JohnBuckner

My Feedback: (1)

I have had a preferrance for runing in all the new engines for my multi's and I tend in most cases to start with new engines, in test stands. This give me a chance to learn the particular engines well.

My normal procedure is to also do them all at the same time and in exactly the same way. Mostly in the past in multiple independant test stands all screwed down to the same table. This seems to be worth the effort both in my learning curve for the particular engine and their ultimate success in the airplanes.

Actually have done up to six engines at once but rounding up all these test stands (sometimes using some borrowed ones) and the hassle of setting them up is a real pain. So, this time for my latest ship that is nearing completion a Fokker FVII Tri motor that I am using three OS LA-10's, I built this arraingement for all three that will be easy to drywall screw to the wire spool tables we use a lot of.

The throttles are all articulated together and easy to operate.

Guys lets hear of what ever types of effort and thought you have put into this for your projects.

John[8D]

pkoury

My Feedback: (7)

I start with new engines. Run a coulpe of tanks on the test bench then put them in an airplane and fly them. By the time the airplanes is done the engines are broken in and reliable. I also fly any new radio eqiupment in an old airplane before using it in any new airplane I build.

JohnBuckner

My Feedback: (1)

Thank you Pkoury. Come on fellows lets hear some more, I know a lot of the fellows have different approachs to breaking in engines specifically for multi engine airplanes (any number of engines) and this thread is for shareing.

John

BarracudaHockey

My Feedback: (11)

I'm not a fan of bench running. I put them in a single engine plane and fly them till broken in

JohnBuckner

My Feedback: (1)

Fair enough BH, keeps the thoughts and ideas coming guys.

John

CanDo

#1, choose your motors wisely. I installed my new OS .91s in my Bronco, ran 4 tanks through them and adjusted them a little rich. When the motors had a good idle, transition, and steady RPM at full throttle, they were ready to fly. I used the same technique with a couple of new OS .25FX motors. The time on the ground helped me get familiar with each motor.

JohnBuckner

My Feedback: (1)

Could not agree more with you Can Do, engine choice is so important. I suppose that is why I cringe every time I hear someone who is getting into their first multi and the first question is, I have an old ? (Fill in the blank) and a new (fill in the blank) can I just use these.

Like you I love the 25FX's and it was my favorite for the majority of my multi's that is untill I discoverd the 25 and 35AX's. They have become my new favorite and I have re-engined even a few of my multi's with them.

Those unfortunately are too large though for my latest which is a triple of course and that limits choices in a .10 size So the LA-10 is it.

Used the triple stand this morning and I am delighted as there was an additional learning curve with these engines which do not have mid range needles or a bleeder circuit. Much better to go through this curve on the triple stand I think than the airplane itself which being a conventional triple the center engine well forward makes the process a little ackward.

Anyway they will perform well I beleve, here are a couple photos from this morning. Unfortunately I also did some vidio but but the cam batteries pooped out.

Keep the thoughts coming guys as this can be quite helpful to the new multi folks.

John

earlwb

I like your multi-engine test stand. it is very innovative, something I never thought about doing myself.
I normally just bench test each engine one at a time and run a few tanks through them to make sure they are working Ok and there aren't any problems. I then mount them in the plane and fly them on the rich side some and take it easy getting used to the plane, et cetera. Then as I fly the plane i lean out the engines as needed.

I have found that over the years of flying twins etc. that the engines do not have to be synchronized all that much, they can be off from each other. Normally I adjust the strong engines to match the weakest engine if possible, but even 500 or more RPms off between engines doesn't seem to do much to the plane's handling in the air. It is a little aileron trim and that is about it.

Ed_Moorman

My Feedback: (1)

I bench run all my engines first for 5 or 6 tanks of fuel. If I have time I like to fly them on an engine test Stick to check then out in the air.

I have flown several types of engines on the 20+ twins my buddy and have built and I have flown. I found OS to be the most reliable in a twin. I have had great luck with GMS & Magnum 2-strokes on singles, but never could keep both running reliably on a twin. In the same plane, OS engines ran great. I had 2 GMS .47s in two different twins. They would quit alternately. The same with 2 GMS .32s on a TwinStar. A friend also had 2 GMS .32s on a TwinStar and we both had reliability problems. OS .46AX solved one problem and TT .42GP solved the other.

