Hello All,

I've been converting two Ryobi's over the past few weeks and am coming up disappointed. I purchased my hubs, spacers, mounts and flywheel machining from wacker engines. Peter has been very good to me and his prices are reasonable. The problem is I am getting substantial wobble out of both units. They are going in a Spitfire and a Hurricane and the spinner backplate wobble is really evident. It appears the either the:

A) Cranks are bent, on the longshaft I used a dial and got .002 run out, loads more when the hub is on and tightened. The shortshaft was too short to get the dial on.

B) The flywheels are not machined right or don't sit right on the crank. The short shaft flywheel wobbles like a gobblin' about 3-4mm out.

C) The Hubs are machined off center or when they are cut to length they were cut at an angle. My prop washers are without a doubt "not square"

It seems that Peter believes these engines are quite crude and wobble is normal......is that so ? should I expect more ? If so, Peter has said he would take the parts back and give me a refund. I hate when things like this happen, I'm not angry at Peter, just disappointed that I am not making progress with my planes.

What do you guys think ?

Mike

This does sound strange. I guess the first thing I would do is make sure that the fly wheel is completely seated when tightened down. But that is kinda obvious. Maybe the keys arent seated properly preventing the fly wheel from fully seating on the taper. Are both engines the same? IE: both long or short shaft. Just pulling straws here. Assuming the seating is ok I would pull the fly wheels off, mount the engine in a test stand, pull the plug and rotate the crank shaft to check for any wobble. Hard to see a wrong cut on a hub or the flywheel when done on a lathe. I suppose its possible but I cant see Peter turning out something like that.
Edwin

Wobble is not acceptable on any engine...The taper on the Ryobi crank is very close to the front bearing, and any runout at all there is highly unlikely...The best way to make it square is to put some Loctite on the taper and tighten the flywheel as tight as possible..Let it set up for a few hours and take the hub off..Bolt the engine on a mill table so you can slowly rotate the flywheel and mill the top surface perfectly flat and 90 degrees to the crank..If the hub is drilled and tapped correctly it will not wobble when put back on...Without a mill there is no way to make it perfect, as you can't be sure the top surface of the flywheel is 90 degrees to the crank...
Unless the flywheel is held in the lathe ON THE TAPER it's not possible to get the top surface perfect....
U S 41s had this problem a few years ago...The fix was to put the flywheel on a tapered shaft in the lathe and machine both front and rear surfaces, and make a new hub.....
THIS IS NOT TO SAY THE PARTS YOU RECEIVED ARE NOT PERFECT, don't anybody get all hyper [:@] and start flaming

Is it possible to take a cut-off crankshaft....the end with the taper.... mount it in a lathe with flyweel in place but without nut/hub and macine it carefully on lathe. But like you said...with flywheel loctited in place. Just wondering? [:-] Capt,n

That works very well...The taper on the Zenoah cranks is the same on both ends, I have lots of cut off pieces...

Guys,

Thanks for the help. I do not have any machine equipment to do the work, that's why I was using wackerengines for parts. Peter insist that these engines are really crappy when it comes to wobble and runout. I guess the best option here is to return the flywheels and hubs to Peter and get my money back. Can anyone recommend another source to machine the "new" flywheels Peter will return to me ? I also need to make sure I get a 26mm long shaft hub and a 46.5mm shortshaft hub, I've already spaced for these.

Is the .002 runout on the longshaft crank normal ?

Like I said, not angry at Peter, just want to get my birds flying.

Thanks,

Mike

.002 at the end of the long shaft is not bad at all....002 at the end of the taper on the short shaft would be unusual....Any runout at all would be unusual...If there's a problem it's with the way the flywheel fits on the taper and the surface of the flywheel...The top surface of the flywheel is usually not machined relative to the taper....Even a perfect hub can't track true on a crooked cast surface....
One of the reasons the engines are so cheap in the first place

For a Ryobi .002 aint bad. The newer ones have the taper and key cast into the flywheel. The early ones had the taper and key slot machined into them and are much better but still a bit off.
We have machine prob hubs for our conversions, but they don't work with with the magnets. Maybe get one of our hubs abd run glow fuel

Ok, so it looks like it's the fit of the flywheel or the machinging on the front of the flywheel that is causing the grief, these are the new cast woodruff key deals. The .002 runout is the crank only, not the flywheel, the runout gets worse (.015) when I tighten down the hub and flywheel.

