Gray Beard

My Feedback: (-1)

ameyam

To answer the question of how much I ran through the engine, I guess I used a litre of oil a weekend and flew this for a good 3 months in the first stint and a couple in the second. So I guess that would be around 4-5 gallons.

Regarding the Dle20, I took that one off the model and discovered I had the #4 DLE ignition module which people were telling me had issues in the idle speed and sudden increase in power around 15-20% of throttle. Same issue which I had with the engine (it was fine otherwise, but the sudden increase in power in the approach made me uncomfortable with the landings). Discovered the module number on the back side of the module when I was removing it from the airplane yesterday to install the 75ax. A replacement module should fix that

Ran the 75ax indoors today at idle for just a minute or so. I have put some sealant around the one stripped retaining screw with some Teflon tape on the screw threads, testing with this carb before I get a replacement if the engine is OK. Wouldnt start at 1.5turns of LSN as expected for an engine full of lube, it required some coaxing to start at idle at 2.5 turns out of LSN and when I pinched the carb tube, it died immediately, couldnt prevent if from doing that. Then it wouldnt start again at 1.5turns, but sustained a 2.5, so I left the LSN there with the HSN at 3 turns. Once it runs a tank through I will lean out the LSN with the pinch test. With my back condition, I wont be able to do the remaining testing myself, a fellow flier has volunteered to do it for me, he will just run a tank through blubbering rich both needles and then we will lean it out hopefully next week end. Using Klotz synthetic-castor blend with 20% lube and about 5% nitro just for ease of tuning. Still old plumbing but this one came from the tank which I ran the 91 on the same airplane, so its pretty good. Put in a new Sullivan flex tank 12oz though

Regarding the experienced hand part.... its always been that way. My original mentor no longer frequents the field due to his health. Some others help but there are commercial interests involved and sometimes they just dont know where I am uncomfortable (the dle landing approach issue, for example) . Its always been like that, some have experienced it more than others. While I do get some help occasionally, in the last year or so I have been mostly finding out things on my own steam. Thats the way we two buddies taught ourselves to tune engines, building, setting up things etc in this year, from being too scared to even touch the needles lest we lose flying time because the instructor doesnt have time or is simply not available. Thats just the way the hobby is in my country currently. Sorry for being so direct and curt but you guys only see my messages, not my struggle to fly[:@]

No offence meant, I am known to release some steam occasionally ... and cool down very quickly subsequently

Ameyam

jester_s1

I'm going to suggest you don't use the pinch test for setting the idle. My way is to set the high speed for peak rpm, idle down fairly low and listen. If the engine drops in RPM, it's too rich. If it stops suddenly after rising a bit (or sometimes staying steady) it's too lean. Once I get a steady idle I set the high speed needle for just rich of peak, then tweak the low speed again if I need to. The last step is to check the transition. I idle for 30 seconds, then slam open the throttle. If the engine accelerates slowly, I'm still too rich on the low end. If it hesitates, I'm too lean. Once that's all done, I set the idle speed at the lowest setting where the engine will idle reliably for at least 1 minute.

ameyam

I set the HSN first and then the LSN (if I have messed with it). Then I quickly throttle up (without slamming it) and listen the same way you do. I prefer to keep the LSN a bit rich for safety, the pinch test is just a way of finding an initial position if I have a slightly clogged needle or have messed with it recently

Ameyam

RCVFR

My Feedback: (7)

ameyam, I admire your tenacity in working through the stages of this hobby. Most people, today have enormous amounts of help available to get through the learning process. I call this "learning by doing it right..," There is another way, called "learning by doing it wrong..." That's the way I learned to fly RC models 30+ years ago, before buddy boxes and/or web forums. It was OK, I had model building experience, just not RC flying. So, I learned by the "fly-crash-repair", syndrom, whereby one learns what was wrong in that crash and corrects for it. After a while I ran out of (or nearly so) wrong things to do and got to crashing less and flying more. It can work, but it does get expensive.

I can sympathize with your situation in a lack of "hands on" help. Often, a problem is identified in a moment or two working with the equipment, whereas days of internet chat doesn't quite get to it. There is a lot of expertise available on the net, some good and some not so. The challenge is in sorting out the good from the bad. I don't have any advice to offer you on that score, that is something you need to find out what works for you. Determine who you trust, and go in that direction.

