It problably sounds ancient but I just bought an ol NIB DF engine (OS 77) for my Byron F 16. I had conflicting statements about the power delivery for that engine using the Byrojet system. Some said the .91 would be a must upgrade(from a person selling a .91) and another who flew a Byron F 86 with the OS 77 and found the engine to be flawless. Yet another said his Byron F 16 was as fast with the 77 as it was when he upgraded to a .91.
I am opting to stick with the .77 and keep it simple on my beginner level. How do I go about knowing and tuning this engine for max RPM and how long or what distance the pipe should be from the head. Ive heard 10.5 inches from glow plug to Tuned pipe end, but that could be just something I had heard wrong.
Is the old method of pinching the fuel line a good method? In addition to that I have not yet invested in radio with more than 6 channels and wanted that 7th to set mixture. I came up with putting the mixture control on the retract servo arm and with gear down =max leaning for power on rollout and climb and on return it would be maxed for that just-in-case-go-around. In flight with gear up it will be rich but not so rich to be detremental to performance but rich enoung for longevity of the powerplant. That can be adjusted only on the ground by setting the pushrod position on the mixture control arm.
Some input here would help a great deal and hopefully be enough to get my F 16 in the sky.

Tuning ducted fan engines is almost a lost art. During it's heyday, the OS77 was definitely a workhorse. I still run a bunch of 91s but, obviously, none of the "numbers" in my notebook will help your 77. With one exception, all of them have been massaged by John Ackerman of JFA Engines [see link <http://rcboat.com/antjfa.htm>] and I'm pretty sure he could get you in the ballpark with some good tips if you contact him.
Fwiw, the 91 package will give you more static thrust for sure and that would be a good thing on takeoff or if needed for a blown approach and you need a go 'round.
I would NOT recommend configuring in-flight mixture control in the middle of the setup you describe - it needs to be on a dedicated channel so you can use it for what it was intended for: IN-flight mixture control. The difference in cost of a good 8- or 9-channel radio (compared to a 7) it not that much; certainly less than the cost of dorking up your jet if you can't get out of a lean run and deadstick... the F-86 is not exactly a glider.

Mike

I would have to concur regarding the inflight mixture control, this is a must and needs to be on a separate proportional channel. With a 6 channel radio, you should have a knob for flaps. The Byron F-16 doesn't need flaps, so spend just $40 more and get an inflight needle valve assembly. Adjust it in such a manner that you have max power for take off, and then after rotation, dial it back to where you hear an audible change in rpm. With this audible change you should see a nice smoke trail blowing out the back. If you see smoke, the engine is getting the lubrication in needs. This is especially important with the Byron's configuration, since there is no fan air blowing over the head.
Of course, make sure you use a fuel with 22 to 24% oil content, my preference being a touch of castor to mostly synthetic. The castor goes to the hotspots, and the synthetic takes care of the rest. The combination of good oil content and slightly rich running during flight will combine to give you longer life and will greatly reduce the chance of shearing the crankpin or the lower end of the conrod, which is in my experience where most DF engines fail.
Other thoughts or opinions on my opinions?

Regards,
GPB

good advice here. take your time setting up the low end mixture as well. I like to set mine up so they will idle a full minute plus and be able to throw the throttle up without hesitation. for fuel I have always run a 10% nitro 11% castor 11% synthetic. too much oil and the low end gets hard to set.

on the high end let it hit the pipe and go in a bit more. the byron is not a speed demon so wrenching in on the needle is only going to shorten the engines life

for pipe I'd contact top gun www.tgajets.com for a shorty or quiet pipe. these are at a preset dimension for the 91, but should work for the 77.

if you come across the opportunity to do it over I'd get the 91 just because they still make them and parts and accessories are readily available. the 77 has been out of production for probably 10 years.

I hate to bring this up, but the OS.77 connecting rod has been known to fail and most people that used to run them, replaced the stock rod with an aftermarket rod (no longer available).
Some people got away with running the stock rod in a Byron, but it almost always failed in a Dynamax. I knew a couple of guys that broke 3 rods in one day and they were in a Byron powered Regal Eagle. There was a guy (Col. Thacker maybe) that was modifying the stock rod and getting it to work without failing, but I wasn't using .77s by that time and so I'm not sure what he was doing.

As far as inflight needle, I agree with what's already been posted. An inflight needle is more important than flaps or flaperons. The Byron F-16 doesn't need either one. In fact mine acted squirrely when I tried flaperons so I went back to ailerons.

