John_M_

Yes it cools the exhaust gases, and as a result, has an effect on the velocity of the exhaust gases... super heated exhaust gases move faster down the header and exhaust pipe which provides an increased in vacuum scavenging created in the exhaust that acts on the overlap... when you set the carb, you are setting it for the conditions at the time the adjustment were made... when you introduce the smoke oil, it cools the exhaust gases, lessen its velocity and changes the vacuum scavenging in the exhaust system, which changes the tune of the engine while the smoke is on.



John M,

acerc

I guess you never read where I am gas/diesel and small engine certified. And, spent a good deal of my younger years dealing with engines in most every aspect including fabricating most parts as well as exhaust. I even built a dyno for my R/C Nitro racing engine's years back.

Jim Branaum

My Feedback: (3)

I think you might try an extra 2 wraps.

All the discussion you and John_M_ have going on about where to inject and what the implications are is good but if the oil is cold all bets are off. *I* think the trick is to have the mixture occur just far enough downstream of the exhaust port to avoid it being sucked back in but that does require more heating of the product prior to injection. What about injecting it at the end of the header pipe or in between the jug and the joint? If you preheat the oil enough, it shouldn't take away too much RPM.

John_M_

No I knew you had a background as a mechanic / technician, you had mentioned it a while back... I wasn't arguing with you, I was agreeing with you... but as you know with the way the smoke is generated, you have to sacrifice something in order to generate the smoke; a little performance drop.

What would be a another idea to generate the smoke without it upsetting the tune, would be to isolate the two and use the exhaust to super heat a metal chamber with its own pipe coming out of it, and then have the smoke oil pumped into the chamber, if you could get the chamber hot enough it would vaporize and burn the oil, which would expand and come out of the pipe from the metal chamber; like spaying WD40 on a hot plate... or maybe an electric heating element, like the old HO locomotives had .



John M,

FlyerInOKC

My Feedback: (6)

John, are you talking about something like running a tube through the length of the muffler and then exiting at the exhaust pipe outlet?

John_M_

Well not exactly, but something like a heat exchanger, like an air heater box on the old volkswagen bugs.... put a box around the hottest part of the exhaust header, that box having a pipe coming out of it for the smoke to exit, then spray the smoke oil into the box, as the smoke oil contacts the hot exhaust header it vaporizes and burns, and then expands and comes out the pipe... the smoke oil never interacts with the exhaust gases, so it shouldn't upset the tune, but like Ace mentioned, as the smoke oil burns it will cool whatever it contacts, so sustaining a good smoke stream this way may be difficult if the exhaust header pipe cools too much... what would help is if you could atomize the smoke oil down to a fine mist, which would help it burn more readily.


John M,

Jim Branaum

My Feedback: (3)

That is where most of us make our biggest mistakes and many of the aftermarket smoke mufflers help that happen. Too many just dump the oil into the muffler chamber. Part of the atomization problem is that as the smoke oil burns (in a chamber or in the exhaust) it causes the fine holes used to create the mist to clog up with debris (mostly carbon) and slowly but surely disable the smoke ability. If the oil is preheated significantly, and under enough pressure rather than dribbled in, that problem is somewhat mollified. Then the problem becomes on of managing the volume of oil during smoke operations because too much oil at too low an engine RPM does not work well and the pressure tends to lend itself to higher volumes.

But you guys are the experts.

acerc

Jim, you understand how it is. What I am trying to do here is a number of things, one is to alleviate the effect the smoke oil had on the engine whether it was just the sound or actual rpm drop. Two, in the quest for one, I still want real good smoke at minimal fluid use. I believe I can achieve this with the number of wraps around the header preheating the oil. My understanding is, as Jim has pointed to, and that is to not heat the oil to the point of vapor while in the preheat tube. The exhaust has to carry the vapor in order for it to vacate the pipes. I don't see the injection point being further away as a problem as long as I can preheat the oil enough without being to much. I don't really know exactly how it will work out but I do know learning through trial and error is part of the fun.

