Flite Test | Servos 101

[@firstnamelastname4494]

Good job Peter! I learned more about servos in 20 mins than I have in 2 years.

[@DobyxRC]

Very cool episode. In 25 years I have only taken apart a servo 3 times and each time I frown and toss it in the garbage, this helps me make sense of these wonderful little devices. Thank you for this video!

[@manicdee983]

Thank you for this awesome instructional video. The Q&A style presentation was great, basically asking the same questions I was interested in asking myself! Peter did not go too deeply into any one topic and covered a great range of knowledge. I especially appreciated the testing jigs for torque, speed, and browning out.

[@NettAirLa]

one of the best episodes I've seen (I like breaking stuff down and figuring out how it works). Little Bits are awesome, my 5 year old daughter received a set last year for Christmas and loves them.

[@tiagopadua]

Actually the torque is the same, no matter the length of the servo arm. It's the FORCE applied that changes. The torque is a fixed number for the servo.

[@44R0Ndin]

Tiago de Pádua Correct. Torque = force * lever length. Okay, technically the lever length is called "moment arm" or something like that, but I'm keeping it simple so non-nerds can understand it better.

[@SuperLoopholes]

44R0Ndin Let's try working that formula with actual numbers. force * lever length = torque 5 *10 = 50 5 * 20 = 100 Looks like torque changes when you change the lever length even though the force stayed consistent.

[@44R0Ndin]

SuperLoopholes Exactly as I expected. Of course, if you hold torque constant in the equation, shorter lever arms apply more force. torque = force * lever length 2 oz-in = 0.5 oz, 4 inch arm. 2 oz-in = 1 oz, 2 inch arm. 2 oz-in = 2 oz, 1 inch arm Mechanical advantage. It's all about ratios.

[@SuperLoopholes]

This is reminding me of ohm's law. Which makes sense because it's a similar 3 variable formula.

[@azgarogly]

SuperLoopholes That would be correct if You'd be turning a servo shaft by constant force applied to the lever. Torque would change. In our case servo produces some torque on a shaft, regardless of how long the lever is. And the longer the lever the less force You have on a pushrod and more it travels.

[@incubrian]

oh my god, i have been doing this for 15 years, and man, THIS is the video i have been waiting for!! seriously, what an amazing job you guys did on this! please do a servos 102, 201, 301, i will watch all of them :) love this!

[@wiltonsmith3397]

“Foot-pounds, inch-pounds, inch-ounces, newton-decameters, etc...”

[@afterdeth]

So glad you guys keep putting out videos. You're such a help to people just starting to get into the hobby, keep up the good work, and get Peter to do more in-depth technical walkthroughs, it's awesome!

[@TheAdambausch]

Every question I had as a beginner to understanding what a servo is, was asked and answered in that episode!! Great work!!!!

[@crossthreadaeroindustries8554]

All your vids are great and this type of video has its special place. From a techy perspective, one of the best - answers many many questions quickly. Reviews of multicopter controller boards and other components would be appreciated! Thanks, guys.

[@joelsterling3735]

Make more videos! I am so impressed. Never have I ever come across a video that actually explained everything that I had questions about. Very thorough...just the way I like it.

[@digitexstudios5634]

Here's some basic Motors 101 for you: There are many types of motors used in almost everything: Brushed motors Coreless motors Induction motors 3-phase motors Brushless motors Synchronous motors Permanent magnet motors Stepper motors Almost every motor has three parts: the stator, the rotor, and the commutator. The stator is the magnet that does not rotate. In a brushed motor, it is just a permanent magnet, as it is in a coreless or a permanent magnet motor. In a brushless motor, an induction motor, a stepper motor, or a synchronous motor, it is a set of coils. The rotor is the rotating element. In coreless motors, the rotor is just a set of coils. In an induction motor, it is the squirrel cage assembly. In a brushed motor or a synchronous motor, it is a set of coils wound on laminated metal. In a brushless motor, a stepper motor, or a permanent magnet motor, the rotor is a permanent magnet. And finally, the commutator is responsible for the timing. In a brushed motor and a coreless motor, the commutator is a brush. In a brushless motor like that in a computer fan, the commutator uses hall effect sensors. In larger motors like those in drones and planes, the ESC relies on timing alone. Induction motors have no commutator. Synchronous motors use slip-rings to provide power to the rotor, but do not use a commutator for timing. Stepper motors require a special controller and have no commutator.

