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Engine input for contest

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Engine input for contest

Old 05-01-2014, 03:08 PM
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I agree. The break in prop should have very little load and think of it as just a cooling fan while the .45 class engine has an easy time spinning something like a 8x6 at a slightly rich 2 cycle scream.
I like to use light wood props for break in just because it seems like the best option if you buy into this line of thinking.

Last edited by combatpigg; 05-01-2014 at 03:10 PM.
Old 05-01-2014, 06:48 PM
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I don't see the point of recommending Jett mufflers. They are great, don't get me wrong, but for $90 a pop they would be a considerable investment for the program. They make a lot of sense when you have a .46 and you need just that little bit more oomph, or if you are racing and the class you are in won't let you go any bigger on the engine displacement. The kind of program this is could use any engine currently produced; the teams would simply have to build planes that performed with them. Take the baffles out of the stock OS muffler and let the teams pick whatever props they want. The planes will be plenty fast and the engines will last a good long time provided the teams learn how to tune right.
BTW, tuning right is more than just peaking the engine on the ground and going a touch leaner. A properly tuned engine is peaked in flight in the leanest scenario. With the kind of unloading you guys are going to be doing, that could mean upwards of 1000 rpm rich on the ground. Unless you want to buy lots of replacement pistons and liners, I'd invest in some telemetry so the teams can walk their way up to that peak setting without getting overzealous in leaning out the HSN.
Old 05-01-2014, 08:27 PM
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I didn't realize they are $90 now.
I bought a used Sport Jett .46 [muffler and all] for just a few bucks more and it will do 150-160 mph all day with a $2 prop.
Old 05-01-2014, 09:21 PM
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lol dont buy a 60-90 dollar muffler because its too expensive but tell them to buy telemeter equipment. Now that funny right there.Stock engine with baffle removed is plenty fast. maybe to some. i think CP and I will agree that there is no such thing as fast enough and fast starts at 120+
A stock jett 46 will turn a APC 9x8 at around 17,000 with the red muffler on 15% fuel. Work it over and you will see 18,000.
Old 05-02-2014, 06:11 AM
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The telemetry idea wouldn't require a unit for every plane. They'd only need a couple to let each team take a testing day to figure out how their engines run in the air.
Old 05-02-2014, 06:43 AM
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I think we are pretty committed to OS and the likes because of the known availability and the reasonable cost. I think one ting you guys have helped us think through is that the challenge should not be so much about the engine but the design. if the engine puts out enough power, in terms of the contest it doesn't really matter if the planes are doing 115 or 130. Take the power you have and do the best you can.

Can anyone tell me the typical rpm gain by removing the muffler baffle?

Thanks!

Dan
Old 05-02-2014, 06:44 AM
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FYI, we use telemetry regularly.
Old 05-02-2014, 08:46 AM
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Originally Posted by why_fly_high

Can anyone tell me the typical rpm gain by removing the muffler baffle?


Thanks!

