ZoomZoom-RCU

Ok, so heres the deal. I currently have a rather draggy biplane that flies on an OS LA46. It flies fine but uses a lot of fuel because you must always keep the engine at full throttle to fly the machine. This is ok for now, it works, but I got to thinking, a slightly larger or more powerful engine would be nice, as it should then fly the bird, but at less throttle, thereby extending flight time and using less fuel. I pondered 4 strokes but don't want the extra complication or the change of prop etc etc. So then I started looking at ball bearing engines in the .46 size so that hopefully, they would fit in the same footprint space as what is currently in the craft. Secondly, could use the same propellor size, and thirdly, would simply be more powerful and thereby use less fuel creating longer flight times on the same tank of fuel. My question: Is my assesment here correct? Thanks in advance for any experienced advice.

ZZ.

ronwc

My Feedback: (404)

Normally putting a higher performance engine on a plane is not going to reduce fuel consumption, but will give you a little bit better performance. You may want to also try experimenting with props, you are probably using a 10x6, try a 11x5 or 11x6.

da Rock

You want to keep flying at the speed you like? That speed requires a certain amount of power. The more powerful engine and the less powerful one are going to provide the same power to pull the plane the speed you like. They are probably going to burn almost the same amount of fuel to do it.

They might not simply because one might be more efficient than the other. They will probably have significantly different props to spin. That blows the consumption estimates right off. The different props are model airplane props. Different props for model airplanes are very different in efficiency and suitability to your model and to the engines that spin them. Some more reasons the consumption estimates are blown.

No matter how convoluted our model airplanes' motor/prop/etc selections are..... bottom line: Ain't enough in that glass to make picking it up worth the drinking.

ZoomZoom-RCU

I see what you are getting at daRock. But a more powerful engine should generate the same power of the lesser at a somewhat reduced throttle setting. Thereby saving some fuel. Correct? Perhaps you are saying it would be too minimal to matter?

ZZ.

PS. I also understand the props changing throwing things off too, I'm being general and hypothetical and ignoring this at this point.

JohnBuckner

My Feedback: (1)

I disagree the LA 46 is really a rather lame engine. What will make your airplane sit up and sing though is either an OS 46AX series 11 or the OS 55AX.

Not cheap but the great engines never are. Oh and no matter you will have to change props and that goes for any engine you may hang on there over the an LA's weak output.

Always use an appropriate prop for the engine and that definately can change between different types even of the same displacement.

John

da Rock

We can't guess which engine is the most efficient producing the power needed for the airplane to fly at the original speed, which is about the only time the two different engines would need to produce the same power. Also, there is little probability the flyer will fly the newly engined plane at the original speed, even if he could judge airspeeds accurately, which almost none of us can do. So his idea leaks water from so many holes, it's pretty much impossible to answer his question, and he has no hope of knowing if we gave him the correct answer. And like I said already, we have no idea what engine he plans to put on the new plane. Nor if he actually will try and fly the same prop. Chances are the same prop the 46LA liked just might be less efficient on whatever engine he winds up slapping on the plane.

Hypothetically, if he does fly the plane at the same speed with both engines, the same power should be required. Then if both engines are equally efficient when producing that amount of power, the fuel burn should be more equal than not.

And I left out an number of other things....

We could choose to cut down the number of things we're going to consider hypothetically and we'd still be so deep in the jungle, Tarzan couldn't find us. But heck, these ideas are kewl to think up.

jetmech05

If it were me I'd go with the 55AX...

speedracerntrixie

My Feedback: (29)

In order to fly the model that he is currently flying at full throttle at a reduced power setting he will have to go to a more powerful engine and larger prop. John's suggestion of an OS 55 is a good one. Get the 55 and throw a 11X6 on it .

da Rock

I really hope the OP will jump on a 46AX. I've run a number my self and they are flat awesome. I think OS might have gotten all the details right in that sucker. Right alloys for each part. Right amount of metals in each part for strength and heat dissipation/control. Right timing and gas flow. The suckers are strong and as long as you stick with one fuel and don't vary the nitro content much, they seem to last forever. The last one I sold (on it's original plane) was the first one I bought.

I've promoted them to every student I had. Everyone of them had me break theirs in. Every one of them was running great after the one tank I used following the mfg recommended breakin. Every one gave every one of those guys huge value for their money.

I'm a fan.

I've also heard the fuel efficiency arguments before. They're an excellent way to rationalize the purchase of an engine you lust after. Hope this is the case, because if anyone is really serious about saving money by better fuel economy, Tarzan needs to buy a good quad runner.

Luchnia

My Feedback: (21)

Another vote for 55AX. I have two of them and they are solid performers.

da Rock

BTW, since all the motors suggested so far are maybe twice the price of the 46LAs, I've got to wonder about the value of their not using more fuel.

I did from the first in fact, but couldn't pass up the discussion to see if anyone would give as estimate how long it would take, not spending any more money on fuel than before, to make up the cost of moving to a more powerful engine. And why moving to any different engine yet not use it's power in order to not spend more money on fuel made any sense at all.

speedracerntrixie

My Feedback: (29)

I think that going to a new engine to save fuel costs is weak justification. Now a new engine to gain longer flight times is a different story. I have not run many plain bearing engines but the couple that I have seemed to go through fuel faster then same size BB engines.

