willits18

My Feedback: (25)

I have been reading about the new smaller gas engines from OS. They use a 50:1 mix. How different are the internals from glows? Would the 50:1 mix be sufficient to oil the bearings/bushings and rings? I know that these take a different glow plug, require a pump, the yellow gas fuel line, and a different stopper in the tank. Has anyone tried to do this?

aspeed

There is some good reading here http://www.rcuniverse.com/forum/glow...ow-engine.html The Norvel uses an extra hot Turbo style glow plug, and a different carb with lots of castor oil as you can read about. I think a bit less oil could be used with a roller bearing on the rod, but 50 to one, I doubt.

Sport_Pilot

But the Norvel is ported for gasoline, the converted OS will not be, so the OP may be disappointed with the power. But then again for the cost of a glow plug, try it. You could also test a methanol gas blend to regain some power. But you would still need to use a lot of oil, maybe not 20%, not sure how much. I have no idea what OS has done. I suspect that they used ball bearings in the connecting rod. They exaggerate all of their engines power, so it is likely the 50 to 1 mix would cause the engine to crap out right after the warranty is up.

1QwkSport2.5r

Warranty? Bahaha.

aspeed

I would have to read through the posts again, but don't think the porting is any different in the Norvel. They likely just paid extra attention to the compression ration, head space, and I believe the carb was a bit larger for more power, and the needle tapers customized. The original glow motor that it was derived from was stronger than many others as well, so the slight drop in power would still be average compared to other sport engines. I think the OS had a totally different carb unlike the normal glow stuff with a diaphram or whatever. Being a larger motor, I think the OS had a bearing on the rod which could use somewhat less oil as you have mentioned. I have not seen either one in person, so it is only IMHO which is free. I might think about getting a Norvel at some point though, just for interests sake, or make one up to try out of an old motor that I care little about.

controlliner

http://www.osengines.com/engines-air...510/index.html
The Con Rod is forged steel with a needle bearing lower end. Hence the ability to run on 50:1

Sport_Pilot

Past the warranty anyway. I would never run the oil content that low on such a small engine.

daveopam

My Feedback: (9)

I don't think the bushing at the con rod can take the heat of gas. That's why you see roller bearings in most. And 50:1 is not near enough oil IMHO. There is just not a lot of bearing surface area in that size of engine.

david

earlwb

Well to convert a glow engine to gasoline using the simply method is you use either the OS G5 or OS P3 glow plugs and lower the compression ratio. Now then if you are using it for control line or free flight, you are good to go. For gasoline the RC carburetor is calibrated for glow fuel which is run at a much more rich air to fuel ratio than gasoline. So then you need to either make a adapter for a Walbro carb to use on the engine or acquire a Evolution 10cc gas engine carb or a OS 10cc gas engine carb. But you may still need a adapter of spacer for it. Then you may need to lower the compression ratio some as glow engines work at a higher compression ratio than the gasoline engines use. Now you only need to use higher oil levels with gasoline when mixing the fuel to use. Since the engines have a bushed rod, they need more oil to keep the rod working OK. But other than that you would be good to go.

Now then the better small gas engines have needle bearings on the connecting rod. They use a steel rod with a needle bearing inserted in on the big end. The crankshaft crankpin is hardened as well. The crankpin and rod serve as the inner and outer races for the needle bearings. This does let them use less oil in the fuel than you would normally have to use with a bushing connecting rod.

The carburetors or throttle can be a big problem with a gas engine conversion. Trying to use a glow fuel carb results in the air fuel mixture being way too rich. You may be able to lean out the low speed and lean out the high speed, but the mid range winds up being the problem. If you had a carb with a third mid range adjustment, then you may be able to dial it in. Fox was the only one I know of that made a three needle carb and that was way back in the 1960's. Some people with some skills may be able to reshape the needle tapers and spray bar in a carb or make new needles for it too. Normally we wind up using a Walbro carb instead, but this requires an adapter of course.

Sport_Pilot

I understood that the glow carbs are good for gas if the needles are fine and you file the needle to a sharper taper. Or maybe blunter taper, but sharper make sense off hand. Fox recently made a .50 sized gas ignition engine with their stock design. It was their latest finer threaded Teflon sealed carb. But they may have modified the needles or added a midrange airbleed for all I know. The pump is not necessary for small engines. For large engines the tank is further from the carb and the engine leans out too much on climb out.

tony0707

They can run on gas with the correct mods ,gas carb etc
The loose of power ,makes the change questionable due to its cost
The low end on the glow engines ,will not hold up very well long term

Sport_Pilot

The original gas engines made in the 30's and 40's were cruder than the bottom end of our glow engines. They will hold up fine if you have enough oil, I believe that to be 10% or 1:9 ratio or higher. Cost is cheap, Put in a gas glow plug and experiment with adding methanol. Don't bother with the carb if you don't want to. Adding methanol improves the power and mitigates the carb issue.

