ameyam

I am currently flying a GP Reactor 46 with a 55AX. Besides the fact that I am having problems with the engine (which I will resolve in due course) I am also thinking that the engine may not have sufficient power. So I am considering putting in a FS91-SII which I have. I know the 81A is ideal but its too expensive, in fact the 91 is actually cheaper. My concern is the weight- the 55AX weighs 18.92oz or 525g whereas the 91 weighs 24.2oz or 686 g. If you think it out, the difference is only 150 grams or so. Will it really make a big difference to the way the airplane flies. I havent got to 3d-ing the Reactor as yet due to the engine issues and because I didnt get enough time with it last season. problems with the engine are also partly due to the same

Ameyam

ThumbSkull

My Feedback: (57)

I would work out the likely fuel delivery issues with the 55AX. It's a great engine for 3D up to 5lbs. total.
You will add almost half a pound by the time you get an appropriate size fuel tank with the 91.

If you need a little more out of the 55AX, I highly suggest the macs 6720 or 6724 one-piece muffler.
With it you lose 2.1oz and gain a significant amount of power without harming the midrange throttling.

Put an OS F plug in the 55 and carefully set the LS mixture screw for no RPM change in the idle when
you remove the glow power. Adjust the HS needle with the nose up and about 100RPM below peak.
Have someone help you hold the aircraft while you do this.

Be sure the prop is balanced and I suggest a Xoar or JXF 13x4 or an APC sport 13x4.

The next issue with light airframes is fuel foaming at certain RPM's due to mechanical resonance.
Be sure the tank is in foam rubber and is allowed to move enough to stay still while the airframe vibrates.

TruBlu02

Ameyam,

The Reactor has a very Light wing loading and will handle the extra weight of the 91 just fine. I used Saito 82 in mine for awhile but ended up switching it to electric power. My batteries are heavier than I planned and I know the model is heavier now with the electric setup than when it was gas. The extra weight really does not seem to bother it much. It still flies as awesome as it always has.

As for the 55AX what problems are you having with it? do you have it inverted or is canted at a 45 Deg angle like is shows in the manual? I have used the 55AX for awhile and it is great motor and I have never had a single issue with reliability. All the ideas listed by Thumbskull are what I would suggest as well. I wouldn't give up on the 55 just yet.

ameyam

Well, like I said, I will thrash out problems wih the 55AX first. Its a brand new engine on this airplane- I already lost one Reactor with and older unreliable engine.

On Sunday at the field, I had problems keeping it running. With the original #8 glow plug, I first tried to "run-in" the engine as it hasnt been run for nearly a year. When I gave throttle it cut. After many tries I noticed that engine seemed to be turning over with hardly any compression. There was also a lot of trouble starting it

I consulted the experienced hands on the field. First I was told to replace the glow plug. I didnt have a spare so club members gave me a used one. It started and flew ok but after a fer minutes it seemed to be running exceedingly rich and I landed in the nick of time. Then I gave up and left. After reaching home I replaced with a brand new plug. It ran fine but exhausted black oil meaning something was loose. I checked the bollts of the cylinder head for tightness. They were quite tight but did turn a bit. I also checked that everything else was tignt and it was. I still got some black oil initially and then it began to get less black after a half a minute of running. I was only running at idle and at 2.5-3 turns of HS needle due to noise issues. Noted that the black oil is not coming from anywhere else. Interestingly I now have compression again but I had tightened everything before I put the engine in last year.

I will take it to field again and try on Sunday, then I will take a call. I am running a 13x4 K series MAS with Klotx-100 based fuel with 20% oil and 10% nitro. There is a lot of rumble at idle- you can actually hear the tail surfaces buzz due to vibration. I have balanced the prop, still I even tried a 13x6 S2 that I know is balanced and I still get the vibration at idle. It goes away with a couple of clicks of throttle

Ameyam

ThumbSkull

My Feedback: (57)

I hope you don't have one of the few 55ax's with a bad liner. Black in the exhaust is usually aluminum wear.

ameyam

Actually, I have run it in already last year but not fully. About the time flying was stopped, I had one day with a number of deadsticks following which we ran her rich for a couple of tanks again and then had one day with no dead-sticks. However, I have not put her vertical yet so I am not sure of the engine.

Before heading to the field this year, I packed the tank with foam as far as I could reach and balanced my prop. I have a APC 13x4 but I dont want to risk it till I can get the thing running properly. However, it may be a good idea to try and see whether it improves vibration at idle- I will give it a try.

How do you identify whether my engine is one of those with a bad liner?

Ameyam

ThumbSkull

My Feedback: (57)

Here is one of a few threads about it. You have to pull the head to see it but post #20 shows a liner that peeled.
[link=http://www.rcuniverse.com/forum/m_8759145/mpage_1/key_/tm.htm]http://www.rcuniverse.com/forum/m_8759145/mpage_1/key_/tm.htm[/link]

To identify the peel, you will see the nickel peeled off the brass. If that's not it then it's another problem.

ameyam

I dont think its a liner issue. Remember, this engine ran for over a 3-4 weeks without issues. Yes, we never completed the run-in procedure properly and we are still running it rich now. And yes, we did keep having deadsticks till before the break, but this is the first time we had black oil coming out. I did seem to feel no compression but only with the engine very hot and that too intermediately. I have been recently only flying the FS91SII so I am not sure whether it wasnt just a feeling.

