Elevons

[Alan Dorrell]

Hi out there

Can anyone help please. I am just finishing off my latest project which is a converted free flight delta to R/C and EP.

My Tx is a Futaba 6EX and my Rx is an Orange FASST which has so far proved totally reliable. The problem is, having programmed in for elevon mixing strictly according to the manual, it is working beautifully, except for the fact that the elevators work on the lateral (side to side) movement of the stick and the ailerons on the up and down.

I have tried changing the servos on the appropriate Rx sockets, altering the throw % and reversing the servos, to no avail.

Any suggestions or help would be gratefully acceptable. I'm puzzled.

Cheers. Alan

[chris basson]

I think I had this problem, setting up my Wildthing, if I recall I got around it by swapping the servo connections into the rx and sorting it out from there, reversing servos as required.

Alternatively just turn the tx round 90' & Robert is your Mothers Brother!

CB

[Simon Chaddock]

I found it easiest to connect only one servo and then get that performing correctly to the stick movement by reversing the servo direction on the elevator and aileron circuits as required.

When it was working correctly plug in the other and it should be fine.

Failing that get a separate elevon mixer unit and return the TX to normal!

I actually did this on 2 of my deltas simply because the DX6i did not make a particularly good job of the mixing ad limited the throws to 50% on pure elevator or aileron movement. The mixer seemed to be cleverer and gave nearly 100% on each but when both were fully applied it took one to 125% and reduced the other to 75% which seems to me a better combination.

I could not programme the DX6i to do this.

[Frank Skilbeck]

Posted by Simon Chaddock on 13/01/2014 13:46:39:

I actually did this on 2 of my deltas simply because the DX6i did not make a particularly good job of the mixing ad limited the throws to 50% on pure elevator or aileron movement. The mixer seemed to be cleverer and gave nearly 100% on each but when both were fully applied it took one to 125% and reduced the other to 75% which seems to me a better combination.

I could not programme the DX6i to do this.

I think you'll find the Futaba 6EX is the same it seems to be the way the entry programmable Txs do it. On the Dx6i there is a work around if you are using a 6 channel Rx and that is to set it up as a dual aileron wing with flapperons and then mix in elevator with flap (with trim enabled) and you get full movement for both aileron and elevator and you can even program in aileron differential if you wish.

[John A H]

In the older Futaba 6EX manual there was an error in the Elevon mixing instructions (page 22).

In step 1. of ACTIVATE ELEVON MIXING it should read :-

"1. Connect the servo in the right wing to channel 1 (aileron) in the receiver and connect the servo in the left wing to channel 2 (elevator) in the receiver."

The manual has it the other way round.

Onvce right servo is plugges into right channel set the servo direction for channel 1 and 2 to NORMAL (not REVERSE) you should end up with the stick "on up and down" (elevator) operating both elevons up and down together. If UP elevator (pulling stick back) applies "down elevons" then you need to reverse both channels. Once "elevator" is working in correct direction the "aileron" will operate the elevons as ailerons (one goes up as one goes down)

The key is to get the right servo in the right channel and start with channel 1 and 2 direction set to "NORMAL" .... the error in the manual means you start off on the back foot with the servos/channels the wrong way round and then get lost messing with servo reversing.

Hope that all makes sense - it had me stumped the first time, I wrote the correction into my manual with biro.

Once sorted double check that "up is up, left is left" etc. on the controls it is quite easy to have brain fade after messing around with elevons for first time ......... luckily I doing a test glide of a foam wildthing when I discovered my mistake so it bounced OK without damage.

The manual may have been corrected for newer transmitters, mine is from 2008.

[John A H]

P.S. the 6EX allows you to set the aileron and elevator percentage movement. I would start on
+50% for each. The manual says the value range go from +100% to -100 .......... I've not played with it but I would assume -ve values would act like servo reverse ... which could be confusing.

[Shaunie]

Can't be specific as I changed from Futaba to Spektrum when I went 2.4GHz but look at each elevon individually, disconnect the other if it messes your head up! check to see if it goes the correct way for an aileron input and the correct way for an elevator input. I think you will find one elevon is reversed. When this happens it appears that the aileron/elevator axes are crossed over. Be methodical and it will make sense.

Shaunie.

[John A H]

Shaunie's comment highlights the fact that there was an inaccuracy in my explaination - even with the servos plugged in the right channels "elevator" may look like it is operating ailerons with the control surfaces moving in opposite directions, it depends which way round your physical servos are "pointing".

so...

1. plug servos into correct channel in the receiver taking into account the manual may suggest wrong way round.

2. operate elevator stick - if control surfaces go in opposite direction reverse either channel 1 or 2 (if surface on right wing goes in the wrong direction reverse channel 1, if left wing then reverse channel 2

3. now aileron stick should operate the ailrerons correctly as well

- the issue is that if you don't have the servos plugged in the right receiver channels initially one control will always operate in wrong direction (e.g. you "fix"elevator by setting up servo reversing but then right aileron input applies left aileron control surface movement, so you reverse both channels to fix that and now up elevator input applies down elevstor control etc. etc. etc. you end up going round in circles.

