another darn ryobi post (ryobi performance modification, analysis and comparison)
10-08-2014, 04:49 PM
#652
Click here for definitive info: http://www.rcuniverse.com/forum/engi...-comments.html
As far as I know, you have to pull the backplate to be sure. There are two different flywheel keyway designs too, but to my knowledge that is NOT related to whether it is an externally balanced engine/flywheel.
AV8TOR
As far as I know, you have to pull the backplate to be sure. There are two different flywheel keyway designs too, but to my knowledge that is NOT related to whether it is an externally balanced engine/flywheel.
AV8TOR
Last edited by av8tor1977; 10-08-2014 at 04:52 PM.
10-08-2014, 06:24 PM
#653
Not positive, but I am sure some engines had a tab device on flywheel that indicated that the tab device had to be is same place to maintain balance. Should have took a photo!
10-08-2014, 06:41 PM
#654
Junior Member
Join Date: Oct 2014
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
I really like electronic ignition, and in fact, out of a rather large fleet of planes, I don't have a single magneto equipped plane.
The benefits are lighter weight, easier starting, better idle, more power, and nicer looking as well. I can't give you an exact figure on how much more power, but you would gain some. You don't have the drag of the magneto aerodynamically, nor the drag of the magneto magnets as they make electrical power for the spark. Also, you can optimize the timing, which can result in net power gains too.
I have a Ryobi 31 in my Giant Tiger Moth Biplane. As usual for me, I have hopped it up by raising the compression, increasing the exhaust port timing, using a free flowing muffler, and a larger than stock carburetor along with electronic ignition. But it works, as it turns an 18 x 6 Top Flite wide prop at 8500 rpms! No, you should never turn a Ryobi over 7500 static or you risk blowing it up. In my case, I can't make a larger prop fit the spinner size for this particular plane, so I either don't use full throttle, or limit it to a few seconds at a time in this case.
The benefits are lighter weight, easier starting, better idle, more power, and nicer looking as well. I can't give you an exact figure on how much more power, but you would gain some. You don't have the drag of the magneto aerodynamically, nor the drag of the magneto magnets as they make electrical power for the spark. Also, you can optimize the timing, which can result in net power gains too.
I have a Ryobi 31 in my Giant Tiger Moth Biplane. As usual for me, I have hopped it up by raising the compression, increasing the exhaust port timing, using a free flowing muffler, and a larger than stock carburetor along with electronic ignition. But it works, as it turns an 18 x 6 Top Flite wide prop at 8500 rpms! No, you should never turn a Ryobi over 7500 static or you risk blowing it up. In my case, I can't make a larger prop fit the spinner size for this particular plane, so I either don't use full throttle, or limit it to a few seconds at a time in this case.
First thing, I'm building a 1:1 scale motor bicycle and all the kids on YouTube say you should use a weed whacker motor. I bought a 2004 Ryobi string trimmer which had a broken flex-shaft for $25.00 on a lark. I fooled around with it a little and have it idling at 250 RPM with 3 or 4 degrees advance on the timing. Easy since the key on the flywheel was kind of weak and I broke it. I haven't modified it otherwise, although I am tempted to make a little scoop to ram air into the carb at speed. Time will tell whether that is practical or sane. Otherwise the motor seems to be fairly clean and in good shape. My spark plug socket is in storage so I don't know what the top of the head looks like, but judging by the way it runs there can't be anything seriously wrong with it.
In my initial review of the crank case was positive. I'm not up to disassembly of the engine much beyond that; for lack of tools and also for not wanting to screw up things that are not screwed up. I can't really see the main bearing, but I estimate there is one rather large roller bearing in there rather than two ball bearings, but I'd need an X-ray machine to tell for certain. I can't easily find a parts list for the motor since the model number is unique and probably specific to Costco or something. Possibly I can buy another one for parts if it comes to that but scuttlebutt seems to be that these things are bulletproof.
Your point about running it at high RPM in a static configuration is reasonable. I plan on using some extruded aluminum U profile heat sink (salvaged from scrap) to fashion a case around the flywheel to keep good airflow around the coil and over the head. I doubt I'll ever be running it at top RPM given the expected use case, but there's always the chance I'll get bored and attach a starter motor to the shaft to make a cheap 12V gen set. In that event who knows what kind of revs it might achieve? Whatever happens I'll try to keep the revs below 8K on the basis that it wasn't designed to work that fast.
Since I don't know anything official about the motor I have no way to assess its specifications. It would be interesting to know it's KW rating, and if anyone knows what it is capable of producing I would love to know. As an I.C. engine amateur I also don't know what it's power band profile is like. My gut tells me that peak power will probably show between 5 to 7K RPM, and since I don't plan on running it at those speeds any quick advice for improving low-RPM torque would be golden. In a similar vein, I might as well keep the factory carb which has a venturi aperture of slightly less than 8mm. I may fiddle with the reed-stop when I replace the carb-mount gasket.
Other than that, the only big change I might (eventually make) is to make a small ECU with a handful of sensors and a servo to drive the throttle. That would give me the data to make long-term measurements to characterize normal operation and to have some ability to handle the unexpected. I estimate I can pirate a little juice from the plug wire, enough to run a low-power AVR, but a servo is something else entirely. Perhaps a small supercap would have enough juice to run the throttle back to idle at engine shutoff time. Something I'll investigate if I get that far into this project. Mainly though this has become a project to inexpensively add dinosaur power to my bike as well as a way to make a funny spectacle of myself about town. Not exactly RC content, but fairly close.
Captain Obvious