Dan
The gain is noticeable but not stupendous. The outlet stinger can be hogged out a little bit, too.
I'll guess that in this .45 size, OS has had 80% of the market in this area, maybe more.
It's interesting to hear the the ST .45 is the most powerful of the mass produced .45 engines. Over the years I've run into quite a few "SuperTigre's Forever" fans but have heard mixed reviews after ST went Chinese.
I had a ST .35 combat engine that "spontaneously fired up" a couple times just sitting out in the hot sun with some fuel inside of it.
Whenever working around any of these engines I grab the prop and hold it out of habit.+
Old 05-02-2014, 09:14 AM
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The gains from removing the baffle depend on the RPM you are running. The higher the RPM, the more gain you get. In my TT .46 Pro, which is essentially a copy of the OS .46 FX, I was running 14,100 on the ground and got to 14,300 by removing the baffle in my Kaos. That's with a 10x6 prop running 10% fuel. Watching the plane fly, I think the gains are actually higher in the air because the engine unloads a lot. So I think it's reasonable to expect 300 RPM in actual flight. With your planes, I would expect more improvement than that. So as combatpigg said, it's not a stupendous gain, but it is a gain and it's free. With more heavily propped engines on draggier planes, it doesn't help at all. I tested the same engine on the ground with an 11x6 prop and actually lost RPM.
Old 05-02-2014, 06:33 PM
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CP what i didnt get across to you is that the St 45 when compared to the other will turn higher numbers on the jett muffler. try one your self. you will be supprised how well it turns. The reason for this is St was first to run the 1/4 wave mufflers. Jett and Nelson both used this design until jett put a patient on the design. The ST 45 perfectly matches the ST/Jett/Nelson mufflers perfectly where as all the other engines out there have very wide exhaust openings in the case. MFG designed these engines to accept muffler that had the bolts go thru the engine case. if they kept the exhaust port small then the engine weight more. OS even put the E port on in the 5 o clock position in the sleeve yet kept the 90 degree outlet for muffler. very poor for tuned exhaust applications. sure they work but not as well as they can. You need a smooth transition for the exhaust to go in and out of the engine. The St does this well as it shows on the gains.
Old 05-02-2014, 07:50 PM
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It's interesting looking at the numbers on the Jett website to see the huge gains on an OS .46. It looks right to me here, I hope this cut 'n' paste job posts correctly. 16,700 on a 10-6 APC, the SJ46 ain't too shabby in the hp department.

[TABLE="width: 600"]
[TR]
[TD="bgcolor: red, colspan: 4"]Jett-Stream Muffler Comparison Data - Sport Jett .46
[/TD]
[/TR]
[TR]
[TD="width: 150"]Prop Size (APC)
[/TD]
[TD="width: 150"]Stock OS Muffler
[/TD]
[TD="width: 150, bgcolor: #ff9999"]Jett-Stream Muffler
[/TD]
[TD="width: 150, bgcolor: white"]Turbo-Jett In-Cowl
[/TD]
[/TR]
[TR]
[TD="width: 150"]10 x 6
[/TD]
[TD="width: 150"]14,700 RPM
[/TD]
[TD="width: 150, bgcolor: #ff9999"]16,700
[/TD]
[TD="width: 150, bgcolor: white"]15,800
[/TD]
[/TR]
[/TABLE]
[TABLE="width: 600"]
[TR]
[TD="bgcolor: blue, colspan: 4"]Jett-Stream Muffler Comparison Data - OS .46
[/TD]
[/TR]
[TR]
[TD="width: 150"]Prop Size (APC)
[/TD]
[TD="width: 150"]Stock OS Muffler
[/TD]
[TD="width: 150, bgcolor: #ff9999"]Jett-Stream Muffler
[/TD]
[TD="width: 150"]Turbo-Jett In-Cowl
[/TD]
[/TR]
[TR]
[TD="width: 150"]10 x 6
[/TD]
[TD="width: 150"]14,200 RPM
[/TD]
[TD="width: 150, bgcolor: #ff9999"]15,900
[/TD]
[TD="width: 150"]15,400
[/TD]
[/TR]
[/TABLE]
Old 05-02-2014, 08:09 PM
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Originally Posted by airraptor
CP what i didnt get across to you is that the St 45 when compared to the other will turn higher numbers on the jett muffler. try one your self. you will be supprised how well it turns..... You need a smooth transition for the exhaust to go in and out of the engine. The St does this well as it shows on the gains.
I don't doubt it, I haven't kept track of what is going on in the ".45 engine world" in years...not since I was a steady club member. I didn't know ST pioneered the tuned muffler...are you talking about their old muffler design that you could swing to any angle..?
I've already got too many .45s to buy a ST .46 but it's good to know they are a hot engine if I ever get involved in some horse trading.
Old 05-02-2014, 08:46 PM
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MJD, as far as I know, Jett is the only engine builder who furnishes real world X PROP = X RPM data instead of the useless HP figures.
Back in the day when this was "The Jett Engine / Diamond Dust / Q500 ARF Forum" , there was so much praise for not just the power, but how easy they are to tune, how consistent, wear resistant, etc....that my curiosity got the better of me when I had a chance to buy a good used one. It really is what everyone says and it delivers what Jett says it should.

