RE: Considering a large Glow engine ??? For big engines, GAS is better in every way :)  
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RE: Considering a large Glow engine ??? For big engi... - 10/3/2006 8:23:27 AM   
DarZeelon



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From: Rosh-Ha'Ayin, ISRAEL
Status: online
quote:

ORIGINAL: RVM

So lubrication, or lack thereof, is the sole reason for 4-stroke gassers being undesirable for anything other than scale applications?



Robert,


Even "scale" models are not always flown scale-like.
I keep thinking of that four-turbine Boeing 747 being flown inverted, some 5 feet off the runway...

A four-stroke gas engine, that does not have an 'all-attitude' lubrication system, cannot be suitable for any type of aerobatics, as it could sustain damage due to lack of lubrication.


Why are you asking? Did you see an offer for a four-stroke gas engine yet?!


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RE: Considering a large Glow engine ??? For big eng... - 10/3/2006 9:00:25 AM   
ZAGNUT



Posts: 2436
Joined: 2/26/2003
From: tel-aviv, ISRAEL
Status: offline 		there are a few 4-stroke gas engines on things like weadeaters and brush cutters that work just like the YS, gas mixed with oil is drawn through the crankcase on it's way to the intake valve. same "supercharging" effect but done with reed valves instead of rotary. these are very good power to weight wise but also very expensive as is any new technology. given all the EPA restrictions these were designed to comply with they will no doubt become more widely available and much cheaper.



dave

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RE: Considering a large Glow engine ??? For big engi... - 10/3/2006 9:13:49 AM   
RVM


 

Posts: 1975
Joined: 3/12/2006
From: Sacramento, CA, USA
Status: offline 		RCS has a 4-stroke gasser.

The main reason I'm asking is because I don't know the answers to my questions. With full-size gas engines, and diesel engines, and even our small glow engines, 4-strokes have some very definite advantages over 2-strokes. Yet, with the gas engines designed for model use, 2-strokes reign. I simply want to know why.


quote:

ORIGINAL: DarZeelon

Robert,


Even "scale" models are not always flown scale-like.
I keep thinking of that four-turbine Boeing 747 being flown inverted, some 5 feet off the runway...

A four-stroke gas engine, that does not have an 'all-attitude' lubrication system, cannot be suitable for any type of aerobatics, as it could sustain damage due to lack of lubrication.


Why are you asking? Did you see an offer for a four-stroke gas engine yet?!




< Message edited by RVM -- 10/3/2006 9:14:47 AM >

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RE: Considering a large Glow engine ??? For big engi... - 10/3/2006 9:18:02 AM   
RVM


 

Posts: 1975
Joined: 3/12/2006
From: Sacramento, CA, USA
Status: offline 		Here is another RCS 4-stroke gasser. It's a honker!

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RE: Considering a large Glow engine ??? For big engi... - 10/3/2006 3:49:32 PM   
Sport_Pilot



Posts: 7728
Joined: 1/21/2002
From: Acworth, GA, USA
Status: offline 		IMO I would think four stroke gassers would work. You simply put in a concentric sump behind the crankcase with an oil scoop on the con rod to pick up the oil and force it into the bearings. This is just one of the methods used by the new four stroke weed wackers.

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RE: Considering a large Glow engine ??? For big eng... - 10/3/2006 3:57:27 PM   
Dr1Driver



Posts: 3589
Joined: 7/25/2002
From: Spartanburg, SC, USA
Status: offline 		IMO I would think four stroke gassers would work.

Weight and size are the two drawbacks, I'd think.

Dr.1

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RE: Considering a large Glow engine ??? For big eng... - 10/3/2006 4:07:02 PM   
DarZeelon



Posts: 7108
Joined: 4/9/2003
From: Rosh-Ha'Ayin, ISRAEL
Status: online 		The main reason for changing from two-stroke, to four-stroke gas engines is pollution that results from burning the oil with the fuel.

If a four-stroke engine uses a mixed fuel, it will still burn oil as a matter of course, so what do we achieve?

...A glow compatible engine, maybe?


The 'raison d'etre' for glow four-stroke engines, in 3-D applications, is their better response.

With spark-ignition gas engines, a four-stroke has no real transition advantage, over a properly adjusted two-stroke engine, or does it?

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RE: Considering a large Glow engine ??? For big eng... - 10/3/2006 6:16:47 PM   
Sport_Pilot



Posts: 7728
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From: Acworth, GA, USA
Status: offline
quote:

If a four-stroke engine uses a mixed fuel, it will still burn oil as a matter of course, so what do we achieve?

