Question converting from dx7 to dx8

[guyguerra]

I am copying settings out of a dx7 into a dx8. The subtrim on the pitch servo in the dx7 is H21. The dx8 uses positive and negative. Is the H from the dx7 positive or negative as it relates to the dx8?
Thanks,
Guy

[guyguerra]

Second question.mthe dx7 shows travel on thr gear from -60% to positive 60%. The dx8 only goes from 0 to 150. How would that transfer to the dx8?
Thank you,
Guy

[aerocal]

You arent going to be able to directly copy the settings from the DX7 into the DX8 and expect everything to be the same.The best thing to do is forget about the DX7 settings and set it all up from scratch again.It should be fairly simple if the mechanics are already correct.

[Desolas]

Originally Posted by guyguerra

I am copying settings out of a dx7 into a dx8. The subtrim on the pitch servo in the dx7 is H21. The dx8 uses positive and negative. Is the H from the dx7 positive or negative as it relates to the dx8?
Thanks,
Guy

H refers to high or positive.

BUT like what the last reply said, you need to start over. The servo zero points are not going to be the same so you will need to reset your servo horns for 90 degrees and rework it.

Pitch and throttle curves will be the same, gyro gain is substantially different. Around 40 is a good starting point if your gain was 65-68 in the DX7. There is an actual formula for figuring it out exactly but its easy to reset the gain as you fly.

[guyguerra]

Originally Posted by aerocal

The best thing to do is forget about the DX7 settings and set it all up from scratch again.It should be fairly simple if the mechanics are already correct.

Thanks for your reply on H representing positive. I bought a trex 600 and 450 from a friend last week. I replaced the receiver in one to an ar8000 from an ar6200. I copied the numbers out of his dx7 last night and am very happy with the results. I had to do a little tweaking but it saved me time and effort on setting up both a trex 600 and trex 450. The 450 was perfect on the change over. The 600 needed just a few adjustments, but not much.
For me, I'm glad I didn't start from scratch. By using the dx7 I knew what needed to be reversed, what the servo settings were and the pitch/throttle settings. I'm not sure why I would have been better off doing that from scratch?
The servos centered right up on both Helis too. The swash is perfectly level using the dx7 settings and all movements are correct. I had to adjust the travel a very small amout on the 600, but that was all. I'm going to spool them up today and see what needs to be fine tuned and adjust the gyro settings.

Am I missing something? I'm not an expert, and your post are much appecited, it makes me wonder if I'm wrong and don't see it. I'm trying to avoid learning the hard way, and on this subject I have some learning to do.
Thanks,
Guy

[Desolas]

Originally Posted by guyguerra

Thanks for your reply on H representing positive. I bought a trex 600 and 450 from a friend last week. I replaced the receiver in one to an ar8000 from an ar6200. I copied the numbers out of his dx7 last night and am very happy with the results. I had to do a little tweaking but it saved me time and effort on setting up both a trex 600 and trex 450. The 450 was perfect on the change over. The 600 needed just a few adjustments, but not much.
For me, I'm glad I didn't start from scratch. By using the dx7 I knew what needed to be reversed, what the servo settings were and the pitch/throttle settings. I'm not sure why I would have been better off doing that from scratch?
The servos centered right up on both Helis too. The swash is perfectly level using the dx7 settings and all movements are correct. I had to adjust the travel a very small amout on the 600, but that was all. I'm going to spool them up today and see what needs to be fine tuned and adjust the gyro settings.

Am I missing something? I'm not an expert, and your post are much appecited, it makes me wonder if I'm wrong and don't see it. I'm trying to avoid learning the hard way, and on this subject I have some learning to do.
Thanks,
Guy

If at mid stick you got your servos at 90 and the swash is in the middle of its travel and level, and your blades are at 0 degree pitch then your dialed. Just tweak the other stuff.

Sometimes you luck out, in my experience that's not the case! When I switched almost all of my heli's had to be recentered, but not all of them.

Just double check their function, make sure you don't have any binding and go fly.

[aerocal]

Yeah you got lucky.I think the last update recentered some of the channels.verything does come out fairly close but I had to do a little tweaking here and there on just about everything I changed over.I guess if your not real sharp on the setup yet its just as well to copy and then tweak.

[guyguerra]

Well, not as lucky as I thought. The 600 ended up flying great and just needed trim. I thought the 450 was flying good and wobbled because of the landing gear. Popped the sticks off, brought it in the garage because it started raining, and hovered it fine, but didn't want to fly it long in a small garage.
I tried it after the rain and after the 600, and it wobbles pretty bad. I've tried several gyro adjustments, with no luck. I can make it worse, but not better. It has a Futaba GY520 gyro. I'm a little lost but will keep trying or start seeking someone local with more experience.

[aerocal]

Originally Posted by guyguerra

Well, not as lucky as I thought. The 600 ended up flying great and just needed trim. I thought the 450 was flying good and wobbled because of the landing gear. Popped the sticks off, brought it in the garage because it started raining, and hovered it fine, but didn't want to fly it long in a small garage.
I tried it after the rain and after the 600, and it wobbles pretty bad. I've tried several gyro adjustments, with no luck. I can make it worse, but not better. It has a Futaba GY520 gyro. I'm a little lost but will keep trying or start seeking someone local with more experience.

What do you mean by "wobble"? Do you mean tail wag? Or the whole head is wobbling around?
If its just the tail wagging you probably just need to keep turning the gain down.If you were using gyro sens to adjust gain with the DX7 It goes from 0-100 with 50 being center/off.DX8 goes from 0-100 in both directions from center.So if you were running 70 on the DX7 that would be 20 above 50.On the DX8 that would be around +40.Maybe a little less.
Im kind of confused about how you said gear channel only went to -60/+60 unless you were using gear channel endpoints for gain control.If so then +60 would be about +20 on the DX8.Tail gain can be kind of finicky until you get a feel for where to set it.If you cant seem to get a tail wag/wobble to stop with the gain you might check that the tail linkage is perfectly smooth.Keep the slider well lubed.Sometimes the gyro sensor foam will age and vibration getting to the sensor will make it act up.Its also possible that a tail servo gets a bit wimpy and slow and it just cant keep up with what the gyro is telling it to do and its chasing the commands to stay centered.

If the head itself is kind of wobbling that is usually from low headspeed.

I havent played with the 520 gyro much.IIRC it has a cord to plug it into a PC for tuning.
Since your kind of new at this you might go to the Finless Bobs Tech Room and watch some of his videos.Look through the Heli Skills 101 and watch the gyro vids.Watch the ones for the DX8 also.Im not sure if there is one specifically for the 520 gyro.Theres a wealth of information there on setups.Ill have to look at the 520 manual again and brush up on it.

If this doesnt answer your questions ask again.Its kind of hard to tell what you have going on without actually seeing it.I know its also kind of hard to define at first so someone else can get the true picture too.Keep at it and ask questions.Thats the way to learn.Its alot at first.It gets easier.

[guyguerra]

Aerocal, thank for your advice. I also talked to the seller and he mentioned head speed. I found that I somehow missed putting the throttle curves in, I had it linear, where it's more like 0, 45, 60, 75, 100 (not exact, don't have the controller as Im typing).
You were also correct about the servo gain. I had it at 70 from the DX7, your explanation was perfect, so I moved it down to 30, and fiddled with it and am zeroing in somewhere around 33, till the battery went low. It's almost rock solid now, which it was when I bought it. Now I have to wait for the rain to stop again lol. Much better. Thank you so much for your help. I've been watching the videos and will keep on studying. You really helped me out a lot, thank you,
Guy

[aerocal]

Sounds like your on the right track