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Futaba 14SG chat

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Tim Flyer27/04/2018 11:06:41
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847 forum posts
139 photos

Interesting point there. Maybe there is a marginal benefit putting the Y lead on the elevator as they’d the last thing we would like to fail?

Frank Skilbeck27/04/2018 12:32:01
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4217 forum posts
98 photos

Tim, is not a matter of protecting against a failure but just that if you are using a Y lead to connect the battery up then it effectively divides the current between the two loads connected to it, in my example rudder and then receiver and remaining servos. There is a small voltage drop across every connection which is proportional to the current. On a big aerobatic model the most powerful servo is usually the rudder so it will take most current, by connecting that direct to the battery the current flowing to the receiver (and remain servos) is reduced and hence the voltage drop across the connector feeding the receiver is also reduced.

Adrian Smith 127/04/2018 12:40:06
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2124 forum posts
828 photos

Trust me to get hold of the wrong end of the stick, sorry Frank! blush

I am thinking of putting the y-lead on the Rudder CH (3) as suggested and there is only one servo on that. I have 2 elevators and 4 ailerons and of course the throttle CH.

The way the Test A/C set up on the TX is as follows:-

CH 1 aileron one, CH 2 elevator one, CH 3 Rudder, CH 4 aileron two, CH 5 aileron three, CH 6 aileron four, CH 7 throttle and CH 8 elevator two. On the Futaba 7008SB RX the battery plug is suggested for CH 7, but I would rather keep that away from the throttle given that connection goes straight to the ESC.

Tim Flyer27/04/2018 14:32:06
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847 forum posts
139 photos

Thanks for clarifying Frank. I’m certainly no electrician! The 14SG is a great radio (apart from weak antenna)and this chat is very useful as is Malcolm’s book.

Edited By Timothy Harris 1 on 27/04/2018 14:33:10

Adrian Smith 110/01/2019 15:56:33
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2124 forum posts
828 photos

As one who never sets any Expo, I thought I would experiment on introducing some on the ailerons on one on my aerobats. The reason for this is my thumb occasionally slightly wanders when doing a loop, introducing a slight aileron effect. Not good! I thought a bit of aileron Expo would stop this effect. I know doing this in isolation without the model (in workshop) is not the most sensible thing to do, but I just want to be clear on the methodology. So here goes - into the MDL menu for Dual Rates.

p1050610.jpg

I have assigned the rate to SA switch which has three clicks to it.

p1050611.jpg

I have set the Expo to +20 on the ailerons. This appears to be operational when the switch is fully UP.

p1050612.jpgThis is what the ON/OFF menu looks like. When the switch is fully DOWN then the rates don't register on the screen menu. Am I going in the right direction?

Edited By Adrian Smith 1 on 10/01/2019 15:57:02

Gary Manuel10/01/2019 16:18:19
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1772 forum posts
1507 photos

I'm not a Futaba user but the curve looks to be the wrong way to me - i.e. try -20 instead of +20.

Here's a tip for checking that you have gone the right way with the expo. Set it initially to some really high value that allows you to really notice the effect. e.g. -50 or more. If it's working the right way, reduce it to a more suitable figure with the same sign i.e. -20.

Jon Laughton10/01/2019 16:20:21
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1105 forum posts
94 photos

As a Futaba user I can confirm that the pictures / curve do indeed show +20% exponential not -20%

Malcolm Holt10/01/2019 16:29:14
83 forum posts
2 photos

You only need to assign a switch if you want to be able to switch between different rate and/or exponential settings. If you simply wish to add exponential to a model without an aileron rate switch you should remove SA by re-setting it to --.

Now go to the two EXP settings and, as noted above, set NEGATIVE values of your choice such as -20.

If you want to use more than one rate and/or exponential then leave the switch assigned. When SA is UP you will see the black arrow next to the number 1 (First rate). Any rate and exponential settings entered on this screen will apply when the switch is in this position.

Now move SA fully DOWN. You will see the arrow move to number 2 (Second rate). By default, the rates on this screen will be 100 and the exponential will be 0. Change the rate and/or exponential values to those you require for the second rate setting. You might, for example, want the rates reduced to 70 while maintaining the exponential at -20.

Finally, doing this without the model is absolutely fine. That’s what the servo monitor is for and, as it gives precise values, you can sometimes get a clearer picture of what is happening

Adrian Smith 110/01/2019 19:09:02
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2124 forum posts
828 photos

Hmmm .... as you can see Gary & Jon I am not too clever on this! Appreciate your input.The Futaba manual is none to helpful I can tell you.

Thank you, Malcolm. Your explanation makes it all clear and I will give it a go later. I do have the download of your book somewhere, but it's some while since I looked at it so I just have to go and search where it is on my PC!

Thanks again.

Adrian Smith 111/01/2019 15:36:49
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2124 forum posts
828 photos

 

I am a bit puzzled, Malcolm.

With the plane in front of me in the work shop, I removed the SA rate switch setting and added the Aileron EXP settings at an arbitrary -30 for both readings. I didn't notice any perceptible difference.

p1050615.jpg

The curve graphic seems ok, but I didn't really notice any difference on the plane. Tuned in to -90 to see what the effect was. Didn't see any different when activating the ailerons even with such a large reading. I must be missing something obvious here although for the life of me I can't see it.......

Edited By Adrian Smith 1 on 11/01/2019 15:37:27

Malcolm Holt11/01/2019 16:25:06
83 forum posts
2 photos

With the exponential set to -90, move the aileron stick from its central position half way to the right while watching the amount of aileron movement. Now move it from the half way position to fully right while again watching the aileron. The amount of movement in the first case should be less than in the second. What happens on your model?

Adrian Smith 111/01/2019 16:50:52
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2124 forum posts
828 photos

Will do, Malcolm. I will have a look tomorrow. I am prepared to believe that I am not prepared for the subtlety of it. I am not sure what to expect really I guess. Will report back tomorrow. Thanks for your patience Malcolm.

Adrian Smith 112/01/2019 15:44:52
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2124 forum posts
828 photos

So after a bit of testing this what I have established. Firstly, the ground rules. The aileron servos are Savox Digital SC-0251MG's. The full throw is 30% either way.

I set the EXP at -90.

p1050617.jpg

I moved the stick halfway across its range and the aileron registers around 8% as per the next snap ( not too clear, but take my word for it)

p1050621.jpg

So next I reduced the EXP to 30%:-

p1050615.jpg

Stick movement again to halfway, the aileron throw now increases to around 15%.

p1050623.jpg

So the EXP function seems to be doing its job. I just wasn't sure what to expect visually and the effect of these arbitrary readings would have.

Edited By Adrian Smith 1 on 12/01/2019 15:45:50

Malcolm Holt12/01/2019 15:56:55
83 forum posts
2 photos

Yes, the exponential is working as it should.

I can't help but ask why you are only using 30% throw on the aileron servos. This places a much higher load on them and reduces the resolution. Can't you achieve the required throw by moving the connections to the horns and servo arms?

Malcolm Holt12/01/2019 18:31:46
83 forum posts
2 photos

Just occurred to me. Do you mean 30 degrees?

Adrian Smith 113/01/2019 08:05:27
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2124 forum posts
828 photos

Yes Malcolm its 30 degrees. My Apple keyboard doesn't seem to have a degrees sign and I got lazy! That said I should probably look at servo geometry as well as part of the whole deal. I find the current the roll rate is quite fast with 30 degrees, but for anybody wanting to do 3D it would not be enough. Thanks for your observations, Malcolm.

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