Throws, travel adjust and Expo???

[Ross Clarkson]

Hi all,

 

I am currently still in the process of setting up my new plane with a DX7 Tx.

 

I have set all the pushrods and linkages so they are all neutral but now getting a little confused with the above to get the right movement from the controls.

 

I think i have expo sorted. That is just relating to the sensitivity of the sticks at near centre position, right?

 

Travel adjust: Used to stop servo's binding and rods bending too much?

 

Now, throws??? Are these dual rates? Basically, are these so you can set up 2 x different set-ups. I.e. Low rate = a preset amount so the controls dont move as far.

...and High rate = a preset amount where controls will move further giving more sensitivity.

 

Giving you an ability to switch easily between the two in flight.

 

?????

 

Cheers.

 

[flytilbroke]

U got it Ross. Only you don't want the rods to bend under pressure, not just "too much".

 

Cheers

[Stephen Grigg]

You and me both Ross,someone put Expo on a model for me and I couldnt cope with it ,bit spongey,first nothing then it came all at once

[Simon B]

Sounds like they put too much on.  With mild expo it should be fairly subtle.

[Biggles' Elder Brother - Moderator]

Stephen, you often have to tweak expo quite a bit to get it just right. It shouldn't be spongey then all come in at once - that sounds like you had too much on.

 

The idea of expo is based around the concept that we tend to use the controls in two basic ways:

 

1. small corrective movements when just flying around

 

2. Much bigger, almost 100%, movements when we either fly very slowly such as landing or in aerobatic manoeuvres.

 

Without expo, 10% stick movement from the centre or at the extreme both give 10% control surface movement. This tends to mean that the corrective movements used in normal flight can be very very small indeed. To desensitise the centre and allow bigger movements for small control surface movements in "normal flight" we use expo. This should feel less "twichy" and easier to fly - whilst still giving you the big movements for your flick rolls etc. But the change over should not really be discernable - it should be seamless.

 

Try experimenting with it more - it really is worth the effort. Just add a little to start and go from there to find the amount that suits you, your style of flying and the model

 

BEB

[Tim Mackey]

Expo is a very personal "feeling". I have some models where I have almost none, and others as high as 90% on ailerons.

[Stephen Grigg]

I do like a model that goes exactley where I put it,as I give direction it reacts immediately.My Pulse diid just that.When landing \\\iwas in full control,if my approach was a bit short thr tiniest readjustment worked,if to high it still could be brought down and landed on the strip without any fuss or to much speed. It landed exactly where I wanted it to every single time.How would expo help me in this instance?

[Biggles' Elder Brother - Moderator]

Well, not all planes are as "sweet" as the pulse! If you want precission in your manoeurves at high speed a lot find its easier if you have rather less sensitive controls - you can achieve more "feel" that way. - But if you optimise your controls for that situation then full stick movement will not give you enough deflection for high roll rates or that final flare without expo.

 

What Timbo says is quite true - it is a individual thing, individual to the person and the model. It could well be that the Pulse does need expo. But try it on a scale biplane's ailerons - or more significantly - on the elevator of an aerobatic model with its CoG set fairly far back and you'll soon find the benefit!

 

BEB

Edited By Biggles' Elder Brother on 01/02/2010 00:24:16

[Stephen Grigg]

So,is it more beneficial on the highly twitchy models that have barn doors for controls

[Biggles' Elder Brother - Moderator]

Mmmm? Interesting question. I don't do 3D - but I'd guess they might almost want inverse expo - if you watch the control surfaces their all very big movements - they don't do subtle!

 

I find its most needed on models that have twichy elevators or ailerons that are over effective at high speed. So it helps me to stop flying along either in a series of undulations or rocking from side to side.

 

For example, if the ailerons are really sentivtive at high speed then you often find yourself unintentionally banking the model when you are using the elevator (assuming mode 2) or vice versa puting unintentional elevator into your rolls - resulting in the model moving off the centre line during the roll and exiting to the left or right of where it went in. All this can be helped by expo. Tiny unintentional movements dont have disproportionate effects then.

