Patxipt

With the breather vent plugged, all excess oil will be expelled by the exhaust.

Think of it this way: the engine is started with no oil inside. As it runs, the oil in the fuel passes from the combustion chamber to the crankcase thru the large ring gap. This is how these engines get lubed up. At a certain point, no more oil can pass into the crankcase, which is filled with oil, enough to reach equilibrium. So all the oil in the fuel will be expelled thru the exhaust from now on. If part of the oil gets past the pushrod tubes into the rocker cover or lost in some other way, the equilibrium will no longer be valid and a small percentage of oil in the fuel will pass thru the ring again to compensate. And back to the point where it completely exits the exhaust.

I hope I didn't sound too complicated

EDIT:

I think I got lost from your main question Planepounder.
Going back to my upper explanation, only a small amount of oil would need to be carried to compensate loses, besides the small amount needed for normal running lubrication.

Patxipt

Just to prove my point a bit regarding wet sump model engines

http://www.modelenginenews.org/proje...pet/index.html

and

http://www.modelenginenews.org/cardfile/feeney.html

This last one has a breather vent on top of the head, next to the rockers.

All I said above take sinto account the engine will be running upright.

planepounder

Hey, I may have not made it clear what I was concerned about. The typical glow 4 stroke moves oil around the engine until it exits the exhaust or breather. That is because there is oil in the fuel. Take the oil out and run the engine on an oil-less fuel, then oil must be maintained in the crankcase. The glow 4 stroke is made to expell the oil. I feel sure it would soon disappear with out a large supply. Even if hamaoki suceeds with what is a dry sump venture, I think, there would have to be by design high oil consumption.

Arceenut

Planepounder - The reason for the two tanks in my setup was to measure the amount of oil passing thru the engine and also to measure the amount of oil being expelled\burned thru the rings. In the brief amount of running (45 min.) approximately 1 ounce of oil was drawn from the reservoir. About 2/3 ounce was returned to the second tank. Conclusion - 1/3 ounce per 12 ounces of gasoline was being lost thru the rings, possibly even less as there seemed to be a considerable amount of oil around the front of the engine due to leakage from the front bearing. This is the first time I have heard of any passage between the crankcase and cylinder. Anyone else hear or know of this???

Patxipit - Please explain to me the equilibrium of oil in the crankcase?? The crankcase is vented to the atmosphere, Combustion pressure forces the oil into the crankcase? (high pressure). Re "sump oiled engine" would be entirely feasible if the engine were to be run upright at all times. Inverted however would cause the oil to settle around and under the piston and I can imagine the problems that would cause. The system in our model engines provides just enough lubrication without a large amount of loose oil sloshing about in the crankcase. I believe the system I am experimenting with achieves that goal. The proof that this "just enough oil" system works is in the many hours of operation all 4stroke engines produced up till now by all the 4 stroke engine manufacturers, Saito, OS, Magnum et al. All reputamle manufacureres i am sure. Oil under the rocker covers? I thought the problem was "not enough oil" on th valve train???

Arceenut

Just did some quick math in my head. 1/3 ounce oil in `12 ounces of fuel = 1 in 36 -- just under 3%, right??

planepounder

Hamaoki, your oil consumption is good. Quick math says it is about the same a a 40:1 ratio ( around 3oz/gal). That would certainly keep a plane clean! Yeah seem like Saitos like to spit it out the front too. Your idea seems feasible, sorry I gave you a hard time.

Arceenut

As I said before apology accepted with thanx. I do not get upset at criticism that makes me think and makes me investigate aspects of things that I may overlook.

captinjohn

planepounder: I admire you for saying you are sorry to hamaoki. It takes a big man do do that. Not many people on RCU do that. I sure am glad things worked out. One thing I try do do in going through life, is to find the best in everyone you encounter. Then everything goes better! Best Regards capt,n

planepounder

Thanks Capt,n.

av8tor1977

My Feedback: (6)

Was it "Bambi's mom"? "If you can't say something nice, don't say anything at all...."

Whoops, just "dated" myself.

AV8TOR

jcloran

I give you much credit for doing the sort of R&D that many of the manufactures should have been doing for us a long time ago. I spend the day discussing this very topic at my local Hobby Shop. I'm working on the exact same solution, but for other reasons. First I'm looking to build an ultra quite hell with extreme endurance. The idea is to hover in position for over two hours and be almost inaudible. It's a waste to throw away 30% of your fuel on lubrication when you only need a few ounces that can be easily be recycled. That gives me 30% more fuel right off the bat. A four stroke gives me twice the endurance and can be made to be as quite an electric and with no smoke. Now bear in mind this is not a competition heli, it’s not designed for 3D. It’s designed for a specific purpose. These new four strokes have amazing untapped potential. And I’m sure eventually the same thing is going to happen that happened to motorsport. Eventually there will be an environmental issue. As a matter of fact it’s already brewing in congress. California has already banned 2 stroke motors and model RC engines are next. That will eventually sweep across the county. It may not happen for ten years, but it is coming. I’m not sure why manufactures haven’t addressed this issue in the past? They could have had extremely fuel efficient and yet still powerful engines out a long time ago, engines that don’t spew lubrication out onto the aircraft and into the environment. That technology was mastered in WWI. I think it's amazing that ten years ago a model airplane could cross the Atlantic with less than a gallon of gasoline. Since then nothing has really changed. Great Job! I moved my oil intake up by the cam and also drilled the valve covers. my engine sits vertical, so I have a few advantages.

av8tor1977

My Feedback: (6)

All good fun, and all true.

