tukkus

My Feedback: (2)

From what i'm learning about breaking in engines is that it is better to break the engine in the air than to bench run it. I can understand the first tank or two on the bench but I've been reading that some people run a whole gallon before they're ready to take it up. It would seem to me that the engine should be in the air for the break in because it needs to be cooled properly and running it on the bench would simply have more heat involved than it would have while flying.

Since heat is such a big factor concerning engine life and performance why do some people bench run engines?

Richard L.

My Feedback: (24)

Some people run a whole gallon through the engine for fear they might get a deadstick in the air if they take the engine up too soon. Some engines take longer to break in than the others. I like to run a tank or two on the bench at a super rich setting to let moving parts micro polish each other and to get a rough idea of where the needle settings will be. I run mostly YS four strokes, and they can hold a reliable idle after the first tank on the ground and can be taken up in the air for the rest of the break in process.

JohnBuckner

My Feedback: (1)

There are a lot of reasons to use bench runs first, Here are just two:

Not all engines come out of the same mold i.e. there are lapped piston engines, ABC/N, AAC and ringed types and they are not all run in the same. In fact breaking ins an ABC the same way as say a Ringed engine can ruin it as well as vice versa. Not all these running methods are condusive to good controlled flight especially on a new or unknown airplane to to. Simply put it ain,t much fun flying around for an hours worth of flight at a very rich setting with your new ringed engine.

Now you say, but my ABC should be broke in at higher RPM at a two stroke mixture? and right you are but what you are leaving out in that senario is the fact that what will do more for the brake in than anything else is 'Thermal Cycles". heat that puppy up and let it cool down every few minutes. Something thats hard to do on an airplane in flight.


In most case with only a few exceptions (yup there are always exceptions) I will break in an engine with the intended flight prop and fuel. Always on a stand and irreguardless of pistion/cylinder metalurgy will use short thermal cycles. I have mounts that will mount the engine in vertical sideways or inverted position so it can be broken in as it will be used.

The multi engine airplane in my avitar has Magnum .28's and all four where mounted on a single two by twelve with the
spacing and fuel tank positions as in the airplane. All four where broke in simultaniously with a gallon throuh each be fore they ever saw the airplane. I even wanted the same vibration harmonics for the brake in. Sure would not wanted the resultant wear and tear on the airframe. The reliability rewards was certainly worth it.

One last though I commonly see people running in an engine on the airplane and never even get the midrange needle set right for the life of the airplane. Simply because its to akward to get to, as a result they never even learn how to set 'that' engine. Of course every idividual engine is differant. All of this makes a whole bunch easier to do on a stand and not ignore it. I think the one that gets me the most is someone will come out with a beautiful new airplane ARF or kit or ?, with a new engine and not even provide a way to set the main needle through the cowling. Expect to brake in the engine, set the engine and flight test the airplane all in one setting. I don,t think so.

John[8D]

jettstarblue

Here's a good reason: I have a real old (68?) S.T. .40, that I thought was in good shape. I could have mounted it in a plane after the couple of tanks I ran through it when I got it. (A couple of years back)

I just re-mounted it on the test stand "just to make sure it was gonna run O.K." and guess what? I apperently didn't do as good a job at storing it as I thought for the poor storage conditions it was in, and the bearings crapped out (technical term) while I was running it today...at least it didn't cost me anything, and it didn't quit in the air. (not that that is the death knell for a plane, but it could be for someone who is a beginner.)

ronwc

My Feedback: (404)

For about 35 years now I have mounted my engines on planes and flown without any problem. It is true that on ABC engines that they need to be cycled somewhat, but I do that with one run on the ground. The rest I do a quick tune up, set a little rich and fly. Very seldom as an engine cut off on me, if they do I land and retune. In my opinion, bench running engines at home pisses off the neaighbors, waste fuel and cuts into my flying time -

Ernie Misner

Hi Tukkus,

Your question about excess heat during break in is a good one. Bottom line though, is that breaking an engine in on a test stand is a very controlled situation compared to that of taking a new engine up in a plane. Only on the test stand can you ensure that the engine will not be leaning out at any time and causing a very hot run. Experience will bear this out for you.

Also, on the test stand, run a prop that is slightly smaller in diameter, but slightly higher in pitch if you have any concerns about cooling. This doesn't seem to be usually necessary though, because guarding against an overly lean run is the main goal.

