Nice looking bibe! Just curious, is the engine mounted with the cyl strait up? Do you have the engine forward as much as posible? Best Regards, Capt,n

hi captin
i mounted the motor with piston straight down because i didn't want to see the motor out the top. i made a few standoffs, experimenting with the length and CG while trying to keep factory spec in mind.
once the CG was right i turned up some standoffs and made nylon washers to spread the load over th "firewall"
i can take the cowel etc off and take some photo's if you need ?

Wondering if anyone else has ever had this...... I have a DLE 55 in a plane and have been flying in wonderfully. It has very little burble and runs great. The curious part is that if I find the right spot on the throttle where it has a little burble, then flip the plane inverted, the burble stops completely and it purrrrrs like a kitten.

Any of the pro's care to lend a thought?? My other 55's have no burble at all. Thought maybe the input on this may also help some of the guy's trying to tune their 30's.

Thanks!

Terry i'm no expert but have you got a tube running from the diaphram cover to a bottle inside the fuse? Sometimes the atmospheric pressure can add more pressure to the diaphram in certain cowls and this seems to take care of it.
Here is what I have done to all of my gas engines.

this stuff is killing me.I am going to order my b'day present a week early.I looked over everything and decided a DLE30 with rear set up was what the doctor ordered.I suspect I will enjoy gassers again.I love the smaller sizes.I had a 60cc and just to much plane to haul.

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Terry i'm no expert but have you got a tube running from the diaphram cover to a bottle inside the fuse? Sometimes the atmospheric pressure can add more pressure to the diaphram in certain cowls and this seems to take care of it.
Here is what I have done to all of my gas engines.


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I have not tried the vent line, I hear mixed ideas on how much this does for you. This is not a sloppy burbble and it is not an issue. The curiosity is coming because the plane is going at level flight steady speed, just find the spot on the throttle where it pops a little (about 1/4), then without touching throttle I flip to inverted. Same air-speed should have same pressures in cowl, but the burbble goes away.

Things that make ya go Hmmmmm?

When you turn inverted the pressure in the cowl can change as the angle of the air will change even though the speed has not. Any change in cowl pressure can effect the mixture. Rolling inverted will usually put the hole for the escaping air on the top of the plane which could have better suction effect due to angle of attack. This would lower the pressure in the cowl causing the engine to lean out a bit. Their are so many variables it would take a while to go through them all. This is why I as well have adapted the practice of venting my carb into a box inside the fuselage. To date it hasn't caused any tuning problems and it is some nice to be able to tune it on the ground and not have it change in the air.

Thanks Doug
I have seen the very same thing over and over also, at some point it seems there is always a gurgle or burble that can't be tuned out due to the pressure differential as you indicated and so far the tube and pill bottle has cure them all.

Well I guess I have a good candidate to try a vent line on. I'll give it a try next week and see how it changes with the needles where they are right now.

Thanks!

It sure can't hurt to try it, as I had a Extra with a gas engine which no matter how well I tried to tune it would go quite rich as soon as the model left the ground and installing a vent line from the carb's diaphram cover to inside the fuse solved the problem. I never even used the pill bottle option but just left the tube dangling inside.

Karol

It's the lever height adjustment. When the plane is upright the diaphram is up also which means the fuel that is in the cavity is being pulled thru the engine with vaccume from the venturi and assisted by gravity, when inverted the the engine has more work to do to pull the same amount of fuel thru because gravity is now working aginst you-thus the engine will run a little leaner. Adjust the lever height up a little at a time and test it you will see the difference.

Do notfollow this advice unless you know exactly what you are doing. Most of the time people make their problems worse by changing the lever height. Trying to get rid of every last bit of midrange burble is futile and unproductive. Some midrange burble is normal and natural for these lightly loaded engines, raising the lever height will only increase it,instead of decreasingit. If it's gone by 1/3 throttle and you have the adjusted so it's as lean as possible and still have a good transition when warmed up, it's good to go.

You're next engine "warranty service" repair is being discussed in advance....

Maybe just placing a higher pitch prop on your engine will load it more & maybe most the burble will go away in mid range. Your landing speed may increase a tad...but with the rear-induction carb set-up, the engine should now Idle like a dream! I got a 18x10 and it has instant spool-up! Capt,n

Thanks, but no lever height adjustment or prop changes for me. Not that serious, and I normally prop for the performance not for engine tuning. I flew my new DLE-30 with the Cyberplate conversion tonight and it does the same thing, almost identical with Vess 19A. Great little engine, I have to say. I will probably try the vent line on this DLE-30 first because I will be checking the nuts and bolts and will have the cowl off anyway.

