RC Basics: The importance of good linkage geometry
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- Опубликовано: 16 янв 2017
- If your linkage geometry isn't right then your RC plane won't fly nearly as well as it should. This video looks at the importance of linkage geometry as found on the elevator, rudder or ailerons and uses state of the art super-computer-based graphics to demonstrate the basics (yeah, right!)
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This is why I love this man, great vid Bruce.
such a nice way in showing how the linkage geometry works - thanks for this very informative video.
Best explanation I have seen good job.
Although, sometimes a non-proportional control surface throw is desired, especially for a flying wing. Aileron differential is an example. It can be a desired trait for models that have an undesirable amount of adverse yaw when turning. A flying wing, designed to fly upright and without a rudder, may need some aileron differential to make the turns more coordinated. Aileron differential can also be a desired trait for gliders to reduce unwanted amounts of trim drag when turning in a thermal. Heck, aileron differential can also help prevent tip stalls in a low speed turn :-)
On the other hand, you have to set up aileron differential correctly. If you reverse it by accident, you can make you model fly even worse and the chances of a tip stall go up.
But yes, for my standard models like 3D planes and sporty planes, straight and parallel linkages are very predictable for inverted flight and make your control surface behave as you'd expect. There's nothing more annoying when your wing's control surface throws don't match, haha.
These are awesome. There is a real lack of information for those that are moving through to an intermediate level that are wanting to start tinkering. Keep up the good work
Thanks Bruce. Im in the middle of designing a 3D printed plane and i never even thought about this. Now i can make sure its right.
love these basics videos!
9 dislikes??? what is there not to like about this. its a fantastic video demostrating the correct control linkage set up. good job! 👍
James haters?
they mad cuz they had poor linkage geometry
10 dislikes a year its probably within normal self-dislike rate
Maybe because they have a single round hole in the back of their boat and the wire bends there.
Now there's zero dislikes, thanks to RUclips's genius opinion canceling technology!
Now you've explained this so eloquently, you'll have to do a section on ratio and resolution. Appreciate what you do for the hobby, your videos make it so much easier for me to explain tech & tricks to people. Thanks Bruce.
Bruce, thanks for yet another very good educational video. Cheers from Portugal
amazing nobody else on YT does these such important basics, THANK YOU!
Great video... Really makes it clear.. And the inner drafter in me loves it.
Very helpful! I was looking for this exact advice and it only took me a few hours and 3 months to finally find it.
Fantastic Video Bruce.
Keep up the great work.
Your videos are always a pleasure to watch lol not only are you very good at explaining things, but also an excellent sense of humor
This makes it so much easier to understand being in the physical world over CGI. Thank you.
And again...i keep on coming to this class
Exactly what I was looking for! Thank you as always. I appreciate you, sir.
Just what I needed to watch. Thanks!
Thank you so much for sharing the knowledge! This is GREAT.
Good videos!! This is the difference between good fliers and lousy planes!!
This is also the source of so many flutter problems!!
I loved the graphics!!
Keep the awesome work mate!!
Saludos.
This was in my first batch of beginner's mistakes. The elders called it mechanical differential - I fixed it first thing that day and never made it again. Thank you for covering the basics.
Your CGI is amazing!!!! Loved it, as usual!
P.S. I have to assume you've run into this, but lots of guys like to do this ( @ 6:35 ) to make a mechanically actuated differential on the ailerons. Do you still take issue with it? I personally just want to use the Differential on my DX18.
Thank you! I built a combat wing, first go on a kit, no guides. Now I know why it liked to dive so much, and didn’t want to pull up. Back to the work table. Cheers Bruce!
This is really useful, was struggling for ages trying to get my rudder worling
Also, regarding torque- the center will give you the most torque(rotational force) for both up and down. you could customize the push rod to customize up/down needs on your aircraft.
Just what I needed. Thank you.
Same can be used for rc cars as well. Thank you sir for this video, it's very educational and easy to understand.
