OS .61 FX break in for payload

Sorry for the unstunt like topic but you guys make know best on this type of subject.

A group at my school is putting together a r/c (YUK) plane for a SAE payload competion. They are green horns to the hobby and need help. A sailplane guy, tony naccarato, and me are helping them build and run there trainer. They are learning fast but sometimes like me lose site of what things realy count in model airplane design.

I was wondering what is the best break in process for an stock OS .61 FX (BB, abn(?) liner)? The engine must be stock like fox racing but extentions on the end of the exaust mufler are allowed, remote needle, and different plugs. The airplane can run any amout of fuel and must just take off circle and land. The fuel that is contest supplied is 10% nitro and most likely byron orignal brand. They may be able to remove the BP & head gaskets but I don't know for sure. Do you guys have any special way to break in and engine for a pey load type event? Dana at [email protected]

I'd reccomend you folks to break in the engine with the same fuel you'll be using in the real situation.

I don't think you want to take out any gaskets.

About the plug, you can ose the recomended manufcterer;s plug, I guess it'd be an OS A-8, but a RC fox plug with an idle bar might also be fine.

The first runs shouldn'd be too fast (a fast 4 cycle is OK) nor too long, some 40 seconds.

Then you can increase the time and the revs, and after some 5 minutes of total running time youcan star putting is to gos fast.

lean it for a minut, open the neeedle to let it cool a little and get it fast again.

Let the engine cool thoroughly between runs.

Remember, ABC or ABN engines are to be broken in at the regime they

are going to be operating. If you break them in too slow you'll spoil the sleeve!

If you want to be on the safe side, an hour is more than enough.

But don't take my word, wait for more knowledgable folks to advise you.

God bless,

In Christ,

My approach would be to send the engine to a reputable tuner, one you can trust to get the engine back to you in time for test flights. He must be made fully aware of any and all rules which apply to the powerplant.

Having a nice, strong motor is not merely having it tweaked--against the rules here in any case--but in very careful fitting of bearings to shaft and crank, for example. And "simple" assembly of a really good motor is not so simple. The ideal would be the equivalent to the very best motor of this type to come off the assembly line where it is totally hit 'n miss.

In other words, a "blueprinted" motor, although that term has been thoroughly beaten up over the years.

I'd have the tuner get it run-in for me as well. Your kids may know a fair bit about structure and aero, but cannot be counted upon to know anything worth repeating when it comes to handling the engine properly.

Hmmm, if your tuner is a local guy, can he set the needle when it comes time to jerk a ton off the tarmac?

For the critics, what I am proposing is not cheating, at least as I understand the rules and blueprinting in the traditional sense.

Cheating would be robbing wifey's whipped-cream dispenser of its nitrous cartridge, routing a small line to the vicinity of the carb for introduction of serious juice upon command. I would never suggest such a thing, of course.

The engine must remain stock, no removal or adding of matrial. that is why I am douting whether we can remove the head gasket for increased performance or removing th BP gasket for CC volume reduction (like stuffer plate). As to the nitrous it would work but the plane must pass AMA rules that outlaw gasous boost.

I would recommend going back to an article in Model Aviation (within last year I think) to see the problems they had.

As I recall, they spent very little time actually running the engine and had some problems. I think they actually believed the HP ratings for the engine, and designed to it.

One item that I would explore is to see what the maximum diameter/lowest pitch prop you can run on the engine/plane combo that will give adequate airspeed.

One thing which amazed me was that a lot of credit was given to the documentation of why the plane should fly, rather than to the plane actually flying - at least that was my impression from the article.

In any case, it looked like it was a lot of fun.

alan, who is "they"? Was the article about the sae design contest or the os .61 fx engine?

The "they" I was referring to were the students who were designing/building the plane for the payload contest.

I ment what team, but the author sent me an email so I don't need a answer.