FlyerInOKC

My Feedback: (6)

You got that right Robert trial and error is part of the fun of being a builder! I guess were all a bit touched!

acerc

All of the nagging, LOL, got me to reconsider the injector site. So! I moved them back closer. Ok, now I'm done, and we'll see how it works out.

John_M_

It would tend to clog the small orifices with the injector nozzle stuck in the exhaust stream... but if you could atomize outside of the exhaust stream, and have the oil mist spray onto a hot enough surface you could develop some good smoke without clogging the orifices... something like a electronic fuel injector, but on a smaller scale; maybe a piezoelectric atomizer spraying into a chamber off the header pipe as I mentioned earlier... would be something to experiment with on the bench to see just how well it would work.

My understanding how this smoke system works, is you want to spray the smoke oil into the hottest part of the exhaust stream to burn or vaporize the oil which gives you your smoke, the further down the exhaust stream you inject, the cooler the exhaust gases are which won't vaporize the smoke oil efficiently... by placing it up where you have it now in the header, you have sufficient heat to vaporize the oil, and a longer time to vaporize as it travels down the exhaust system.

Ace being a diesel tech, you're probably familiar with an afterburner, now something like that and introduce the smoke oil into it, would work a treat... good ideas on paper, just got to get them to work on the bench.

Now that looks like you got it in a good hot spot, much better in my opinion... very nice work Ace!











John M,

acerc

I think we keep chasing the same circle over and over. My attempts with the preheater is to get the oil near to the point of a vapor without actually becoming a vapor. I really don't think the temp difference on the pipe from the head to tail will make an extreme difference if I can get the number of wraps right. I moved the injection point because of being a four stroke I could see where the oil could go into the head. Granted I may have moved it to far being at the end of the exhaust pipe, who knows for sure, but where it is at now is better.
Now, building an actual smoke system with heater and blower would be quite simple and I have all the needed materials. But! Why, when there is one readily available on board.
The short of the story is I am trying to get the most for the least without causing any possible harm.

And, Yea! It would be cool to throw flames out the pipes, been there done that.
At least until the plane burnt to ashes.

uncletwist

Hey Ace, looking at that pic., is that copper tubing (right next to the head) that you have wrapped around the exhaust pipe to preheat the oil before it`s injected into header...???, just trying to figure out the system,

acerc

Yes it is.

uncletwist

I`ll have to say, that`s pretty ingenious..

acerc

Thank you!

John_M_

Right!... but one thing to remember is the first couple inches of the exhaust header has raw flame coming out from the combustion chamber on the exhaust stroke... where you have your new injection point is the hottest point, so you should get a good burn / vaporization of the smoke oil... it should work well there... and you won't do any harm to the engine injecting at that location.

I think you misunderstood what I meant by an afterburner, or maybe I used the wrong terminology... not an afterburner like in a jet fighter... what I was referring to was an afterburner canister (I think that's what they're called on a diesel ), which is much like a catalytic converter, but what it does is to collect all the unburned gasses expelled from the cylinder and burns it off before it comes out the tail pipe, hence the term afterburner, its the hottest part of the exhaust system, as with a catalytic converter on an automobile... what I was driving at, was a means to generate a continuous source of heat, so you could have unlimited smoke, without things cooling off too much and the quantity of smoke dropping off... just pondering different ways to generate the smoke without interfering with the running of the engine, R&D work in other words .



John M,

Jim Branaum

My Feedback: (3)

Duh! Do you happen to know or can you find out the vaporization temp of the oil in use? Do you have a temperature device? You know, one from Radio Shack that reads temperatures from surfaces. Get the engine running at WOT and shoot the temperatures every inch down the header pipe and take notes. Consider where the temperature is lower than the vaporization temp of the oil as a probable good injection point. One of the guys I fly with plays with the smoke oil mix rather than move and adjust the system itself.

