My main question is: Does engine orientation effect its performance? (example: Can I mount an OS 46FX upside down, or cocked off to the left at 7 or 10 o'clock?)

Next questions is: Is there a place I can go to learn about all the various engine types, what the 40, 46, <whatever> really mean; how engines compare, what all the various specs mean? Basicly, is there a place I can go to learn everything there is to learn about RC aircraft engines?

Thanks for your time in even reading this .

Rob

the answer of your main question is NO
the engine peformances aren't affected by the engine orientation.
the only diference is that the engine may be more difficult to start and to tune in the case the engine is mounted upside down.
with an upside down engine you have to count with the gravity during start wich will quickly fulfill your cilynder with fuel.
in extreme cases you may experiment hydro lock and damage your engine

Yes, the engines forum here on RCU!
The .40 .46 ect, is refering to cubic inches, ie-.46 being just shy of a half cubic inch. Not to confuse, but the numbers are fairly secondary. A good .32 can out power a crappy .46. So..... best to learn all you can, and a decent .40 size is a good engine to start with. The Evolution TPS is a good all around starter engine, reviewed here on RCU.

Jetts

As with any hobby forun, whether it is RC airplanes or not, anyone can have his say. You have to learn to separate the wheat from the chaff, so to speak. In some cases, you will find a good bit of bias expressed in the engine forum. Pro and con OS, is one area. You will also find many, many "old wives tales" expressed here.

Basically, with the advent of the web and instant communication, no bad engine can last very long, so you won't find very many. You will find engines less tolerant of abuse than others and engines that need some special operations, such as the pressureized YS engines. Since I started running engines in 1950, and that's a lot of running, I have yet to find one that did not run.

What we call 40's, 46's... 120's is the cubic inch displacement. a "46" has a displacement of .46 cubic inch or just under a half cu. in. displacement. You will also find a few, inexpensive, plain bearing engines. These are less costly to make and have simplier carbs. They are intended for trainers and other applications where an inexpensive engine is needed. These are normally .40-.42 cu. in. displacements. Even though they have less power that some .32 engines, the .32 costs $130, while the plain bearing .40 is $60. The .40 starts easily, runs well and is perfectly adequate for a trainer.

Your best bet for learning about engines is to first get one of the engine books published by the publisher of our RC model magazines. There are several, just look in the rear part of the magazine where they are usually advertised. After reading and studying a couple of these, you'll understand most of the comments.

Next, check out what guys are flying at your field. See which ones are the most reliable for the experienced fliers.

For advice on the web, I have found you get better engine advice for each specific type of airplane in that forum, the fun fly forum, for example. Check what these guys are running if you want to fly fun fly. The same with other areas.

After you read the forums for a month or so, you'll find out who seems to make reasonable answers and who is biased toward one engine to the exclusion of others.

As for specs, do you believe car advertisements? I remember when they touted 400 horsepower. Horsepower is, in my opinion, a totally worthless spec for the normal RC flier. Hp is torque times rpm over a constant. Torque goes down less than rpm goes up so hp is related very closely to rpm. You'll see hp advertised as 1.8 at 16,000 rpm, for example. You are never going to get 16,000 rpm on a normal plane with a normal prop. And if you were racing, you wouldn't be running that engine. T

he fact of the matter is that for all the major ball bearing .46 size engines, run stock, the power is pretty much the same. I'm talking OS, Thunder Tiger, Magnum, GMS, Tower. I have all of these and they all run good and start in 1 or 2 flips. If I need more power, I go to a Saito 4-stroke.

Thanks for all the great info . (Esp. Ed Moorman-great write up, thank you very much for taking so much time on my newb of a question) .

but after reading what you guys have to say, and looking back at the Reason i asked that main (orientation) question...... another one comes to mind.....

On my OS 40LA engine, there's that remote needle valve(sp?)..... and i was wondering if it matters how care away it is from the carb? (like could i remove it from the engin's backplate, mount it on the inside of my firewall (so that it protrudes enough to adjust) and run a line from it to the carb?

(i'm thinking about my second plane, and looking at the Venture 60 from BTE, or the Sig Somethin' Extra (both i won't even think about getting till i'm more than proficient with my trainer)..... what i wanna do is a cowling mod but move the needle valve of an OS 46fx back out of where the cowling would be so that only the glow head and muffler would prodrude from the cowling......and with the engine's "glow plug end" rotated to about 6 o'clock it would be accessable, and the exaust from the muffler would clear the plane almost completely.)

the second plane won't get built till winter next year.....if then, cause i'll be in the army then (i ship out for basic trainging in January) and i'll need time to settle in and get a shop together............. IN THE MEANTIME , i'll be flying my PT-40 trainer absolutly whenever/wherever possable

I have to say something about salmonbug's comment about engine orientation. I understand what he is saying that an engine will run fine no matter how it is turned and he is absolutely correct.