As for synchronizing, I rarely bother. As a test to see if the same rpm on both sides made a difference, I pulled a pair of .46AXs from a plane and installed a TT .46PRO/11-6/Tower muffler on one side and an old TT .42GP/10-6/stock muffler on the other. It didn't seem to make a difference in how the plane flew. See photo.

We have also run 2 OS .40LA, 2 OS .46LA, 4 OS .46AX on two planes, 2 OS .65LA, 2 OS .25FX/Jett mufflers. All of these were 100% reliable.

CanDo

Folks, if you are getting into twins, pay attention to John and Ed, they know what they are talking about. John, that 3 engine test stand is cool!

earlwb

ED, I love your twin delta. That is great. Nice.

Some of my current twins:

kram

My Feedback: (7)

I break all my twin engines in the plane.

It may help that most of my glows are OS, which break in fast.

I think it gives you a chance to learn things about the fuel system, the cooling, the cowls, the throttle linkages, high and low needle settings, mufflers, etc, and just plain gives any pieces that wanna shake loose a chance to do so on the ground.

Always attach the full wing to the plane when testing/tuning the engines. Wings absorb and dampen a significant amount of the vibration produced, esp. wth gas engines.


mt

JohnBuckner

My Feedback: (1)

Thank you Earlwb and CanDo. Glad you came aboard Ed also. I have enjoyed the somewhat eclectic choices in multi's that tends to paralell my tastes also, you and your buddy have produced over the years and please let him know for me that its appriciated.

Kram, excellent point about the cooling and one that often too little thought is given to. On most of my non scale multi's I have choosen to go with completely exposed engines so that was not a big issue at break in time. It seems to me that a common mistake where fully cowled installations are used (singles or multi's) is the failure to allow sufficient outlet flow and in the most aft and usually down positions. That so no hot spots develop within the cowl.

Here is the Fokker that the little LA's are for thats nearing completion. There are no fuselage pushrods, the elevator and rudder are operated on external pull/pull as in the full scale.

Keep the thoughts coming guys this is good stuff, its great that we seem to have attracted many of the experianced multi enthusiast here at RCU but you new timers out there please don,t be shy lets hear your thoughts and experiances also. Of course pictures too (smoke'em if ya got em')

John

CanDo

John, you might get a kick out of this. Here's an extreme multi engine plane. It started as a Tower 40 trainer and my friend kept adding motors, one at a time, until he got up to 7 engines. I think the 3 engine version was his favorite. The motors were whatever he had and some loaners from friends, all used, and ranged from .25 to .40 size. Needless to say, he is a very experienced multi engine pilot and quite proficient at flying with an engine out. He came up with an engine pod with a throttle servo and a tank that allowed him to make any trainer a multi engine trainer. All motors were run a few minutes on the ground and run slightly rich.

JohnBuckner

My Feedback: (1)

Now that is just so cool CanD0, I love it! Practical, well not likely. A good flyer Not to likely either. A challange, Oh you bet and so much fun as well as a testiment to the experimentation that makes all this Stuff worth[8D]while

So far my limit has been a sixer.

John

CanDo

-Wow, very nice! With that many motors, you could afford to lose one and still get it back home safely! I saw a picture of a "Spruce Goose" model once that had .049 motors; how he got all of them running at the same time was beyond me! Be bold, have fun!
-The Tower 40 trainer makes a good platform for breaking in motors and learning about multi engine planes without all the time and $$$ investment. If you dork it during a flight test, you patch it up and try it again. It's not a plane that you get really attached to. BTW, it was a really poor handling plane with 7 motors, but the pilot did bring it back in one piece!

earlwb

I love it. Actually that isn't a bad idea at all, to make engine pods and rubber band them on the plane.


CanDo, many years ago I built a Godberg 1/2a Skylark and put on the two Cox peeWee .020 engines like they show on the plans. some days the engines would fire right up, other days it was a major hassle too. If a engine was stubborn, you had to be quick with the syringe to refill the fuel tanks before the first engine running ran out of fuel too. it actually flew Ok on one engine, albeit you weren't doing any stunts like that though.

CanDo

Earlwb, you are the man! Anyone who can get a couple of .020s running at the same time has my respect!
Just by adding the engine pods, you have a good twin trainer without having to buy another plane. If you put a couple of .25 two strokes on a .40 size trainer, you are gonna have some fun! Since you already have a nose mount, etc, adding a third motor is a piece of cake too.