Hi ,

Looking for any opinions pro or con regarding using digital servos in a trainer. I know they can hunt if the control connections aren't set up correctly and drain the battery faster.

And of course the price is prohibitive but I can get a good deal on them as they came from someones' defunct setup.
I'm assured they haven't been in a crash.

Anything else?

You've already covered most of the factors. The biggie is that they drain your battery faster than analog servos. For this very reason I wouldn't use them in a trainer. And besides, they are overkill for a trainer. If you can get a good deal on them buy them and save them for your 2nd or 3rd plane.

Ken

Make sure your controls don't bind (something you should do anyway) and go with them. Keep an eye on your battery charge levels with an ESV and/or get a bigger battery pack. The industry is heading toward digitals anyway, you're just leading the way.

Thanks for the reply Ken. I'm a little confused on the battery drain though. My understanding is the battery would drain faster due to the slop in the contol rods or binding.

This is from futaba.

Q: What can I do to ensure that my digital servos offer long life?

A: Your number one concern should be that linkages are tight, with absolutely no friction or stiffness from binding. Standard servos don't notice common problems like slop at neutral, but a digital servo will - and in the process of struggling to hold the rod in position, it will quickly drain your batteries and eventually ruin its motor. Digital servos always work to hold positions at full strength. If at any point the servo must "fight" the linkage to locate and hold its position, it will literally burn itself out.

While what Futaba says is true, there are other concerns. Plain and simple, digital servos draw more power. With an analog servo they move to the center position and "sit" there until they are commanded to move again. With a digital servo it constantly needs to "check" it's position, so they are always "thinking" about where they are. And they will be making minor adjustments to their position.

Ken

Thanks Bruce,
I was setting up the controls and noticed some binding while using the metal rods especially in the throttle. Even though it has a very gentle radius to negotiate, I noticed some stiffness when compared to its' straight through position.

I can either reduce the radius by relocating acces hole through the F1 former or use some other type of control rod. The only drawback with #1 this is that the rod will take up some space in the fuel tank compartment and result in the foam surround there compressing a bit.
For #2, I was thinking I could use some Sullivan Golden Rod left over from the rudder control.

I didn't feel comfortable using the balsa and thread method. Well that and the golden rods are very easy to work with.

I like Gold-N-Rod's. Remember not to leave too much unsupported length and any control should be as straight as possible to reduce drag. Don't use oil as it will only pick up dust and cause drag. Clean and dry is best.
Ken is correct in that whenever a digital servo moves it does so at "FULL" power whereas an analog does not. That is one reason a digital draw more current. Even if only rotating one degree it is at full current/power for that moment.
The power switching can be compared to turning a faucet (analog servo) or flipping a wall switch (digital).

I appreciate all the good advice. I'll get some analog standard servos to use and save the others for something else.

I followed Kens' build on the LT40 and applied many of the techniques there for setting up the control rods. Thansk Ken

I'm still debating what I will do about the throttle control. I 'm trying to avoid too many extra holes in the firewall. I'd have to enlarge the hole to use he golen rods but I don't see any disadvantage.

Probably best choice. Bigger hole should be no problem. What trainer do you have?

I have the Goldberg Eagle II trainer and I have to say it's a great kit for a newbie.

I also figured out the control rod for the throttle. I made a dumb newbie oversight and tried to complicate the matter.

I'm sitting there fiddling with it and realized I had the smallest diameter servo arm that I was trying to line the rod up to. I look up and see the bag of extra servo horns and right there is one with a long arm.

That brings the rod into a straighter position and eliminates most of the bend I was trying to alleviate.
[sm=spinnyeyes.gif]

Sounds good. Now, what radio system? Gosh, this is like pulling teeth.

OUCH!!!! I'll talk,I'll talk.

I have the Futaba 6exas and a Futaba 127df receiver. I think it will be a good setup for a beginner.

Excellent radio. Make as much of the control adjustments (Centering,amounts of throw and such) as you can by adjusting the mechanical linkages first and then use the EPA functions to fine tune if needed. You shouldn't need to worry about the other functions (dual rate or Expo) on a trainer. Makes it easier for the buddy box too. Be sure you can use the engine kill function to shut down the engine too, I think it has that function.
I've actually got an old Eagle 2 stuck away that I don't fly anymore. Got it along with a lot of other stuff in a large purchase.
Yup, just checked, you got a cut button.

It does have a lot of features that I probably won't need for a while. I bought it thinking I might progress in the hobby and I can use it for a second and maybe third plane.

I actually bought it before the trainer to use with a rocket plane I have that is built and still not maidened.

I realized after i got that i'd better start small and work my way up.