For years, I have often had idle daydreams of a "lubricated two-stroke" engine. Somewhere, not so long ago, I saw something about one. Apparently it uses a diaphragm for the intake. When the piston goes up, the "vacuum" pulls on a diaphragm in a chamber which is connected to the carb, thus drawing in the fuel/air mix. When the piston goes back down, the resulting crankcase pressure pushes on the diaphragm, pushing the mixture in the diaphragm chamber into the combustion area, all this being accomplished through a system of reed valves I believe. Meanwhile, the "un-contaminated" sealed crankcase area is lubricated by a conventional wet sump oiling system. Kind of a neat idea, but it seems like it would be severly horsepower limited by the intake system.

The two stroke power to weight ratio is hard to beat for airplanes and other weight sensitve vehicles. How about a "closed bearing" oil system? Oil is pumped through a system of passages that consists of the main bearings and the rod bearing, through passages designed just for this purpose. The system is re-circulative and sealed so that the crankcase is basically uncontaminated. I say "basically uncontaminated" because one would have to provide a squirt hole somewhere to oil the wrist pin bearing and the piston/cylinder. This oil would also have to be scavenged out by a scavenge pump dumping into a oil reservoir. (Some of it would get "whisked away" by the incoming/outgoing fuel/air charge and burnt anyway, but a relatively small amount I believe, since so little would be required to lube those areas.) Complicated, but with advantages....

How's that for "out of the box" thinking?

AV8TOR

Arceenut

Does anyone have the specifications of this engine that I am experimenting with?? This is an OLD Saito 45. The box says FA-45 MkII I believe I bought this engine circa 1973 -1978. I would particularly like to know what the compression ratio is?? I do have the operating instructions that came with the engine but it does not give any information other than the bore (22.4mm) and stroke (19.0mm). If no one can help me I guess I will have to buy a graduated syringe and measure it. I was hoping to avoid this excersize.

planepounder

Hello hamaoki, I have been doing some "clean sheet" thinking about your clean 4 stroke. It is obivious the the engine is dry sump since there is no sump. So if you wet sump it the oil is in the crank/rod area-not good. So the only way is a dry sump system. I believe this is feasible (your are proving it so) but I see it as only working on certain models with enough fues. area to handle the system. I dont think we can get into a Twist or a Dazzler. Seems to me the other approach is to clean up the fuel. I have been running an ST-3000 on gas/ignition @ 25/1. It runs very clean. I think it might go 30:1. I am still running the bushed rod. There was a guy in the gas glow thread I believe from Europe running an ASP .52 on gas/ignition with the stock rod. If you dont mind sacrificing the engine, why not try either gas/glow or a gas/oil mix starting say@ 20:1 and learning from there. Just some thoughts.

planepounder

Hey AVATOR, I amost forgot, remember the Oribital engines from Australia a number of years back? They had a oil in sump 2 stroke, that made great power. It had high pressure direct injection. Chrysler bought the rights and developed a small, maybe 2.5-3.0 liter V-6 that made over 400hp and weighed almost nothing. Fuel consumption was also good (for a 2 stroke) because of the injection. For some reason Chrysler killed it.

Patxipt

Planepounder, our engines are a mix of wet and dry sump. I say this because if you open up the backplate on a 4-stroke after a run, it will have oil inside, normally up to the externall shell of the main bearing. Of course, the oil is always getting renewed by being flushed out at the breather and ingested thru the piston ring blow-by.

____________________________

To explain my thought on the post above.
Consider the crankcase sealed, with nowhere for oil to go, except up to the rocker cover and an occasional lose thru the front bearing, and optimum oil level is half full; also, lets focus on the compression and explosion strokes.

