RE: axe cp thread
 

Actually my friend that is just about right....
Now that you have a T-Rex you will read that many of the more experienced pilots recommend that you set up your normal mode PCs & TCs to achieve hover at about 3/4 stick up. Why? If you switch into idle-up where do you think your left stick will be while hovering in that mode? If you leave it set to hover at about half stick, when you switch into idle-up the heli will drop out of the sky like a rock. Half stick in idle-up = 0 degrees pitch, you get me now? Hovering at 3/4 stick in normal mode will not only train you for hovering in idle-up but also allows for switching modes in midair as the PCs will be more in sync between the two modes.

RE: axe cp thread
 

Markind,

Did your swashplate move only left and right before you added the mix or did it tilt a little front and back?

The stock Axe only tilts the swash left or right with the two servos on the left and right. With front and back cyclic, all 3 would move, the front going up and the two rears going down for example.

Perhaps the mixing of left/right was not balanced causing one to go up more than one would go down and viceversa. Adding mix will fix it, but its fixing a sympton not the cause.

RE: axe cp thread
 

DX7 Programming Mayhem Continues

Thanks for the feedback guys - I think you are realizing now what a strange control problem I have been dealing with.

I got some more stick time this morning. Pre-flight check pass. I double checked the Balance - its dead on for both axes.

Ok, fine. I unplugged the mains and again stared at the swashplate. Dang - it seems perfect! Right Cyclic input should give a pure Right reponse through the rotor disc. Foward Left Back all look fine when looking at the static model and servos.

BUT when hovering and slow maneuvering - I cannot get a decent true slide. I have to give a LOT of back elevator to slide straight right. Otherwise, she shoots forward way too much.

I increased the Mix to 60% then to 80% - it helps!!! I can now get a nice almost true slide to the right with only a little back elevator needed to keep her straight.

Ok fine. The problem also affects Forward Cyclic input - she slides to the Left way to much when all I want to do is nose forward a bit.

So, I added Mix #2, and set that to 45% Right AILE for Forward stick and 45% Left AILE for Back stick.

I ran out of time but she is maneuvering much better now. By the end of the session I could slide hard Right, keep her straight and pointing forward (the tail is rock solid and smooth), and flare to a hover, then slide hard left, keep her straight, and flare to a hover again. Rinse, repeat.

Not too shabby, but I must still compensate for these illogical forces acting on this bird. Its almost like my right stick is somehow mechanically rotated about 45 degrees to the left - BUT you can't see it on the servos or swashplate. [&:]

Strange. A few more packs and tweaking these mixes, and I just might have it though.

I took another close look at the Control Block, See-Saw, and Control Hub. They all look perfect - they keep the flybar at 90 degrees to the rotor blades, very little play. Hover is smooth and I can't notice much vibration - I don't think the blades are too far out of balance, if at all. Tracking is within a half-blade thickness.

The See-Saw and flybar can swing freely - just a little bit of friction from the O-rings, but still a smooth swing. So, the Head is as good as its gonna get. Its all new parts again. I even put in a new Main Shaft.

HINT: Here is a great tip for installing a new Main Shaft. Before you install it, polish it a little with 600 or 800 grit sandpaper. Make the aluminum shiny then you'll find it will slide all the way down to the Main Gear with little difficulty.

Thanks for the Stick Position at Hover tip. I will tweak up the Normal Mode Pitch and Throttle curves so the stick is about 3/4 up at Hover. Blade Pitch at Hover looks to be about 7 degrees. I will adjust the headspeed to get that.

More later. Must... Fly... Again...

RE: axe cp thread
 

I talked with an experienced TREX pilot today and he thinks problems like this always boil down to the geometry of the setup.

Hmmm, but it looks so correct? He says borrow some digital calipers and make sure the linkage lengths are in spec, plus the 50% Collective Pitch condition from the radio sets up the Axe with 90 degree servo arms and a PERFECTLY LEVEL SWASHPLATE.

Arg arg arg yes yes yes been over that a million times, ok fine, I will again check the setup geometry tonight and make sure of the above.
I am 99% sure its as close as the design will allow, but I'll have another really close look.

He says you'll never be able to completely 'mix out' the control problem if there is a problem with setup geometry. doh.