The only recommendation I can offer is to focus on the fundamentals of this hobby: the principles of flight (what makes an airplane fly), engine operation and set up, system set up. especially servo linkage and forces involved, battery selection and maintenance. None of this is rocket science, though some would have you believe otherwise.

There is a lot of chatter around problem solving: very often well meaning people offer a solution that has nothing to do with the problem at hand. Need to sort that out.

Ultimately, it all boils down to the basics of the issue.

Good luck to you.

ameyam

Well, I havent had a single "crash" since I have been flying from 2007, though many hard landings. Its been over ten years now in the hobby. I would say I am a good flier (touch wood!) but due to engine problems, I may have had an equal number of deadsticks and proper landings but always land on the gear. I have a number of times where I have shattered the LG block due to this and repaired it. So I wouldnt say that I 'crash and learn' but I do tend to mess around with the setup if I dont feel comfortable with it. One of the more experienced members at the club has been watching out for me recently but his thinking is 'if it works dont touch it', which doesnt always equate to it doing what I want it to do, if you know what I mean.

People had me feel adjusting engines was rocket science till a couple of years ago. Then, you guys and some at the field made me realize that it really wasn't and from then on I have grown in confidence. It really went up when I took apart my rotting 55ax an year back, saw the internals ans the issues then put it back together and it worked fine inspite of the scrubbed piston. Likewise my flying buddy. Now we setup and adjust on our own. I am working and am always short of time, so more proactive in what I do and analyse at the end of the day, so I feel I have made a error, I go around and correct it, as we all do. Sometimes, you dont know whether what you have done is right or wrong and thats when you ask, I take in all I can then make my own decision. No offence meant to anyone.

I am keeping my fingers crossed that the replacement ignition module and work I have done on my carb on the 75 sorts both of them out

Ameyam

jaka

Hi!
You must have missunderstood how to run in a modern glow engine! Nearly all two stroke engines today are of the ABN,ABC or AAC configuration and that means they should be run at near full rpm, at full throttle opening, adjusting rpm with the high speed needle. These engines can be flown right from the start if set a little rich! They don't need any leghty running in!!!!

It's only ringed or lapped engines (Engines with steel piston running in a steel cylinderliner) that need long , rich running in times!

ameyam

Yes, the standard procedure in those days (when I had opened the engine) was to run atleast 3 tanks blubbering rich and at full throttle on the ground with time to cool down in between. Subsequently, we would gradually lean it out gradually in flight. Sadly, for this engine we didnt even do that

Though everyone has an opinion on this, I feel there is some sense and protection id doing the break-in as per manual. I did that on the FS91SII and it has only had one deadstick in two seasons of flying including hovering etc. Something to remember when I have the next go at this

Ameyam

RCVFR

My Feedback: (7)

I hope the new ignition will solve your problem, but it is likely a matter of linkage geometry that could be corrected on the stock unit. There are hundreds, if not thousands of DLE 20 engines being successfully operated with the stock ignition. It's your money. Enjoy!

ameyam

Well, on the Dle I tried to set up the throttle for the mid position of the carb arm at neutral on the servo and then adjusted both end ATVs to get the required result. The required result being 8000rpm at WOT, 4000rpm at neutral and 1700 or so at idle with carb closing to throttle cut. But with the onboard tach, I had to add nearly 100% expo to get that. Then, in the landing approach, I kept 15% power (to prevent the bounce due to too low an airspeed, this is an over weight glow conversion). Controlling the sink, when I would add power to maintain altitude, there would be a sudden increase in RPM and the airplane would gain height. That would force me to go to idle and then the airplane would bounce due to either overspeeding or stalling beforehand. In 7-8 weekends with 3 flights each time, I had only a couple of satisfactory landings.

A colleague on the field also tried to setup the same way but they tried to do it without expo but with the engine running to get the 4000rpm adjusted using the e-z connector on the throttle. That day we were both struggling with understanding the interface on the 8FG and we didnt get it right and gave up. Subsequently, with the 12FG I never got to try it. Since you cant see the carb opening in gas, it is difficult to setup the throttle like in glow. Another variable was the idle stop screw and the needles. When I tried to adjust the LSN from factory settings after a gallon of fuel, it went up to 4000rpm at idle. Had the idle stop in then, next time I tried it with the screw removed, it hit 4000rpm while no one was holding it (my left had was firmly stuck in the fuse as I always do whether or no someone is holding the airplane, so it didnt budge) and I had quite a scare trying to get to the ignition switch with the 16x8 running. Needless to say I didnt try that again

I know there is a writeup from Jedijody on throttle linkage geometry, I tried it, but setting up the geometry like he showed didnt give me the servo movement at idle to have the throttle cut working properly. I did do the setup with all trims at neutral though.