When I was on field this Sunday, I finally flew with a second-hand glow plug. Till that time I never had the black oil problem but again I didnt have a stable running engine. Then, with the mentioned plug that I had borrowed from someone, I had two deadsticks when I applied throttle just before take-off. After taking off, I noticed that the engine was going slowly rich. Finally when I landed, I was at full power on the stick but not on the engine. When I removed the plug and connected directly to the glow booster, the coil wouldnt even glow. The engine started fine with a brand new plug except for the black oil. I think that this is a glow issue, but I will only know when I run it on this weekend

Ameyam

ameyam

Well, I put the APC 13X4 on the airframe and I have a observationa to make

1) There is no reduction in the vibrations at absolute idle. However, as with the MAS prop, they go away with a click or two of throttle

2) It didnt start till I applied the starter even after choking (as always, I had completely after burned it on Sunday). After filling a little fuel, I choked it with a thumb over the carb till I felt fuel on my thumb inside the carb. But even then it didnt start with several flips of the chicken stick. Once I applied the starter and it had run for a few seconds, I was able to hand start it. Think this is characteristic of the engine as it is mounted at 45deg from the inverted as per manual and so any fuel after choking doesnt stay in the carb but drains out. I recollect having this and the reverse starting problem last year as well

3) I didnt get any black oil in the exhaust even after momentarily running at full throttle (jerking the throttle at full an back quickly, this did not cut the engine either (as it had done on Sunday). However after running for a few seconds at 2.5 turns of HSN I got a lot of brown cooked castor as seen in the attached images I ran the engine for about a minute so as not to irk the neighbours

The engine had sufficient and normal compression

Any suggestions?

Ameyam

rcflip

No offense but running an F plug in a OS55AX is rather silly, it would widen the tuning sweet spot but I think you would be far better off learning to properly tune the engine.

ThumbSkull

My Feedback: (57)

We are in the 3D forum where the sweet spot needs to be wide with all attitudes of operation.
Even perfectly tuned, I prefer the F plug in 2-strokes that 3D.
It's good insurance that the fire stays lit.

ameyam

Actually, as I see it, the F-type plug retains more heat as it has more platinum required for 4c engines. However, I foresee two problems- one, it will increase the compression by reducing cylinder volume and two, more importantly, it could cause pre-ignition- since it retains more heat, the fuel-air mixture would fire before the piston reached TDC. The second effect would be more pronounced in my country where summer temperature will rarely drop below 30 Deg C and it will actually cause more vibration and potentially engine damage. Thats why we exclusively stick with the #8 plug for 2c engines

Any comments on the color of oil and my other observations though?

Ameyam

TruBlu02

To me that looks alot like the oil that accumulates from the exhaust of any 2 stroke Glow motor. My 55AX I am using right now in a leaves a pretty good trail of oil on the tail and it runs without a problem. If the oil still seems excessive I would consider trying to lean it out some more. Have you tried running the engine wide open throttle on the ground, then (use a buddy to help) pick the airplane up and point the nose straight up in the air. If it cuts out then it is to to lean. If not then it is close but I would consider leaning the motor to peak RPM then backing it down a couple clicks rich.

As for the starting issue the 55AX was designed to be started with an electric starter. I checked the manual for mine and it says it as the first step in the start page. For the first start of the day I always hit mine with the electric starter. After that it will flip start every time. There is nothing wrong with your motor in that respct.

The vibration is normal especially with the light airframe of the Reactor. At low the idle the motor is going to vibrate. All the 55AX's I have had do it at low idle but as you noticed it goes away after a couple clicks up on the throttle.

ThumbSkull

My Feedback: (57)

I will work on the answer part by part.

Yes, and this prevents flame outs on 2-strokes.

It does not reduce the cylinder volume. I have seen no indication that pre-ignition is caused by using an F plug.

That just looks like a bit of collected lubricant that has come out when the engine warms up.

It seems like you have been reading a lot of internet mythology about two strokes.


I will post a video (for the audio) of one of my 3 55AX's on a 5lb. profile so you know that I am experienced.
No one at the field to video me but this shows what a good running and good throttling AX55 sounds like.
It has a macs one-piece #6724 Scotsman muffler.
AUW of this plane is 5lbs. Running 30% Nitro with an extra head shim and an OS F glow plug. Spinning a Xoar 13x4 wood prop.
This is just to show that I know what I'm talking about and not just copy/pasting someone else's mythology.