Last edited by combatpigg; 05-02-2014 at 08:48 PM.
Old 05-02-2014, 09:19 PM
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i will see if i can find it on tower. St made a Q500 muffler its tuning is very close to the Jett black/Q40 muffler. much cheaper though but they didnt last more than 30-40 gallons and then would fall apart. The jett mufflers seem to be good for 50 or gallons on normal runs. if get them hot then much shorter time.

here is the link on Tower's site.
http://www3.towerhobbies.com/cgi-bin...?&I=LXFW05&P=7
Old 05-02-2014, 10:14 PM
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$40 is well worth it. Is there a way to prep the muffler..[like a high temp solder. or support the far end] to keep it from coming apart...?
Running as hard as a Q40 is pretty extreme for an unsupported muffler.
I keep saying that I'll try this idea some day....make an upper cylinder support that ties to the firewall.
Old 05-02-2014, 11:22 PM
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I don't recall ST being the first with the tuned muffler. If they had, I'm sure I would have a couple boxes of them in the basement. The Magic Muffler was developed in Australia by Ian McCaughey, imported by Condor Hobbies a very long time ago (mid-80's). The first engine that came with an attempt of a one piece design (one piece until you ran it a while) was Rossi, but when Nelson put it on his early Quickie motors in the early 90's it was pretty well developed. To the best of my knowledge, the magic muffler was never patented, so it was considered "public domain" for future designs. Dub Jett developed a spiral can version that is slightly down in power from the longer pipe versions. I had suggested folding a magic muffler to Dubby in an email back in 2000, but his implementation was very clever (I had no practical idea how to build it) and he received a patent on the design around 2004.

Viewing the presentation videos of the Orange and Black teams was very enlightening. A fair bit of analytical analysis by the students for their preliminary designs, CAD design, CNC machining of molds, learning to do composite layups, and assembly of rather impressive models show a lot of dedication by all involved. The tools available to the students now make me jealous, thinking back to punch cards to run simple programs on the old IBM 360 we had back in the 70's that filled a room. It took me a week to plot an elliptical wing and 10 or 12 ribs with a CalComp plotter using a program I wrote 40 years ago. I think the turn time was about 12 hours, so mistakes were costly to the schedule.

Even the HS groups are doing very good builds, and this might boost engineering enrollments further down the road. I noticed Dr. Larry Kruse in one, who grew up about 11 miles down the road from me. I think Larry has retired from running a university, but has not lost the love of teaching. I have done programs with HS students a few times with groups from companies that I worked for in the past. It's tough to herd cats but not too different than working with HS students on a project. One group was a business group - fairly easy because the concept of making money is near and dear to teens, but the other was to build robots that could perform certain tasks. Very tough, because the idea of limited time and money didn't seem to register (same as congress).

Anyway, if there is a point here, try to get some kind of program going with the youth in your area. Most modelers are getting old, and the problem solving involved with actually building a model airplane provides hands on experience that seems to be sorely lacking today.
Old 05-03-2014, 08:04 AM
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Originally Posted by HighPlains

Viewing the presentation videos of the Orange and Black teams was very enlightening. A fair bit of analytical analysis by the students for their preliminary designs, CAD design, CNC machining of molds, learning to do composite layups, and assembly of rather impressive models show a lot of dedication by all involved. The tools available to the students now make me jealous, thinking back to punch cards to run simple programs on the old IBM 360 we had back in the 70's that filled a room. It took me a week to plot an elliptical wing and 10 or 12 ribs with a CalComp plotter using a program I wrote 40 years ago. I think the turn time was about 12 hours, so mistakes were costly to the schedule.