NOTE: On the 50% Collective Pitch condition, you center the left stick. You are on Throttle Hold to kill the mains. Your Throttle Hold Mode Pitch Curve is linear from 0% (Full Negative Collective) to 100% (Full Positive Collective). The important thing is that the radio's display tells you when the stick is at 50% (centered) position. BUT the stick itself is mechanical and may not be actually perfectly in the center when the display says its at 50%. This is OK. Set for 50% to make these adjustments, don't just center the stick.

On my radio, when the stick is exactly centered mechanically, the output position reads about 48%. This is acceptable, but when I am checking geometry, (in particular the Sub Trims) I will confirm the radio is outputting exactly 50% regardless if the stick is slightly above center.


And By the WAY:

I am and have been trying to GET BACK to where I was with this model: Confident Forward Flight! I had it down, bro!!

I can prove it:

http://www.rcuniverse.com/forum/fb.asp?m=5544848

This 'proves' I got the stick skills to fly this thing! It seems so long ago...

I just gotta get this control problem fixed and I *SHOULD* be able to JUST FLY again!

RE: axe cp thread
 

I remember someone mentioning they had this problem also but don't remember if a solution was ever found. My Axe leans to the right in a stable hover - it looks like I've put in right cyclic...but it doesn't slide right and is in a stable hover. The hover is stable enough to the point where I'm able to let go of cyclic controls for a couple of seconds. I can't figure out how to fix this for the life of me. Any suggestions?

RE: axe cp thread
 

Get rid of your Axe. :D

RE: axe cp thread
 

JZ we all know you hate the Axe, but how is that helpful to Mark?

RE: axe cp thread
 

Mark I'm not familiar with the DX7, but the Axe uses a standard CCPM set-up. Mixes shouldn't be necessary. Is there some wierd mix coming on with the throttle maybe? I know the DX7 has alot of programming options. Maybe some obscure throttle mix is turned on.

RE: axe cp thread
 

Well...I guess it isn't helpful in any way. I guess I need to leave this forum. I am sorry that I have been such a negative person here. I wish all of you guys here the best of luck.

CYA

JZ

RE: axe cp thread
 

I just received my DX7 the other day and installed the AR6100 receiver in my Axe. I'm impressed with all the programming options with the control over my Axe. I just wish there was a way to turn off the beeps on the control so I can change the programming without disturbing others. Anyway after messing around with the programming and getting frustrated with setting it up, I think I just about have it. I am able to do fairly quick turns and have quick response with my current setup. So far this is what I have for my Normal flight mode:

Throttle Curve: 0, 50, 77, 89, 100
Pitch Curve: 50, INH, 60, INH, 70 (seems to work best for me, what are your PC and TC settings?)
Revo Mix: all at 0%
no programming mix
Sub trim: Rudd=R20, (to keep it from moving), Elev=D20 (center servo), Pit=H25 (center servo)
Travel adj: all at 100%
Swash Mix: 3 servo 120 - Aile=-100%, Elev=+100, Pit=+100 (Max movement on my swash for quicker response)

After a bit of tweaking, I found that this setup works well for me with the control responding similar if not better than the stock controller over my Axe. What I don't understand is the pitch curve that others have and recommended. If you noticed my pitch curve is from 50-70 and not 0-100 like others have set. The reason why I have mine setup like this because I noticed if I go to much over 70, it seems like I give it to much pitc and the motor sounds like it gets bogged down, the battery doesn't last long (5min), and the motor gets hot. With a PC of 50, that gives me about 1-2 degrees of negative pitch to get my back down when I cut the throttle. I can hover at 1/4 over mid stick.

My flight times at not that good using 1350 Lipo's. I'm getting about 7-9 mins. The main motor temps are down to 125-130 degrees after a session. I'm wondering if it's my setup that is reducing my flight time ever though it is flying pretty good for me.

RE: axe cp thread
 

Yay! Another DX7 user with which to share my torture!! :D

Ok then, I spent about 2 hours fiddling with the swashplate setup on the Axe, and playing with the DX7.

Here then, is a solid procedure to get the default setup.


1. First, get your swashplate type, mix, and servo reversals in correctly. This should be straightforward. Also, servos should already be centered and the arms screwed in to the correct orientation (i.e. there is one spline that will be the closest to the correct position).

2. Now then, get the linkages to the spec length. See the Axe Manual.

3. Here is where I may have introduced an error. I can see now that it is more important to get the swashplate level than to have the servo arms at exactly 90 degrees to the linkages. Set the radio to Throttle Hold Mode, unplug the mains and tail, and verify a linear Throttle Hold Mode Pitch Curve from 0% to 100%.

