Fin on Flywheel Broken..Advice Appreciated

[Brit101]

Jonsered 455 rescue saw, one of the fins on the flywheel is broken off. Tech says to;

A) Replace it, which he thinks is the best way to make sure there are no bearing problems in the future.

B) Break off one opposite or 180 degrees from it.

C) Do nothing.

Saw is in good shape, looks like the orighinal bar and chain due to the sproket and paint on saw/bar.Presently not running, not a carb kit or compression issue, these have been checked out. Saw will be used little, and is a backup to a new Husky 55, with less than 1 hr. on the meter.

Would like to hear from any informed tech their views on the matter or any other who has experienced the same concern and would care to chime in.

Thank you in advance for your replies.

 

[HiOctane]

Hmm,I would say do nothing.I dont think it will affect the saw,as you say its only a backup saw.DId you check for used one .I didnt check but i guess flywheel from other models from saw or clearing saw should fit on your 455.

 

[Lawn Masters]

I'd knock the opposite fin off and keep it balanced so its even and wont cause wear on the bearings.

 

[thompson1600]

I agree with the assessment to replacement the flywheel. The out of balance rotation can lead to the bearings going quickly. Breaking one off 180 degrees may be an options for a little used saw, however, you can buy a used flywheel for very little on ebay or probably from someone on this site.

I would not leave it as is, I would replace it.

Tom

 

[trimmmed]

I'd knock the opposite fin off and keep it balanced so its even and wont cause wear on the bearings.

Nonsense, breaking another fin off won't balance anything.

 

[Bob Wright]

Yes it will balance itself knocking off the fin 180 degrees across. I did it 25 years ago on my Echo CS-60S, while adding the little ing module. it should break off in the same spot as the already broken one. Unless its on the meaty part. My saw still screams today...Bob

 

[eric_271]

Nonsense, breaking another fin off won't balance anything.

Explaination?

 

[klickitatsacket]

Replace it, if you like your saw. If you do not care about it, knock off the other fin. If you are going to sell it on ebay, do nothing and sell it as a mint condition saw

 

[trimmmed]

Explaination?

If you could break one fin off at 180* from the previous one, it would not balance the flywheel. It will still run eliptical. Breaking one off on the opposite side might minimize the elipse, but that's it. It wont be balanced.

Looking at the face of a clock, the broken fin is at 3, so if we break the one off at 9 to "balance" the 3 and 9 axis might be equal, but they will not be in sync with the 12 and 6 axis. Unless we break those off as well Of couse we could extrapolate that out and break all the fins off, equally, to get it balanced....lol

It's better to get the new part and much easier to replace than bearings will be down the road.

 

[trimmmed]

Yes it will balance itself knocking off the fin 180 degrees across. I did it 25 years ago on my Echo CS-60S, while adding the little ing module. it should break off in the same spot as the already broken one. Unless its on the meaty part. My saw still screams today...Bob

Bob, regardless of the saws vocal capabilities today your flywheel is not balanced.

 

[Bob Wright]

Maybe so in exact words but it does run better. I ran it both ways...Bob

 

[cbfarmall]

Last time I checked, my Mac SP80 has six fins knocked off. And it is perfectly balanced....if I use a crooked scale.

Chris B.

 

[lesorubcheek]

I had the same questions. Look at this thread P40 .
I opted for Pioneer's advice. Drilled and tapped it and inserted a bolt with loctite.
Dan

 

[eric_271]

If you could break one fin off at 180* from the previous one, it would not balance the flywheel. It will still run eliptical. Breaking one off on the opposite side might minimize the elipse, but that's it. It wont be balanced.

Looking at the face of a clock, the broken fin is at 3, so if we break the one off at 9 to "balance" the 3 and 9 axis might be equal, but they will not be in sync with the 12 and 6 axis. Unless we break those off as well Of couse we could extrapolate that out and break all the fins off, equally, to get it balanced....lol

It's better to get the new part and much easier to replace than bearings will be down the road.

Ok I understand what you are saying. Its not balanced from say 12 to 3 or 12 to 9. You are talking about static balance.

 

[Simonizer]

Jonsered 455 rescue saw, one of the fins on the flywheel is broken off. Tech says to;

A) Replace it, which he thinks is the best way to make sure there are no bearing problems in the future.

B) Break off one opposite or 180 degrees from it.

C) Do nothing.

Saw is in good shape, looks like the orighinal bar and chain due to the sproket and paint on saw/bar.Presently not running, not a carb kit or compression issue, these have been checked out. Saw will be used little, and is a backup to a new Husky 55, with less than 1 hr. on the meter.

Would like to hear from any informed tech their views on the matter or any other who has experienced the same concern and would care to chime in.

Thank you in advance for your replies.

Option "B" will work. Don't break it off though. Machine it off with a die-grinder and carbide burr. Take away the same amount of material as to mirror the amount of metal lost by the initial failure. Cheers.

 

[klickitatsacket]

In all seriousness I have found that almost all flywheels have an odd number of fins and you can not break off one directly accross. I find that if you are going to go the route of trying to balance it out (not the best choice but works in a pinch) I like to take off a total of three fins in a triangle pattern.

 

[Chain_Bit_Me!]

Make sure the one you remove is directly across from the broken one. If its not, it will still be seriously off balance. If you luck out and remove the one directly accross from the broken one, it will not be perfectly balanced, but it will definitly vibrate less than leaving it on. This is only a temp fix for saving your crank bushings.....but.....get a new one on order as soon as you can (if they still make them).

 

[Big Woody]

The same logic and technique applied to balancing car wheels applies to chainsaw flywheels as well. They both obey the same laws of physics. In the case of car tires your adding weight opposite the heavy side of the rim where as for flywheels your removing by breaking off an opposing fin if there is an even number of fins.

The logic is pretty obvious since there is only one opposing lug on the flywheel to balance out the magnets not 4 lugs at 90 degrees apart (or 8 lugs at 45 degrees). Four lugs would also be balanced but it would be a waste since it is not needed and would cost more and weigh more. They must also account for the magnets themselves having a different density than the flywheel material for balancing when they design the opposing lug.

For an odd number of fins, taking off three fins would work but only if the total number of fins minus the 3 missing is divisable by three. Then you have three equal regions where each region has the same number of fins. For example with 9 fins at 40 degrees apart (9*40=360) you remove the three that are 120 degrees apart and it is balanced since each region has exactly 2 fins
(9-3)/3=2. If you have 37 fins (37-3)/3=11.333 and you can't have 11.3 fins per region. 39 total fins would give you 12 per region which would then be balanced. The astute mathematicians will realize that the 3 missing fins must be exactly 120 degrees apart in order to be balanced.

Hence depending on the total number of fins (if an odd number) breaking off three may not fix the balance problem any better than breaking off 1 of the two "closest" opposing fins. You would have to do a more detailed analysis to prove which would provide the smallest out of balance rotational mass.