Will a ryobi 31cc engine work off of the magneto for an airplane or do you have to convert it to an electronic ignition? If so where can the parts be obtained?

Thanks, Chris

Go to jagengines.com It will give you all the info you need. Good luck, red

Read the "gas fuel glow plug no ignition" tread you can convert your Ryobi into glow and use a mix of gasoline with glow fuel and eliminate the ignition weight period

no you can run the magneto that came on the engine you dont really even have
to cut the fins off the flywheel but it gets rid of weight and air resistance .Pete at
wacker engines can help with your parts needs and machining.The advantage
of electronic ignition is removal of about a pound of weight (flywheel&magneto are
removed for cd ignition) its also expensive.

Exactly. Many "model airplane purpose built" engines use a flywheel and magneto. They work fine and for most sport applications they are perfect. If you have a model where you don't have room for the flywheel, can't have the extra weight, etc. then EI is for you. Performance gains are anywhere between 10% and 0% with EI Vs flywheel. On some models such as WWI warbirds the extra weight in the front is needed and would otherwise end up being lead.

Also removing the flywheel means less drag resistance and weight for the crankshaft to move thus meaning more RPM's and less effort for the engine.

Moparcolt,
I am installing two Ryobi 31cc gassers with magneto and flywheel into my Ziroli 101" B=25J. I believe she will perform well. Good luck.

"Keep 'Em Flying!"
Flak

My friend was telling me that the flywheel is balanced to minimise vibrations from the crank...

Will removal of the flywheel completely, cause too much vibration?

the fly wheel is balanced but not to alleviate engine vibration, no. the fly wheel is balanced to keep it from adding to the vibration. when you cut the fins down if you do it by just cutting them with a cutoff wheel you have to rebalance the flywheel. but if you use a lathe to cut the fins down you dont even have to balance. removing the flywheel alltogether doesnt add vibration. inside the crank case there is a weight on the crank to counter balance the piston when its combusting. DA engines makes a 50 that vibrates horribley but i think its due to the counter balance on the crank is too small to cope with the size of the engine. to see what i am talking back if you take the backplate off the engine you will see a solid almost triangular shaped dodad on the crankshaft. that is the counterbalance. it is the sole source of crank case balance to reduce engine vibration.

I have test run my Ryobi on the bench with magneto ignition.

Bill

Your friend is correct. The flywheel along with crankshaft is designed to reduce dynamic vibrations. If desired I will provide a reference to engineering textbooks that describe the design of dynamic balancing. The reading is heavy.

It probably does not matter much.

Bill

Well I have my engines run on GAS/GLOW fuel without the flywheel and I don't feel any vibrations differences as to the use of the flywheel, mine run smooth ecxept at low idle where you can feel a very small vibration which I dampen with the use of vibration isolators on my engine mount. this vibration is normal even with the flywheel installed,so to me there is no difference with or without the flywheel.

Hey Flak;

I built the Ziroli 101" with two Ryobi's. She is ready to go but do not want to fly it for a year or two. Might display it a time or two and when I get tired of tripping over her I'll give her a try . I believe it came out at 36 lbs. I left the fly wheels on it and it balances out perfect, no weight needed anywhere.

Peter

The balance issue comes from the fact that some motors don't have enough room inside the crankcase for a crankshaft with a large counterbalance. Usually, just the counterbalance on the crankshaft is used to !QUOT!balance!QUOT! the motor. Sometimes you need more eccentric weight. In short, there are two methods: Internal Balance and External Balance. An Internally balanced motor has all of it's eccentric bob-weight (counterbalance) on the crank. Externally balanced motors have some on the crank and some on an external rotating component, like the flywheel. Hence the name. If the flywheel has a !QUOT!heavy spot!QUOT! it would appear that the Ryobi is externally balanced. Either that, or they balance the flywheel and crankshaft as an assembly, so the weight of the magnet in the flywheel is of no consequence. This still implies that the motor is in fact externally balanced. If you remove the flywheel, you WILL affect the balance overall. How much? Since no one seems to know the balance factor for this motor, I would be guessing if I gave an answer. Since a lot of people are doing this, I would say it's probably not enough to cause problems. When you !QUOT!balance!QUOT! a motor you weigh all of the reciprocating components (piston, ring, wrist-pin, small end of the rod) and all of the rotating components (big end of the rod, bearing). You multiply the weight of the reciprocating components by the !QUOT!balance factor!QUOT! (for singles this is usually 50 - 55% but sometimes more), add the rotating weight and come up with the eccentric bob-weight. For static balance, if you put this weight on the crank-pin, the crank should sit in any position without any noticeable heavy side. If not, you need to lighten the side that !QUOT!hangs low!QUOT! (or add weight to the opposite side). For an externally balanced motor, you need to add the flywheel to the setup. Keep in mind the motor will still vibrate, even if it's perfectly balanced. The reason being that singles are not in perfect primary balance like an opposed twin. A good balance job on a single is just a compromise. As long as the hinges don't break on the elevator and rudder, and the servos last more than a couple of hundred flights - you're doing OK. <VBG>

