Lightening flywheel - by how much?

[VTRDark]

correct the ballance? [the 3 shallow holes on the std one]

Is that what they are for then. I was wondering about them. I thought they where just left over from where it was machined originally.

(:-})

[lloydie]

If it was trued up and no run out when it was placed in the turner it will be as balanced as it once was .
I read many threads about this before I had mine done .
If it was turned down correctly it don't need rebalanced as mark knows what he is doing I'm sure it will be fine

[Stephan]

you can take more off than that ;)

I know, but this is quite noticeable when accelerating, and without any negatives, bike is still smooth on closed throttle. So for me there is no point taking more.

[AMCQ46]

If it was trued up and no run out when it was placed in the turner it will be as balanced as it once was .
I read many threads about this before I had mine done .
If it was turned down correctly it don't need rebalanced as mark knows what he is doing I'm sure it will be fine

Lloydie, its a good question, and without the parts in my hands I may be making an incorrect assumptions, but I think you are right and wrong

you are right that as long as it is trued up well before turning it will have the same balance as it always had, but only up to the point that you remove the balance correction features that were done at the end of manufcturing to get it balanced in the first place, then it will become unbalanced.
it's then like you just removed the wheel weight off a well balanced wheel......you only had good balance because it was corrected after building, take the correction off and it will go back to unbalanced.

As I said, this is my opinion based on other engineering practices for rotating machines [like electric motors], but I havnt studied the Storm flywheel, and also dont know how significant the error will be on the whole crank assy. so it could be that it is only a theoretical issue that has no effect in practice.

[lloydie]

I did Speak to Rodger about this and he said "as long as it is trued up with 0 runout before machining it will be fine"

If it was a il4 with a longer crank then a rebalance would be needed as the inbalance would have a greater effect .
On the vtr as it has a narrow crank it wouldn't need done as long as it was done right .

I did question him with what you said al but he reassured me it will be ok
But all this is based on his flywheel specks .

[benny hedges]

Roger used alan Richard engineering in heysham for his mchining... The same guy who turned mine
I gave hime 3 to play with and said take as much as possible off but keep the timing marks.
Dimensions on here somewhere and weights etc.

The motor does feel more buzzy with the lighter flywheel but the first thing you notice is it loses rpm faster too when you clutch in... Youll probably stall a bit til u get used to it!

[gl_s_r]

I'll try and explain it a bit (my thoughts on it anyway)..

Imbalance should and will be reduced as the amount of material is removed..By that I mean the more material I remove the the more the imbalance will be less of a factor... even more so taking it from the diameters. I found the biggest imbalance to look at was the magnet basket (or whatever it is called) as when true on the taper that particular thing wobbled everywhere.. But as I machined that down as well then that imbalance should also have disappeared. All in all there isn't going to be that much to go wrong.. especially with a short throw crank like there is on the VTR and only two pistons that work in opposites.

I am also quite sure that I read somewhere that roger agreed that if machined correctly and to true then there shouldn't be a need to balance.

Now I've probably written all that for someone to blow my theories well out of the water ha ha ha!

[VTRDark]

I am also quite sure that I read somewhere that roger agreed that if machined correctly and to true then there shouldn't be a need to balance.

It's been said over on the hawk site. And the whole discussion on whether it should be re-balanced or not has almost turned into a fight in the usual Superhawk way.
http://www.superhawkforum.com/forums/mo ... nce-16643/

(:-})

[AMCQ46]

I'll try and explain it a bit (my thoughts on it anyway)..

Imbalance should and will be reduced as the amount of material is removed..By that I mean the more material I remove the the more the imbalance will be less of a factor... even more so taking it from the diameters. I found the biggest imbalance to look at was the magnet basket (or whatever it is called) as when true on the taper that particular thing wobbled everywhere.. But as I machined that down as well then that imbalance should also have disappeared. All in all there isn't going to be that much to go wrong.. especially with a short throw crank like there is on the VTR and only two pistons that work in opposites.

I am also quite sure that I read somewhere that roger agreed that if machined correctly and to true then there shouldn't be a need to balance.

Now I've probably written all that for someone to blow my theories well out of the water ha ha ha!

As long as the imbalance is in the metal you are removing and not the magnets, then the more you machine off the better it will get. if it is in the magnets, then once you remove the balancing drillings, the imbalance will come back.

but I think it is such a small % of teh VTR crank inertia, and it is a narrow crank so the effect will be 3/10's of bugger all, so just fit it and see

[tony.mon]

Just to throw an extra factor in, there are two types of balancing, static and dynamic- just like wheels.

A static balance will show up any imbalance from the centre of the shaft outwards, (eccentricity) but dynamic will also show up imbalances sideways (wobbling, for want of a better word) along the shaft (if, for instance, the riveting holding the magnet basket isn't properly flush with the backing plate).
Not sure if Honda originally balance the whole assembly, or just the backing plate, then affix the magnet basket, as it'll be a lot easier to machine or drill the balance holes BEFORE the magnet basket is affixed.

However I agree, there's no point balancing this after machining.

There might be a point balancing the whole crankshaft, rods, pistons, rings, circlips, (and quietening gear inc. springs, if fitted) and alternator as a complete assembly, to reduce imbalance and therefore bearing wear, get fractional performance gains, as well as reducing vibration.
But only if you're racing for serious money, or are very anal. (Pot, meet kettle....)

But frankly these engines are going to vibrate anyway, because the pistons aren't in line with each other, so you get a rocking couple. Live with it!

[VTRDark]

Thanks for that Tony. I have heard of static and dynamic balance and did not no what the difference was. For some reason I though static meant still and dynamic being something in motion. So static being eccentric is more of a wobble like a cam shape, not a circle but more oval, and dynamic is a straight line side to side. Is that right, just trying to get my head around it. Ooo I've gone dizzy.

(:-})

[AMCQ46]

Thanks for that Tony. I have heard of static and dynamic balance and did not no what the difference was. For some reason I though static meant still and dynamic being something in motion. So static being eccentric is more of a wobble like a cam shape, not a circle but more oval, and dynamic is a straight line side to side. Is that right, just trying to get my head around it. Ooo I've gone dizzy.

(:-})

yup you got it.... dynamic looks at asymmetric mass distribution which would cause a wobble about the axis . so this would be why you get wheel weights on both sides of the wheel rim, when weights on just 1 side would give you a static balance [bit simplistic but an easy way to visulaise],

[Rob]

Just fitted rob...'s lightened flywheel.

For anyone interested the weight (total including sprag clutch) was 4.3Kg

My original one was 5Kg. So about 12.5% less.

Haven't tried it yet - doing that tomorrow.

[lloydie]

Just fitted rob...'s lightened flywheel.

For anyone interested the weight (total including sprag clutch) was 4.3Kg

My original one was 5Kg. So about 12.5% less.

Haven't tried it yet - doing that tomorrow.

it will make a good difference you will like it

[Rob]

it will make a good difference you will like it

Me likey.

Not a huge difference but then I think it was lightened conservatively, but definitely a noticeable difference. Now I've got a spare one I might think about getting that lightened even more. Do you know much much yours was lightened by?

It's maybe a little more jumpy at very low revs but not a problem, probably shouldn't be down that low anyway.