Different engine sounds

[ferincr]

Hi, I hope this is not considered double posting, if it is , my apologies and feel free to act as you fit.
I was posting in another thread (the ones about the shims in Engines and mufflers section) and I thought it would be great to have sound recordings for engine problems (like 4stroking, predetonation, too rich, too lean) with the most common causes and solutions.
May be there are already posted somewhere, as a fairly new pilot I heard a lot about these terms but is impossible for me to picture how a 4stroking or predetonation sounds like.
Anyone else there with the same problem???
Or a solution?

[Bestview]

I think it's a good idea. You can read on the net about engine troubleshooting and if for instance the engine makes a "woopa-woopa-ching-zing-ptooey" sound, the rear left screw of the backplate is loose, but hearing the actual sound would really help a lot!

[HeliDan]

"woopa-woopa-ching-zing-ptooey"



:lolol :rolling :lolol

[Rafael23cc]

It might prove very difficult to accomplish something like that. Think about it, on our helicopters there are a LOT of parts making a lot of different noises, main gear, belts, spinning mains shafts, spinning blades.... It will be near impossible to record a particular helicopter with a particular problem and be able to post it as a symptom of the problem.

If you take the engine by itself, maybe with a propeller attached, then you could do this more accurately. On helicopters, visual and performance cues are just as important as sound cues.

This is why I suggest going to your local RC field and talk to the more experienced people there, even if they are plankers. You can always learn something from anybody.

Rafael

[ferincr]

Thanks Rafael, but I wish that would be a possibility in my country, I'm not sure how many people flies helis here, at my field there is only another one and I'm not sure he knows a lot more about engines than I do, as for the plankers... well they fly very nicely , well I'll keep experimenting, as far as nothing sound horribly wrong I guess I'll be ok.

[Rafael23cc]

I guess one more question is in order.

Do you have experience with plank engines?

If you do, then it is not too hard to apply that experience to helicopters, listen for weird noises, look at the exhaust for a nice cloud of smoke, and feel the performance of the helicopter.

If you don't have the experience, try to get with the plank fliers in your area to get a feel of how the engines react. Keep in mind that helicopter fuel has a lot higher oil content than airplane fuel.

Rafael

[ferincr]

Well, I'm not a guru but I can recognize if something is wrong with the engine.
The problem is that I'm a PITA and need to know everything, that was the main reason why I asked. I'd like to be able to get it not just right but as perfect as possible :wink:

[Rafael23cc]

I see from your signature block that you have a Raptor 60 with an OS 70. That's exactly the same set-up I have in one of my birds. With the change of season here in the States, I've been doing some fine tuning of the needles, (I never stopped flying for the winter).

What I do, is to bring the heli up in a hover, and watch for smoke. If I'm happy with it, I go into Idle Up and fly around for about 1-3 minutes. I bring the heli back land it and check the backplate with my finger. If I have to remove the finger from the back plate before 5 seconds I richen the mixture. If I can leave the finger there for more than 10 seconds (You can probably leave it there indefinite) then I lean the mixture a bit and repeat the flying.

After tweaking a bit, I check the full power climb-outs to try to see if the engine bogs. Then I either adjust the top end pitch or play with the needles a little more.

I try not to chase the needles too much. I have much to practice if I want to get better, so if the engine is running consitently and providing enough power, I just leave it there and go fly.

Rafael

[ferincr]

Rafael,
Where I fly temperature wise is pretty much the same all year round, (about 80's) high humidity and it's about 3500 ft ASL.
I read a lot about using different plugs, head shims, but so far I haven't found a site where explains how to choose the right ones. Which are the mayor factors determining A vs. B? Is it temperature, humidity, altitude????. :dontknow
The only thing I noticed with the OS70 was that after warming up it didn't sound right at idle.
I tried adjusting the needles but didn't do anything.
I solved it opening a tad the mixture control screw.
I know if I touch everything eventually I'll get to it, I was just thinking in something that allows me to go straight at the cause without messing with everything first.
Well, I guess I will need to stay with the empiric system
My 70 is running ok (I think) don't know if it is 100% but at least is not being abused.
Now I'm getting ready for the 91, that one I'd like to get it to 100% that's why I'm trying to learn as much as possible :mrgreen:

[Rafael23cc]

You are getting into a subject that I have very little experience. I went to the Hobby shop and loaded up on the "middle of the road" glow plug, (after doing some homework). I think it was the OS#8. Some people use the Enya #3 I beleive.

As far a shims go, I knew that I was going to be using 30% nitro fuel, so I put in the shims that came with the engine as the homework that I did at the time suggested. I could probably find my sources but the research I did was about 3 years ago. Since I have not had any problems with blown plugs or lack of power, I haven't felt the need to change anything.

After a little searching I found this: http://ronlund.com/shim.htm
As far as glow plugs go, I suggest that you create another thread asking the question directly.
I hope it helps.

Rafael

[slikrx]

Just a general note about shimming, though I am far from an RC engine guru: if you are at 3500 ASL, tou will need to run thinner or fewer shims than someone running at the same temperature at sea level.

At 3500 ft, you will lose roughly 10-12% of your power compared to the same temp at sea level. this is simply due to the fact that there is less air, and less oxygen.

Click for data (http://www.flymetothemoon.com.au/content/Pressure%20to%20Altitude%20Conversion.pdf)

Another way to look at this, is your altitude does the same thing that a 25C increase in temperature (45 F change) That is a BIG change.

Don't know if that will help, but the temp change vs altitude change thing might... :dontknow