Won't be until after the weekend though, no flying for me for a few days.[] Will report when I do add the vent line.

Thanks again.

Didn't sound to me like there was anything wrong to begin with, I don't warranty the work performed by the end user who followed poor advice and made things worse.

Using a lighter loading prop again is the wrong thing to do, the reason our engines burble in the midrange is because there is not enough load on the engine to begin with. Take a chainsaw and start cutting a log, reduce the throttle to a little above idle but keep it in the log cutting away, it runs clean. Now, pull the bar out of the log, and keep it at about the same RPM but spinning free and unloaded, it starts to burble.

Load the engine a little more with a BIGGER prop to help minimize midrange burble.</p>

I only hovered the plane once for 5-10 seconds because it was the first time up for that engine, and I wanted to see how the pull-out was with the Vess 19A. If I went to a Vess 19B it would load the engine slightly more, but I wonder if the thrust for pull-out would be equal, more, or less? Had decent pull-out, but nothing to write home about.

Anyone else tried these props with a plane around 12-13 lbs.?

Aircraft performance is a balance of compromises, the pilot must prioritize what is most important to have and what is easiest to go without. There will always be some areas lacking and others excelling.</p>

A little burble it is..... Unless someone can report on a 19B Vess or Zoar 19-3DB.

Thanks agian for the input, always valuable. I will try the vent line next week just for the fun of it. Again, all of this is just for learning and playing. Nothing serious enough to really worry about.

Jody is right about the balances. I can give you an engine that makes a whole lot of power but then you have to deal with more heat. You won't be able to run it cool without a cooling shroud. May have to deal with really bad throttle response too. I can give you an engine with a real good mid range but you'll suffer with how much weight it could pull. I could give you one with a super low end but you'll never get any speed out of it.

Most of us have to settle for an in between where the engine will perform relatively well in all areas but excel in one or two. The trick is spending the time with the engine necessary for getting all the way through the break in process, and for all of us Chinese engine owners that's a very long time. From there we get to do the basics with high and low end tuning and live with what the middle leaves us. Props have a lot of influence in the mid range also. Experimentation is the key here and not always believing what this or that person says works best. Planes, engine, and other condition differences stack up where one or two props does not fit all.

When a variable pitch prop comes out on the market...the mid range burble will be solved. But the price of a prop we can vary in flight may be way to expensive. Capt,n

Yeah you are the only person who can do anything right!!

I wouldn't say that, but there are a whole lot of people that can do so many different things wrong. Not intentionally but their lack of experience and understanding puts them in situations where great intent turns to poop because they did one little thing wrong along the way. With time, experience, and repetition people develop greater knowledge and skills, leaving them in the position to do more things right. You can read this thread from start to finish and if you had the knowledge and experience you would be able to note that 80% or more of the problems and issues noted were user induced. If one read this thread from start to finish and discarded the errors promoted through inexperience and followed the advice of those in the know they would gain quite a bit of knowledge that would provide later positive experiences. That is far too much work for most to consider though. Those that do come away much wiser than they started.

What I have seen Jody do more often than not has been to softly warn people away from doing things that have the potential to generate more of a problem than they started with. He has also been a very good teacher and has explained much that many needed to learn. One of the problems with teaching is that the instructor is often dealing with people that do not want to lean, or lack the capability to learn. In those events the teacher is always blamed for the failure of the student.

You try to give good advice and get flamed...Tell 'em all to get BENT [:@]

Ditto regarding T.O.M.'s words. I am a corporate instructor by profession and a modeler by passion. In both fields I have learned there is a difference between ignorant and stupid. Ignorance is simply a lack of knowledge. Stupid is a refusal to learn.

I am grateful for T.O.M.'s and Jody's training on this, and other gas engines. I have about a year's experience with gas but with their tutelage, in reality, I have gained much more. (Overall experience in the hobby is over 45 years, but mostly with glow, and rubber many years prior to that.)

One thing I would like to point out is that the phrase "...to agree to disagree" would be well learned and should be applied to most opinions on RCU. I have never seen anything gained by the inflamed emotions evidenced on these threads, but it happens nonetheless. Be thankful for those who share genuine experience for free. Experience is usually the most expensive education you will ever pay for.