming apart at high rpms, possibly taking the gearbox and your legs with it.

 

Second paragraph of the link i posted...

[camerondownunder88]

Hi,

I have seen a few lightened flywheels for K motors and never seen one break yet.

 

Start witha 4K fly wheel. Lighter than a 3K one. 3K fly wheels are 22lbs And can't quite remember the 4K weight but think it was 17lbs so it is all ready 5lbs lighter. So bin a 3K flywheel.

 

Also ones I have seen lightened what they usually do is if you flip the fly wheel over adn look at the back of it on the outer edge there is a ridge that starts half way out goes up to the ring gear and is thick. Machine that flat. So start where the metal starts to rise 50% of the way out abotu adn cut it to the ringgear the back of the flywheel will look flat takes out heaps of weight. Seen it done this way down to about 12lbs weight.

 

Also when lightenign a fly wheel only take metal from the out side of the fly wheel. If you take it from the middle you will have less effect. So don't bother keep the metal there for strength.

 

Lightes K fly wheel I have seen was jsut over 6kg it was s tock one machine reving VERY hard so they can be made very light.

 

Also don't laugh BUT do you want a really light flywheel. I have seen tis done don't laugh.......

Get an auto flex plate and machine up a piece of metal to resemble the friction area a clutch plate grips on a normal fly wheel adn weld it to the flex plate. UBER light then and strong will hold but can cost a lot making that one :P

 

Cheers

Cameron

[KENut]

I disagree with Camerondownunder88 about his method of lightening. If you lighten just the outside you will lose torque.

 

You should get the centre area lightened; torque = force x radius, therefore the more weight on the outside (ie larger radius than the inside) the more force and therefore torque.

Also the main prupose of lightening is to reduce the moment of inertia of the flywheel so that the engine can gain revs more quickly without losing torque,

so I believe this is the way to go.

[Taz_Rx]

I disagree with Camerondownunder88 about his method of lightening. If you lighten just the outside you will lose torque.

 

You should get the centre area lightened; torque = force x radius, therefore the more weight on the outside (ie larger radius than the inside) the more force and therefore torque.

Also the main prupose of lightening is to reduce the moment of inertia of the flywheel so that the engine can gain revs more quickly without losing torque,

so I believe this is the way to go.

 

 

Couldn't be further from the truth mate. :P

 

For starters you don't lighten a FW to improve torque. You lighten it to assist the motor to rev up quicker and also deliver more power through the drive-train to the wheels....... with the expectation of loosing torque!!

 

Have a think about this. Where do you feel G-forces more on a merri-go-round? In the middle or sitting on the outer edge? :P

AND, if you were spinning somebody else on a merri-go-round, would it be easier to spin if they were sitting in the centre or on an outer edge? ;)

Edited May 28, 2009 by Taz_Rx

[altezzaclub]

I also think you remove weight from the outside, which removes the inertia of the flywheel making it quicker to spin up and easier to stall.

 

When we converted from auto to manual I had the local motor engineers take the stock 4k flywheel from 8kg down to 6kg. Nothing flash, but it helps.

 

It was very noticeable in the Altezza when we went from the stock 15kg dual-mass down to the TRD 7kg one. It accelerates much quicker in 1st and 2nd.

 

This is the machined flywheel beside the auto flex plate.

 

Edited May 28, 2009 by altezzaclub

[camerondownunder88]

:P Sorry has to be said lightening from the inside will waste your time. Keep strength there and get rid of the outer area. As Taz said lose torque gain revs.

 

6kg is about right I can't say I have seen a K motor one lighter really. Any less and the flywheel will become Swiss cheese..LOL

 

Also original K-B motors have the lightest Flywheels of all K motors but only were in KE15/17 SL sprinters so RARE as were factory lightened.

 

Cheers

Cameron

[Taz_Rx]

Just casue the old school commentator makes me laugh :P ........

 

[KENut]

Sorry obviously I wasn't being clear with what I said before.

I did not mean to say that you can improve torque with lightening a flywheel which is why I said this;

"the main purpose of lightening is to reduce the moment of inertia of the flywheel so that the engine can gain revs more quickly without losing torque"

or much torque at least.

Like I also said before torque is the force times the radius, so the further out the weight the less loss of torque.

[rob83ke70]

less flywheel weight = less inertia. torque is exactly the same from the engine. torque is twisting force, it does not change.

 

if i spun a bowling ball around myself at 20km/hr it would take longer to spin up and longer to slow down than if i used a soccer ball. if that makes any sense? how strong I am is not affected.

 

Robert.

[rob83ke70]

orange brake and clutch said a general machine shop can lighten the flywheel, they can only resurface it, their machine tip gets damaged if they lighten it.

 

Robert.