Raptor is Holding engine speed when i drop throttle...

[JaseGill]

Hi Guys,

Wondering if anyone else has experienced this.

I hover my Raptor and all is fine, I then set it down and lower the throttle. For a while it seems that the head speed keeps the engine speed up, its almost like the head is constantly connected to the engine till the speed drops off a bit and the engine speed is all over the place. I dont know where this is coming from.

It used to be the fact that you dropped the throttle and the engine revs dropped right away too and the head free wheeled, it doesnt seem to be doing that now. Could it be the clutch is binding and holding the speed high or is ot maybe the Auto hub not disengaging ?

Anyone who has experienced the same and knows a fix would be extremely helpful,

Cheers,

Jase.

[Raptorite]

Hi Jase,

It sounds to me like the engine is too lean at the bottom end. Have a look at this thread and try doing the pinch test, that should sort the problem out.

http://www.rcheliaddict.co.uk/module...ght=pinch+test

If on the other hand it was running fine, but has suddenly started behaving like this, I would first check the fuel lines inside both the main tank and the header if you have one. Over time the nitro in the fuel breaks down the silicone tubing causing it to become very fragile, eventually leading to cracking or complete failure. This can lead to air leaks and therefore the engine will run lean at certain revs, tickover being the most obvious sign of trouble.

It is well worth changing those clunk lines they are known as on a regular basis, say every 2 or 3 months to insure their condition.

I have had models crash in the past because the engine has stopped in flight due to clunk line failure, so it is an important part of routine maintenance.

Cheers,

Pete.

[JaseGill]

Found It

Pete,

Thanks for your always insightful help but I found it, partly engine low end as you said and also my throttle settings on my RD8000.

Firstly yes the mixture was all wrong and after having reset it to the factory settings and a little twaeking it was fine there.

Also I have been playing with the throttle curve for a few days and when I went back into the settings I noticed that the P1 (1/4 throttle) on my RB8000 was way too high. Im new to this and was trying to get the middle stick throttle position to not be too jump in throttle around hover so had mistakenly set P1, P2 and P3 within 10% of each other, as a result at 1/4 throttle the engine throttle was way too close to hover setting and was holding the throttle high. This along with my crappy tune of the engine in the field the other day was the problem.

Of course I didnt find this out till I had the engine and Auto Hub out ops:

[Stuart]

Jase,

Glad to hear you got sorted, no need to be embarassed, believe me the no. of 8O I've made its scarey.....

How many have went inverted while in normal mode and low that's got to be a classic and it costs you a few to get back in the air.

[Stuart]

p.s. if its okay with you I'll delete the other post with the same topic.

[Raptorite]

Hi Jase,

I am glad it is all sorted now.

We have all been there and done that, as Stuart says the classic being to flip a model inverted without putting it in idle up first. As I mentioned in an previous post, I did this myself last year, with fairly catastrophic consequences 8O

One pointer for setting throttle curves, you need normal mode to be tickover at low stick, increasing to full at top stick. This is fine for hovering but when you move on into circuits etc. you will need an idle up 1 curve also, set points 1, 2 and 3 the same as your hovering throttle in normal mode. You will need this for controlled decents where you would otherwise have very little throttle.

An example of this is the following;

Normal: 0 - 30 - 60 - 80 - 100
Idle 1: 60 - 60 - 60 - 80 - 100

In order to maintain a smooth transition throughout the entire stick movement try to keep the points as evenly spaced as possible, so if as in our case hovering point is 60 and full climb out is 100 then set point 4 to 80% which is half way between 60 and 100.

Cheers,

Pete.

[JaseGill]

Thanks again

Pete,

Idle up 1 now makes sense to me. I guess when I move from hovering to circuits I want to get it up and hovering in Normal Mode, switch to Mode 1 and do the circuits from there ?

Im guessing that this way worst I can do in Mdoe 1 is chopstick and take the machine back to hover settings. Also Im guessing atthis point with Mid to high stick having say a 40% movement in throttle using your figures that the stick is also less sensitive between Mid and Full Stick. Is this correct ?

Im trying at the moment to get it at constant head speed so Im having a bit of a learning curve as far as Pitch/Throttle Mixing goes but hey its all fun

Gotta tell you it was a shed load easier on the real thing when you have a bunch of well trained techies to get all this sorted. Got even more respect for them now than I even had then and thats saying something.

Cheers,

Jase.

P.S. Stu, yeah mate delete the other one, I had a brain fart and hit submit twice after I got a page not found error, I had assumed it didnt go and so submitted again ops:

[Raptorite]

Hi Jase,

Yes, you are right, you will need to bring the model up into the hover and then engage idle up 1 before moving off into circuits. You will also need to remember to disengage it when you are preparing to land, as with it on when you lower the stick to land the model will maintain a high head speed, which you really dont want for landing.