 

There are lots of other examples as well - to do with giving you more feel at the small movement end of things. As I say, just experiment a bit. Try different amounts, try it on different models. Eventually you'll start to judge when it would help and when it wouldn't. But honestly its not just an expensive gadget put on the trannies to justify the price - it really can help tame an otherwise difficult to fly model.

 

BEB

Edited By Biggles' Elder Brother on 01/02/2010 01:04:32

[Tim Mackey]

Another scenario ( that affects me anyway ) is that as a mode one flyer, when I whack open the go stick for a nice low fast pass down the strip on my small EDF Sabre, the ailerons are very sensitive on this model and the slightest movement of the stick will have an immediate effect on roll. It is virtually impossible for me to quickly move the throttle stick over its whole travel without adding a little bit of aileron movement with it.

90% expo helps in this case, as the first bit of stick travel is nulled, so the modl maintains a nice level attitude for the strafing run

I would expect that some mode two flyers may also find it beneficial to "seperate" stick movement between ail /ele

[Tim Mackey]

Sorry BEB - I have just realised you mentioned mode 2 latterly in your post above.

[Biggles' Elder Brother - Moderator]

No prob Timbo - good to have the mode 1 case as well! And a good example of the fact that what ever problems you have on one mode - there are, generally speaking, equivalent problems on the other. For me as a mode 2 flyer its turning out of rolls and loops - for you its unintentional rolling during strong throttling up - it all amounts to the same probelm. There is no such thing as "the right mode" - only the right one for you!

 

BEB

[ken anderson.]

hello ross-to be honest with you-the model you are flying will not want any expo put on the controls---i think/know this will make it harder to fly than it is....fair enough have the dual rate's...and after a maiden flight-if you feel a need for expo(which i'll be surprised).if you do...apply some then......really i think you are complicating matter's-for basically what is a very stable model...which has a fair amount of good characteristic's allready built in.....

 

    ken anderson...

[Ultymate]

The main joy I find with expo is that if you set it up correctly the model will feel exactly the same around centre stick whether your on low medium or crazy 3D rates. Thus if you do get into bother whilst attempting something on high rates providing you keep your stick movements small the model will feel as if it does on low rates and you don't have to scramble for switches whilst trying to get out of the do-do

[Myron Beaumont]

Re: unintentionally moving one control with another syndrome

Answer ? Stronger springs on the sticks !

[Vecchio Austriaco]

First I have to say I use expo on all models - especially on the elevator it is of great help. But what Myron wrote is true as well - to avoid mixing things so easily I have a stronger spring setting on the aileron then on the elevator - this helps finishing loops at the same point where they started. (if there is no gale blowing...)

VA 

[Myron Beaumont]

Vecchio

I think you think like me .Mechanical solution ! It works doesn't it ! I always tended to mix up the right stick (mode 2) and using elevator & /or aileron using thumbs on approach  always managed to feed in a bit of the wrong one .As has been said Expo helps -But that is not the point of it .

By the way ,I start off with 30% on everything nowadays on everything & my dual rates are 75% of max &100% (max) .I can't say that I've altered far from that but then again I'm not seeking the ultimate settings  eg 3-D etc

G-umpy

[Andy Harris]

I really learned the practical side of expo on indoor models.

 

They tend to be twitchy anyway so the application of expo calms them down, too far and you'll find turns less than crisp ... and you have so many short flights, plenty of chances to try stuff.

 

Andy.

 

[Stephen Grigg]

Are you getting it Ross, IM understanding expo more now thankyou Gents

[Stephen Grigg]

Are you getting it Ross, IM understanding expo more now thankyou Gents

[Ross Clarkson]

Yep, crystal clear now Stephen.

 

Thanks guys, exactly what i was after.

 

Just one quick further question, might be silly but please bare with me.

 

Is NO expo 100% or 0%?

[Ultymate]

No expo is 0%.On Futaba negative expo softens response while on JR/Spektrum positive expo softens the controls

[Ross Clarkson]

Cheers all.

 

I have gone for:

 

+30% expo on all surfaces.

 

55% and 75% dual rates on all surfaces.

 

Travel adjust set up as required.

 

Thanks for all your help. Really getting to grips with it now and it has helped massively to set my aeroplane up properly.