Four more silly novice questions..

[paul devereux]

I have looked on the internet for answers to these but have still been unable to get my head around them. I am new to computer radios.

1. Dual rates generally. I can understand one might want to make control throws less fierce, and be able to switch between a gentler response and a more savage one, but how can you have + or - alterations? Presumably manufacturers set up their servo arms to travel just a bit less than 180 degrees to give maximum movement, so I can understand how putting in -50 will halve the movement. But how can you have more (+50%)? Surely that would take the movement more than 180 degrees? 

2. And is reducing the movement via dual rates by 50% just the same as adjusting the end point so there is less travel? Could I just reduce the end point movement of the ailerons to give the same effect as -50% d/r?

3. Looking at a slightly wobbly motor, I also noticed the rudder was set to give a bit right, and the ailerons to give a bit left, I think think both may have been bumped through hanger rash and fortuitously cancelled each other out. I set both centered, and the plane seems to fly faster, and the controls more fierce- I think this must be due to decreased drag from the ailerons and rudder no longer "fighting" each other. Am I right i thinking I can just adjust the aileron endpoints, to give me a more controllable plane?

4. And this takes me to my last silly question- I've now trimmed for straight and level flight at 3/4 throttle, but I felt I had to land the plane to input adjustments, and then try again. Do most people manage to alter trims while in the air- (I felt that if I took my thumb off the main control, the plane would bank off into the ground)?

Edited May 10, 2023 by paul devereux

[GrumpyGnome]

For 1. and 2., I could explain this for my radio but not yours.

 

I think Youtube is your friend here as you'll possibly get more value by spoken word and demonstration, than by a written response.

 

You can achieve 3. by adjusting throws mechanically, by changing endpoints, or by use of Expo.  Again, Youtube can help (but watch a few as some are dire and full of rubbish.  Also, your manual will explain Dual Rates, Expo, End points etc..)

 

AFAIK, most people adjust trims in the air.  On a maiden flight, it is not uncommon for someone to adjust the trims in flight for the pilot.

Edited May 10, 2023 by GrumpyGnome

[Cuban8]

The way I set things up is to start with dual rates set to 100% and 70%. I then adjust end points to ensure that there is no binding of the control surface or whatever it is that is being set up.  End point can be adjusted individually for each side of the servo throw (up/down, left/right, etc.) whereas DR sets both ends together to whatever figure has been chosen and sets the overall movement available.

All this must be carried out after any mechanical settings involving the centering of the servo and output arm, and postitioning of the pushrod with respect to where it'll sit along the surface control horn and servo output arm. Get the mechanics and geometry of things right before anything else.

Far easier to demonstrate than to try to describe TBH. Useful just to play around and experiment as well.

 

[Martin Harris - Moderator]

To a certain extent, servo movement is specific to each type and to the radio you’re using but generally, 100% gives something like 45 degrees either way of neutral. 
 

By going beyond 100% you can increase deflection which may take the servo to its physical limit.  Some radios allow you to set an overall limit which is useful should you employ mixes which add movement to existing settings e.g. crow braking.

 

When setting up your movements it’s good practice to aim to use around 100% of the movement to give anticipated full movement of the surface - you do this by selecting appropriate holes on the output arms and control surface horns.  This gives the servo optimal mechanical advantage and resolution. 

[Jon H]

14 minutes ago, Cuban8 said:

Get the mechanics and geometry of things right before anything else

 

absolutely. And use the right size arm on the servo for the job. No point using a long arm with the linkage at the end, and then reducing the travel to 20%. Use a smaller arm/move the rod closer to the middle and use the full travel. 

 

The use of rates depends greatly on the model in question. I use them on my warbirds for takeoff and landing as i often need a bit more movement to give the required authority at lower speeds. So for takeoff my pre flight would be elevator rates high, aileron rates low, flaps up. Once the wheels leave the ground its gear up, rates low, timer start. For landing the following procedure is followed from the start of the downwind to the start of final. Throttle back, gear down, elevator rates high, flaps half, flaps full, aileron rates as required depending on the wind. 

 

For an aerobatic or 3d model you may use high rate in the air and low for takeoff and landing. My Nieuport biplane, my Tomahawk, spacewalker etc do not use rates at all (they are set up but never needed) so you need to evaluate the model you are flying and work out what you need. Dont just follow someone else's setup blindly. 