However, it does make a difference which way the engine is turned because it changes the carburetor location in relation to the fuel tank. Ideally what you want is the centerline of the fuel tank to be slightly below the centerline of the needle. One of the easiest ways to accomplish this is to turn the engine until the relationship is right and then mount the engine in that location. Of course, while you're doing that you also have to ensure the prop shaft is on the thrust line.

See Cafeenman, i had NO idea about that . will have to figure that into the designs i'm thining about

thanks for the info..........all of you..... it's DEF appreciated

Leuphan - I have some info on my site about engines that may be helpful to you:

http://www.airfieldmodels.com/inform...ource/engines/

Moving the remote needle valve further away: The longer the fuel line is from the needle to the carb the longer it will take for a needle change to take effect and the greater chance you have of the mixture changing due to flight orientation, g's etc. These little engines, with a few exceptions, don't have fuel pumps and only use venturi suction to draw fuel. Really, the most reliable location is to have the needle valve on the carb. The remote location is the result of someone sticking his finger in the prop and a lawsuit.

If you want to try a longer remote location, K&B makes an excellent remote needle valve assembly that comes with a mounting plate that you can locate anywhere. I use one on my OS .91FX. I never could get reliable running from the OS one on the back of the engine. You can leave the OS one in place and hook to the K&B one for testing, returning to the OS if your long remote doesn't work well. Search for K&B or Mecoa. They run about $15.95.

Finally, be careful about cowling an engine too tightly until you get a calibrated ear and can tell a lean run. Air cooled engines can overheat quickly. You will need a minimum of twice the outlet area compared to the air inlet area.

Moving the needle valve farther from the carb, and closer to the tank will not make adjustments "take longer" as the flow of fuel is immediately changed. Close the valve a little, and the flow will slow down, not wait to slow down dependent on the length of the fuel line, we are dealing with fluid here.
Just make sure when changing the position of the needle valve, you don't excessively lenghthen the fuel line's total distance.

Jetts

That is interesting about a cowl causing overheating. I was thinking of making a cowl for the 4* I am going to build with an evo .46 NT. Will this be a problem?

Wings,

Having a cowl isn't a problem. Like the man said, you just need to make sure there is adequate cooling air flowing over the engine. The exit needs to be larger than the intake so that air doesn't get stuck inside the cowl which significantly reduces its cooling effect.

Jettstarblue,


I am by far an engine expert. As a matter of fact about all I know how to do is adjust the high speed needle to get the mixture right.

However, I agree with your post. Take hydraulics for example. You have flow control, directional valves, proportional valves, all sorts. Usually the valve stand is located a good distance from the equipment. If you had a delay every time you gave a valve a signal to do something, it would be a mess!


Wings

Roger that, Wings. That's what I was sayin'. Hydaulics. The location of the needle valve makes no differenc, but as I stated, don't make your line from the tank to the engine TOO long....though I have had them with tanks over the C of G, which was 3 times longer than normal, with no problems. Look around at your LHS, you'll find remotes for under 10 bucks, and you CAN use an O.S. or other needle valve assembly, just use your imaginator to mount it- 5.95.
BTW, the standard inlet to outlet ratio is 150% of your inlet area for good cooling, you can, and may need to go bigger if needed, but 150% is the general standard for full sized aviation.

Jetts

Well, maybe in theory the needle valve location doesn't matter, but I've noticed a definite hesitation in response to changes in the needle setting for engines having remote needles. When the needle is on the carb, the response is instant. When it is remote it takes a few seconds. My experience with remote needles is 3 or 4 O.S. engines.

Not talking theory here, but real live experience. My experience with remote needles goes way back before they were standard issue, with several makes of engines, and several makes (and types) of needle valves.
Though perceptions may vary, the fact is fluid dynamics do not change, and we are talking flow here, not like when you adjust your hot/cold ratio in the shower, and it "takes awhile".
Perhaps the reason you percieved it to take awhile when using a remote is this: thread pitch on reg. valve is different from the thread pitch on the remote needle valve.

Jetts

Jetts - Possibly. I don't know what the difference is because it makes no sense to me either. I mean it is just one run and where the needle is in the tube shouldn't really matter. It's not a big deal, just something I've noticed with my planes.

Please excuse my ignorance...

I have seen cowls on planes before, but never really looked at them in great detail.

