fatflyer41

Anyone that has converted this engine balanced the flywheel to be purposely "out of balance" with a certain area heavier than the others? An old RCM article said that the flywheel should not be perfectly balanced to compensate for an internal out of balance condition. Any comments on this? I have the new, 2-ring engine.

AtomHeartMother

I've got a ryobi, the flywheel was chopped on a metal cutting lathe. After that I put it on my prop balancer and discovered that it was out of balance exactly opposite the magnets. I drilled a small hole there and opened it up gradually with larger bits until it balanced. I ended up with a quarter in hole about a quarter inch deep. The plane shakes pretty good until the engine warms up. It idles at about 25-2600 rpms. It seems ok at that setting. Throttle it up and it smooths right out. Now...for balancing. If you choose not to balance the flywheel, you must remember the wheel goes on only one way, with the wedge on the crank. So if it's out of balance on the "wrong spot" it'll make vibration worse. You could also choose to not balance your prop, also in an attempt to achieve crankshaft counter balance. From what I've seen on glow motors this is a hit and miss process. Personally, I stick with balancing everything I can and let the engine run as is.

kevin mcgrath

My Feedback: (1)

I remember those articles by Joe Guzardi I think.Teaching your weedwacker to fly and son of.....I also had an E exchange with him on the subject of balancing and his opinion at the time was to put the flywheel back to the same balance as it had before it was shaved to offset the weight of the magnets in the flywheel.
Some folks place the prop in a certain relationship with the piston at TDC too to try to smooth out the inherent vibration of a single cylinder engine.
You can also get into heavy discussions on the smoothing affect of the flywheel vs a CH conversion where the flywheel is vestigal.
Personaly I use the CH unit,and ignore the prop postiion and get a steady idle below 2000rpm which is somewhat lumpy albeti reliable due I assume to the fact the CH unit for the Ryobi does not change the timing of the engine with RPM.
I am most interested in any other experience and opinions on this subject......

fatflyer41

Thanks for the answers, guys. I ran the engine last night with the flywheel completely balanced. It seemed to have more vibration than as a weedwhacker. Since I have another weedwhacker I'm going to pull the flywheel and run it on the RC engine. I'll let you know if it's any smoother. I'll also try a slightly out of balance prop, in several positions, with both flywheels to see if there is any difference.

w8ye

My Feedback: (16)

I noticed the out of balance situation on my Ryobi when I converted it also. I balanced it and the motor appears to have no more vibration than when it was a weed whacker and is also no different, vibration wise, from my Homelites or McCollochs.

Then I read the articles mentioned above and thought that maybe I had messed things up but It seems to run just fine.

As far as I can see.. How do you know just how out of balance it was to begin with? After you turn the fins off, can you assume it has the same amount of out of balance? I knew in which direction it was out of balance but not by how much. My conclusion was that it was considerably out of balance according to my High Point balance.

Good luck,

Jim

wrhardin

Greetings gentlemen. At RS Engines we turn down a lot of flywheels. One thing that must be remembered is dynamic balance. Like when a car tire is spin balanced. If the flywheel is turned down correctly, the same amount of material is removed all around leaving the balance as it originally was. Originally, the flywheel was dynamically balanced to run smooth at the higher rpm's so expect the idle to be a little rough. If the flywheel is put on a static balancer it will be slightly out of balance but my recomendation would be to leave it there. About the only time we fly at idle is during long down hill runs or landing approach. If we put the flywheel out of balance at higher rpm's, we will be making most of our flight with unwanted vibration.

tkg

My Feedback: (1)

What Ive seen is not so much out of balance, but out of round.

wrhardin

True, they are a cast part and some of the flashing is left around the edges. The counterbalance is inset a little and over all, when you look at them they look a little funky. But on the bright side, it doesn't cost the mfg's a bunch to make them. If all the cast parts of the weedie engines were machined, only the rich could afford to trim their lawn. The weedy is still an economical way to fly though

flipflop

After reading John Benarios column on engine balancing in the March 2002 RCM a couple of times, I decided to check the balance of one of my Ryobis. The crankshaft counterweight doesn't have nearly enough weight and the way the crank is designed, you can't remove material from the crankpin side. I JB welded lead into the two holes in the counterweight and had to add lead to the flywheel on the side opposite of the magnets. I still don't have it completely balanced, but it does run noticably smoother than before.

w8ye

My Feedback: (16)

Keep in mind that there are two different brands of flywheels on Ryobi's. There the Phelon (spo) and then there's the Walbro. The ignition modules generally match the flywheel in brand name.

