Scooterotica

Ihateyoubutler wrote:In my humble opinion, balancing anything that rotates is only ever going to cause less axial or radial movement at certain rotational speeds (vibration). To "balance" a flywheel, and to be effective across the total rev range of even a standard Lambretta engine, never mind the increased rev range of a tuned engine, might be difficult to achieve. What I'm suggesting is that it will only be "balanced", ie causing less vibration, within a specific rev range anyway. If a flywheel is machined to run smooth at, say 5000 rpm, it doesn't mean it will do at 3000 rpm. Maybe a flywheel should be machined so the engine run as smoothly as possible at the constant speed the engine is generally run at, but in this country and on our roads would this be possible?

Really?

Surely if it's 'balanced' the actual speed of rotation doesn't matter?

I've seen wheel balancing done with a machine at high speeds and by hand at low speeds. The end result either way is that the no matter where you set the wheel it stays put, there's no 'roll' either way, no 'heavy' side. Usually with wheels this involves adding weights to the 'light' side so that a balance is achieved. With drilling a flywheel you'd expect to be removing metal from the 'heavy' side to even it up.

hands up who runs a balanced flywheel?

highly illogical captain .. !

Elite-225 wrote:highly illogical captain .. !

quite true....
ok...nobody has actually answered the guys initial question...
this is my take on it...
No it does not need to be balanced...
in an ideal world with the right equipment/know how/time/cash..yes it would be a bonus to balance a flywheel..
but in the real world who actually offers this service?or has it done?
so "logically" speaking...the flywheel runs on the crank taper,so any machining would be best done bolted to the crank, running true between centers on a lathe...at least this way it replicates what its doing in the motor,therefore machining it all true
so any balancing that came from the factory shouldnt be disturbed...too much
grip the jaws on the magnets internally with a 3 jaw chuck wont machine it true..

oggy wrote:Hi,made a ss cover for my cowling,but the fixings inside the cowling foul the flywheel,there 5mm nylocs,can i have that much machined of safely without a cooling issue,thanks.

Bit of interesting reading for you (especially the last post! )

http://scooterotica.org/forum/viewtopic ... g&start=10

I machined the flywheel in my guzzi and ran it for 1,000's miles. I balanced it staically, ok I checked it and it was within the limits of the kit I had available.
The maching is best done off centres, so making some sort of mandrel may be necessary.
As the lammy uses a single cylinder engine, the crank/rotating masses will not be 100% balanced. Some balance factor will be applied. A few grams either way are unlikely to alter things much. Where care needs to be taken is ensuing the weight removed is done evenly. otherwise a precession or wobble will be caused and that will likely cause stress reversals leading to vibration which is high speed bending. It may even snap the carrot. Sorry, crank.

Vibration free
Basset Down
2 well respected places, Basset did my guzzi crank. VF do loads of F1 stuff, but claim to be willing to do anything.

camel wrote:hands up who runs a balanced flywheel?

I do.

Rb20 with a no fin AF light flywheel. Balanced to 10k rpm. By far one of the smoothest accelerating (and idleing) motors I've ever run.

I run a giant center plug head for cooling.


Even a small amount of out of balance in the flywheel will cause uneven pressure on the flywheel bearing, eccentric wear on the seals and cause abnormal vibration in the motor. Ideally every spinning part should be rotationally balanced to minimize loss.

Now for an everyday road bike with a minor tune I wouldn't bother but if I wanted to make as much power and be as reliable as possible you can bet I'd balance every part I could.

I will just perhaps buy a lightened f/wheel ,not worth the aggro

camel wrote:hands up who runs a balanced flywheel?

yes m8 - balanced in a cnc balance machine on a mandrel, took the technician ages to balance a SIL flywheel that had had the "holes drilled"

camel wrote:

Elite-225 wrote:highly illogical captain .. !

quite true....
ok...nobody has actually answered the guys initial question...
this is my take on it...
No it does not need to be balanced...
in an ideal world with the right equipment/know how/time/cash..yes it would be a bonus to balance a flywheel..
but in the real world who actually offers this service?or has it done?
so "logically" speaking...the flywheel runs on the crank taper,so any machining would be best done bolted to the crank, running true between centers on a lathe...at least this way it replicates what its doing in the motor,therefore machining it all true
so any balancing that came from the factory shouldnt be disturbed...too much
grip the jaws on the magnets internally with a 3 jaw chuck wont machine it true..

that's why I always lighten flywheels held on a mandrel locating in the boss taper (old crank, cut offat the web) in a lathe using a running centre, then balance.
why would you give a flywheel to someone to put in a 3 jaw chuck on the magnets to lighten then just put back in the engine? - white finger springs to mind