...A glow compatible engine, maybe?


Small four strokes do not use mixed fuel. They make four stroke weed wackers here now. Their advantages would be the same as with the glow four strokes. That is they sound neat!

quote:

With spark-ignition gas engines, a four-stroke has no real transition advantage, over a properly adjusted two-stroke engine, or does it?


I would think the gasser four strokes would have the same advantage. Since they run at lower speeds the carb would be small, ergo better throttle control.

< Message edited by Sport_Pilot -- 10/3/2006 6:19:11 PM >

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RE: Considering a large Glow engine ??? For big eng... - 10/3/2006 6:36:52 PM   
JettPilot



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Joined: 4/18/2005
From: Paradise, USA
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quote:

ORIGINAL: Sport_Pilot

quote:

If a four-stroke engine uses a mixed fuel, it will still burn oil as a matter of course, so what do we achieve?

...A glow compatible engine, maybe?


Small four strokes do not use mixed fuel. They make four stroke weed wackers here now. Their advantages would be the same as with the glow four strokes. That is they sound neat!





Some gas 4 strokes do use mixed fuel and oil The honda does not, but some of the cheaper 4 stroke engines did not put in an oil system and you mix the fuel and oil just like a 2 stroke

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RE: Considering a large Glow engine ??? For big engi... - 10/3/2006 6:40:10 PM   
JettPilot



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From: Paradise, USA
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quote:

ORIGINAL: DarZeelon

Wilson,


At least at first glance, it wouldn't work.

While glow four-stroke engines use fuel that has 20% oil mixed into it and most (non YS) receive their bottom end lubrication through the huge amounts of oil in the blow-by gasses (YS engines flow all their fuel through the crankcase), all small gas four-stroke engines have an independent lubrication system.

It could be with, or without an oil-pump (like a Briggs & Stratton), but it needs the oil 'sump' at a certain location, so oil can be picked up and used for lubrication.

Large engines in full-size aerobatic planes, like the Lycoming AE series of engines, use an elaborate lubrication system, to provide the engine with a constant oil supply at all flight attitudes.

This would be too expensive to utilize in any affordable, four-stroke, gas model engine.


You are wrong on several points. The Honda small 32CC 4 stroke has a very simple oil system that works in any attitude. There are also some cheap 4 storke gas engines out there that did not go to the trouble of putting an oil system in the motor, and they mix the gas and oil just like a 2 stroke

JettPilot

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RE: Considering a large Glow engine ??? For big eng... - 10/3/2006 6:41:22 PM   
DarZeelon



Posts: 7108
Joined: 4/9/2003
From: Rosh-Ha'Ayin, ISRAEL
Status: online
quote:

ORIGINAL: Sport_Pilot

quote:

If a four-stroke engine uses a mixed fuel, it will still burn oil as a matter of course, so what do we achieve?

...A glow compatible engine, maybe?


Small four-strokes do not use mixed fuel. They make four-stroke weed whackers here now. Their advantages would be the same as with the glow four-strokes. That is they sound neat!



Hugh,


Re-read previous posts.

Four-stroke gas engines that do use mixed fuel were mentioned.

Those that don't are not aerobatic capable due to lubrication constraints.


< Message edited by DarZeelon -- 10/3/2006 6:42:49 PM >

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RE: Considering a large Glow engine ??? For big eng... - 10/3/2006 6:50:25 PM   
JettPilot



Posts: 1151
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From: Paradise, USA
Status: offline
quote:

ORIGINAL: DarZeelon


Four-stroke gas engines that do use mixed fuel were mentioned.

Those that don't are not aerobatic capable due to lubrication constraints.



You are WRONG. The honda 32 cc 4 stroke engine does not use mixed fuel, it has oil in its sump, and is aerobatic capable. It is a weedwhacker engine that is designed to run in any attitude. It uses a paddle system to vaporize the oil and spread it throught the engine. You need to do some research before making inaccurate statements.

JettPilot

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RE: Considering a large Glow engine ??? For big eng... - 10/3/2006 6:58:46 PM   
bla bla


 

Posts: 1580
Joined: 9/19/2002
From: Oslo, NORWAY
Status: offline 		Here's a nice 50cc 4 stroke gasser, runs on mixed fuel.

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RE: Considering a large Glow engine ??? For big eng... - 10/3/2006 7:05:02 PM