> Sorry for the unstunt like topic but you guys make know
>best on this type of subject.
>
> A group at my school is putting together a r/c (YUK)
>plane for a SAE payload competion. They are green horns to
>the hobby and need help. A sailplane guy, tony naccarato,
>and me are helping them build and run there trainer. They
>are learning fast but sometimes like me lose site of what
>things realy count in model airplane design.
>
> I was wondering what is the best break in process for
>an stock OS .61 FX (BB, abn(?) liner)? The engine must be
>stock like fox racing but extentions on the end of the
>exaust mufler are allowed, remote needle, and different
>plugs. The airplane can run any amout of fuel and must just
>take off circle and land. The fuel that is contest supplied
>is 10% nitro and most likely byron orignal brand. They may
>be able to remove the BP & head gaskets but I don't know for
>sure. Do you guys have any special way to break in and
>engine for a pey load type event? Dana at [email protected]

I would suggest just following the directions. There's nothing special about break-in for particular applications. I would just break it in according to the instructions, and then just run it for a while, like a few hours, to make sure it's reasonably loose. And, if you can get the chance, let somebody fly it in an airplane for a while just to make sure. For this application, all it needs to do is run reliably. If it runs well, it will be sufficient, because half the other groups won't.

Then do good job on the design. Mr. Naccarato will probably tell you, but if he doesn't, go with a conventional, conservative design with a minimum of "new features" and fantastic weight-lifting "improvements". I've followed the competition over the years, and RELIABILITY is very important. I also suggest TEST FLIGHTS - a lot of the first flights were in the competition, and simple-to-solve problems have torpedoed the groups over the years. A "trick model" might be able to lift more weight, but most of them will never get off the ground, and a fair number more will never make the flight intact. To be honest, something like a Telemaster (high-wing trainer type) with maybe some permantly-deployed flaps would have won most years, just because it's a sound design that flies well.

Brett,

Well, that was going to be the second part of my answer, the one I didn't think of until you elbowed your way in here.

Good advice. Rarely followed, but good advice nonetheless.

I was intrested in whether a break in like GMA decribed on his page would help keep the p/l from getting to louse and creat blow-by

LAST EDITED ON Dec-01-03 AT 04:31 PM (CST)
 
>I was intrested in whether a break in like GMA decribed on
>his page would help keep the p/l from getting to louse and
>creat blow-by

No offense to anyone, but the manufacturers know what needs to be done for their particular engines. As I recall, George had two versions - one for iron-liner motors, and the other for ABC motors (and in particular, his ABC motors which were set up to be VERY VERY tight). Neither is entirely appropriate for the OS ABN; either will be safe enough, but neither is necessarily ideal. It's not a huge issue in either case, most guys just run it and it's good enough.

I would caution you against trying to "improve" the motor even if the rules allow it. If it was something simple, they would have already done it at the factory. Those guys are not dummies, and the market is highly competitive so it's probably already as good as you can make it without significant changes. Just run it, learn to set the needle properly, and go for reliability.

In particular, removing the backplate gasket is really way off base - the power improvement is very minimal if at all (could even be reduced), but a leaky backplate can completely screw it up. The head gasket might be a better choice, but I would suggest extensive testing under a variety of conditions to see if it worked all the time - or if it simply started running badly on cold days. And it has to work when it has to work. The situation is very similar to competition stunt, where performance is nice to have, but the engine absolutely has to run reliably in a variety of conditions.

If you are really dedicated to getting the best engine, I would suggest going out and getting 5 of them and testing them to pick the best. The variation from piece to piece, even with the legendary OS quality control, is probably far larger than you would get from any reasonably simple modifications.

Brett

p.s. For reference and inspiration, I have seen the current WAM (Western Associated Modelers) payload record setter. WAM has a bunch of, well, crazy, events like payload. C/L of course, but the current record holder is something like 10 lbs. Doesn't sound like much, but it's powered by a stock HOLLAND HORNET .049 - not exactly a powerhouse by any standard! It's a reasonaby conventional design, with a pretty high aspect ratio, but nothing unusual like a flying wing or lifting body, nor is the wing flapped or even undercambered.

p.p.s. If you decide to do test-runs with high-nitro fuel (like 60%), you might want to do the last test-run immediately before the competition starts. Be sure and run it all out, of course...