[@grumpyjohntxredneckrc6346]

This Is One of The Most Informative Videos That Flite Test Has Produced & I Have Watched Nearly The Last 7 years Worth Totally! Soo Thanks & Keep Up The Great Jobs Guys!!!

[@zoltanguitar]

Great overview - Thanks for taking so much time to put such a comprehensive tutorial together.

Eric and Peter are getting really good, they work really well together. At the moment, best presenter duo in the channel.

[@vipero00]

11:30 Alright Torque is the Lever arm length times the Force of the thrust. T=LxF So for a lever arm 1" long and a Force of 100 oz you get T=1 in x 100 oz = 100 oz-in of torque. Unlike what they say at 11:30 as the lever gets longer the torque doesn't change. The torque is the torque. However as the lever gets longer the force goes down. There is an inverse relationship between the lever length and the max force of the thrust. As one goes up the other goes down.

[@rcflight13]

Learnt from experience to always pay extra and get metal gear servos, that way they won't strip and when move up you can just take all your electronics with you. Best servos for acro I've used so far are the Corona 929MG. Excellent upgrade just to replace the standard 9g servos most planes seem to use these days are dirt cheap ($5.50 per unit from Hobby King).

[@Acula33RC]

Excellent video and very informative. I've been flying for some time now and this video helped me understand more about servos and thier operation. I love Peters graphs and displays. I'm a visual learner and that helps me out tremendously. Great video fellas!

[@Zxenmusic]

Thank you guys. This is the only useful servo explanatory video I've seen - and I've seen scores of them. You have answered all my questions. Thank you!

[@rguptaca]

Awesome:) At 13:30 with regards to servo speed. The rating is how long to move 60 degrees so LOWER is faster and usually better; not higher.

[@jordanh9520]

Rav Gupta lots of little bits of misinformation in this video. still really good for anyone with a cursory understanding of physics.

[@aerialboy55]

So basically you guys didn't get back to magentic induction servo?

[@b5a5m5]

My guess is that it uses a hall effect sensor to sense position rather than a potentiometer. This has the benefit of a longer lasting servo since hall effect sensors have no physical wear like potentiometers where there's a wiper arm skimming across a resistive surface. I also believe this to be true because Peter physical rotated the servo a few times in one direction where if it was a normal potentiometer it would only rotate to the endpoints of the pot.

[@richard76rama]

Good Job Peter!! you really are an asset to the flite test team!!

[@pspeijer]

Well done flitetest, very educational, entertaining and simple to understand. As a experienced pilot, i really enjoyed this video. Keep on going guys !!!!

[@RCPrairieFlyyer]

Excellent video Peter and Eric. Lots of information to absorb and basically love what you guys do!

[@bigbuckoramma]

Wow, awesome video. Super informative. I honestly think this is one of the best educational videos you have ever done. Eric made it that much more engaging by being genuinely curious. Really well done. Thanks for that.

[@kls2020]

Not only informative but presented in a fun, entertaining manner

[@AudaciousRC]

Not sure if this has been mentioned already, or if this is even correct, but i THINK the reason they move the servo 1 inch to measure the torque is because in the U.S. torque units are pounds per foot or 'foot pounds' etc so moving 1 inch is easy to convert to ft/lbs because it is 1/12 of a foot.... i'm just speculating haha i'm not totally sure. -Colton

[@hotdogx2]

Nice informative video, folks. I would, however, like to point out an error. When you were discussing moving to different positions on the servo arm, you stated that the torque changes - more torque closer in and less torque further out on the servo arm. That is incorrect. The torque never changes; it is always the same regardless of where the pushrod is attached to the servo arm. What does change is the force. More force closer in, and less force as one moves outward on the servo arm. You showed this in the video at the 11:00 point when you had twice the force on the scale because the attach point on the servo arm was at 1/2 inch. So 48 ounces at 1/2 inch is equivalent to 24 ounces at 1 inch - both are the same torque; only the force changes.

[@pjwlk]

Thanks for the fantastic video! I've learned a lot from you two. I'm just getting into the hobby now and every little bit helps. You've inspired me put together a better power supply setup that will prevent the servos from browning out the receiver power in the event of low battery and/or overload. Cheers!

[@fr33rid3r33]

Man this video was amazing, thank you. Its always easy to pay the money to get the better SERVO's, but it is nice to know WHY it is worth spending the extra money. THANK YOU Flight Test Crew!

[@a330turbinex7]

The torque is constant in a servo. The force is smaller if the arm is bigger and the force is higher if the arm is smaller. "Torque = Force x Distance Arm" 11:45

[@richardsailors9762]

Outstanding. Accurate, clear, excellent interchange, please consider teaching as a future career.

