Engine break-in without wing?
 

I have just completed putting together a Dragon Lady with OS 91 FX. I need to run-in the engine and was thinking of taking just the fuselage to the field, tethering it as normal and doing the run-in like that. Are there any reasons I should not do this and need the wing attached?

As long as it is tethered properly, I can't see any advantage to having the wing attached for this. Am I missing anything?

Dave

RE: Engine break-in without wing?
 

Dave,
just as long as the exhaust doesn't blow up into the open area of the fuselage it will be fine.

RE: Engine break-in without wing?
 

Lots of us break engines in on a bench so what you're proposing should work fine. You may be surprised at how the model jumps around under the vibration though.
Allan

RE: Engine break-in without wing?
 

Consider covering the wing opening to keep dirt/oil out. Even if you just stuff a rag in there it will help. Run it away from your friends or you may not have any when you are done. :D

RE: Engine break-in without wing?
 

Hi!"
It's not a good idea to run an engine sitting in the fuselage on the ground...lots of dirt is going to be sucked into your engine intake...one ruined engine.
It doesn't matter wheather the surface is tarmac or fine grass...small dirt particles is always getting into the engine if you run it on the ground.
Regards!
Jan K
Sweden
30 years in this wonderful hobby

RE: Engine break-in without wing?
 

Jan K, I hate to argue, but I think this is the same as taxiing. It shouldnt bother it running on the ground unless you are in a very dusty area

RE: Engine break-in without wing?
 

Thanks for the feedback. The muffler on this engine points almost directly at the ground, so shouldn't blow anything up into the fuselage opening, but I will cover it just to be safe.

I don't think the concern about the engine picking up dust etc is a major problem. Most of the guys I've seen run in engines this way, just usually with the wing mounted. Besides, have you *seen* my workshop? ;-)

Dave

RE: Engine break-in without wing?
 

Now how would we have seen that? Keep stored engines protected from dust/dirt.

RE: Engine break-in without wing?
 

Here's the deal. On a small, two stroke/four stroke motor, it won't hurt it at all as long as no oil/exhaust gets into the working/electrical systems.

Now. For larger, gas powered, especially single cylinder engines, that's a different story. When running one of the larger motors on a fuse only, there's quite a bit of vibration that can tunnel down the fuse and through out the entire system. With large airplanes especially with gas motors, swinging big props, it's always a good idea to have the wings on the airplane to dampen the vibrations.

RE: Engine break-in without wing?
 

Yep, that's what I have heard. I don't even run my Saito 150 in my GP Giles without the wing on. Too much vibration.

RE: Engine break-in without wing?
 

Dave,

I am literally in the exact same position as you - I am just completing my Dragonlady ARF I have an ASP 91. in mine, I have run it with out the wing on and I had hideous vibration, I thought I may have been doing some damage to the tail as it was shaking so bad. I have just this minute finished running the engine - with the wing on this time - it was a lot better - LOT Better, although I just tried another prop - thinking my 1st one might have been out of balance and I think it may be. Are you using the engine mounts provided?

RE: Engine break-in without wing?
 

Jan is not completely wrong on this one. An engine at full throttle can pull a significantly larger amount of stuff off the ground than one that's taxiing. How much stuff is open to debate, and does depend on how clean the area is.

The last time someone decided to break in an engine in this manner at the field it was extrememly irritating to the rest of us. He tried to keep it away by doing the runs in front of the cars, but the endless minutes of an engine running wide open was not pleasant.

My suggestion is if you don't have a test stand that you mount the engine to a piece of plywood that's big enough to securely clamp to something heavy, like a workbench. It's pretty simple to cut the opening for the engine, drill 4 holes and mount the engine with bolts and blind nuts. Do your runs in front of your garage on a Saturday morning when the rest of the neighborhood is making noise with lawn mowers, weed eaters, blowers, etc. You'll fit right in, and who knows, maybe the sound will attract some people who are interested in learning about the hobby.

RE: Engine break-in without wing?
 

I was just wondering what the advantage is to leave the wing off. There is a slim chance that the internal components could get exhaust residue on them. There is also a slim chance that there could be damaging vibration from not having damping from the wing. It probably won't hurt anything to run it with the wing off, but why take the chance? That being said, when I switched from electrics to glow, my first glow plane was a Superstar 40. I did do some high speed taxing with it to get the feel for it. I did this with the wing off to ensure I didn't get off the ground unitentionally. I only did a couple runs, but it didn't hurt anything.