Edited By John A H on 15/01/2014 09:20:56

[Phil Green]

Wings are very pitch sensitive and its usual to use much less elevator than aileron in the mix, 75:25 ail:elev is a good starting point. The older 6EX didnt have the option to reduce throws individually, hopefully yours does. Mine didnt, and the only way to get anything other than 50:50 was an onboard mixer. As commercial mixers are very poor resolution I ended up doing my own, I used CPPM so theres only one single lead to the receiver carrying power and all the servo signals. I found it helped to ignore logic and instead write down a list of the eight possible combinations of rx channels & reversing, & to tick off each attempt, otherwise I was repeating myself and getting nowhere! ie

left in rx ch1, right in ch2, ch1 normal, ch2 normal

left in rx ch1, right in ch2, ch1 reversed, ch2 normal

left in rx ch1, right in ch2, ch1 normal, ch2 reversed

left in rx ch1, right in ch2, ch1 reversed, ch2 reversed

left in rx ch2, right in ch1, ch1 normal, ch2 normal

left in rx ch2, right in ch1, ch1 reversed, ch2 normal

left in rx ch2, right in ch1, ch1 normal, ch2 reversed

left in rx ch2, right in ch1, ch1 reversed, ch2 reversed

Its a brute-force method but I found it quicker than thinking about it!

Cheers

Phil

 

 

Edited By Phil Green on 15/01/2014 10:16:38

[Alan Dorrell]

Thankyou guys for your inputs. I believe (with your help) that I got it sorted and all worked as it should.

However , suddenly there was no activity from the 'aileron' servo. So I am now in the process of servo checking at the junctions meaning that I am having to thread thread the leads back through the model. Very fiddly and I may have to cut an access hole in the covering. Ah well !!

Alan.

[Phil Green]

Before ripping any wires out Alan I'd check the servo in situ with a servo tester, this will prove whether the servo has died. If its ok on the tester, maybe your mix has changed and isnt outputting to that servo. Or maybe you're on the wrong model memory!

[Alan Dorrell]

Hi Phil,

I had to do just a little cable withdrawing, not as bad as I thought, in order to be able to check the servo.

That proved to be as dead as a dodo, so has to be replaced. Unfortunately I dont have any more servos of that type but will be going to my favourite model shop towards the end of this week. Fortunately I have several minor finishing tasks to keep me occupied.

Cheers. Alan.

[Paul Marsh]

Luckily it didn't happen in the air, deltas don't fly well with only one elevon...

[Alan Dorrell]

Elevons now successful !!! I had damaged the servo with setting one or the other at 100%. John A H'S posts were key. Mine must be old manual. Any way, thanks again guys. Unfortunately our field is virtually under water so will have to wait for the maiden. (who is she ?)

Alan.

[Mowerman]

Field under water? I was about to suggest fitting floats but then re-reading your posts I see it is a delta, Could this be done?

Another thought, could you build a raft then hand launch followed by 'carrier landings'.

Yes I know I am being silly but in this weather it helps to pass the time.

[PatMc]

Allan, you will probably be able to download a pdf copy of the newer version manual from Futaba's website. Google's you friend if you need to find it.

[Alan Dorrell]

Mowerman

Seriously, I would love to go with floats or flying boats. Unfortunately I am now classed as disabled and fly from my wheelchair. Just a tad restrictive. Roll on some dryness and even calm weather.

Alan.

[Paul Bray]

Hi Guys,

looks like Alan got this fixed which is good news.

Slightly off-topic but driven by posts within this thread..........

When a form of mixing is applied where 1 servo performs 2 functions, like elevons, the 100% throw is actually 50%. Sounds odd (stupid) but if you think about it, a servo has an angle of movement which it can move through which can never be more that 180 degrees (if it was it would start coming back, could make life interesting). As this angle is limited if you had 100% throw for one function and then added another 100% for the other function you would have 200% of movement, add some trim and a slightly off-centre photometer and you would have an angle which could be larger than that which the servo can mechanically move through.

However, most servos move around 60 degrees in each direction which if we multiply by 2 (elevator movement plus aileron movement) we would get 120 degrees on each side so you may be thinking no problem, still below our magic 180 degrees. Thing is, the idea of a servo is to create movement and once the servo arm moves away from an angle of 90 degrees relative to the pushrod it starts to move 'in' as well as down (or up) because it is moving through an arc. The further it travels the less movement it produces on the pushrod so it we did use 200 % total travel (120 degrees) and you had a situation where you had full elevator or aileron you would have next to no movement on the other function, could also make for some very exciting moments!

The answer my friend is to fit longer arms which will give the correct deflection required on the control surface when using only 50% throw and to take the hit that you will loose a bit of movement when the sticks are getting near the corners.

Why is nothing as simple as it seems in this hobby???????????