Switching From Spek. DX7 To JR 12X Issue

[oseeler]

Hi All,

Short version of my question:

Is there a reason anyone can see why 80% (high point) on the collective pitch curve on the 12X a would give noticeably different results in flight(weaker climb) than 80% on the Spektrum DX7?

Long version, blah, blah:

On a recent road trip, at a little LHS, I foolishly asked to hold a 12X that the owner said he was about to send back "because nobody around here can afford it." Instead of replying, "well, neither can I" and instantly handing it back, I got all sweaty fondling it and gazing, half hypnotized, at its forest of gleaming switches, knobs & buttons ... it was worse than playing with the world's cutest puppy at the animal shelter! Damn! There was no way I could have left without it, I was a complete goner! When I got home my wife casually asked if I'd stopped at hobby shops along the way ... I answered nonchalantly, "Yeah, picked up a radio..." and waited for the obvious question with clenched teeth, but all she said was, "That's nice." Whew. It really does work, guys, to buy her a horse - you might be broke but those $$ questions about your stuff fade away pretty much permanently (what with the horse being front and center, and nipping at your wallet all the time, unlike fancy jewelry or such that's forgotten in a drawer.) Anyway, after a week with the 12X I'm still in love with it. I can't imagine ever wanting anything bigger or better. It's fabulous. Be careful if you get around one, you will no longer be happy with whatever you're flying with now.

I do have a question for anyone else who has switched from a Spektrum DX7 to the 12X. I transferred my TRex 500's throttle and pitch curves, expo, etc. number-by-number to the 12X. A very careful test flight, just some close hovering, went well although the increased responsiveness surprised me a bit (yes, it's noticeable, even when just paddling around which is what I mostly do, my interests being scale & AP, not 3D). But on the next flight I ranged out a bit and found that the vertical climb rate was way less than it had been with the DX7. This is with a mild setup, with mechanical pitch set to about 10 degrees either way and the pitch curve topping out at 80%, and a flatline throttle curve. I don't think the throttle curve is in issue, because the sound is right and the 500 isn't doing the notorious low-head-speed nodding thing. Is there some reason anyone can see why 80% pitch on a DX7 would give different results than 80% on the 12X? Or am I overlooking something? (Or maybe I made an error...).

Have Fun & Fly Safe,

Oliver

[Coolice]

Hey Oliver,

First thing that springs to mind is the high & low pitch trimmers on the sides of the transmitters, just to the left and right of the top switches. If these have not been inhibited in the device select menu then they can alter your high and low pitch setting and if you move them while getting the transmitter in and out of it's case it can make you wonder why no pitch.

Personally I'd say pop a pitch guage back on the model and double check your settings after the transfer from DX7 to 12X, just to even be safe and not risk damaging the model. At the same time operate the trimmers while the throttle/colletive stick is at the low & high position and see if they are indeed active.
.

[oseeler]

Hi Ian,

Thanks for the reply and advice. This continues to be a mystery to me, though it's not anything I can't work around. I've now checked and re-checked that nothing in the background is active on either the DX7 or the 12X that would account for different swashplate heights with the same numbers plugged into each radio. A pitch gauge verifies that the 12X shifts the swashplate and thus the entire working pitch range downward by a couple of degrees. Maybe it wouldn't be noticed in an aggressive setup with lots of pitch in both directions. In my case, I've set up this T-Rex 500 to be as mild as possible (I know, I know), running about 10.5 degrees of pitch at the top and minus 2 or so at the bottom (just enough to give me downward authority in gusty winds (I like flying in wind...go figure). The numbers on the DX7 are 80% at the top and 40% at the bottom. I fly this pitch curve from and to the ground, with a constant-value flat-line throttle (so nominally constant head speed) just high enough to avoid instability. Anyway, the result of this setup is of course that any change in pitch is real noticeable. With that 80/40 dialed in on the 12X and the collective to the wall, the 500 climbs like a limp balloon. Fortunately I didn't find out the hard way that at the other end it comes down like a pile driver, the negative pitch being about double the expected amount. By the way, by setting the top of the pitch curve to 100% on each radio one can easily see the difference in height at the washout.

All of this was easy to correct, of course, by simply punching in different numbers. 90% and 45% on the 12X give me pretty much what I'm used to. But it still bothers me that I don't understand what's causing this downward pitch shif. I'm presuming now that it's just a design difference in the radios, but that seems odd what with the close relationship between JR and Spektrum. .

For the record, the cyclic servos are Hitec 5245mg's and the receiver is a Spektrum AR7000. There's also a Helicommand (A) on board.

I haven't had a chance to transfer settings from the DX7 over to the 12X for my T-rex 450, but will be doing that soon - it will be interesting to see if the same thing happens.

Any comments? Anyone? JR?

[Coolice]

Hi Ian,

Thanks for the reply and advice. This continues to be a mystery to me, though it's not anything I can't work around. I've now checked and re-checked that nothing in the background is active on either the DX7 or the 12X that would account for different swashplate heights with the same numbers plugged into each radio. A pitch gauge verifies that the 12X shifts the swashplate and thus the entire working pitch range downward by a couple of degrees. Maybe it wouldn't be noticed in an aggressive setup with lots of pitch in both directions. In my case, I've set up this T-Rex 500 to be as mild as possible (I know, I know), running about 10.5 degrees of pitch at the top and minus 2 or so at the bottom (just enough to give me downward authority in gusty winds (I like flying in wind...go figure). The numbers on the DX7 are 80% at the top and 40% at the bottom. I fly this pitch curve from and to the ground, with a constant-value flat-line throttle (so nominally constant head speed) just high enough to avoid instability. Anyway, the result of this setup is of course that any change in pitch is real noticeable. With that 80/40 dialed in on the 12X and the collective to the wall, the 500 climbs like a limp balloon. Fortunately I didn't find out the hard way that at the other end it comes down like a pile driver, the negative pitch being about double the expected amount. By the way, by setting the top of the pitch curve to 100% on each radio one can easily see the difference in height at the washout.

All of this was easy to correct, of course, by simply punching in different numbers. 90% and 45% on the 12X give me pretty much what I'm used to. But it still bothers me that I don't understand what's causing this downward pitch shif. I'm presuming now that it's just a design difference in the radios, but that seems odd what with the close relationship between JR and Spektrum. .

For the record, the cyclic servos are Hitec 5245mg's and the receiver is a Spektrum AR7000. There's also a Helicommand (A) on board.

I haven't had a chance to transfer settings from the DX7 over to the 12X for my T-rex 450, but will be doing that soon - it will be interesting to see if the same thing happens.

Any comments? Anyone? JR?

Hey,

Your welcome matey, hopefully someone will chime in with a true reason why the changes between transmitters. Otherwise I'd just go through the bench setup again and reset accordingly as it won't take you too long and will give you peace of mind that it's correct.
.

[trexbelt1]

No TX expert here--but I have seen Spektrum radios get "out of calibration." One of my buds sent his dx7 back for repair and it came back fixed and HH said they "calibrated" it. Well it was totally different from what he was used to and he had to re-figure out all his P and T curves. New "fresh" TX just might be a tad bit different from your old unit.

Hope it all works out for ya.

Doug