Flywheel

[Stevo302]

Hi, has anyone done any flywheel lightening? I know you should not over lighten them or wether its a benefit or not but some info would be good. I've had the gearbox out before so its something I could do. I know someone with a lathe.
Cheers.

[Stevo302]

Just done some more searching on other sites about this. Looks like I'm talking out of my arse unless you know where exactly to remove weight and how to get things matched up.

[Fiscracer]

Stevo302 said:

Just done some more searching on other sites about this. Looks like I'm talking out of my arse unless you know where exactly to remove weight and how to get things matched up.

It depends. Lightening a standard heavy cast iron flywheel is pretty straightforward and most engine preparation shops will do it for you. You can probably lose 25% of the weight without having any problem. Lowering the rotating mass allows the engine to spin up quicker ie faster throttle response.

It is possible to go too far but most people who want a light flywheel will buy a lightweight steel one or an ali one with steel inserts. Just make sure the register depth is thge same so you dont have to buy a new clutch as well....

R

[brhmtvrs]

I had the flywheel lightened sightly for a TR3. There was a noticeable increase in acceleration, but there was also a noticeable change in starting off. There is a little lag after starting off. Not too much, but noticeable.

[Slow M]

brhmtvrs said:

I had the flywheel lightened sightly for a TR3. There was a noticeable increase in acceleration, but there was also a noticeable change in starting off. There is a little lag after starting off. Not too much, but noticeable.

Where, before, the inertial mass of the flywheel was being traded for the car's forward motion, afterward there was less of it to use.

Adrian,

I think one of the Carroll Smith books has a diagram on how to lighten a flywheel. Remember that the further out from the center the mass is, the more difference it makes.

Best,
B.

[Stevo302]

Now that would be good to see, many thanks all.

[RCK974X]

In case it helps, all the piccies I've seen say the most effective place to remove metal is right on the outside, effectively the 'lip' which the ring gear sits next to, and the casting supporting that lip.

This of course means you have to be careful if replaceing the ring gear, as there's no nice fixed register to make sure it's on squarely...

A couple I remember also had extra holes drilled around (and in some cases under) the ring gear too.

[Slow M]

RCK974X said:

In case it helps, all the piccies I've seen say the most effective place to remove metal is right on the outside, effectively the 'lip' which the ring gear sits next to, and the casting supporting that lip.

This of course means you have to be careful if replaceing the ring gear, as there's no nice fixed register to make sure it's on squarely...

A couple I remember also had extra holes drilled around (and in some cases under) the ring gear too.

The holes are typically for balancing purposes.

Best,
B.

[Grantura MKI]

It is best to do this job whislt building the motor. Rods, crank, clutch cover, flywheel all need to be balanced at the same time.