Even the HS groups are doing very good builds, and this might boost engineering enrollments further down the road. I noticed Dr. Larry Kruse in one, who grew up about 11 miles down the road from me. I think Larry has retired from running a university, but has not lost the love of teaching. I have done programs with HS students a few times with groups from companies that I worked for in the past. It's tough to herd cats but not too different than working with HS students on a project. One group was a business group - fairly easy because the concept of making money is near and dear to teens, but the other was to build robots that could perform certain tasks. Very tough, because the idea of limited time and money didn't seem to register (same as congress).

Anyway, if there is a point here, try to get some kind of program going with the youth in your area. Most modelers are getting old, and the problem solving involved with actually building a model airplane provides hands on experience that seems to be sorely lacking today.
Also keep in mind that the OSU college teams start mid January and we are flying original composite planes the first of March. That is complete design, tooling, and fabrication. The students spend A LOT of time in the lab. If any of you have college engineering contacts and want to get a team involved just let us know.

Dan
Old 05-03-2014, 11:08 AM
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Hey Dan!

I just had the privilege of competing and being the "Team Pilot" for a group of FIU Seniors working on their BS. There was one woman(25 yr), and two men(29&22). Claudia, the 25 year old woman, is already hired at NASA to work on the next big rocket that goes to Mars. OK!! This event was sponsored by SAE International/Lockheed as an Engineering contest for these future Engineers. First, these kids, I call them kids, due to being twice their age, were for a thesis for a Degree, were required to calculate the design, design the plane and then design the internal structure of the plane for maximum payload. All planes were electric with a 1000W limit of power from 4 cell battery. Lockheed threw a monkey wrench into the contest, by distributing and requiring all planes use a "Power limiter" . Problem was, there were no instructions to the limiter on how it reacted with the different speed controllers. I am NOT an electric guy, but due to the limiter, it would read the "spikes" of the power system and limit it to 700 Watts. This issue was truly more then half of the competitors' issues. We, our Team, only flew 2 flights out of 5 Flights or Rounds. So, FIU did quit well.

Now, to answer your question about the glow engines. In an event, glow can be temperamental, if not properly tuned by the pilot/owner/mechanic. At the SAE contest, Byron Fuels sponsored the fuel, so that all had an equal glow fuel, or a given in Engineering terms. Problem is, those who knew how to tweek a tuned pipe, which all glow engines were running, successfully every flight. Most would tune them to what they though was correct, only to have it go rich in the air, or over tune it to the lean side. Something that can't be heard, and only seen on a tack. Took me a couple years of proper tuning of a glow tuned pipe to see the right results. Not something learned by a local pilot helping those students that don't have pilots. So, due to the temperament of a glow engine, the owner, how it was broken in at the beginning of it's life, engine for engine it is hard to compare.
That being said. I have had a OS .46 engine and even the Thunder Tiger Pro .46, best engine ever, on the same Quickie 500, and switched it out with an OS .55. The .46 would kick it's ass in speed!! So, as a judge, contest director, and wanting to make it fair for all competitors, please consider these suggestions and observations.

I encourage any of you that are asked to help as a volunteer r/c pilot for SAE/Lockheed...........do it!! Totally fun!

Last edited by RCFlyerDan; 05-03-2014 at 11:17 AM.
Old 05-03-2014, 05:46 PM
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Also keep in mind with your thoughts dan true the 46 would out perform the 55 but the quickies were under four pounds. I think the 55 should out run it but would have to use a different prop like a 9x10.

high plains thanks for the update but I still think the St g-500 muffler was first. when did the St 40 Q500 engine come out?