RE: Engine break-in without wing?
 

kainisrj, interesting to hear about the vibration. I'm usually careful to make sure my props are balanced, so perhaps I won't have that problem. On the other hand, I'm thinking I might run it with the wing on after all just to be safe.

I did not use the supplied engine mount, I replaced it with an OS aluminum pre-drilled mount. I also used the firewall spacer, did you? One problem I have is the hole in the back of the engine mount is aligned with the hole in the firewall. This means that the engine itself is somewhat offset from centre, which is quite noticeable with the cowl on. Did you have any issues like that? The manual doesn't say anything about thrust line offset, so I assumed it was built in and did not allow for any myself.

I agree that running-in at the field is annoying, but my house placement does not allow running it in at home without annoying many more people.

Dave

RE: Engine break-in without wing?
 

Your engine is off center of the firewall to compensate for the right thrust that is more than likely built into the firewall. This offset allows the spinner to be in the center of the cowl. The thrust is still in the center of the fuselage.

Have fun.

RE: Engine break-in without wing?
 

Hi!
If I got in a engine for warranty and heard that the owner had run it in like that, plane sitting on the ground ..I would be very cautious to replace any parts for free.
Heck! Why not just fly it in!:D.
Regards!
Jan K
Sweden

RE: Engine break-in without wing?
 

Yeah, that's a great idea, rather than an extremely small risk of anything getting into the engine on the ground, why not risk the whole plane, radio, etc. by flying with an engine that isn't ready.

RE: Engine break-in without wing?
 

Why not just leave the wing on and dial in a lot of down trim on the elevator? I've done this many times just to show newbies that it won't take off while they do taxi practice.

CCR

RE: Engine break-in without wing?
 

Hi Dave,

Yeh I did use the spacer provided, mine lines up pretty good (with the cowl etc), although i did noticed that you cant actually get the cowl to be parallel to the backplate of the spinner? anywho, yeh I think I def need a new prop and I am still running the engine very rich ,i havent really played around with it to much so I think it is almost 4 stroking a little bit. Has anyone had the problem of buying new props - I brought a new Master Aiscrew Scimitar Profile Prop and the hole in the middle isnt big enough to fit on the shaft of my ASP 91? its a 13x10 prop so you would think it should fit - I bored it out although I think I have shagged it because it might be off center by 1 millionth of a mm and this is what causing all my vibration. How does everyone else gt the hole size bigger? I am obviously missing a vital piece of information!

Cheers

RJ

RE: Engine break-in without wing?
 

I run a tank or two on the ground first on all my engines. Always without wings or cowlings. Never had a problem. I think as long as its not a really dusty area you will be fine.

RE: Engine break-in without wing?
 

RJ,

I also had to widen the prop hole, I have a 13X7.

Did you have to add any weight to get it to balance? I have had to add 5.5 ounces to the nose, which I was kind of expecting since the OS 91 FX is relatively light. That is to get it to balance at the 3 3/8 mark.

Dave

RE: Engine break-in without wing?
 

Most planes will take off without any elevator. Thats why when i taxi around the street and such, i make sure no wing is attatched because i dont want to accidently take it off.

RE: Engine break-in without wing?
 

I beg to differ. With down elevator trim dialed in, it's all but impossible for the plane to takeoff. I've seen people who accidently had down elevator trim race down the runway and not takeoff. BTW, how fast does one want to practice taxing? Without the wing, the plane will tip over a lot easier.

CCR

RE: Engine break-in without wing?
 

Hey Dave,

Ok - I have been mucking around with the engine and have sorted it - top speed mixture setting sorted, still a little rich due to it being a new engine and the idle mixture sorted out the vibration, Oh - I also put another smaller prop on - one which I think is balanced! and the vibraton is way down to an acceptable level! So all to do is pretty much go fly the thing! The whole thought scares the hell out of me really! How do people enlarge the holes in the props? with a reamer I am guessing? Oh about the weight thing, I am just behind about mid-range weight mark, no weight added at all - I am going to re-check that again though, I really want to get this right - it far to nicer plane to come home in a rubbish bag! I'll throw in some photo's, got any of yours? and when do you expect to make the maiden flight?

RJ

RE: Engine break-in without wing?
 

Hi RJ

Great pics! I have the "Dragon Lady" decals on mine where you have the lettering (cheesy, I know, but what the heck...). Also, I have a plastic spinner - I should probably replace with aluminum, looks much nicer. I also didn't bother to put the decals on the wheel pants since those will come off before the first flight anyway.

I see you had to cut a hole for the engine head. I didn't need to do that.

Where's the pilot?!?!

Dave