DEVO 10 snafu

[phil]

So you've spent a couple hours carefully doing the mechanical setup on your rotor head - swash level & centered, servo horns (almost) at 90 degrees at mid-stick.

You go to the "subtrim" menu to tweak your ail & pit servos to get them perfectly at 90 degrees. No problemo. You power everything down & go eat dinner.

Later, you figure you'll spend a couple hours developing some throttle/pitch curves and try crashing your heli into the walls and bookcase a few times before sleepy time. You power everything up, the heli initializes properly BUT...the ail and pit servo arms are skewed exactly the way they were before you put a few ticks of subtrim into them. OK, you try it again, being extra careful to make sure you've done it right. Power everything up again and BOOM! Same thing. Your fancy, new, super duper computerized DEVO 10 ain't telling your heli where to hang its servos on startup.

The old-timey 2801 Pro dinosaur didn't have that problem.

So, like whadaya do?

[majic1]

I'm certainly no expert. But, my understanding is that all Devo's reset the trims when powered off.

I'm not sure what the reason is? It doesn't make a lot of sense.

Call me old fashioned. When I first got into RC's (Cars and planes) years ago, there weren't any programmable transmitters. Sure there were manual trims. But the best way to get your car or plane to drive or fly straight and level was to get the mechanical setup as close to perfect as you can.

I have a V200D03 and a Mini CP. With the V200, the servo horns are not exactly at 90* either with the throttle at mid-stick. The pit & elev servos are, but the aile servo is just a little off. I tried to get them as close as possible, then level the swash. Since nobody makes a swash leveling tool that will fit a 4mm shaft, I used a pair of digital calipers. I have the swash within 1/100th of a mm all the way around. That's really tight. Probably couldn't get it that close with a swash leveling tool anyway. Once that was done, I set the blade pitch to 0*. All my trims and subtrims in the Tx are all at '0'. With this setup I can lift off, without any cyclical input, right into a perfect hands free hover. With the Mini CP it's a lot harder to get the mechanical setup perfect because everything is so tiny. But, with it close, it doesn't present too much of a problem flying it, even if its a little off. Not like the V200, which would be in the weeds if it wasn't close.

I've just been used to doing it this way for years. I don't like using trims. Having said that, I think with the Devo 8, it will keep the subtrims, but not the manual trims? I could be wrong, since I have never actually tried it.

You also may want to check Walkera's website to make sure you have the latest fw update for your Tx.

[phil]

Thanks for the input. I sorta figured that was the case. I ended up leaving the trims at 0 and leveling the swash with the ball links. BTW - I like to use the mainshaft collar as a leveling tool - just snug it up at the midpoint and let the swash sit on it 'til you can get the ball links the right length.

It seems somewhat disingenuous to include programmable items in a device that reset themselves when it's powered down. You're required to re-tweak at every flight of every model. You're right - it doesn't make sense.

I don't yet have the updated software for my TX. Although what I've read about it doesn't give me much confidence that it will address this problem, the power-saving feature and telemetry fix might be useful.

[majic1]

Unfortunately, I can't use the shaft collar to level the swash on the V200. The collar is on the underside of the frame. Not on top. I've tried using the zip-tie method, but could only get it kind of close. Not close enough for the kind of head speed the V200 generates. Even if it's 1 or 2 deg. off, this heli would be off in the weeds.
I needed it to be tighter than I could get it with the zip-tie. That's why I used the digital calipers.

As far as the trims being reset when the Devo is powered off. Someone in another forum had mentioned it has something to do with the gyro?

[cds1950]

My Devo 10 using version .5b saves both sub trim and trim settings when I power it off. I verified this yesterday and it works fine.

[majic1]

It's not that the Devo's don't save the settings. They actually do. The problem is when you re-initialize the gyro, the settings are ignored becuse the gyro assumes everything in the Tx is at '0' when initialized.

For example, let's say your heli has a tendency to drift slighly left after takeoff. So, you apply say one notch of right aile trim to compensate for this. Great, the heli is now hovering the way you want it. Now, you set the heli down to change batteries. You put a fresh battery in the heli and plug it in and the Rx initializes. You spool it up and take off and now the heli is drifting to the left again. You're thinking, what the hell? I just fixed that problem. You look at your Tx and sure enough the trims are the way you had them set, but now you have to add another notch of right aile to correct the problem again.

This happens because the gyro assumes everything is at '0' when it's initialized. So, it ignores your trim settings.

Why this is the case is beyond me? It kind of defeats the purpose of having a programmable Tx. This is why I am old school and prefer getting the mechanical setup right and therefore don't need to use trims.

[Rodney]

Jul 20, 2012 16:32:01 GMT -8 majic1 said:

I'm certainly no expert. But, my understanding is that all Devo's reset the trims when powered off.

That is not the case for the Devo 10. It saves the trim settings when switched off. At least, mine does. I find that to be a nice feature, doing set-ups or change a battery on the heli.