Also in the previous post it appears that there is an attempt being made to balance the entire weight of the rod and piston. I may stand corrected. (Help me here TKG.) The accepted standard in the past has been to counterbalance only the weight of the big end of the rod? There may be some other inturputations here like the big end plus half the weight of the little end and piston?

I know that, good or bad, I statically balanced my flywheel and the engine doesn't vibrate any more than the other brands of weed whackers that I have converted.

Good luck,

Jim

mglavin

My Feedback: (31)

Has anyone ascertained if the Ryobi's are internally or externally balanced?

Would you guys provide:

Prop and rpm stat's?

Engines weight in stock aero form and then setup with C&H Ignition??

wrhardin

The Ryobi is internally balanced. The flywheel counter weight is for the magnets.

normal rpm with Top Flite power point 18*8- 6700

Stock weight-61 ounces
with CH ignition- 41 ounces excluding ign. module & battery.

Plane should have at least 1000sq" area

planes I have personally flown with this engine with good performance:

Dynaflite Chipmunk
Dynaflite Super Cub
Hanger Nine Ultra stick w CH ign.

Its Sunday, lets go flying

Flypaper 2

w8ye, you're right, rod, wristpin and part of weight of piston. No single cyl. engine can be perfectly balanced at all rpm. Must be balanced at rpm that it's most used at. Because the piston is reciprocating, and the rest of the crank assembly is rotating, it never is in perfect balance.

kevin mcgrath

My Feedback: (1)

And amid all this discussion of balance lets not forget that the other if not major cause of rough idle is the fixed timing of approx 28o BTDC,rather than a more ideal figure of say 8oBTDC,and even the CH conversion uses a fixed timing set up although it is adjustable.

tkg

My Feedback: (1)

For those of you who are determined to turn a pigs ear into a silk purse, CH has the Syncro Spark as an opition on all the ignitions. So you can have auto timing adjustment.

kevin mcgrath

My Feedback: (1)

HEY tkg (aka CH Ignitions)....why do you supply a fixed unit for the weeders and a variable one for such as Zenoah, or am I naive in the terms of how one makes a profit in the ignition conversion biz?
I know your literature sez weeders do very well without the variable feature but the cost to produce one cant be very different from the full blown product,can it?
Im planning a twin Ryobi project in the near future and if I want the added insurance of an idle with low advance Im forced to buy four units from you ,right?
Not complaining (particularly),just asking

tkg

My Feedback: (1)

The weedies are basically through away engines. The ring seal is not that good at cranking speeds, so little chance of kick back.
The Zenoahs are bigger and have two rings they will kick back and its hurts. So the stock ignition kit for the bigger engines has the Syncro Spark.
Any body who flies weedies is into cheap
so we make the cheapest conversion possible. We do offer the Syncro Spark as an option on all ignitions and sell about 25% of the weedie conversions with it.
Is your Ryobi twin a boxer or inline??

kevin mcgrath

My Feedback: (1)

Well I certainly understand your marketing logic,although I may not agree totally with it.Im using one of your units on a Ryobi mainly for the weight saving and flywheel fit, in 1.20 sized planes,and if the engine craps out Ill just put your unit on another Ryobi, or sell the ignition through RCU.
I was referring to a twin aircraft (Twin Otter) not a twin cyl engine.I dont have the machining expertise so would buy a 3w48 (2)or zdz twin 80,if I was in the market for a small twin cyl engine.

wrhardin

Good explanation tkg. I agree with you completely. Lets not forget, the weedies are aimed at the sport flier as an economical power plant. If you want auto advance simply purchase a CH unit with auto advance.
I have a Ryobi with the fixed timing CH unit and it works great. If you want to advance the timing for a better high end, simply move the pick up a few degrees. On the other end of the scale, we are presently flight testing a stock Homelite 25cc with 7, 10, and 15 degree advance using the magneto (flywheel, coil) ignition. On the ground we are getting 8750 rpm on a 16*8 APC with the 15 degree advance unit. I'm sure its unloading well above that in the air. The engine 'hits' a little harder at idle but I wouldn't consider it a rough idle. Our Homelite project should be complete this month (Hooray) and we should start on the Ryobi by the first of september.