[@mathlind]

Extremely educational and illustrative demos. Many thanks.

[@ZachRice]

Peter seems like he was truly in his element in this episode. Awesome presentation!

[@Williamhenry23]

Thank you FT Crew for the digital vs analog explanation...this very insightful as I am prepping to build my first foam board plane. Thanks again.

[@jet_flyer]

What about using a capacitor for avoiding brown-outs or at least to help?

[@arturhernadi3555]

Basically count 00:11 00:13 01:14 01:44 03:05 04:02 04:54 05:31 05:34 05:38 05:44 06:37 07:30 07:55 08:04 08:37 08:51 09:58 10:02 10:09 10:11 10:16 11:16 11:47 11:50 12:54 13:28 13:31 13:58 14:20 14:31 14:32 15:17 16:45 16:54 17:00 17:08 17:33 17:35 18:03 18:32 19:21 19:28 19:29 20:13 21:57

[@FergyA]

The 1 inch is just to make your life easier, you could measure it at a different distance, but then you'd have to multiply the reading to get the actual torque. It's easier to just be able to read the number straight off of your force sensor\scale.

[@jayfromaz]

Fantastic. At the airfield I was asking some of the senior pilots some of these same questions. But they couldn't answer. Now I know. Great video.

[@sailorjohn2224]

The best show this year!

[@ventureswithjoe1776]

They completely missed that the point of a servo is that it can go to a specific location and hold it unlike a motor that just spins and stops

[@Ybw200owns]

ive been in the game for 3 years and learned a few things that have always bothered me from this video, thanks for your work guys =D

[@juanandrade9553]

Love these videos! You guys do a great job on informing us on even the smallest detail and sometime that's exactly what I'm looking for, other channels do a good job but not exactly like you guys! Thank you for you guys taking your time to inform us. I use rc buggies/truggies, but the electronics have the same principles as far as my knowledge 😂

[@NeoToX86]

Hi guys. I was wondering if Josh Scott was coming back?

[@peterescapement6414]

That was a fantastic tutorial - really clear and pitched just right. Thanks.

[@SeanCullUK]

Learned a lot and am away to check the sizing of my 6 servo speed controller :-)

[@thomasmore260]

13:35 there is an important error: The lower the number is the faster the faster is the servo. It s/60° - this the reciprocal of a speed as the speed is measured in °/s and the 60 is because its measured as the average speed in a 60° move. That was the important stuff, now comes the pedantic stuff: It's µ not u (someone else posted that already). The servos torque is dependent of the supply voltage not of the leverage. If the leverage gets longer the thrust gets lower. It does not change the torque which is the product of force and leverage. Torque can neither be measured in kgcm nor oz-in as kg and oz are mass units. Correct would be Nm, Ncm or to have it compareaple to the lift force of kg on earth near paris kp. oz-in would mean the same servo could not move anything in space but in fact the torque there is about the same. So if someone writes 1kgcm he's talking about kpcm or ~0.1Nm (exact: 0.0980665Nm) To do the measurement on the scale exact you need some shims or an adjustable rod to make sure the servos lever is perpendicular to the rod and parallel to the scales surface. Anyways it's a great explanation and I'm happy know that I know now a 9g Servo is called so because of it's own mass. I was guessing that but didn't know it and is was for some time quite confusing. It would be great to establish size and mount standarts for servos. The model train guys have an associations (NEM, BRMSB and NMRA) to standardize couplers, coupler mounts, gauges, wheel and track profiles... I'd appreciate to go for one international standard association for the RC-stuff. Peter, would you want to do that? Maybe you could get a paid job in such an association. You're smart enough to understand the stuff. You'ld need to learn to be pedantic when defining standards. Maybe someone else could be employed for that. It should be a group of at least 10 people as there is also radio stuff to define which is far more complicated as when I was a kid - I know an engineer who is specilized on that and unemployed as he rejects all military jobs. You're internationally known. So you're the right guy to start such a thing. Everyone whatching RC-plane videos on youtube knows your face.

[@JosephHarner]

Really liking this more technical style of video.

[@jake6087]

Fantastic video guys! Learned a lot of things I usually assumed. Some of my assumptions were correct but a lot of things you mentioned I never actually thought about. Thanks FliteTest!

[@henryhb6302]

Man, I wish they made more informative videos like this nowadays

[@MkmeOrg]

It's the rotor not the stator :) Technically a commutator but no worries though. Great video as always Guys! Stellar job Keep em coming.