 

When it comes to adjusting trim in the air its a skill to learn. The method i teach is if you need up trim as the model is diving, pull the nose up 45 degrees and then start beeping. Similar situation with ailerons. This method gives you time to add the adjustment without the model steaming towards the earth. One thing you need to be able to do is find your trims without looking at the radio as taking your eye off the ball can be fatal. On maiden flight however it can be helpful to have an assistant next to you as they can beep your trims for you if its all a complete handfull. 

Edited May 10, 2023 by Jon - Laser Engines

[leccyflyer]

...and don't inadvertently turn the radio off whilst searching for the trim levers 😉

[Denis Watkins]

I think think both may have been bumped through hanger ( by Paul )

 

Be extra careful moving models Paul

Casual bumps on surfaces destroy servo gears very easily.

Test servos for full throws carefully as usually teeth are missing from ( bumped ) gears

[Cuban8]

36 minutes ago, leccyflyer said:

...and don't inadvertently turn the radio off whilst searching for the trim levers 😉

Oh yes, it has been known........not guilty myself, thankfully.

The on/off switch slider on my DX8G2 could do with being a bit stiffer to operate IMO so could do with being shielded more effectively against accidental operation.

[Simon Chaddock]

paul d

Just a thought but the servo moves the control surface by means of a mechanical linkage.

If you are sure you want less travel why not adjust the linkage by moving to a hole nearer the centre of the servo arm and/or use a hole further out on the control horn? This has the advantage that the servo will be working at a better mechanical advantage so will use a bit less amps to apply the same force on the control surface.

 

Before the wonders of modern radios this was how servo travel and thus control sensitivity had to be set up and it was up to you to mechanically set up each plane so it worked satisfactorily using common settings on the transmitter.     

[toto]

For what it's worth ( in my limited knowledge so far ), your point about altering how savage throws work, in an example,e of the throttle, can be adjusted via the throttle curve function. This let's you allocate say 20% of the throttle power to say the 1st 50% of the stick movement. The rest of the available power can be allocated  y percentage over the remaining 50% movement left available ..... if that makes sense. 

 

I'm just dabbling in this myself so might be an idea to take a second opinion on that just to 3nsure that I am technically correct.

 

Toto

[Wookman]

On the up side, you couldn’t take off with the wrong model memory selected. 

21 minutes ago, Simon Chaddock said:

Before the wonders of modern radios this was how servo travel and thus control sensitivity had to be set up and it was up to you to mechanically set up each plane so it worked satisfactorily using common settings on the transmitter.     

 

[leccyflyer]

15 minutes ago, Wookman said:

On the up side, you couldn’t take off with the wrong model memory selected. 

 

That's only the case with transmitters equipped with Model Match - a Spektrum feature. Unless things have changed you can certainly take off with the wrong model memory selected with a Frsky module - the receivers are bound to one unique transmitter, but multiple receivers can be bound to that transmitter. If you have two glders both switched on, my Frsky module equipped Futaba FF9 will happily operate both models at the same time.

[Martin Harris - Moderator]

I think that was Wookman’s point - Simon was was referring to pre-computer radios which had no model memories therefore all you had to do was make sure you zeroed the trimmed positions after test flying or remembered the trim positions for each model!
 

Early proportional radios didn’t even have servo reversing, let alone adjustable travels.  As Simon said, you learnt to plan a radio installation to give you your desired travels (and directions) during a build.  One enhancement was the availability of reverse direction servos - or you could take a soldering iron to the servo’s motor and pot connections to DIY. 

[paul devereux]

Thanks everyone who responded. I've got a bit more knowledge now.

One tip I hadn't thought of with regard to trimming ( thanks @Jon - Laser Engines !) - put in opposite before you reach for the trim, gives you a bit more time. And it is possible to do it bit by bit while still in the air. 

And @Martin Harris - Moderator that clears things up in my mind- if 100% is 45 degrees, I can now see how you can go beyond that.

@toto- it sounds like the throttle curve function is the same as expo. To be honest, the throttle is the least of my worries, lol! The elevator is of little concern either, altitude is controlled by the throttle anyway. As a newbie, you probably find the same as me- it is overcontrol of the ailerons that causes problems! (Once one wing unexpectedly tips up too much, my concentration is used trying to get the plane level, and by then the plane is pointing in an unexpected direction!).

Still, only one crash and that was because I had the wrong model memory  and I cut the throttle before the plane met the ground, so it's not too bad. I fully expect this training plane to get pretty beat up before I move on. The acrowot has been put in the back of the wardrobe and may not see the light of day until next year.