Good luck.

uncletwist

It`s called old school, Jim, if I was Ace, I would be doing it the same way as him , just for the FUN of it. Radio shack was`nt around when the Wright Bros. created there first plane, smoke or not. I`m sure the pipe temps. would be diff. on the exhaust pipe running the plane on the ground, as apposed to flying, probably not by much, but he would have to the test without the cowl, not an in flight scenario. Your idea is sound, all I`m saying is, I don`t think it might be as accurate as you might be implying, as apposed to the method that Ace is going. JMHO

John_M_

Like ethylene glycol (anit-freeze), which produces a very nice billowing white smoke ( you can always tell a car with a blown head gasket by the smoke), but not very eco friendly... I'm just waiting to see if the EPA starts regulating this stuff... home brewed smoke oil, like using anit-freeze is not healthy to breath, nor safe for wild life leaving it lying around in its liquid state... if it happens, California will be the first to regulate smoke oil use in RC aircraft I'm sure.


John M,

Jim Branaum

My Feedback: (3)

Now THAT is NOT funny John! Not any part of it met the test of being even slightly socially redeeming. While my acquaintance is of the lower integrity group and causes me much trouble and grief, he is at least smart enough (so far) to not use anti-freeze.

However, if I recall correctly I over heard him tell someone he was using 2 quarts of AFT and a quart of diesel and 1 cup of gasoline. Not a mix I think is wise, but there you are.

@UncleTwist: While you are correct about some temperature difference the measurement is being taken outside the header pipe so that makes up for the airflow at speed because we are trying to guesstimate the internal temperature. Not trying to be accurate, because that is the wrong instrument for accuracy just trying to get close. Not being able to weld, I look for better answers to take to the welder who wants my hard fought for dollars for every second of torch time. I don't know if my answer is better but my tricky tool has helped me resolve a few temperature problems with engines over the last few years.

YMMV

acerc

After the mentioning of optimum oil temps I emailed Super Dri and we are currently conversing. Will let you know.

John_M_

I wasn't being funny, nor was I accusing your acquaintance of using it... I was merely reflecting on your statement "One of the guys I fly with plays with the smoke oil mix rather than move and adjust the system itself"... my statement "Like ethylene glycol (anit-freeze)" was just generalized, a comment spoken or written in response to your comment... not everyone is aware of the bio hazards of using and handling anti-freeze... when I made the reply and previewed it, I didn't feel it was humorous, or out of line... ethylene glycol has been used by others, which is not a wise thing to do, nor is the use of ATF, diesel, and gasoline mix... here in California the EPA jumps on stuff like this, and I'm surprised that it hasn't been regulated here yet.



John M,

acerc

Now that we are through tooting our horns, there is one thing to note on the Ethylene, anti freeze no longer contains it. And without doing the research I am pretty sure Ethylene Glycol can not be purchase by the average Joe. As for other types of mixing, I have enough common sense to know thing's can get very explosive and/or very toxic real easy if one does not know what combinations do what.
I will buy Super Dri, it really is not that expensive and is perfectly safe for our aircraft and for the most part the people around us.

John_M_

You mean blowing smoke, ... now I was being funny!



The new formula for the all aluminum cooling systems don't ... but you can still walk into any auto parts store here and buy aniti-freeze that contains ethylene glycol, concentrated or diluted 50/50 premixed for the bi-metal cooling systems... it has a distinct smell when its burned, kinda like maple syrup, and it has a sweet taste to it which animals are drawn too, but it is very destructive to their liver and kidneys, and a very agonizing death... I always wash it away when I see it in the parking lots after someone had a hose burst, or coolant leak... less than 1/2 a gallon will kill any size tree in a matter of just a few weeks, it nasty stuff in the wrong hands... you and I are from a different upbringing, with respect and consideration toward others, but as the generations go by, no one seems not to give a damn anymore.


Chevron makes an aviation smoke oil, its like 85 bucks for a 5 gallon bucket, or something like that... super refined mineral oil, but from the sounds of it the super dri leaves no residue, which is a plus.... if the std smoke oil leaves a residue anything like what you get from running on glow fuel, I rather watch someone fly with smoke, than have to clean up my own aircraft... matter of fact I haven't seen anyone run smoke at our field outside of the events.



John M,