I strapped this motor to a test stand and ran it for the first time a couple of weeks ago. It ran good with a 16x8 prop (7000rpm) on it I was running it on 32 to 1 ratio I think it will run a bit faster with a 50 to 1 ratio. NOW I JUST NEED SOMETHING TO MOUNT IT TO. are there any 3D planes out there that I could strap a ryobi 31 to?

Chris

My Ryobi on Gas/Glow does seem to vibrate more than I would like, and more than my other engines. (Also Gas/Glow) I can't say if it vibrates more than it would with the flywheel, because I never ran it with the flywheel. If indeed the Ryobis are externally balanced, a person could run an "out of balance" prop situated to put the weight where you need it in an application that is not using the flywheel. I may have to experiment with that on my Ryobi sometime when I get the time. Meanwhile, if anyone throws their Ryobi flywheel on a balancer, please let me know how it turns out, and if it is not neutrally balanced, where the heavy side is located. Following jrpav1's line of logic, it would theroetically be in line with the crank counterweight when the flywheel is mounted and the keyway lined up.

Let me know what anyone finds out about this please,
Thanks,
AV8TOR

I hate to complicate this issue further but I would like to propose another theory. If the flywheel is used to counterbalance the crankshaft then the weight would have to be opposite the crank weight. Since they are also on opposite ends of the crankshaft, it seems the oposing weights, as they rotate, would create a rocking back and forth in the engine. In other words, as the crank and flywheel rotate together the heavier side of the flywheel would pull the engine in one direction while the heavier side of the crank would pull the engine in the other direction thus creating the rocking or wobbling motion. This action would be worse the further apart the flywheel and crank are. I don't know this to be true, just wondering if the theory holds any water. But if it is true, it would make far more sense to balance the crank rather than use the flywheel to balance it. Anyone know?

Brian

The counterweight on the crankshaft is there to "counter balance" the weight of the piston, ring(s), piston pin, and about half of the rod. If the crankshaft counterweight has insufficient mass to do the job, a flywheel can be balanced in such a manner as to provide the extra counterbalance mass needed.

Some engines are entirely balanced internally, and the flywheel is "zero" balanced. (no imbalance). Other engines are "externally balanced." This is somewhat of a misnomer, because "externally balanced" engines are balanced both internally and externally with the flywheel in combination. I have no idea which weedeater or chainsaw engines are balanced in which manner.

However, if one finds that an engine has either too little or too much crankshaft counterbalance, you can compensate with an "unbalanced" prop, depending on where the weight is needed and how you position the prop.

(I bet this is as "clear as mud" huh?)

AV8TOR

With a Ryobi I would worry more about out of round than out of balance. Especially of those with the key in the flywheel as tha taper is cast not machined.

I have taken apart about 15-20 differant engines now. A couple had a steel bob-weight on the crankshaft between the flywheel and its retaining nut. This bob-weight had a warning to make sure of the same position on re-assembly. Have any of you guys seen this? Capt,n[:-]

Peter G,
You have a Beautiful B-25J! Sorry I haven't been back to this post for a while, let'e see, it's October and you posted your photos in May...SHAME ON ME!!! I have been busy finishing my C-47, as well as working on three BIG Warbirds. Oh yes, I have a family, a house and a job somewhere. So many planes, so little time...LOL! Good luck woth you Bomber.

I am making some modifications to my Ryobi, and wondered if knife edging the counterweight on the crank would throw it out of balance? and if so how could it be rebalanced? what would be the procedeure/ steps?I did some port work and milled down the lower case to increase the compression but was curious as to what else I could do to increase the performance on a low budget. what about a bigger carb, has anyone tried different carbs?

A little larger carb will do FAR better than a knife edge crank, even if you could make it balance.

got any part #s on a carb i could use?

Lots, I like a WT-9, its got a choke that works nice with the rear carb