Thanks again Bruce.
Yesterday I was working in a new chinese wing, and had this very problem. Now I understand it all...
You are not aware (or maybe yes?) of how much you are doing for our hobby.
Cheers from the antipodes (Madrid)
Great advice, awesome CGI graphics! 😁
Thanks for that very informative video!
Great explanation, Thank you!
Excellent Chewtorial !! The correct setup here gives you stable Control.
One thing..... For a Pro Tip, on Ailerons ONLY. Having MORE up travel than down travel, actually allows for easier bank turning.
This is because the air pressure is Higher UNDER the Wing than ABOVE it. For the less experienced, this particular *wonky" setup, works better for controlling Roll, without Rolling Over too easily! Just a thought.
However, the one thing you pointed out that is VITAL, and should always be applied, is keeping the control horn Rod holes, in line with the pivot point! 👍👍
Great video. Really helpful.
Thank you so much for this video. You helped me a lot with my builts !
yes more technical stuff!! more advance stuff!! yes yes yes!! this is why i follow you.. been watching a lot of joshua bardwell videos and that got me thinking.. when am i going to get another great lesson from mr RCmodelreviews.. gotta love the accent as well
I've been doing it wrong for 5 years. So embarrassed. Very effective graphics, thank you Bruce.
I wish I had seen this video a long time ago. I learned the hard way. You might also talk about the little holes that go up and down the control horn and what happens when you connect at the top of the control horn vs the bottom. Big differences there as well. But a great video just the same. anyone who flies fixed wing will need to know this.
thank you for this video Bruce, it helped me to work out why my RC helicopter was getting more pitch in one direction! I definitely got my patreon monies worth this month! keep em coming buddy!!!
Nice work Bruce! You're a talented teacher
2023r and still useful. Thanks :)
This is a good control vid, cool stuff
amazing that skills that have been forgotten as computer radios and pnf models have become more popular, and clubs have declined
found my reversing you harnesses ( with tuning pots!) the other day. I can remember when they where the new hot technology. I also remember showing up to the field with a futaba 7c on fm and people having a fit wanting to look at it...
Thank you very much, this video is a really big help for my project!
It would be brilliant if you showed this in three different height holes. Some horns have adjustment holes on both ends... It would be awesome to show the geometry differences in this fashion! Thoughts?
Yes would also have liked to see that Bruce👍🛩️
Thanks, glad that I stumbled on this just now. Nothing that I don't understand, but something that I haven't kept in mind.... 😅
A Bruce this is a great video! I've been fling wings for a while and have a pesky Reflex38 that isn't quite right. Studying what you describe and going over my setup has revealed some build flaws thanks so much!
Thats exactly how differential ailerons work, except you would need the horn on the underside of the control surface so you have more upward throw than downward throw to prevent adverse yaw and drag on the climbing wing in a turn.
For rudder and elevator, you want it to be as you state.
Holy shit.
I've been fighting with an EPP model, building it without a manual. In EPO models I just installed the control horns where the producer told me to and never payed attention. In this one I had to choose the place myself and the control surfaces worked like crap. Thanks to Sir Bruce and this video I know now where's the problem!
Great video, I never paid enough attention to this geometry and I suffered the consequences. Thanks Bruce!. BTW those 3D graphics are awesome, they looked pretty much like real cardboard horns and servos!!!
This is what I look for on a beginner's plane. It will tell me whether the student pay attention to small details.
Very good presentation.
this is great Bruce, many of the new pilots really don't have a clue, nothing like having to set up a ccpm helicopter to learn and master control linkages! :)
Thanks for this! Now I have to go check and possibly tear off the linkages on all my scratch builds.
It is probably worth making a follow-up to this for more advanced uses of offset geometry. Quite often we use these offset effects for good! For example, a full house glider, you want (in your words) "Snot loads of down" flaps for Crow Brakes (often more than 80 degrees) and a little bit of up, for full span aileron mixing, or camber/reflex.