[@torque5563]

Eric William -MKme Tech It's actually an armature which is usually a laminated iron core, not a commutator. A commutator will convert AC current into DC current in a generator, or vice versa in a motor, and is in the form of copper sections insulated from one another which the brushes would run on.

[@katanamd]

Eric William -MKme Tech The commutator is the part of the rotor that had the contact pads for the motor brushed :)

[@DrPACIFIER]

Eric William -MKme Tech true. and i always thought it's plain simple to remember that stator is static and rotor is rotaiting.

[@MilanKarakas]

HeadShot360IN Actually, brushless motor has two subcategories: inrunner and outrunner. Inrunner has windings fixed (outside, close to the casing) and rotor (with magnets) spinning, while outrunner is what you describe - it has fixed (central) stator with coil, and spinning bell (magnets are outside, attached to the cylinder).

[@grahamgfm]

Stators are stationary while rotors turn. If the "rotor" rotates and has a commutator, we call that an "armature".

[@scottjamison1602]

Thanks for the info, only correction is torque remained the same regardless of the length of the lever arm what changes is the forever or load, further you go out on the arm, greater throw but less forage. Think of a pry bar. Torque of 1lb/in says at one inch from the center of rotation is equal to 1 lb of force, go out 2 inches you get 0.5 lb of force go out 1/2" you get 2 lbs of force.

[@raykiii]

Enjoyed this video very much. Thank you for the information.

[@YouMockMe]

As someone JUST getting into this, THANK YOU for the tutorials!

[@AerospaceMatt]

2:00 Where can I get one of these? That would work great for a Sweep Wing system in an F-14 Tomcat or F-111 Aardvark.

[@albert3361]

Great demo.

[@willson8246]

11:45 That you said "If you go out your torque drops off", this in not correct. The thing changes when distance changes is "force" not torque. The torque is still constant.

[@lusicilusci4420]

And difference is? Torque is basically force

[@willson8246]

@@lusicilusci4420 It's totally difference bro. Torque = Force x Distance. Torque still stand there the same value even you change the servo arm length (Comparing to the same power the system spends). Example, give the servo has a torque value at a rate power = 10kg.cm 1) Config#1: Servo arm length = 1cm. Force will be 10kg while Torque is still 10kg.cm 2) Config#2: Servo arm length = 10cm. Force will be 1kg while Torque is still 10kg.cm Torque and Force are completely difference.

[@tindjin07]

Outstanding, glad you guys have done some more tech style videos like you used to do.

[@SuperLoopholes]

I liked this. It was more informative than most of the videos I've seen here.

[@inniyewtesfaw2003]

+flitetest the stator is the part that stays static (no movement) the rotor is the moving part

[@cha3119]

Yet another great vid guys. Great failure-mode demonstrations. If somebody knows of an aerodynamics program that discusses forces on RC control surfaces, that would be great. That would solve that issue where you just look at "what the other guy is using." Better to actually calculate and know.

[@markliles4113]

So if I were using 18-20 analog servos, what type of power supply should I use?

[@Rundumsfliegen]

Probaly a good BEC in your ESC, bufferd with 4-5 nimh cells Or a separate BEC, but still bufferd

[@jacknimble1]

Great stuff! Thanks for the knowledge Peter! I have been flying for a few years now and never knew this stuff.

[@chriscuster3684]

You guys are awesome. I am ready to start playing with netduino, I will be doing servo projects. This episode helped so much...

[@krikey72]

Great video Guys. Well done Peter, very intuitive.

[@brucepuana6648]

Is it true that digital servos draw more power? If I'm using multiple servos (ailerons, rudder, elevator, pan, tilt, roll) for my fpv... Would I be better off using analog to try to prevent brown-outs? Or am I better off using digital with a stronger bec?

[@mirkohaeberlin]

Do you guys have a link to that very small horizonal sliding servo at minute 1:46? I have no idea how it is called but I need it.

[@stevecomer3908]

Great explaination of how servo's work. Thanks

[@JD_1]

Very awesome video guys. You guys answered every question i've ever had about servos. Now i have some updating to do on all of my models. Thanks!

[@grahamgfm]

Excellent work guys. Please keep up the good work.