4. Set the stick to output 50% (the actual stick postion may not be exactly at center, but be sure the radio says the stick is at 50%).

5. Set the Sub Trims so the Swashplate is EXACTLY LEVEL. Be sure about this! It may mean that your servo arms are not at exactly 90 degrees from the linkages. If they are too far off, consider a turn or two on the ball links. (Ah ha! My swashplate was a full turn off one of the linkages, plus I went over all my Sub Trims with an eye to keeping the Swashplate level - so my servo arms are not all at exactly 90 degrees, but close.)

6. Verify that moving the left stick full up and full down keeps the Swashplate Level. If it tilts near the top or bottom, adjust the Servo Travel percentages to achive a level swashplate throughout the entire range of up/down movement. (Ah ha! Mine was tilting near the bottom - a slight Travel adjustment on the ELEV servo (front servo) fixed this.)

7. Interestingly, the AILE and PIT servos (rear servos) act just right with +100% / -100% Servo Travel settings. (Defaults)

8. Set the Tracking Linkages to set exactly ZERO DEGREES collective pitch on the main blades when radio output says stick is at the 50% position.

That's it! This is where you need to be to start playing with the Normal Mode Pitch and Throttle Curves.

Testing


I got some stick time this morning.

Pre-flight: Pass. Plus, I turned off both of the custom MIXES I had set up prior. I want to see if I can slide straight now without those mixes. I also stabbed at the Normal Mode Pitch and Throttle Curves with the idea of getting the hover at about 75% up stick.

Result: Not bad!! I ran out of time, but even without those corrective mixes I put in, she was maneuvering about as well. This is very good progress.

I was hovering fine at about 90% up stick. Need more curve tweaking. BUT the smoothness and ease of maintaining altitude was GREAT!!! Super smooth liftoffs and landings, with hovering just inches off the floor seemed easy, as it was at 1', 2', 3', 6'.

Sliding left and right still required a bit of forward / back correction. Not sure how much as I ran out of time.

Manuevering: Quite good! I was happily slowly floating over to far left, turning 90 degrees, and floating off to the far right. Very stable and smooth.

Funny! My Swash Mix is: AILE -60% ELEV -60% PIT +60%

How do you account for this, Jumpjet101?

RE: axe cp thread
 

Markind. Get rid of those mixes!!! You have a problem with your head and servos and you are masking it with those Pmixes. The problem you have is called UNWANTED SWASHPLATE INTERACTIONS, it's very easy to fix once you know how to identify, diagnose and cure it.

What causes U.S.I.? Uneven E.P.A. settings. How can we tell if our End Point Adjustments are off? Easy. Let us disconnect the motor from the speed control. Now lets flick on the idle-up switch. Slowly move your throttle stick all the way up and down a few times and observe the swash from the front of the heli paying close attention to the ball links on the front. When you get to maximum throttle position do the two ball links stop moving at the same time? If they do does the ball link in the rear stop at the same time as the ones in the front? I bet they don't. That is because the servos reach their maximum travel before the one of others and this will also cause a difference in speed among your swash servos and this will cause the swash to move unevenly which translates into an unwanted change in direction.

How do you fix this? Use your E.P.A. settings to match the stopping points on all your swash servos. I don't know if you understand what I'm saying here but if you watch these [link=http://helifreak.com/viewtopic.php?t=12455]CCPM setup videos[/link] by Finless Bob then these will explain everything. He is using a TRex in these videos but you can apply this to the AxeCP and any other heli that uses a CCPM swashplate.

RE: axe cp thread
 

P.S. HaAHahaHAhaHa!! Markinf we posted at the same time.....

RE: axe cp thread
 

P.S.S. I need a speeling cheker hahaha

RE: axe cp thread
 

Markind, look at the servos and how they are set up. Two of them are on the same side of the heli and one of them is on the opposite side. Thats why two of them are mixed in - and the last in + since it is rotating in the opposite direct from the others. Set the pitch servo to -60 and watch how funy your swashplate will get hahahaaa.

RE: axe cp thread
 

So...any thoughts about my Axe and its gangsta lean? ;) :) :D

RE: axe cp thread
 

Thats an easy one. Remember that the tail rotor conteracts the torque from the main rotor. With the push of both these forces the body of the heli leans to one side. This happens with real helis too only it isn't as noticeable since their weight keeps them perfectly straight. It is a perfectly natural thing for the heli to do. You could try turning the tail rotor a tiny bit to redirect the thrust to counter the lean, but it will still be visible. If you look at the rotor disc during hover you wil see that it is sitting level even though the heli is leaning.