 

 

 

[toto]

Sounds like you are getting there though. That's the main thing.

 

Keep beating the drum.

 

Toto

[Wookman]

1 hour ago, Martin Harris - Moderator said:

I think that was Wookman’s point - Simon was was referring to pre-computer radios which had no model memories therefore all you had to do was make sure you zeroed the trimmed positions after test flying or remembered the trim positions for each model!
 

Early proportional radios didn’t even have servo reversing, let alone adjustable travels.  As Simon said, you learnt to plan a radio installation to give you your desired travels (and directions) during a build.  One enhancement was the availability of reverse direction servos - or you could take a soldering iron to the servo’s motor and pot connections to DIY. 

 

Exactly. 

[toto]

Just to confirm, yes, it's the ailerons that get me just about every time. Over control then scrabling to find level and maintain height. I will probably jinx myself here but .... of late this problem has been becoming slightly less frequent. 

 

I'm mastering the sensitivity in my throw movements a bit better and am a bit quicker in levelling the ailerons whilst applying gentle elevator and / or throttle where need be.

 

I'm not saying I have mastered it but I need far less intervention to get out of the situation than what I have previously required ....... must be progress .....

 

Toto

[leccyflyer]

4 hours ago, Martin Harris - Moderator said:

I think that was Wookman’s point - Simon was was referring to pre-computer radios which had no model memories therefore all you had to do was make sure you zeroed the trimmed positions after test flying or remembered the trim positions for each model!
 

Early proportional radios didn’t even have servo reversing, let alone adjustable travels.  As Simon said, you learnt to plan a radio installation to give you your desired travels (and directions) during a build.  One enhancement was the availability of reverse direction servos - or you could take a soldering iron to the servo’s motor and pot connections to DIY. 

Fair enough - and of course it's best practice to set up linkages to be mechanically optimised. There's certainly something to be said for adding an extra layer of foolproofing by using identical mechanical set ups.

[Cuban8]

A bit dated now, but David Boddington's bible  is still full of good advice and common sense. Loads on the mechanics of setting up, as the book was originally published before computer radios were affordable by the average flyer and dual rates and expo were thought to be expensive and frivolous extras by the old guard.  Servo reversing was also considered to be the work of Satan and a trap for the unwary, so it was a good idea to install one's gear without using the reversing function - no model memories back then - so a change of model often meant flipping the reversers - disaster in the making.

I have a couple of copies of different editions myself and still enjoy thumbing through them. Some of DB's comments about very small models and the radios to control them are amusing IIRC.

For little more than the price of a single model mag, I reckon it's a good buy for any beginner. A few even cheaper ones on sale as well. The earlier editions are more useful as they are without the coverage of 1980s and 90s electric flight which is very out of date and not very relevant in 2023.

https://www.ebay.co.uk/itm/364214875950?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338268676&toolid=10044&customid=CjwKCAjwge2iBhBBEiwAfXDBR-uyix9OvcECBtv80jUxg-gYadPQOgCqsiVITnR2S4kiA5af0-cUHxoCK0oQAvD_BwE

 

Edited May 10, 2023 by Cuban8

[paul devereux]

2 hours ago, toto said:

I'm not saying I have mastered it but I need far less intervention to get out of the situation than what I have previously required ....... must be progress .....

 

Toto

In my experience, it takes a lot of practice. You think you have cracked it, then you get confident and fly faster and more daringly- then you find you are experiencing difficulties again! But each difficulty you get into and then get out of, teaches you a bit more.

[Frank Skilbeck]

6 minutes ago, paul devereux said:

In my experience, it takes a lot of practice. You think you have cracked it, then you get confident and fly faster and more daringly- then you find you are experiencing difficulties again! But each difficulty you get into and then get out of, teaches you a bit more.

The skill is to aim for the ground and miss.😁

[Graham Bowers]

5 minutes ago, Frank Skilbeck said:

The skill is to aim for the ground and miss.😁

Sadly missed ;-)

[toto]

You are probably right Paul. The minute you start to get complacent, it turns around and bites you in the ass.

 

It's still encouraging to see some progress even if it doesn't turn out to be quite consistent as you'd like.

 

Toto

[Ron Gray]

1 minute ago, toto said:

even if it doesn't turn out to be quite consistent as you'd like

Practice, practice, practice and then when you've done all that, practice again, and again and again! 

[toto]

Yes ... and that's the frustrating thing about limited stick time as it really does determine the rate of progress. Never mind ..... I'll get there.

 

Toto