earlwb

I forgot, but some guys had good luck simply using more oil in the mixture. The extra oil thickens up the gasoline/oil mix. Thus it makes the fuel act more like a methanol/oil mix then. So simply going with more oil will likely alleviate the problems with the carbs being setup for methanol. So using, say 16% oil, would make the fuel more thick and behave more like glow fuel then.

aspeed

I am surprised no one has mentioned diesels. They work pretty good once you figure out the compression lever, and are very economical. They just sip the fuel too, and have a smaller diameter carb, will swing a huge prop......

rgburrill

I didn't see anyone bring up the issue with the plastic/rubber seals, etc. Gas and fuel don't usually mix there. Different fuel tanks and fule lines indicaatie to me that you neet to change any seal in the carburator, needle valve, throttle assembly, etc. Better yet, buy a gas engine.

1QwkSport2.5r

Those gas glow plugs have different thread pitch than standard plugs - especially the P5 turbo plugs. If one wanted to use one, a new head would need to be made or drill/re-thread the stock head.

Converting to gas to save money is pretty moot if you ask me. The 30% loss of power and still having the need for higher oil content fuel doesn't make it any more appealing. Not to mention the stink of gasoline.

If the liners are nickel plated, I'd definitely not want to run a hotter burning fuel with less oil!

[email protected]

My Feedback: (1)

why not get a bigger plane with a 20cc gas engine and have some fun

Sport_Pilot

Good point, having the same oil content would seem to make it cost the same. Methanol is about the same price as gasoline, but methanol fuel uses a lot more oil. Even without rod end ball bearings you can cut down the amount of oil because gasoline is more viscous than methanol. Also mineral oil is cheaper. But like you I would not want to give up on the power in most models. Maybe a floater.

Sport_Pilot

Maybe because of the space the bigger plane takes up and the higher cost.

1QwkSport2.5r

Yup. Hardly cost effective to completely replace the model and the engine just to run gasoline fuel. I couldn't in good conscience switch my engines to run gasoline to (literally) save a few dollars. 20cc and above I can see running gasoline engines, but below that, I don't see there being that much of a coat savings when you factor in the engine cost, retrofitting the fuel system, and adding the ignition system and battery to drive it. Especially for a modeler that already has glow engines that aren't worth nearly as much used in the secondary market. One would have to sell 6-8 engines at least to recoup enough funding to buy one new purpose built engine. I don't see the benefits of burning gasoline fuel as a method of saving money, especially in a converted glow engine. Perhaps that's my naivety talking.

Sport_Pilot

I recall one fellow modeler at my club claim that the gas models were cheaper because of the fuel costs. He did fly a lot but doubt it would have been more than the equivalent of a gallon of glow fuel a week. Back then glow fuel was 12 bucks and gas was about 2 bucks so maybe he saved 11 bucks on fuel a week. He almost never crashed, but maybe a hard landing now and then. Then a month or two later he crashed a gas model worth almost a thousand dollars. Then a week later he crashed an even larger model worth about 2K! I mean he totaled both, not repairable at all, and the engines and some of the radio gear was gone as well. I don't think the fuel cost offset his replacement costs.

earlwb

The OS G5 glow plug uses the standard 1/4x32 thread size of the glow plugs. The PS P3 plug is a Turbo plug and it is different of course.
Now then the OS G5 plug has a tip that is a little longer than the OS F glow plug. They look the same but the G5 has a longer tip to it. So you need to ensure it doesn't hit the piston on some engines.

earlwb

Diesels are great. But Unfortunately the model diesel fuel is much more expensive though. The ether used in the model diesel fuel is tightly regulated and that makes it more expensive. Thus it isn't all that practical in real use. Small diesel engines though tend to work better as they use very little fuel per se. Thus a expensive quart of model diesel fuel can last a while then. But a big model diesel engine can use up a quart quite fast though.

1QwkSport2.5r

I'll make note of the G5 plug thread size/pitch. I thought I'd read somewhere that all of the "gas" glow plugs had different thread sizes/pitches. Maybe it was the Enya gas plug I was thinking of being different than 1/4-32. Thanks for pointing that out, Earl.

aspeed

The Turbo plugs have a taper seal instead of the loose copper washer with the big gaps in the threads over 3/16". That is a big performance gain with glow, especially on smaller motors under .25 cu. in. I think the thread is 8mm x .75 pitch. I would have to check, but am pretty sure that is it. A new head needs to be made for sure. The Nelson head can work on a normal head, but would only have a couple threads engaged, I think. There is no extra hot plug made for the Nelsons that I know of.