Did I do something incorrect?

Ameyam

RCVFR

My Feedback: (7)

Yes. Man, you sure like to make problems for yourself!

You say you adjusted the LSN after running a gallon of fuel. So, you were running a maladjusted carb for that amount of time - a lot, and you were not happy with the performance. That LSN adjustment should have been done at the first run of the engine, after it was warmed up. When you did adjust the LSN and got the 4000rpm (which should have been dialed in at the first run) it's telling you it was very rich. You created a no win scenario for yourself, getting poor response from your engine and giving you heartache instead of exhilaration.

The idle set screw has no place on an RC plane. The only conceivable use for that screw might be on a test stand installation that does not have a servo control for the throttle. When the engine is mounted in a plane, remove that screw.

Factory needle settings are set to assure that the engine will start and run and not burn itself up. It's your responsibility to set the needles to optimize your engine performance. Nobody at the factory knows what fuel mix, prop, temp, atmospheric pressure and humidity conditions your engine will run in when you get it.

In another post, I commented on the need to adress the fundamentals of the various aspects of this marvelous hobby and I will offer the same advice, again.

Cheers, and best of luck to you.

ameyam

Not a badly adjusted needle, just rich. I had heard it rich but the guy who was helping me out said to better leave it there for a bit. Ok, lets not go there now that I have adjusted the needles and removed the idle stop. May be you could tell me regarding the throttle alignment. Note that now I will not get idle at throttle closed with the stop removed. So should I trim all the way down at 100% ATVs, then set the closed position, then trim up till I get to around 1800 or so?

Ameyam

RCVFR

My Feedback: (7)

Regretably, I have no idea what to tell you about your throttle alignment. I'm guessing that with your efforts to make computer corrections to the problems you were having, the set up is pretty well screwed up at this point and needs to go back to square one.

If you are up to a challenge, consider setting your TX programming for the throttle to zero, i.e., end points at 100%, no expo or anything else, allow yourself only servo reversal (to be sure the travel direction is correct) and throttle cut.

Next, set up your throttle linkage purely mechanically, no computer stuff at all. You will need to note the radius arm of the carb travel and that of the servo. You will need to match them or set up the right difference (probably less servo movement than carb movement) as the servo scribes a larger arc than the carb. you may be surprised to see how limited the servo travel must be, and you will be using servo arm positions close in to the servo to accomplish that. You are already aware that most of the engine power is developed within 60 -70% of throttle movement: match up your linkage accordingly, i.e., where to position the servo arm on the servo to give the right response at the carb. There is a lot of "trial and error " in this process to get things the way they need to be.

When you think you are about right, run the engine, noting what trim inputs are required. Then go back and mechanically adjust for those trim adjustments. Repeat as neccessary. When you find you are about 95% there on the set up, allow yourself to use end point adjustments to fine tune the remaining 5% to the level you wish.

Good luck.

opjose

Bingo!

-

Ameyam set the throttle channel back to it's defaults, adjust the mechanical linkage so your throttle moves smoothly and concentrate on getting the engine set up properly.

Once you get the engine sorted out, you'll find that these perceived "throttle problems" will disappear.

A poorly tuned or mistuned engine will give you strange throttle ranges.

Most of us with gassers never feel the need to adjust the throttle movement in the TX to get good response and control.


Yesterday I was flying a SYSSA 30cc. I had tuned it NOT to use the noise reducing inserts for the muffler.

With no inserts in place ( and the engined properly tuned ), throttle response was perfect accross the stick movement range.

Then I put the inserts in to quiet the engine... effectively putting it back out of tune... and I got EXACTLY the type of problem you are trying to correct with your TX... The engine seems to go from idle to high throttle within a click or three.

But I'm fully aware that this is a MIS-TUNING issue...


DON'T - use a tach to establish mid point RPM's.... save that for more advanced work.

DO - tune the engine properly for a good transition, medium idle ( until fully broken in ) and 200rpm off of max rpms. Then fly it for a few weeks.

DON'T - over think things! You'll wear us all out!

ameyam

Ok, I will do that when I receive the replacement module (not the wearing out part)

Ameyam