CP those St mufflers come apart on the inside. the outer muffler casing is crimped on and you have to cut it off forward of the crimp to remove it.
also not knocking Jett engines either as they make pretty good power and will last a pretty long time. Jett best sport engines are the 35 and 56. these two are bench mark engines. The 35 does need its rear bearing replaced often though and the rod may not last long if ran over 21,000 on the ground. What i mean by that is the rods life span of is cut by 25% or so. it will still last around 7 gallons.
Old 05-03-2014, 07:29 PM
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The Jett .35 doesn't hold a candle to the Nelson .36 Combat Special though. Not even debatable, it was painful to watch the Jett .35 try to run against the Fox and Nelsons. A couple guys tried the Jett.35 and it didn't even measure up to the bone stock $80 Fox Mark 3, 4, or 6 engine.
My OS .32 made a better showing than any Jett .35s that I've seen.
If you are looking for the most bang for your ".35 sized buck" the Nelson .36 is still miles ahead of the rest.
Like when rating the heat of chili peppers there is a group that are pretty hot, but then you see habaneros rated in a seperate universe.
If you see a Jett .35 running with nothing else to compare it to it might seem impressive but there is a good reason why this engine never won even a 7/11 burrito at any fast combat contests in the USA.

Last edited by combatpigg; 05-03-2014 at 07:36 PM.
Old 05-03-2014, 08:09 PM
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Originally Posted by HighPlains
Anyway, if there is a point here, try to get some kind of program going with the youth in your area. Most modelers are getting old, and the problem solving involved with actually building a model airplane provides hands on experience that seems to be sorely lacking today.
Not exactly the same, but for a few years I did one day build and fly workshops in grade 4 and grade 6 elementary school classes.. on contract with a couple of local school boards. It was mostly very rewarding - the kids, whether they were enamored with aviation or not, were nonetheless doing something a lot more interesting to them than the daily fair. I remember one particular late spring day in downtown Toronto, beautiful calm weather, after lunch and the glue has dried.. Out we went with rubber lube and a handful of 5:1 winders. A few minutes later while I was helping one student, I heard a shriek and turned around.. a grade 6 girl was running down the length of the schoolyard, long hair flapping, chasing her Super Delta Dart as it steadily chugged up to 20, maybe 25 feet altitude before slowly freewheeling down again an impressive distance down the ball field. But while she was running she was yelling "oh my god, oh my god, I can't believe I built it myself, look at it flying.." bla bla bla down the field with a huge happy grin in her face. That was most satisfying.

The biggest problems for the kids of course were using simple but unfamiliar tools, including singe edge razor blades, and following instructions, and exercising a new concept called "patience".. But I had a whole thing down and it worked out fine, and of course at recess the trusty CA came out and I would sweep the class "helping" as necessary..to keep the ball rolling, as we were using aliphatic glue.

I would always fly a pennyplane or mini stick or other indoor model while talking through the theory of flight. Blew their little minds.

Other than the hassle of driving through rush hour traffic downtown from 30 miles north of the city.. the workshops themselves were generally a lot of fun, and I think the kids got a lot out of them.
Old 05-04-2014, 05:58 AM
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high plains thanks for the update but I still think the St g-500 muffler was first. when did the St 40 Q500 engine come out?
I had started racing quickie in 1980, but had switched to Formula One in 1984. At that point in history, quickie was a local event and F1 was a national event. About that time, the Rossi had established dominance in quickie, a position it held for about 4 or 5 years. But there was a short flurry of engines developed around 1990-91 by Fox, ST, Webra, and MVVS that pushed the Rossi aside. It was a very short lived period however, because after the first contest a Nelson quickie motor entered, nothing else even came close. Within a year, the course times were dropped by 20%. This did come with a downside, a lot of structural failures occurred until the higher power and speeds was adjusted to. But it also made quickie interesting again. There was also another interesting phenomena I noticed. When the Nelson came out, all the known engine cheaters dropped out of racing. Quickie also became a national event with the advent of the Nelson/Jett engines.

When you can take an airframe that was originally flying at about 100 mph with a K&B 40, and develop the setup under the same rules to 180 mph, you have made a lot more power, along with huge improvements in airframe drag reduction and very good props.

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