RE: axe cp thread
 

Ah, okay. Thanks for the reply. I kinda had a feeling that this was it but I only heard of one other person mentioning so I discounted it. If I were to raise the tail rotor to the level of the rotor disk (hypothetically) the way it is on, say, an Apache or a Cobra, would this correct my Axe's lean?

RE: axe cp thread
 

0-100 would be used in Idle-Up mode. In normal mode the range is less because your not using much negative pitch if any at all. My pitch curves in normal mode are P1-50%, P2-62.5%, P3-75%, P4-87.5%, P5-96%. So your not far off.



Your flights should be longer.
Are you still using the stock motor?
Is there any drag anywhere?
Does the DX7 Rx requires more power?

RE: axe cp thread
 

Unfortunately nope.
The axis of the two rotating 'discs' and the forces they enact on the heli would still create the lean. If you went and reversed the direction of the blades, guess what would happen? It'd just lean the other way. Only dual rotor (Chinooks, AxeEZ, CoCo Lamas, etc) helis do not exhibit the gangsta-leaniness. My Trex leans so I just tilt my head a bit when it gets annoying to look at the heli leaning.

RE: axe cp thread
 

Actually you can lessen the lean. It's not easy though. The tail rotor axis would have to be moved up like you said S Mcflurry, but the T/R would also have to be angled. They use this method on larger helis to keep them level in a hover. Of course all these dimensions are calculated. On an RC heli you'd probably have to use trial and error.

The Black Hawk is a good example of the tail set-up I'm talking about. Notice it's relationship to the main rotor plane as well as the angle of the T/R.

RE: axe cp thread
 

haha... "gangsta-leaniness". Not only is it annoying, it's misleading. I'm practicing nose-in right now and that lean is really obvious and sometimes I forget and I anticipate that drift and correct for it. I know people say look at the disk but I can't get myself to do that - the blades are white and reflect light so it's hard to tell what it's doing. Anyway, thanks again for the reply - I'll just live with it.

RE: axe cp thread
 

...trial and error it is!! To the drawing board! I'll let you guys know how it goes. :D

RE: axe cp thread
 

Ha! Good, luck! The Blackhawk has computer controlled hydraulics and gobs of power - you may get a flat hover out of the Axe but I suspect angling the tail will lead to control problems. Speaking of which:

alienteabagger! Yes we are on the same page. I think I made a big discovery on the setup - its more important to get that swashplate level than to have the servo arms at exactly 90 degrees.

You can't have both a level swashplate AND perfectly level servo arms. Not possible! On those linkages, you can only make full turns, not half turns, so it will always be off if the servo arms are perfect. Level swashplate has priority! That is my big lesson learned today!

My other big discovery is to adjust zero degrees pitch when the radio says its at 50%, regardless of the stick position, which in my case is just a little above mid-stick. I had mistakenly adjusted zero pitch when at exactly mid-stick, so I was off a tad there.

I still don't understand why JumpJet101 has a different swash mix. We are both using HS-55 and its the same heli, same wiring, same orientation, right?

Now then, I deleted the mixes. Ok.

I spent a lot of time staring at the end points of the servo travel. Everything seems perfect now. The swashplate stays level all the way up and all the way down. The maximum positive and negative collective pitch angles are acheived.

More testing is in order. I smell victory right around the corner now. No - not that wall!!! Bank! Flare!!! ARRGH!!!! BLAM!!! OUCH!!!

Reminder: Hover should be right around 55% - 65% up stick, both in Normal Flight Mode and Stunt Mode 1. The idea is to lift off, hover, then get some altitude in Normal Mode, and hover again. When you flick the switch to Stunt Mode 1, the Axe should not plummet to a sudden death nor pop up in an uncontrolled climb. She should just immediately increase headspeed and decrease collective but still maintain stable hover.

RE: axe cp thread
 

I have another question, separate issue (but maybe related to my control problem):

How "loose" should the flybar be? In my friends' TREX, it flops around freely with nearly zero friction.

On my Axe, its smooth and moves easily but there is some friction from the O-rings. Is this bad? Do I need to insure that the flybar is completely free to flop around, I mean teeter-totter with no resistance?