Look how the airframe responds to throttle input at :40 seconds in. Winds blowing about 15-20mph
[youtube]http://www.youtube.com/watch?v=kyAJJ6970VI[/youtube]

ameyam

TruBlu02,

I normally do that (the nose up and then quickly down) test with all my airplanes before I takeoff. Usually, my mentor helps out with the engine tuning, my ears are getting there. Problem on Sunday was that my mentor wasnt there and I could'nt keep it running long enough to do that test. Behaviour of the airplane during that breif flight was consistent with a expired plug as I found out afterwards (it went richer and richer during flight, was quite lean at take-off)

Yesterday I ran the thing in my appartment. I did go to full power but didnt hold it there so as not to invite the neighbours. Usually, if its not set properly and you jerk the stick to full and then bring it back down it will cut somewhere in between. But it didnt do that yesterday, so it gives me hope that all is well- it was only a glow plug issue on Sunday.

Thats oil all right- I was running at 2.5 to 3 turns of needle so its very rich. But its quite dark brown -thats all I wanted to point out.

ThumbSkull,

You are right about the mythology part, but recently I have had so much bad luck with engines that once it gets into my head that there could be a engine problem, the doubt is difficult to dislodge till I fly the airplane again. May be my obcessive-compulsive tendencies at work. Remember, I have already lost one Reactor to a deadstick in hover (with someone else at the stick)

I know from previous posts that you are experienced, I never doubted that. My concern with the F-type plug is that in our hotter climate, there are more chances of pre-ignition. OS must have thought of some reason otherwise they would recommend and sell F-type plugs in 2c as well, wouldnt they? None-the-less, its a good suggestion to be used if I dont get the engine problem resolved. BTW, I really want a profile like you are flying, will be ordering the Mojo soon

Ameyam

ThumbSkull

My Feedback: (57)

Our summer here runs 40-43C with anywhere from 0-90% humidity.
The same setup works great in those conditions as well with a minor change to the HS needle.

Platinum is what makes glow plugs expensive so the mfg's put as little as possible in them.
While a lot of the stuff written about glow plugs being so critical to match perfectly the engine and fuel is true,
it's true mainly for high compression engines which the 55AX is not.
I put in an extra head gasket on my 55AX's so I can run 30% fuel (the same as my YS and Saito 4-strokes).
You would not need the extra head shim for 10-20% fuel and the F plug.

Since Webra is out of business now, I don't think there is a better choice for a 4-5lb. 3D machine than a 55AX.

The plane in my video is a kit from [link=http://www.3dplanekits.com/]http://www.3dplanekits.com/[/link] called a LamYak.
It has a laminar flow wing with no wing rock tendencies and excellent stalled flight characteristics.
It also comes with a building video that is great if you are a first time builder or even an experienced one.
[link=http://www.swanyshouse.com/mojo/mojo.aspx]Paul Swany's [/link]kits are also excellent fliers, all of them.
I like 2-strokes on my 40 size and 4-strokes on my 60 and larger size 3D machines just of personal preference.

rcflip

That F plug is just masking a tune issue, you will eventually kill the plug as well which will cause a flameout, it makes no sense. To each their own I suppose, I would prefer to fix the actual problem rather than just mask it.

ThumbSkull

My Feedback: (57)

What problem am I masking? Please tell me the tuning problem in the engine in the video.
I'm showing an example of one obviously running well and not just talking smack.

It's properly tuned and the F plug gives that margin of difference between nose pointed up and a downline.
This is a tuning condition that varies regardless of the needle setting because the fuel pressure changes.

Been running the same F plugs for two seasons in 3 55AX's and not one has burned out.
The F plug is made with more platinum and therefore is less likely to burn out.
Your mileage may vary.

rcflip

Just simply trying to point out that if you need to run an F plug then something is wrong.

ThumbSkull

My Feedback: (57)

Nothing is wrong with the setup or tuning. There are other reasons.

We are in the 3D thread where things are a little different than they would be for a pylon racer of a sport flier.
Nothing is wrong with a #8 plug. Nothing is wrong with those choices for the norm.

3D is not the norm for the reasons I mentioned earlier about fuel pressure changes because of attitude.
For 3D you really don't care which plug will spin the prop the fastest. Top end is nearly irrelevant.
In my short video, I never did hit full throttle. What matters most is the midrange or the middle 1/2 of the stick.
In my experience and several of the guys that fly like I do, the F is the best choice for this style of flying.

I'm not saying that every 55AX needs an F plug. If I was running a tuned pipe, It would have a proper heat range plug in it.
Tuned pipes are a terrible choice for 3D because they kill the midrange of the engine and make it very peaky.

rcflip

Thats pretty funny Thumbskull, tuning and running a motor is tuning and running a motor, it has nothing to do with what thread or what type of flying you do!!! hahaha, you have made my day with that one!!! Perhaps if you need to run a F plug to 3d the 55AX there is a problem with the OS engine!!! You are also incorrect about a tuned pipe, because a tuned pipe can be tuned for low end or bottom end, it is a trade off. I am glad you do not care about top end because that F plug will be robbing you a little power no doubt, but like I said before to each their own and whatever works for you.