And the best way to do this is to have the servo arm offset as you do at 6:02. Using EPA and Subtrim on the radio to achieve the same effect tends to end up wasting servo torque and resolution as you can't use the full movements.
Before computer radios I always used twice as much up aileron as down in my high lift wing airplanes (rigging arms and rods). This eliminated yaw due to the difference in the amount of pressure between the top and bottom of the wing. Some full sized aircraft, such as Cessna, used the same technique, although to a lesser amount of differential. With computer radios this differential can be done electronically (with differential or aileron/rudder inter-connect).
Brilliant! Thanks Mate!
This helped a lot. Thanks!
The angle of hinge and pivot plays a critical role in movement and very imp. To the agility manuverablity of the aircraft.
That CAD is called BruceCAD.
you should do a video on aileron differential on planes that don't have working rudders or simple bank and yank planes so they can still get some yaw effect when turning, I never seen a video on that. I mean I use it on some of my FPV planes like the nano skyhunter. and some bank and yank warbirds I own. would be an awesome video.
cheers
Farmer
Just got back to flying again and doing searches for all the new things that have evolved in the hobby. Started with the Futaba FP-T6FG 72Mhz, my last radio was the 10CAG (one of the first programable radios). I just bought the Futaba T16SZ. Wow how things have changed. No matter what these new radios can do....they cannot correct bad geometry. (Ok, maybe they can, but how many hours to program out the error when all you have to do is mount your hardware correctly) This video is a must for anyone getting into the hobby. Fantastic visual using the latest computer aided CGI technology. Cheers Mate! Oh ya...what IS wrong with you people.... thumbs down? Really?
the technical videos are the best :)
I hear this method of design and demonstration is called CAD (Cardboard Aided Design). Great video! Great job explaining!
Bummer I just finished building my first fixed yesterday this is the info I had the hardest time to find, until today
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Great video. Next the effect/advantages/disadvantages of long/small servo arm on long/small horns, please
This video was also helpful when using servos in robot design. Linkages with non-standard arrangements almost always do not work efficiently or as expected. This usually causes gimbal locking or unexpected cranking, causing servo overload, damage to the linkage base, and unnecessary debugging. thank you.
I used to do that for differential ailerons, great when you only had one servo for both. That way you could avoid adverse yaw by having more throw on the down going aileron, thus more drag on the correct wing for a nicer turn. As mentioned we now just install 2 servos and do it in the radio.
this opened me a new world
From the second RC plane I've built in my life onwards (didn't really care a whole lot when I made my first one, and even there I made at least sure that the servo arms were as close to a 90 degree angle to the body as I could get them) I've always paid attention to this. I may have had the control horns just a hair or here and there but unless the servo sat a whole lot out of line with the control surface where I had to change the whole angle of the linkage (just think dual rudders with a single servo on like an F-18) I always made sure to have the line from the hinge to the linkage hole as perpendicular to the control surface as possible.
Damn good video and information!
Nice video Bruce..... Would also be nice for you to make us a video on how you set up your CG on the various wings that you fly
Hi Bruce. Good video. Topic not mentioned and just as important, is the additional rotational load (torque) required on the servo in moving the control surfaces when the positioning of the control horns and servo arms are not optimized to the geometry of the hinge system. Similarly, the additional resultant unnecessary strains on the control horn joints to the moving surfaces.
Beautiful!!!
Howdy Bruce, I've made this mistake a couple of times. What happens is that we generally use more up elevator than down, thus we have saggy turns and less response to the elevator AND on a couple of the models, I've got them to stall while turning because of the excessive amount of surface moment. Gone back, checked the horns and yup, wrong placement, doh! Matt
Great video! I have an idea were your inspiration and also your pen came from :)
Very important part of model aircraft flight theory! Unless a model builder has been taught this important technique, chances are good they'll make this mistake and ultimately pay the price for it later down the log.
hinge point direct above the wing point...... this is what I have been looking for thankyou Bruce :-) I have the s800 and the instruction are....... well poop...
