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another darn ryobi post (ryobi performance modification, analysis and comparison)

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Old 02-27-2009, 11:36 PM
  #51
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

Which magnet are you getting? They have many different one on that site. Looks like the round 1/32 x 1/8 might be a good choice.

I've been through Springfield MO a few times on my way to the Ozarks. Do you ever make it to StL to fly? I went to Parks in Cahokia (IL side) and used to fly at Buder Park a long time ago. Crashed many models there! Been a while since I've been there.
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Old 02-27-2009, 11:38 PM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

CH has them for $2.00 but the S&H is $2.00 too[]. The magnet won't go threw the stamp machine, it must be hand canceled so gotta pay the post office an OS rate.
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Old 02-27-2009, 11:48 PM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

Does C-H take Paypal? Do you guys press the magnet into the hub, or glue, or both?
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Old 02-28-2009, 12:24 AM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

I was looking at the 3/16 x 1/16 or the 3/16 x 3/16. 3/16 is .1875 so it should be about right. I tried ordering from there. .70 cents worth of magnets and they want 9.68 dollars for shipping. stupid a holes are crazy if they think there gona jack me like that for shipping. there in plano texas to. its pretty sorry when you can ship stuff cheaper from china than from state to state in th US. I did order my ignition and sensor. I added some servo arms sets like the ones dubro sells for around 10 bucks. these are 2.56 dollars and i got some 18 inch/ 45 cm servo extension wires for 1.10 apiece!!! grand total of 59.68. not bad huh.

I have never flown in st louis. i was through spfd il a couple of months ago when i went to rockford il to get a power unit I had bought. It looks like an ex spfd IL city unit best i can tell from the faded paint markings on it. we spent the night there on our way home. I wish we had more time to explore the town. Maybee this sumer I can get out that way for a fun fly or something.
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Old 02-28-2009, 11:29 AM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

It seems it dosent matter how many magnets your gona buy the minimum charge for shipping magnets is 10 bucks. i can get 50 magnets shipped same price as 4. I am thinking maybee buying 50 or so and them selling them to whoever wants some.
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Old 02-28-2009, 11:33 AM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

Don't you guys have a Radio Shack nearby? They sell a pair of them for a couple of bucks I think it is...

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Old 02-28-2009, 11:45 AM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

Radio shack really??? that would be to easy lol. I didnt think they actually had parts anymore.

Yep sure thing and i called the local one here and they have the rare earth magnet in a 2 pack 3/16" dia for $1.99

Thanks Av8tor1977
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Old 02-28-2009, 05:25 PM
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Old 02-28-2009, 06:56 PM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

I am curious to see what your overall weight savings comes out to be once you convert over to Electronic Ignition. I am currently scratch building a Super Sportster 90/120 and planning on hanging my Ryobi 31 on the nose. I have built a couple of these SS 90/120's from Great Planes kits in the past, and both Planes I used 90 2 strokes on them, but both needed dead weight in the nose to balance and neither was overpowered by any means. I also had the larger Giant Super Sportster ARF with a G38 on the nose, and it seems those big thick wings on the Super Sportsters don't really mind a little extra weight and still be able to fly pretty good. So I am certain the Ryobi will provide plenty on nose weight and perhaps to much....so I am kind of curious how much weight can be saved by converting to EI. A Zenoah G23 or G20 might be a better match for the Plane I am scratch building, but I have plenty of flying airplanes and this particular project I am only doing just because I wanted to build a Plane to hang the Ryobi engine on, and I had the plans for it. So my whole goal is to somehow make this engine work for this Plane, and am thinking it should. I have really enjoyed reading this thread, and appreciate all the good info posted.
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Old 03-01-2009, 01:20 AM
  #60
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

Looks like I'll be making a trip to the Shack tomorrow!

There are a couple of fly-ins/fun flys over the summer here. Spfld is close to four excellent club fields, and good people. I'll see if I can get some dates for ya.
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Old 03-01-2009, 08:19 AM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

I am just guessing but I think the weight savings to be arouind 1 lbs I will keep track of it when i do the conversion. I ordered my ignition a couple of days ago.
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Old 03-01-2009, 11:21 AM
  #62
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

Hey Av8tor1977 I know you recomend 150 degrees for the exhaust timming but what about the intake port timming? I think I am gona try and play with this a bit today.