According to the Byro-jet Tuning instructions you should tune the pipe with a measurement of 11 3/8" from the glow plug to the largest part (diameter) of the pipe. These specs are for the #4 or #5 tuned pipe.

Good luck.

UH... I am still waiting for my maiden flight on my JHH A-4, but I have run the OS-77 (Dynamax) and it runs flawlessly-

I am running Wildcat 10% and the transition is smooth and quick-

The Byron F-16 is bigger obviously than my A-4, the A-4 from JHH was designed around a 45 sized DF engine like OS-46/Turbax or K&B 7.5CC, so I may be able to get away with it-

I have flown a TGA F-15 (Byron) and Y/A A-4 (Ramtec) both had 91's but out of 3 total flights I had 2 flameouts, and guess what--- I did not have in-flight mixture!

My DF experiences have been brief but I always fly what I have got, and smile ear to ear the whole time...

Keep us posted,
james

Regarding the con rod failures of the 77, I seem to remember reading Col Th's articles in RCM mentioning a lack of lubrication. I believe he used sandpaper wrapped around a suitable sized dowel to increase the ID of the end just a tiny bit. Any one else remember the dimensions? I'm a pattern flier, so I never ran DF's, just that I happened to remember the article. Hope this jogs someone's memory so they can help out.

Cheers,
Ken

Col Thacker recommended a clearance of .003" on the crank end of the rod. To get this, he used 600 grit sandpaper wet with oil rolled up or on a dowel to gently open up the rod end. He also said that a snipet of a page from RCM was about right for a feeler gage to judge the clearance.

Here's another way: wiggle the crank back and forth at either bottom dead center or TDC and listen for clicking/ticking sounds. If you hear them, you probably have good clearance. No clearance = no lube = soon no rod. Many folks have freaked when they hear these ticks as they think their engine is defective but acftually it's the best sound a DF engine can make.

Use the mixture on a slider or knob on it's own channel. Your flight should go something like this: power up & start rolling, adjust for optimum mixture for T/O, rotate & T/O, gear up, richen mixture slightly. After a minute or so, adjust for optimum. As fuel burns off, maybe richen again to prevent leaning as the tanks run down. Fly this setting through landing. Sounds unnatural to adjust mixture on T/O roll but quite often, what you set in the pits, or readjusted to after the last flight might not be quite right as the plane accelerates particularly if you got it touch lean. Fly the smoke trail and learn what your airplane likes for a setting. There's lots of threads here on RCU about that.

Wow. Thanks alot for the input. I was originally going to dedicae channel 1&6 for my aerilons/flaps. I have been hearing that flaps are not a neccesity in the model and thata seperate servo on channel 6 (proportional knob) is the way to mix fuel in flight.
As it is I wanted to keep it light but since I modified my F 16 for servos on each aerilon (mounted in the fuse) and a digital servo in the tail for elevator. (I didnt really like the nyrod's) I did leave a nyrod for nose steering and rudder.
As far as my engine I may be ok if I keep the weight under 12.5 lbs and since the plane has no drop tanks or missles, the airframe is pretty clean. Im not sure what off-the- shelf fuel to use. I broke the engine in with coo, power 15% synthetic. I was not aware of the science involved in fuel for a DF engine.
I am hoping K&B will make DF engines again and want to purchase something bigger I can afford.
All the articles I read from "older" RC mags say this powerplant is sufficient to move the F 16 , heck they used to use a .61 and that worked. Well Thanks for the advice on the mixture control( I already have the remote arm) and will use channel 6 and just make those aerilons work on a "Y" harness.

Back when I still ran .77s I started out using Omega 5% and then switched to Sig Champion 5%. I ran OS.91s on the Sig and then Wildcat Jet-A 5% and now I use Power Master Ducted Fan 5%, mainly because it's easier for me to get. Although I always heard that 5% was the max nitro to be used in the OS motors, I have heard a lot of guys say they use 10% with good results (as Patf mentioned). We had Alex Cornish-Trestrail (man I hope I spelled it right) come to Bomber field (from England) several years ago, with a twin OS.91 powered Sea Vixen that they flew all weekend on FAI (0% Nitro) Nitro is alot more expensive over in England and FAI fuel is more common. They burned up almost a whole case of fuel that weekend.

Hello,

About in flight mixture control.
I've been told by experienced R/C DF modellers that it was not mandatory, provided that u use a catch tank which remains full during the whole flight.

What do u think ?