ARUP

Put a four stroker on it and put the largest diameter with flattest pitch prop on it recommended by the chosen engine manufacturer. Biplanes are draggy critters and drag increases by the square of the speed. You want torque that two strokers don't deliver. Fout stroke engines aren't that much more complicated. Just break-in properly and no worries!

Gray Beard

My Feedback: (-1)

I have used the .46 FX but not the newer AX so?? Power wise the FX was better but as for fuel use it could still be a toss up. I have used the new .55 AX in 60 size planes and found them excellent on fuel even with a bigger heavy plane. Prop size may change but it could just require a flatter pitch like a 4-6? The .55 fits into anything that a .46 will and I think you will get a much better fuel consumption with it. You can buy a lot of fuel though if you figure in the full retail price of the engine.
I have used the old .46 LA in several WWI Bipes and didn't have a fuel problem with them. As I recall I used an 8 to 10 ounce tank in them with an 11X6 APC or the MAS scimitar props. The .55 AX can be used in a lot of different planes and perhaps a good choice for your use?

jester_s1

How much fuel are you actually using? I'd expect an LA to use maybe 8 ounces in 10 minutes flying full throttle for most of the flight if it's tuned right and propped right.

airraptor

My Feedback: (66)

I would put a LA 65 on it and swing a larger prop.

Also on that 46 LA I think you could swing a 12x8 prop around 9,000

jaka

Hi!
What plane?
Choosing the right prop for an airplane is vital if you want good performance. In your case with a draggy bipe I would try a 12x4 APC or RAM or the new Graupner "Sonic" prop. 11x6 might also be tried. 12x8 way way too big for an OS .46 LA.

Assume you use a 8-10 OZ tank! That would give you around 12-15 min of flight.

Limitless Aero

My Feedback: (17)

You could but an evolution 10cc gas on it. It burns about half the fuel of a nitro and is priced well.

ZoomZoom-RCU

Thanks for all the helpfull suggestions guys, you've all given me much food for thought.

Speedracin....you've helped come very close to my intent, and also helped me realize how poorly I can express myself at times. Your statement comes very close to defining my true aim:

I think that going to a new engine to save fuel costs is weak justification. Now a new engine to gain longer flight times is a different story. I have not run many plain bearing engines but the couple that I have seemed to go through fuel faster then same size BB engines.

This is the best description of my goal, not really overall fuel savings, but more extension of flight time. This is truly the best description of the goal. Also, gaining a tad more power wouldn't hurt the design (it is my own design) either. The LA46 has juuuuuuust enough to fly it, so with a slightly better engine I may be killing two birds with one stone. Extending flight time a tad, and providing slightly more available power for a bit more authority on takeoff ect, while also reducing the general throttle level during average flight.

The design is a very short fat desing I am experimenting with. I've found that due to its short fat fuselage, a smaller diameter prop has helped immensely in reducing torque generated issues. I've switched to a 3-blader which has assisted greatly in this,so whatever engine I use I will strive for the smallest prop diameter possible. Thats why leaning towards a ball bearing type in the same size range might come closest to hitting/tweaking all of these limiting paramaters.

ZZ.

JohnBuckner

My Feedback: (1)

Then my original suggestion of the 55Ax would be just the ticket. The 55 loafing along as opposed to the LA busting a gut indeed would make a hugh difference.

In addition the revised AX carburation used by all Ax's except the very first 46 is superior at low power idling for extended periods and it is precisely this reason I choose to to reengine my cross country airplane and removing the .70 OS four stroke and replacing it with the OS .65 two stroke when recently preparing it for a fifty mile flight down the Colorado River.

Your airplane is an interesting Characture Airplane, very cool.

John

jester_s1

I remember when you were first working on that funny looking little plane zoom zoom. I'm glad it's working for you. FWIW, I'm running a Thunder Tiger .46 pro on my Kaos. With a 10x6 I get 14k on the ground and it unwinds a lot in the air. That engine is essentially a copy of the older OS .46 FX (I'm pretty sure that's right) which was designed to spin a smaller prop at high speed. The TT engines are good quality and reliable, and would probably just the thing to haul that one around.

tkline

I have to say the os .46ax is one of my favorite 2strokes lots of power and user friendly but I can't say anything bad about the thunder tiger .46 I have one that I have on a 4*40 that performs just as well as any of my os engines. That's just my .02 I don't know how well the TT holds up over time cause I haven't had it very long but the os engines just seem to run better and get more power the older they get

2walla

My Feedback: (10)

In terms of standard mass produced glow engines, power output to weight you are not going to beat a bushed engine. Bearing engines can turn faster rpms and generally have more power, but they weigh more.. For a slow draggy airplane, a 2 stroke spinning up into the stratosphere isn't going to be the most efficent. The efficency of most two strokes is about the same so the same displacment two stroke spinning the same rpm is going to use the same amount of fuel. If you go to a bearing motor and turn the same prop at faster rpm it will burn more fuel.. a four stroke turning a larger prop slower will more efficently fly the plane the same or better with a bit less fuel use. Going to a larger displacment bushed motor would probably be least added weight and will turn a larger prop that will get you a bit more propeller efficiency at a reasonable price. You will probably use the additional power and end up burning more fuel in the end, but if you had a calibrated thumb and flew it at the same airspeed it would probably be slightly more efficent.

oliveDrab

Go electric.

airraptor

My Feedback: (66)

+1
as that is what I said just not in that many words. The LA 65 can swing a MA 13x8 prop and would work great in that plane. Small props turning high rpm isnt a away to save fuel.