Sounds like I need to start getting my camper ready for the fun fly. Do you guys do any combat there? I havent done any in a while.
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Old 03-01-2009, 12:16 PM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

You can't change the intake port timing on a reed valve engine. The reed opens whenever the pressure differential is favorable.

The transfer ports I didn't change, and still got very good results. The transfer ports are difficult to work on. If you modify them, you must be sure to maintain the original exit angle of the ports, and make sure the ports are identical to each other in timing and angles. Unless I am working on an all out effort engine, I just leave them stock. The exhaust timing is more important because it is often set very mild on these engines.

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Old 03-01-2009, 03:12 PM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)


Quote:
ORIGINAL: combatpilot

I am just guessing but I think the weight savings to be arouind 1 lbs I will keep track of it when i do the conversion. I ordered my ignition a couple of days ago.
Well 1lb would be a substantial weight savings using EI. I also considered maybe converting over to glow/gas which would also save some weight. I am getting ready to test this engine with an 18x8 APC. This is a stock single ring Ryobi 31 with no modifications. I will tach it when I do the test run and post my numbers using Lawnboy mix 32:1.
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Old 03-01-2009, 03:34 PM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

EI doesn't remove that much weight, it just lets you relocate it to a location other than the front of the engine. The weight of the flywheel and coil is about a pound, with EI you have to take into account the module and battery, so you only save a handful of ounces depending on the battery you choose...
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Old 03-01-2009, 04:33 PM
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I am sorry and dont take this wrong but I just dont see why you would want to use glow fuel in a gas engine. If thats what you want there are plenty of good glow engines on the market that are pretty cheap. To me the point of this conversion is to have a gas engine and not have to buy the expensive glow fuel. i will be interested to see what your apc runs for rpm. i am using a dynathrust as i really dont like the apc props.

Anyhow I think that sounds about right on the weight. The biggest gain on going to the electronic ignition will be a power gain and being able to hand start and weight savings if any is achieved will be a bonus.
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Old 03-01-2009, 07:08 PM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

Combatpilot

My Ryobi project is not really about saving any money...I just enjoy tinkering. I also make my own glow fuel which isn't really all that economical, but just something I enjoy messing with. I do see your point though if a guy was just trying to be economical, but in my case I just like experimenting. Of course this is your thread, and your project is the main topic of discussion here. I just thought I would ask a few questions about my own little project from some fellows who also seem to have some interest in the weedie engines. I look forward to following along.
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Old 03-01-2009, 08:05 PM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

Man if were trying to save money were in the wrong hobbie lol. Anyhow like I said please dont take it wrong. I am just trying to understand your motives on this and even though I dont understand why, it still interests me. I welcome all thoughts on this thread even if they are a little off topic cause they all still relate. I do understand the need to tinker and experiment with things. If I couldnt I would go nuts in short order lol. my wife says i already am but i think she is biased anyhow.

Again I really want to see how the APC prop does as far as rpm. The main reason I dont like them is they just dont look very scale or real to me. Yea I know this from a guy thats building a coroplast airplane lol. I dont know maybee if they came in black with yellow tips I might change my mind on them lol.

I like how you got yours painted and i may do that to mine in the end. I am wondering if it loses any cooling with the paint on it though. I may be splitting hairs there lol.
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Old 03-01-2009, 09:43 PM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

the thing about the gas/glow setup is you have no ignition system other than a glow plug (you loose that pound completely), you are using 1/3 glow fuel and the rest gas, the glow fuel used is the cheapest they have at the hobby shops, I think I get it for $13 a gallon, nearly the same run time as gas. Sure it's a bit more expensive to run than regular gas engines, but not too bad
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Old 03-01-2009, 09:50 PM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)


Quote:
ORIGINAL: av8tor1977

Also be aware that changes in temperature, and to a lesser extent, barometric pressure and humidity will affect your results from test to test when things are close.

