Boonman

[JKJK]

if you had two flywheels, one with material removed from the circumerference+one with material removed from the face,witch one would you have lightened???

[Yamahammer]

Ok try this make an adapter that fits the center of the flywheel and a rod coming ot bith ends now suspend it in a v from the rod on both ends see if it falls to one side or not if it does start drilling the heavy side.

they sell a prop balance tool at hobby shops it might work for those that oare worried about it

[JKJK]

boonman i believe the flyweel i have is a unmolested factory original,i could be wrong,the holes are the same size,shape,depth but their on the outside circumference of the vertical face.

[JKJK]

so from the factory the tooling tollerences for the flywheel wern't that tight,they figured they could ballence it from the centerline of the crank hole,cheaper than making a perfectly centered hole in the flywheel.

[TheBansheeMan86]

yeah i dont understand how it would be balanced either, assuming u are running the lathe over the balance holes. since then the bit would be taking material off, but wouldnt be taking any off where the holes are so it would look like this ------------- - - - - - --------------------------- - - - - - -------------------------- - - - - - ---- and so on. if that makes sense? say the flywheel without the holes wasnt balanced, so yamaha had to take weight off one side. well if u take 1/4" off the diameter lets say, or even enough to eliminate the holes completely, then you are technically back at step 1, where yamaha had to put holes in it to balance it, because now you have no holes.

[Nighty]

True mate but read what bdbanshee said:

 

 

basicly what i get out of this:

If you would measure the distance from your crankshaft to the upsite of the flywheel then rotate the flywheel 180 degrees and measure again.

you will see a slight difference in the measures.

 

Thats why yamaha had to balance the flywheel with the holes.

 

Since boonman (and others) mill down the flywheel using a template (or whatever) that mills down EXACTLY! from the center..

resulting in a better lighter more balanced flywheel then yamaha could ever make.

 

(addon: since the flywheel now is exactly round)

Edited May 28, 2004 by Nighty

[JKJK]

agreed,except for the material that is left in the center where the pick ups are.it would only be out of ballance by half the difference in weight of the two halfs 180 apart from where the original ballance holes were. if a flywheel was marked in the center of the lightening holes,then cut.the cut depth on each side should be different after removeing x amount of material. i would think.

[mrman99]

TheBansheeMan86 see's my point. From what i understand unless you lathe the od and id to get the wall thickness the same, you wont get a part that is ballanced. Even if you true up the outside dia, the inside dia is not running true. That will affect the balance.

 

BTW Boonman, I'm not trying to flame you. Hope you didn't take it the wrong way. My background is in manufacturing/machining/mechanical design. I'm just trying to understand, its not logical to me. Yamaha puts in the holes to balance it, you remove them and say its balanced?

 

 

FYI....I know how to run a lathe....Acutually I own a mold shop and have enough equipment to make practicly anything.

[TheBansheeMan86]

ok i think i get it. the area of the balance holes is thicker than lets say the opposite side. so when u lathe it down, it might not even touch the other side if the hole side sticks out more... right? i think i understand but cant explain it at 4 in the morning. btw, who, is it boonman?, lightens flywheels for people? how much is it, and what kind of power difference does it make?

[Banshee0028]

OK...I am reading both sides of the story here......I have 2 questions to clear this whole thing up:

 

1) Would there be a simply way to make a device to check the balance after the lightening is complete?

 

2) If so, we can continue to drill holes (or whatever else) to make it perfectly balanced again after its in the lathe.

 

SO, if there's a way to Check and Re-Balance, how much more difficult would it be to implement? NOt saying Boon's are not blanaced once he is done with them, but why not go one step further and test them once or twice to prove to people that they are bal'd? Or maybe test a few he has already done. That would put an end to all these arguments and assumptions and make for a better "documented" product. (Proving that they are in bal after being lightened). I am also planning on sending mine to Boon in near future.

 

Sound Good ??

[JKJK]

the fw.is stamped out then machined on the inside to remove run out from the crank hole location not the centerline?then it is lightened if needed to remove mass from the heavy side on the exterior?1 i have no doubt in boonman's abilitys,2 have no argument with anything discussed here,3 i honestly don't no jack shit on this subject.i'm just curious+appreciate all the input.

[stealthawd]

hope this helps explain things.

 

X = where factory balance holes would be drilled (thicker section of wall)

Y = thinner section of wall

 

You can see how the original OD is off center in comparison to the rest of the part. If you datum off of the center sleeve (this is machined) and grind away the OD, it will be balanced as you end up with identical wall thickness all the way around the part. The inside of the flywheel (I/D), where the magnetos sit, is machined as well from the center sleeve, so that is concentric. The only part not even, due to stamping, is the OD.

 

The reason that some are drilled and some are not is because you cannot predict the stretching of the material when it is stamped and it needs to be balanced AFTER it is stamped and the insides have been machined.

 

The only balance problems would come in when you leave that little "mohawk" on the outside. If the wall thicknesses varied already, then that "mohawk" will still have that variance unless it has a grind put to it as well.

Edited May 29, 2004 by stealthawd