In terms of throttle, the model wont feel that much different in the 40% between mid and top stick, bearing in mind that we are only dealing with throttle here. The pitch curve on the other hand should be as linear as possible throughout the entire stick movement, this is where you will notice the sensitivity most. If you have large gaps in the pitch curve between any of the 5 points on the curve (assuming you are using a radio eqquipped with 5 points, some have as little as 3 and others have as many as 13) then the model will tend to jump around as you move the stick up and down.

As long as you have around 5 degrees of pitch at mid stick where you will be hovering and have around 9 degrees at top stick, the mid point between the two is 7 degrees, so if you have point four of the pitch curve set to equate to 7 degrees, which if the hover point is 50% and the top point is 100% then point four should be 75%, its then just a matter of setting the throttle curve such that it maintains the same head speed from hover right through to full climb out. In order to achieve this, having set the pitch curve such that the points are evenly spaced, you need to do the same with the throttle curve to match the pitch.

Here is an example of how the pitch and throttle curves interact with each other.

Pitch curve 0, 25, 50, 75, 100
Assume that in this example the pitch has been mechanically set on the model so the linear curve above equates to actual pitch on the blades of;
-2, +3.5, +5, +7, +9

Now assuming that with your model's engine, exhaust and fuel combination you need 60% throttle to hover with a nice head speed. You will have a throttle curve looking like this;
0, 30, 60, 80, 100.

What we are trying to do is set the throttle to maintain a nice consistent head speed as the pitch increases when the stick is moved up, as the gaps in the pitch curve are nice and evenly spaced, so we should expect the throttle to follow suit. It might be that you need to tweak the throttle slightly at points 4 and 5 depending on how the engine performs. You might find that you dont actually need 100% throttle to climb out at top pitch, maybe you need something like 95 or even 90%, you may also need to tweak the 80% at point four to be something like 77 or 83 or whereever it needs to be to maintain that consistent head speed.

With regards to flying circuits, once you have climbed to a reasonable height and have flown the circuits, when you want to bring the model back down to hovering height, you will need to lower the stick to get the pitch down which brings the model down. Now with just a normal throttle curve, bringing the model down will need something in the order of 3 degrees, which as in our pitch curve example above means that the stick will be just under the quarter mark. At this point however, we will only have around 25% throttle, which means that the rotor head will slow down too much to be able to stop it decending at the bottom and bring it back into the hover. This is where the idle up 1 throttle curve comes in, as we have set it up to have hovering throttle at points one, two and three, we are now able to keep the rotor head at our nice consistent speed, maintaining control of the model and having the power to stop the decent and bring it back into the hover, before it hits the ground.

Once you have these curves in place, its then just a matter of tweaking the throttle so that the head speed changes as little as possible throughout the whole flight.

I hope this helps.

Cheers,

Pete.

[JaseGill]

Thanks again

Cheers Pete,

That makes a lot of sense now... It was what I had garnered near enough from RaptorTechnique but its nice to hear it from another person whose judgement I trust.

Im hovering pretty steadily now even in varying winds so I guess nose and side in are next

Cheers again,

Jase.

[Raptorite]

Hi Jase,

It sounds like you are doing really well with hovering tail in now. The next step is to start slowly turning the model one way or the other, a little bit at a time until you have it side on. It is best to try little bits each side of tail in, otherwise you will become "handed" as in far more comfortable with the model one side than the other.

Keep up the good work.

Cheers,

Pete.

[JaseGill]

That was the next target...

To be honest whether I have been doing it on purpose or not its going that way anyway. I can hover happily in near as damn it one place but now and then it goes a bit wrong which is why I have the training gear on

I get it back when it goes wrong so I guess Im doing a bit sideways anyway, I have been moving it right and left from side to side and hovering to get an almost side on perspective anyway.

If only I could set Reflex XTR to have the same characteristics as my Raptor Im sure it would be much easier

Cheers,

Jase.

[reboot]

running lean

my raptor 30 keeps doing this i keep richening the bottom needle every now and again but it still keeps creeping back.but ill check out other ideas ok

[Raptorite]

Hi Reboot,

I have heard of this problem before. What sort of engine do you have?

If the idle needle is a scew inside the throttle barrel it is possible that as the throttle opens and closes the idle screw is chaning its setting in flight.

The best way to check this is to count how many turns it takes to fully close it from the correct setting and next time you need to richen it, again count the number of turns needed to close it fully, you will then be able to tell if it has moved.

If it does keep moving in flight, take it right out and smear a small amount of thin oil, something like 3 in 1 is best around the side of the needle, making sure you coat the whole thing, then carefully put it back in the engine.

This should hopefully solve your problem.

Cheers,

Pete.