During the compression stroke, some oil will pass the ring into the crankcase, as it is compressed inside the crankcase during the explosion stroke, part will go up to the rocker area and the oil level inside the crankcase will remain the same - the small amount of oil that got into the crankcase thru piston ring blow-by as gone into the rocker area, lubricating the moving parts on its way.
Now, what if the rocker area can no longer get more oil? The small amount of oil going thru the ring on the compression stroke will be forced back to the combustion chamber during the explosion stroke since it has no more space to go to. Equilibrium is met!
On our model engines, we never reach an equilibrium due to the breather nipple being situated somewhere on the lower 1/3 of the crankcase or on the camshaft enclosure, letting the oil exit the engine; thus, more oil can pass thru the piston ring gap into the crankcase, being effectively a full lose wet sump. I consider hamaoki's lubrication system indeed a dry sump.

planepounder

Hey Patxipt, that was a great explaination and I agree with one exception, as has been pointed out quite a bit of oil comes from the breather on the engines. The oil only enters via the combustion chamber, therefore it must bypass the ring to make it into the rest of the engine. I know the oil will travel around the engine, but would it not soon leave via the ring bypass and non-vented crankcase pressure?

planepounder

Hey guys, not trying to monopolize the thread but thoughts keep coming to me. If indeed we wet sump the motor, perhaps a breather in the valve cover, the classic and least oily place. If we put a check valve in the breather so that it opens on the down stroke and closes on the up stroke (backwards from normal engine practice I believe) perhaps the oil will stay in place. You all remember my Ryobi 4 stroke on gas/glow? it only holds 3oz of oil and does not burn any to speak of. It has an open breather from low on the front with a tube extending to valve cover height. I never even see the faintist trace of oil.

Patxipt

Right! That's why the ring as a larger than needed gap!

If the crankcase breather isn't vented, how come oil will leave the engine thru it?[sm=confused.gif] That was one of the conditions necessary for my explanation, where only the normal ring gap (we won't start making rings with smaller gaps, at least for now ) was the only exit for the oil to come out of the engine.

Moving the breather from under the engine up to the rocker cover area - in a horizontal plane, not really on top of the cover as this would cause the rocker cover to get full of oil and that would cause drag on the moving parts - would help a lot, as in this place there is very little oil mist to be carried away by the engine breathing (which is positive breathing when running, for all purposes, from inside to outside) and no check valve would be needed.

(looks at the freshly customized ASP FS52 next to the desk and sighs - I need a used engine for these tests!)[sm=cry_smile.gif]

EDITED for small writing errors

Arceenut

Please fellows. I am not trying to "reinvent" the engine. The 4 stroke engines work fine now with the oil mixed with the fuel. Lubrication of the valve train seems adequate under the present system as proved by the longevity of most of our engines now. I am just trying to develop a system to lube the engine as it is now without having to pass copious amounts of oil out the exhaust and crankcase vent. Yes, there are disadvantages to the system - extra tank and plumbing, need to check oil levels when in use, etc. I agree others have devised schemes to run engines with different oiling systems, some successful, others not but I am trying to address one aspect of this hobby that annoys ME. I like to think I am making progress in that direction.

Arceenut

Further testing. Ran the engine today. Fuel - hardware store methyl hydrate - no oil or extra additives. (Not sure if there are any additives or the water content)

Ran the engine on 15% nitro 20% oil to establish a baseline.

Ran the engine again on hardware store methyl hydrate.

Ambient temperature 6deg C, 15/20 fuel, 11/7 APC prop

New OS F glo plug

15/20 fuel - no glo after starting
WOT rpm - 90500 rpm - absolute peak. richened to 9000 for duration of 6oz tank
lowest consistent idle - 1770 rpm
Head temp measured between rockers with an IR meter at WOT 5mins int run - 105deg C
At after 2min at idle, measured at the same place 73 deg C.
Second tankful
6 oz tank -14 min 20 sec at WOT

Methyl hydrate - glo power on continuously
WOT rpm 8950 -0 absolute peak, richened to 8900 for testing
Lowest consistent idle 1975
Head temp measured as before - 111 deg C
After 2mins at idle 73 deg.
Second tankful 19 min at WOT

Oil drawn int engine thru engin after 6 min - approx 2/3 oz
Oik returned to second reservoir approx 1/2 oz
Oil lost thru rings and front bearing 1/6 oz.

Methyl hydrate - no glow after starting
Engine ran as expected running on no nitro fuel, rpm dropped significantly (to about 8000 rpm and stopped after ~ 15 sec
Could not idle down long enough to set LS needle.

Conclusions
Need to either increase the compression or use nitro in the fuel.
Would run longer on a tankful by not displacing the alcohol in the fuel by the oil. ( needles had to be leaned significantly when switched to alcohol only.)
Need to run glo permanently to use no nitro fuel.

So far, I have not been able to locate a source of nitro. All LHS do not stock it. Have not had a chance to located a speed shop/go-cart shop yet that may be a source.
May increase compression on this engine by machining a bit off the bottom of the cylinder, but I hesitate to do that to one of my newer engines to use in a plane.

DT56

My Feedback: (18)

Planepounder, are you still running the ST3000 on gas/oil @ 25/1? How are the bushings in the connecting rod holding up?

oldtimer2

My Feedback: (19)

Hi, Source for Nitro Methane! Klotz carries many types of fuel and lubs. Nitro is about $18.00 per gallon if you can find a dealer close enough for local pick-up. HASMAT cost is very high. If you have a drag strip near you, you might be able to buy small amouts from of the racers.