The hopper tank helps, and you should always use one, but you still need the inflight mixture control. The hopper really doesn't quite even out the fuel pressure over the course of the flight but it does keep air from the tanks from reaching the engine. I could always tell when the tanks emptied and I went on the hopper only as the mixture would always richen noticeably in flight. Towards the end of the flight, even with partially full tanks, you will get leaning of the mixture as the fuel pressure head lowers. If your airplane fuel system is perfect and if you're lucky enough to hit the mixture right on for every flight then go for it, but the rest of us have to use a mixture control. It was always normal to make at least two adjustments during the flight. If nothing else, it will save yourself the anxiety of a lean run, or an overly rich run which won't give you power to climb out.

BTW, I never had much luck with the OS.77. I never met a .77 rod that didn't break, but that was before I put a mixture control in the airplane and figured out the clearance problem. The .91's have the clearance issue fixed.

Thanks again for the help. I have an inflight mix valve and plan to use it. I wont be overly aggressive with the leaning only for takeoff's and landings(keeping it a little richer on landings). I think once in flight and a noticable smoke trail is visible I wont be leaning too often to "burn "down the deck at 5 ft for ooohs and ahhhs.(That may come later)I just want dependability and some longevity until the next Jet project grabs me.
Its my first jet so I think I picked a decent airplane to start and a somewhat decent engine if I am lucky and careful all at the same time.
By the way, I want to go with a 2 tone grey paint and was surprised to find that if I did not want to spend a load of $ and do it cheap and is still sharp looking and durable.Paint with Krylon spray paint and use lustercote clear to seal and fuelproof it. Sounds feasable and is a heck of alot cheaper than PPG at the body shop. Ive seen a few planes with this type of paint finish and while it is definately the dull finish I want it is nice enough to pass off as a good paint job.
Any thoughts on this? It has to pass my old motorcycle racing rule:80/80 rule-as it whips by the turn at 80 mph from 80 ft away she looks just fine!

Just some random thoughts:

Even with the Byron F-16, you will eventually get fuel & oil all over the inside of the plane which will eventually seep through the glass fuse to your paint from underneath. The first blown exhaust coupler will start this as will other things. The big hole in the bottom under the engine helps to reduce the problem on this plane. Some folks paint/fuelproof the inside of their airplanes as well. Besides, it looks nicer but it's not mandatory.

The Byron is no speed demon and it takes the right engine setting to get off and climb out comfortably.

The engine doesn't necessariarly need to be richer on landing. What it needs to be is set so that a throttle jam gets you max power immediately after being at idle for awhile with the fuel tanks close to empty. Your first high sink rate landing will clearly demonstrate this. Check your idle and throttle response with nearly empty tanks and the nose up.

The landing gear on the Byro F-16 takes a lot of abuse. Make it strong.

Have fun!

Wow, more great help. I think I will definately spend a gallon or two on the test stand with the engine getting the tuning right. Right now the transition is set as close to perfect as I can get it. I just need to adjust that high end mixture for optimum power and remember to enrichen in flight and se that smoke trail. I was not looking for a screamer of a jet, it will sure be faster than the WW2 warbirds I have been flying. My long didtance goal should the plane see long life is a turbine retro-fit. Wren makes a nice turbine kit with the right amount of thrust and have some input and articles on how to prep the model to withstand the high heat generated by these engines.( I believe one was a pipe-in pipe system that kept the hot inner pipe from contacting and melting the airframe. ) Well see about thatif it comes.
As for the input on the paint, I will use a fuel proof primer coat (Lustercote) before applying my Krylon. Krylon has a god blend which atomizes evenly, dries to a uniform finish and dries fairly quick. I plan to wait 24 hours after applying paint and scuffing it with emory cloth to accept Lusrercote matte clear.

Just get it close on the test stand and then go to the airplane. The fuel tank & plumbing arrangement in the airplane will likely cause some final adjustments anyway. Plus, your engine heating on the test stand will be different than the airplane as well.

I figure that would ne nessacery, since the head is "up"on the stand and the fuel tank is low and it will be opposite in the plane. I just hope it is not too far off and I can get it as close as it was prior to installing.
I plan to "ground test" the model on a long paved open lot near me without the wings for assurance it does'nt get airborne. Ill try the mixture control and get a feel for its ground acceleration to gauge how much real estate I'll need for T/O and taxi it around for a feel of the steering and see if I get the "Byron Boogie" and cure that as well.

Take care of the cars !!! That reminds me of some videos of some crazy japanese people flying their pusher prop jets from populated roads ! Have you seen them ?