Thanks Bruce
great video. I had this problem when connecting a servo to the FPV camera in a 210mm 5" quad. very tight space and I had to try out a lot of lengths and combinations before it worked.
how would you rigg a runcam eagle for instance? the holes where the camera is mounted at not allined in any obvious way with the holes in the backplate of the camera.
Nice explanation :)
WOW I totally just friggin learned something! Good thing I didn't install any servo horns on my brand new scratch build foamies yet! Thank god for the slow boat from China on my parts in this case! THANK YOU
very helpful. THX
Good to know. I never thought of horn placement
If you get a plane with servo horns in the wrong place, like in your example, could you not offset the servo arm position so that the non-linear servo arm throw will contract the weird horn movement? I admit that it would be difficult to get the geometry right, but would you ever consider doing that for a model that would take to much damage removing the stock horns?
Nice one Bruce. I've always wondered what difference the angle makes. The thing is i've found that when you center a servo before installing it into a model when you fit the servo arm they are never straight! They angle one way or the other just moving it to the next tooth on the arm. Which is annoying. Think i will go back and redo some of my push rods to get the servo arms more centered. Cheers.
Bruce...........Brilliant
More on this kind of stuff please.
Does this also apply to steering links in an rc car or boat?.......I know they do but it'd be great to see it in this easy to understand form.
Thanks mate 👍😜
Please discuss 'The Uncanny Valley' with your CGI Guys. It's disturbingly real!
Thanks for that linkage geometry.
Good video. Mr
Would you explain the mechanical advantage when using different combinations of hole selection in the control horns.
For a four bar linkage like this, mech advantage varies as a function of the input angle for a given linkage length
Has nothing to do with mechanical advantage really, it has to do more with the throw of the control surface. So say a beginner can have the linkages set for less thow, for less "immediate reaction" making it easier to learn. If your servos are having to work too hard there is either binding, or your servo is not strong enough for the application, ie needing a high torque servo. This is why matching the correct servo to the plane and flying type is so important, some planes will have a reccomend servo as well so you dont have to guess.
@@110101719 there is actually an advantage. If you use the correct servo hole the servo will work in whole of its span. Let's say, you've used your furthest servo hole and the throws are too wide. So wide that you need to reduce them to 40% in your Tx - it means that the servo is working only in 40% of its swing, which makes it much more strained (arm ratio) and less precise. Also it could happen that you have a cheap/old tx in which you can't modify throws, selecting correct servo arm hole is critical here
Another great video Bruce and perfect timing. I'm just playing with a servo, pushrod and Runcam swift on my quad. The theory is to make a poor mans pitch gimbal based on the video from Painless360. I love your new CGI, does it use a 3D printer interface? I have an older version called the Mec-cano prototyper!
In fact, those problems could be used to make differential ailerons and have less sliding of the airplane. Everything is sin and cos :) Great explanation!
Awesome Bruce, one for the impact of the different holes next time?
Bruce , what about using different holes on the servo arm or the control horn , which is better or worse ?
Good basic vid , Graham
good vid Bruce just thought you could of covered the different ratios using the holes on the horns ! .
Gr8 video thx
very good explanation for new comers. please do for disk or circle horn connection too.Thank you
Thank you so much that was my problem
Great video Bruce. This day many foamy plane use only 1 servo for the aileron. I used to have one and I notice that the angle of the aileron up and down is not the same. Show us how to correctly use the correct servo arm, so the up and down angle will be the same.
Thanks for this it helps a lot! I'm struggling to get my servo arm at exactly 90 deg, can you do a video showing us how you adjust this in a Taranis, I know there are a number of ways without using trim as this will cause you to lose range on the servo??
I always thought it was best when setting up a new linkage to start as far up the surface gmhorn and as far down the servo horn . To give the closest movement while retaining the best mechanical advantage