AV8TOR

In order to accurately compare prop RPM data at different atmospheric temperatures and pressures, normalize all the data to "standard atmospheric conditions". There are many sets of these depending on what organization is defining them but I use these: 59 deg F ambient temperature, 14.7 psi (29.9 inches mercury (Hg)) ambient pressure, and zero humidity.

To normalize RPM, a correction for temperature is all that is needed.

This correction is:

RPM measured divided by the square root of theta (the Greek letter. Sorry, there may be a way to type a greek letter on this keyboard but I haven't learned it yet!).

theta = (Tamb deg F + 460) / 519 or (Tamb deg C + 273) / 288

So to correct to standard conditions -> corrected Np (the letter "N" is often used to denote speed) = measured prop RPM / sq rt [(tamb+460)/519]

So, you can see that when Tamb is 59 deg F (standard temp) there is no correction. When Tamb is colder than standard temperature the corrected prop speed (Np) will be greater than measured prop RPM. Conversely when the ambient temperature is greater than standard, Np will be less than measured RPM.

For example:

Prop RPM measured = 6600 rpm
Ambient temperature measured at the time of the test = 40 deg F

theta = (40+460) / 519 = .9634
Np = 6600 / sq rt. 9634 = 6600/.9815 = 6724rpm

If you record the air temperature with your RPM data for all the runs you make, then you can normalize the data and more accurately compare it to different runs. This should give more meaningful results when you compare engine configuration changes. If you are able to make your runs all at the same temperature then you will get meaningful comparative results for those runs of course. But it's a great advantage to be able to compare runs on different days for it's often not possible to make all your performance measurements on days that have exactly the same ambient temperatures.

BTW the correction for thrust measurements is Fn = Fg x (sq rt theta) / delta
where:
Fn - Net thrust
Fg - Gross (measured) thrust
delta - (the Greek letter) = Pamb/Pstandard = barometric pressure, inches of Hg / 29.91

I usually just log onto a local weather Internet site and get the current barometric pressure. It's not the most accurate way to do it but most folks don't have an accurate barometer at hand and the local weather data is pretty close.

Humidity can be corrected for as well but it's effect is pretty small and can be ignored for these sorts of tests.

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Old 03-01-2009, 10:17 PM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

Um yea ok. Man thats a lot of info. I think my head is still spinnin. Theta? man im just a red neck. Heres my atemp to use it in a sentance. I would have gone down that road but theta closed it. Dohh

Honestly I dont think I have the time or desire to be quite that accurate. lol man that info is gona take a while to digest.

The results that I have so far were all run on the same day within a 4 hour period. this should provide a pretty reliable set of comparisons. the only one that was run on another day was the carb improvement but I dont think weather will factor much into a 500 rpm gain.

Dont get me wrong I do value the input. Hope i dont sound like an a hole lol.
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Old 03-01-2009, 10:41 PM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

combat....

You are doing some very meticulous experimentation on the Ryobi engine and being a Ryobi flyer I'm very interested in what you find out about them.

One of the questions I have is what effect the "side decompression slots" in the cylender walls actually have on performance. I was recently given a Ryobi trimmer that has a single ring, old style transfer ports and a long shaft, exactly my preference for the Ryobi motor EXCEPT it's got those little slots in the cylender walls, which CAN'T be good for performance..... but I wonder what the real measured effect is. It may not be as bad on one would think.... or maybe it is! Have you or anyone else ever done a performance comparison to measure the effect?

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Old 03-01-2009, 10:51 PM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

Normally when I do a test I will post my weather results as either I sweated my ba##s off, or I froze my ***** off! LOL Thats about as precise as I can get!
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Old 03-02-2009, 09:32 AM
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Default RE: another darn ryobi post (ryobi performance modification, analysis and comparison)

Combat, unless you count the occasional intentional dive-bombing of a buddy, we don't do combat here. I used to watch it at Buder park, fun to watch. I've even watched the C/L guys do it. Man those guys are nuts.

Did you get your magnet yet? I didn't make it to the Shack yesterday.
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Old 03-02-2009, 09:36 AM
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CKangaroo, where's London Mills? Darn Illinois weather, you're right though. It's either so hot you get the glunk, or so cold it's hard to move your fingers.
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