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RC Radios, Transmitters, Receivers, Servos, gyros Discussion all about rc radios, transmitters, receivers, servos, etc.

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Old 11-26-2011, 06:39 PM   #1
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Default Expo Question (DX6i if it matters)

I"m having a brain fart..

on a DX6i you can set expo. Default is 100% - meaning no exponential right? No reduced sensitivity around center stick positions.

I can change that on the DX6i to anything less than 100%. So I assume 30% would give me less sensitive center position compared to 70%?

So I could set up dual rates - say, 80% travel and 35% expo to have a mild plane and 110% travel and 90% to have a wild, twitchy one (relatively speaking?)
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Old 11-26-2011, 08:51 PM   #2
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I'm not familiar with that transmitter but generally, 0 expo means there is no change between expo on or off. Normally, on JR or Spectrum, you want to have positive expo, usually start at about 30% and then change as you try it. Some like about 50%, some like less. If you have a Futaba or Hitec, make sure that you use negative expo, the companies do not all define expo the same. Positive for most, negative for Hitec and Futaba.
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Old 11-26-2011, 10:29 PM   #3
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Not quite right.

The default expo setting is INH (inhibited--turned off) when you turn it on, then
you set a number. 0 is no expo at all and to make the controls LESS sensative
around nuteral, you ADD expo so 15% is a little and 70% is a LOT of expo.

The nice thing about computer transmitters is that you can try different amounts
and see if you like it and change it if you don't.

You can also add NEGATIVE expo and that would have just the opposite effect.....
making it MORE sensative. Don't mess with this......

Dual rates is another thing all together. There the default is 100% meaning that the
servos can go end to end, or 100 % of their travel. You can set a high and a low rate
and they can be full (100%) or any amount less than that.

I hope this isn't too confusing for you.......just think about it and experiment a little and you
will find the settings that feel right for you.

Helicopters don't really fly.......
They're just so ugly, that the earth repels them.
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Old 11-27-2011, 12:23 AM   #4
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THat helps...my dx6 seems to start at 100% expo. I'll have to experiment and see what 0 or even - can be like.
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Old 11-27-2011, 01:42 AM   #5
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Originally Posted by prof_fate View Post
THat helps...my dx6 seems to start at 100% expo. I'll have to experiment and see what 0 or even - can be like.
None of the systems start at 100% expo.

You are looking at servo movement at 100% the default value. This tells the servo how far to turn.

Expo defaults at 0%. 100% expo would be nearly impossible to fly...

With Spektrum you use positive values to soften the throws at Center.

So I think you are mixing up servo throw with expo. For a quick test you can set the servo throw to 50% and you will see that servo now only turns half as much as it used too.
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Old 11-27-2011, 02:24 AM   #6
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Originally Posted by prof_fate View Post
I"m having a brain fart..

on a DX6i you can set expo. Default is 100% - meaning no exponential right? No reduced sensitivity around center stick positions.

I can change that on the DX6i to anything less than 100%. So I assume 30% would give me less sensitive center position compared to 70%?

So I could set up dual rates - say, 80% travel and 35% expo to have a mild plane and 110% travel and 90% to have a wild, twitchy one (relatively speaking?)
Just a note of caution with expo.

IMHO, it's best to use no expo on a maiden flight of your model. I used 40% expo on one of my models this past summer. Quickly found out that the model was WAY out of trim, and had to fly it with about 40% up elevator. The transmitter was at the end of its trim adjustment.

That put the model right in the middle of expo, making the elevator very sensitive to transmitter controls. It nearly went in til I figured out what was happening.

Then after all is dialed in, dial in expo in your transmitter to suit your taste in model handling.

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Old 11-27-2011, 10:14 AM   #7
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Originally Posted by prof_fate View Post
THat helps...my dx6 seems to start at 100% expo. I'll have to experiment and see what 0 or even - can be like.
I don't think so. What you're looking at is the servo throw for the dual rates. The first column is the throw and the SECOND column, which defaults to INH (inhibited or no expo), is the expo value.

If you want to use just expo then you leave the first at 100% total throw and set the second to the value you want....and don't forget that it's switched by default so you need to remember if the expo is on when the switch is UP or DOWN (or if you want it permanently on set it twice, once for each switch setting) .

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Old 11-27-2011, 01:53 PM   #8
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Originally Posted by slipstick View Post
What you're looking at is the servo throw for the dual rates. The first column is the throw and the SECOND column, which defaults to INH (inhibited or no expo), is the expo value.

Steve
Good point of clarity. It is the servo throw on dual rates.

Denny while I certainly see where you are going with care on expo I have had planes that wouldn't have survived the first flight without expo.

Most good manufactures will tell you good initial values. Horizon and GP typically do a great job of that.
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Old 11-27-2011, 04:03 PM   #9
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Yeah, I usually throw in some expo, then see if it needs more. But I agree, too much expo can be a very bad thing. Almost cost me one model.
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Old 11-27-2011, 05:11 PM   #10
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OK, I guess it's dual rate that has me confused then.

When I set up a model I set up travel adjust on the servo/plane/radio.
So what you're saying here is I still do that BUT I also can adjust how much movement I have on teh DR setting?
So if I have to set the travel adjust to say, 120% to get full throws then on teh DR setting at 100% that is what I"ll get. And if I set it to say, 80% at the DR the servo will only travel 80% of what I have set up in travel adjust?

This is beginning to make some sense!
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Old 11-27-2011, 11:13 PM   #11
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Originally Posted by rcers View Post
Good point of clarity. It is the servo throw on dual rates.

Denny while I certainly see where you are going with care on expo I have had planes that wouldn't have survived the first flight without expo.

Most good manufactures will tell you good initial values. Horizon and GP typically do a great job of that.
Yeah
Guess it all depends on the model. If its well in trim, expo should not be a problem.

Last week, a fellow club member tried to maiden a rebuilt foamie with about a 3 foot wing span for another club member. The Ailerons and Elevator had over 45 degrees throw on them, the pilot suggested those throws be cut down by half, or more. Owner of the model said, "FLY IT".

Well, after two violent rolls, first right then left, the model went in. Owner of the model didn't stop laughing for several minutes, and indicated he'd rebuild it again, should take about 30 minutes or so. Since it was a pusher, not much damage took place. (The pilot was a very experienced flyer)

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