Flywheel balancing - which balancer?
 

Hi y'all,
I was just wondering which prop balancer you guys are using to balance your flywheels?

I've seen the Robart 'High Point' mentioned in a couple of posts but it seems to be discontinued (not listed @ Tower and 'not available' from the UK shope I've tried). Would the Dubro 'Tru Spin' be a good alternative?

Thanks for any help.
Steve

RE: Flywheel balancing - which balancer?
 

I like the tru spin and I found out that the high point isnt being made anymore too. My true spin is o.k. but I bought a precision ground shaft to replace the original one, it had a lot of small flat spots on it that made fine balance impossible to do. Piper

RE: Flywheel balancing - which balancer?
 

take a look at the hole in the middle of the flywheel. on some this hole is machined with a keyway but on some the key and hole are simply cast in place and getting the little cones of the balance shaft to seat dead center is just about impossible. even with the machined hole the cones will come out off center if the face and back of the flywheel have any imperfections.

long ago when i did a couple of ryobis i just took the fins down by an equal amount all the way around and bolted it back together.


dave

RE: Flywheel balancing - which balancer?
 

Thanks Piper & Dave.

I'm lucky that my flywheel has the slot cut in it for the woodruff key so the cone should sit o.k.

I thought I had this all understood after searching & reading every (I think) Ryobi thread I could find... but, I was recently pointed in the direction of Joe Guzzardi's web-site, "Teaching a weedwacker how to fly" ([link=http://www.geocities.com/CapeCanaveral/Lab/6216/sonof.html]Son of Weedwacker Site[/link]). Here he say's, quote, "The flywheel is made off balance in order to compensate for the mass of the engine's other moving parts.... grind off enough material from the opposite side to regain the original unbalanced condition. This seems to contradict almost every other post I've read which says the flywheel should be balanced 'normally', just like a prop. Help, I'm confused again!

Steve

RE: Flywheel balancing - which balancer?
 

When I was converting my first weed whacker, a Ryobi, I discovered the imbalance of the flywheel. So I balanced it. This engine runs as smooth as any of my other weed whackers.

The Ryobi flywheel was the only one I ever found that was grossly out of balance.

Enjoy,

Jim

RE: Flywheel balancing - which balancer?
 

I don't think you have to worry about the intentional flywheel imbalance, after all, some guys take the flywheel right off to run an electronic ignition system.

My flywheel has a cast-in key, so I balanced it on the short section of straight hole. I just made up a tight fitting hardwood dowel with pointed ends held between 2 wooden uprights with drill indentations. If you try this, make sure the flywheel runs true, no wobbles.

Allan

RE: Flywheel balancing - which balancer?
 

Thanks Jim & Allan. The general concensus seems to be to balance for neutral so that's what I'll do.

RE: Flywheel balancing - which balancer?
 

The Du Bro Truspin is what I use, too. As for Joe's comments on flywheel balancing on his website, I do respect his opinion. However, I have come across at least 3 Ryobi 31cc flywheels and every one of them is off differently. Unless Ryobi purposely "off-balance" every single engine they produce independently - not likely - I would attribute that more to manufacturing vairiances than being purposely engineering that way.

YMMV.

RE: Flywheel balancing - which balancer?
 

BTW, I forgot to mention, that to mount the Ryobi flywheel on the balancer shaft, I used one of the tapered slides backwards on the back side of the flywheel and just used the cone side of one on the front of the flywheel. I have a couple of High Point balancers as well as a Top Flight. The Dubro balancer should work as well as the Robart High Points?

One of my short shaft Homelite 30's has a chain saw flywheel on it which seems to work just fine.

After reading the conversion article from the link above, it brought to mind about using long shaft flywheels on short shaft engines. They will fit and run true but the position is off front to rear. To put a short shaft flywheel (5/16") on a long shaft engine (3/8"), well, as you can see, it's not going on there. I've been there and found out the hard way.

Enjoy,

Jim

RE: Flywheel balancing - which balancer?
 

While looking for something else, I made an amazing find. The High Point Balancer is still available for $35.95

http://bennettbuilt.com/page9.htm

Enjoy,

Jim

edit to Change price

RE: Flywheel balancing - which balancer?
 

Thanks guys. Defintely neutral balance then [sm=thumbup.gif]

Jim, I never thought of the reversing-the-cone thing, doh! I have a little finger balancer for my props (two cones slide on a short metal shaft; shaft has pointed ends to hold between finger & thumb) so I reversed one cone and it works, sort of. My flywheel is balanced heavy toward the non-magnet side, but if I mark this point and then fit it onto the key-way on the motor shaft it doesn't correspond to TDC or BDC which I would have thought were the two places where counter-active mass would've been necessary (but then, what would I know :D). Just an observation...

RE: Flywheel balancing - which balancer?
 

Before you cut the flywheel fins down, you might want to note the location and amount of imbalance on the stock wheel so you can compare to post-machined wheel. You already know the location, just tape little washers, etc., opposite to the heavy point until it balances. Save the weights and try them at the same place after machining. You then have the choice of duplicating the stock imbalance or going to a neutral balance. I didn't read about the factory set-up until after I modified my flywheel, so I couldn't try this procedure.

RE: Flywheel balancing - which balancer?
 

I just put them in a lathe and take the fins down to the highest point on the face of the flywheel. Not even balanced them, not had a problem getting the revs I need. No need to get carried away with trimming the fins right off or anything like that (they add strength!)

Given the nature of a cast flywheel and the limited machining (try comparing some of these flywheels) you'll note they can vary quite a bit. Sure, balancing may yield some more power but so will aligning the prop with the crank pin (which is another controversial subject).

BTW has anyone had a modified flywheel explode yet? Interested to know in any cases to get an idea of how statistically probable this is.