Mike

No way on the goo fuel ! [:-]

Spitfire: Maybe RCIG1 would fix it for you. If he would it will be worth it. Ralf does very good work. Good Luck Capt,n

I'm open to that, RCIGN1, pm me if you're interested and we'll go from there.

Love the Snoopy, Snoops was always special for my dad and I, especially when it came to planes.

Mike

RCIG1: Would you sell me one of the cut off crankshafts? Maybe a couple ...incase there is different tapers. I do not know the taper of these engines. Thanks Capt,n

Only ones I have are G62s....They are the same on both ends and one gets cut off for clearance inside the mount for the ignition.....

Go to your local lawnmower/chainsaw repair shop and he will have a pile of junk string trimmers, quite a few will be ryobi he will probably be willing to give you a couple if not I wouldn't pay but a few bucks for them. take them home and dissasemble , crankshaft counterweight is a press fit ,put in a vise and drive crankshaft out with a hammer and punch. if you have a drill press or access to one, chuck the crankshaft and flywheel in the drill press,now you have a makeshift mill, place coarse sand paper on horizontal work surface and make sure you are 90 degrees to chuck now you can do your own flywheels

I had a few old Ryobis here, so I made a hub for one...The crank had less than .001 runout at the end of the taper...I made a hub, drilled and tapped and machined without taking it out of the chuck, so it was almost perfect...Made a tapered rod to mount the flywheel on and turned both sides parallel and concentric to the taper...put the flywheel on the crank with some green 609 Loctite and tightened it up, let it set up overnight...Mounted the engine case in the mill and milled the top surface of the flywheel exactly 90 degrees to the crank..Screwed the new hub on the end...It had about .012 runout...Only way this could happen is if the threaded end of the crank is not concentric to the taper, the runout was the same at the bottom of the hub as it was at the top...Remachined the OD of the hub so it is now concentric to the taper

Hign quality engine ain't they
When you think about it 49.95 for the whole weedie, $5 for carb,$5 for magneto, $10 for the trimmer shaft and spool. Lots of bucks left over for the engine.

Here is a krazy idea!!! Instead of sandpaper on the horizontal table. Use a lathe tool held in a cross feed vise that bolts to table and use the drill press for a vertical lathe. With a good drill press you can place a end mill in chuck and with a cross feed vise...use your drill press as a mill. be Carefull......Capt,n

If someone machined the fins off of the flywheel using a milling machine with the flywheel backside against the table, the machined surface of the fins may not be perpendicular to the shaft due to the casting irregularitues on the backside of the flywhel. I rough the fins off on the mill, and then mount the flywheel on a sawed-off crankshaft and chuck it in the lathe. I do it this way because I have a very small lathe (7 x 12). If I had a bigger lathe I'd do it all on it. All weedie tapers for the Phelon and Walbro flywheels seem to be the same, so finding a crank donor that works is pretty easy. That said, if you've really got several mm of runout then you've got other problems....

Guys,

Thanks for all the help, the machining with a drill press sounds interesting but is not the direction I want to go. I'm more into building the airframes and flying. I liked the idea of the Ryobis because I could get two engines for the price of one and they fit very nicely in the KMP Spitfire and Hurricane that I have. The engine work required was simple enough and I left the flywheel machine work to the professionals.

RCIGN1 is going to help me out with sending some parts and once they're installed I will report in. I know Ryobis are cheap and could expect some vibration but the amount of wobble you see in the spinner backplate is not acceptable. I can see it tearing the plane to pieces.

Mike

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Just wonder what is the history is on these engines? IF someone used the "bigger hammer is better "method to remove the flywheels, they may have bent the crank ends,same thing if they were dropped on a hard surface with the flywheels attached. I have used peter's prop hubs on my ryobi's and they run very true just my 2cents worth

The end of the crank on a Ryobi is only sticking out about 3/4" from the bearing...Almost impossible to bend something that short...I'm sticking with my thouhgt that the threads are not concentric to the taper...Even a perfect hub will run out on a crooked thread...

In his original post Mike said one of his Ryobis was a longshaft (4 inches +/- as I recall). If it had been dropped I would think that bending might have been possible on the longshaft engine. []

Kinda unlikely[:-]