Ernie

CafeenMan

I bench run engines for a couple reasons. First, it's easy to get to everything and make adjustments. I've found that once an engine is close to being adjusted right, it doesn't matter how you mount it, the adjustments don't change much. The settings do change a little due to different fuel tank location, distance, etc. but if the engine is adjusted properly on the bench it's only a couple clicks of the needles to get it set in the plane.

Also, an engine has to be at least a little broken in before a reliable idle can be set. I almost never land dead stick unless I run out of fuel because I spend a good bit of time getting the idle dialed in.

Second, I want to make sure the engine works before I spend all the time to mount it in a plane. Even if I put a new engine in the plane I'm going to run a tank of fuel through it before I fly. I'd rather use the bench than have the engine throwing oil and dirt all over the plane.

Old engines took forever to break in but that's not true any more. If people are still running a gallon of fuel through an engine then they're living in the past or running old engines. I run a tank or two and then it goes in the plane.

Kaos Rulz

CafeenMan is right on target. (welcome back, by the way)

I like to control all the variables associated with breaking in a new engine, therefore it goes on the stand. I will not allow an engine to break itself in while flying. Too many variables you can't immediately control. (ie. leaning out when fuel lowers, prop loading/unloading during maneuvers, etc...)

Another reason I run on the stand first, is to insure I have a good engine going into my plane. If I encounter problems after I mount the engine, I know to direct my attention to the tank and plumbing, because the engine has already prooven itself to be good.

Breaking in a new engine often times will require replacing glo plugs. While I'm quite comfortable with dead-sticks; I find it safer to replace plugs while the engine is in the stand.
Minute adjustments are also easier on the stand. I prefer ST engines which allow you to adjust the mid range by rotating the spray bar. I sure would NOT want to do that after the engine has been mounted in the plane. Yes it can usually be done, but why make things harder for yourself?

CafeenMan

Greetings. You are wise as are others who agree with me.

FLYBOY

My Feedback: (11)

TUKKUS, As you can see, everyone has their own ideas on how to break in an engine. All you can do is to do what you feel is the best. There is no clear cut answer. I personally don't bench run, and never have. There is nothing wrong with it, well, ok, I have seen one guy do it wrong and he ruins them so fast it isn't funny, but thats another story. If you break them in while flying, you may have to deal with a couple deadstick landings at times. If it is a plane you don't want to deal with deadsticks on, run it a few times and make sure it is tuned propperly. At any rate, have fun! It all works out and neither way is the "correct" way.

gow589

My Feedback: (1)

Flown R/c airplanes for 20 years, everything from .049 to 100cc gas. I have never bench ran an engine. Never had an issue couldn't be solved by running it on the airplane.

Gary

sigrun

Familiarisation, which is simply good airmanship. The bench is a good place to check idle and primary needle settings and adjust as neccessary, determine start and idle characteristics and become aware of any idiosyncrasies or flaws. Even modern engines take a couple of tankfuls to settle down.

rcjon

tukkus,

Interesting question and interesting replys. Seems to me that an engine with that big fan in front of it is going to run at the same temp whether it's on a stand or an airplane, unless it's in cowl situation where it runs hotter on the plane.

I've been playing with this stuff for about a year and have only assembled three ARFs with new engines. I like to run the engines on the bench before I go to the field, but I mount them in the airplane and then tie the plane down to my picnic table. This way I can do the "break-in" and fiddle with the needles without a gaggle of experts standing around giving advice. That way I learn to tune and I do my range checks at the same time. Scr*w the neighbors. Less noisy than a lawn mower.

If I decide to take my next new engine directly to the flying field, I think the 35 years of combined experience of ronwc and qow589 outweighs the "bench run a new engine" opinion, and I won't lose any sleep about harming the engine.

rcjon

Geistware

My Feedback: (16)

I have always broken my engines in on the plane, in the air. Just make sure that you don't over prop them.

mikeboyd

Really some great advice from all the bench guys. I have a bench set up that allows me to set the tank height and distance to match the plane. Break the engine in and tune it, then put it in the model. Glad to hear the non-benchers have great angels watching over them, but most of the time I try to tune the new engine at the field has robbed me of good flying weather and even cost me an airplane or two. I recently bought a brand new FX.91, which had bad bearing right out of the box, had to send it in to Hobby Services under warranty. This kind of represents this Irishman's luck. No body has problems with new OS's, right? when I finally get the new engine back, you can bet it goes on the bench to be set and tested, before it goes back onto the new UCD60. Most manufactures recommend running the engine on the airplane, but I am old and hate bending over for adjustments and so on. My neighbors ride Harleys so my little ole engines don't even come close to their straight pipes. Nearly every member of my three clubs has a good bench and uses it regularly.