Here is what I have in my mind as a cowl.

I cowl is a "hollowed" out piece of balsa (or plastic etc. hull) that goes around the engine. There is a hole in the front in which the shaft for the prop protrudes. There is another hole on the side or bottom for the exhust and engine to protrude.

I am not following the inlet and outlet thing.

Do you care to explain? It help me a lot. [8D]

Wings

The outlet is just any opening behind the engine where air can go through.

Blow in a tube. Where you blow in is the inlet and the other end is the outlet. In this case you want the hole in back to be bigger than the hole in front.

Or... if there is more than one hole in front or back then the sum of the holes in the back should be bigger than the sum of the holes in the back (total area).

What you're thinking is fine. A lot of people used to use the black bottoms from the old style 2-liter soda bottle for cowls.

Thanks for the reply.

I am beginner to understand. But it is still foggy.

Ok, so the hole in the back is the space between the engine and firewall? The whole in front is what?


I think I may be making this more difficult then necessary. Perhaps I need to due some research so I have a better understanding.



Wings

Wings - Yes - the outlet is (fore to aft) between the engine and the firewall, but they must lead to the outside of the aircraft. The easiest thing to do is look at a plane at your local field that has a cowl and it will instantly make sense.

Wings:
If you could find the front view of a Tiger Moth, you will see a slot in the front of the cowl for the air inlet. For us just move it over to the front of the cyl.. The outlet is under the cowl at the firewall, about twice the size of the inlet. There is a lip on the bottom of the cowl at the outlet to aid in causing a low pressure area to help draw the air out.

Hey,

I searched for tiger moths. Didn't find a good view of the cowl.

However, this is what I am trying to do. The guy who made this site inpsired me. I want to make a cowl.

Can you explain on this picture what inlet and outlet is?

[link=http://www.renderwurx.com/rc/sig4star/gfx/cowl.jpg]Cowl for 4*40[/link]

I would really appreciated it.


Thanks,


Wings

With regard to the debate between JetStarBlue and CafeenMan on whether there can be a time lag as fluid moves through a tube:

I have literally just finished reading a book about the Stealth Fighter (David C. Aronstein and Albert C. Piccirillo "Have Blue and the F-117A: Evolution of the "Stealth Fighter", American Inst. of Aeronautics and Astronautics Inc., Reston Va, 1997, ISBN 1-56347-245-7) and on page 99 they discuss some problems encountered with the pitot probe system. Quoting Lt. Col. Stan Stiefke, an Air Force engineer who was responsible for several aspects of the F-117A program:
So, the possibility of a time delay is indeed very real.
I don't have the details at my fingertips (I can't find the old fluid dynamics textbook just now) but there MUST be a finite time delay between a change at one point in a fluid system and its arrival at another point. The fastest a change in pressure/flow could possibly migrate down a column of fluid is equal to the speed of sound in that fluid, which is not really all that fast. Fluids have viscosity and compressibility which tend to slow their response to an externally applied force. As the example in the F-117A book shows, the diameter of a tube can be an important parameter, and for some combinations of viscosity and diameter distinct and measurable time lags can be observed.

I don't think the delay in a 5 cm length of plastic fuel tubing would be significant, but it might be and without having the equations and data handy I can't say for sure.

Wings - The cowl in the pictures you posted does not enclose the engine, it only makes the front of the airplane "prettier" and more aerodynamic... the majority of the engine is still exposed to outside air for cooling purposes. The "cowl" the others are refering to is the type made from fiberglass or plastic, one that encloses the engine, either completely with the head and all under a cowl or mostly enclosed, meaning only the top of the head (or valve covers of a fourstroke) protrude from inside the cowl. I have included a couple pictures of my Funtana to help you understand. As you can see, most of the engine is enclosed. The two holes on the front are the cooling "inlet" holes, the large cutout in the bottom of the cowl which is visible in the bottom veiw of the airplane would be considered the "outlet" hole. The air coming into the cowl is getting forced in by airflow generated by the aircrafts forward speed and propblast coming off the propeller. Once inside the cowl the air gets slowed down by the engine, motormounts, fuel lines, carb and anything else you can see when looking through the cowl from the inlet holes to the outlet hole/holes in the cowl. So, if you loose air velocity as it travels through the cowl you need to increase the VOLUME of air that can exit the cowl so that the hot air coming off the engine is not permitted to circulate in a pressurized, turbulent area outside the most efficient path of travel that the majority of the air is taking through the cowl, hence an "outlet" that is at LEAST 1.5 times the size of your inlet, preferably twice the size. Hope this helps

Brian