The last years winner lifted 24 pounds of lead on top of the unloaded weight. I have heard of some methods that describe putting a lower nitro fuel and small prop on for first few test stand runs. Then going to the std fuel to be used and approximately the competition spec. (the one that will be most likely used) prop and start heat cycling. I have also hear to start it leanish to get the p/l to expand first then start heat cycling. I plan to do some of the testing with diff. glow plugs and props to show them the effects. As you said they need to keep it simple and work on prop and airfoil selection. The prof. in charge doesn't always keep to the KISS principle. They bought (I have no clue why!) an altitude/airspeed data logger. I tried to tell them that that would add unnecessary weight that could have been counted add ballast but the prof. said something about looks good to judges and need to know the flight speed to find the best airfoil. They also want to build a thrust stand instead of buying the good AHP stand on the market. Again something about not liking the amount of area the stand blocks the prop flow. I tried again to steer them strait, telling them that the stand only gives you an idea of the in-air thrust and for the amount of work involved in making one better could be better spent but I guess they(the prof.) will need to learn. At the moment I wonder if they will get a plane build for competition. The group has been slacking off and have only just now finished there trainer plane to learn to fly r/c on. They need to get to designing there comp. plane so they will have time to build it and test it.

Dana,

With this professor I believe you have encountered a characteristic found in many academics: A person educated beyond his or her level of intelligence.

Also worth noting is that tenure, while in general a real bad idea in my experience, at least keeps folk like this off the welfare rolls, which is where some of them would end up if left to their own devices and out in a world where productivity can easily be measured.

Try not to pound a flat spot on your forehead when the going gets really ugly.

At the least, your concerns about getting the motor run-in and working properly may be slightly reduced if they continue to fret about building test stands, static thrust, etc.

You sure are right. As I write he's talking about landing gear supention! He needs to conentrate on airfoil slection. One other thing he mentions is the relationship to full size airplanes. boy i hope i can find some good articles to set him strait that this is not at all like a full size airplane. It looks alike but the perameters are very diferent. I only wish the student in the team were more experienced with model planes.

>You sure are right. As I write he's talking about landing
>gear supention!

Well, that's not an entirely bad idea - the landing gear needs to be pretty darn tough to handle a 30 lb plane landing. But oleo struts are not in the plan.

>He needs to conentrate on airfoil slection.

Very minimal problem - if nothing else, I would do the analysis with a Clark Y or somthing similar. It's not going to get anything grossly superior for model sizes, and it's thick enough to build strongly without excessive weight. Anything significantly better in model sizes will also be significantly thinner, and therefore weaker and/or heavier.

I am amazed that 24 lbs wins. Is there some sort of takeoff distance limitation?

LAST EDITED ON Dec-03-03 AT 01:46 AM (CST)
 
he was thinking of shocks so the plane would not roll on take off. I think the rule is 200 feet for take off and 400 feet for landing. The other planes do use thin undercambered wings like the FFer. They sheet the whole wing and use some CF on the spars. I think they should be looking at the competition fai free flighters and gliders for guidence on wing design but they are so new to aero design that at the moment they are still trying to get the general idea.

[photo not recovered: Team09-15.jpg]

LAST EDITED ON Dec-03-03 AT 02:25 AM (CST)
 
I think the Selig (low Reynolds number airfoil) people have come up with one or two sections specifically for this event. I'd go with those, if they exist, and not bother with anything else.

Does the weight have to be concentrated in the fuselage? If not, the wing can be significantly weaker, as you can distribute the weight along the wing.

"Try not to pound a flat spot on your forehead when the going gets really ugly.

At the least, your concerns about getting the motor run-in and working properly may be slightly reduced if they continue to fret about building test stands, static thrust, etc".

I'm lucky. I'm not on the team, just helpping, or i would tell him what. Any way i'm ok. I just don't try to hard to change to prof. and concentrate my efforts on getting the students to see the real mechinics of model planes.

Come on Dan, Have a heart. The real world is not supposed to know that about us academics!

As I mentioned above, you will appreciate the Model Aviation article.

Come on Dan, Have a heart. The real world is not supposed to know that about us academics!
Jim Thomerson

Jim,

I hereby make a one-time exemption for you alone. You are, after all, a modeler.

Dana,
In the MA article I keep referring to, they also mentioned that you could also use a K&B61 (at least at that time). I am wondering if that included the new Twist-on Head version. I have read (RCReport) pretty good reports on that engine, especially its capability of turning large (read maybe "more efficient") props. Since the teams seem overly impressed by the manufacturer's printed engine specs, I am curious if anyone has ever checked out the K&B.

LAST EDITED ON Dec-03-03 AT 03:55 PM (CST)
 
They eliminated the k&b option because of the engine performace varing too much from engine to engine. To bad because k&b is the local company here in SoCal and we could have had the chance to hand picked our engine at the factory.