[@tranziq]

The Canard at 10:00 are there plans available for that plane, I have been wanting to build a Canard prop pusher for years now and that is exactly what I am looking for

[@ulaB]

Brent David A lot of people are waiting for that plane. It's the Shinden that has been in the making for a long time. Having it placed this prominent only means one thing: It's going to be released soon :)

[@marcussiostrom3346]

Great video, guys! I really liked it. Could you do a similar video on motors? Maybe explain what the numbers mean, how the sizes are specified, brushed vs. brushless, efficiency, KV, and so on. It would be really informative! As always, keep up the good work!

[@LAHegarty]

Are the metal gears solid?

[@Hamza-en3pz]

+LAHegarty lol

[@rowannadon7668]

ahahahhaha XD

[@b5a5m5]

Yeah, when I heard that I instantly said "Metal geeeeear"

[@o0julek0o]

*!*

[@tonywright8294]

The metal gears are made from mercury,so they flow around the servo.Takes up less room.

[@rctv-uk3126]

Great work guys I like to think I know my stuff but I learned a lot watching this. ATB Malc

[@88BuckMeister]

This young man is a passionate nerd AND AS A FEDERALLY LICENSED A&P MECHANIC MYSELF, WHO IS FALLING IN LOVE WITH BUILDING FLYING MODELS ON MY FREE TIME, I ABSOLUTELY LOVE IT

[@flat-earther]

hi 88buck, have you become a flat earther yet?

[@88BuckMeister]

@@flat-earther well the thing about it is that the earth is simply not flat so no I haven't. Although I've spent hours and hours and hours studying it, none of the models work CHECK OUR PROFESSOR DAVE

[@flat-earther]

@@88BuckMeister okay. to learn about flat earth I suggest listening to flat earthers rather then strawman dave. BTW 88buck what do you think about all gubments drawing a line around you and saying you are not allowed to leave?(Antarctic Treaty) If you don't know what I mean, read my about tab.

[@88BuckMeister]

@@flat-earther I've been to Antarctica

[@88BuckMeister]

You can go too. I suggest it. It's not closed to civilians

[@cbf2430]

Thank you so much for making this video I actually built a Tricopter and used a little 9 gram servo and it broke immediately and looked to the right midair did not end very well

[@faqdaworld]

So whats the deal with the Magnetic Induction Servo? You said that you'd get back to it but never did? I assume it works through halls affect?

[@atomicskull6405]

The difference between an analog and digital servo is that with analog servos the motor control is synced to the control signal where with a digital servo it's independent. Some digital servos are also limited to relatively low control signal frequency e.g. the MSK DS1210 can only accept a control frequency up to 120hz.

[@richiebricker]

f you were to use an old cheap two wire motor style servo for steering, could you use the two outside wires on the receiver to make this work? or am I deranged and polluted? Thanks

[@TOPHAT1966GS]

The servo torque is related to the gearing inside the servo and the supplied voltage. This torque will drop off as the supply voltage drops off as the battery is drained. However, the more interesting part is the use of mechanical advantage between the servo arm, rod and control horn for the surface, this is what really needs to be explained. As mechanical advantage is always a trade off between movement of the control surface versus servo resolution. Precision movement of the surface is desired without loosing too much resolution from the servo .

[@brodobroggins]

0:56 Sorry for being pedantic, but torque is measured in Nm, it's a unit of force x distance, not weight (g).

[@xZise]

+Scroto Saggins Sorry for being pedantic but weight is a force. You mean mass ;) Anyway at 9:48 you see on the box that they use kg*cm so understandable that they mixed it up.

[@mrgfpv3741]

Great job guys, peter you are a clever dude, loved your flying drill LOL!

[@hachiroku6593]

Pete Always has awesome projects and knowledge👍🏻 New drinking game: take a shot every time they say “basically.”

[@donwood7700]

Excellent again!

[@OceanicOpps]

So how do you fix the cutoff of the receiver from too many servos? Better receiver BEC or something else?

[@zfotoguy71]

Great episode! Thanks for explaining stuff. I learned several things. One thing, I wish FT would have showed how to reverse a servo by rewiring it. This is information some people need to know. Especially with airplanes with gyros. The gyro in the receiver does not know which way the servo is running. If you just replaced a servo in your airplane and the new brand run the opposite direction, reversing it in only the transmitter will cause the gyro to push the control surface in the wrong direction when the transmitter pushes it in the correct direction. The result is an out of control plane. I'm talking from experience. :)

[@OffroadMXbohemia]

This is precise tips and informations. Thank you for that!

[@deen911]

Great video! Wish my lectures at university where as good as this

[@BOKI797]

Eric & Peter A Really Nice Servo Test Video very Interesting & I learned about Servo's ! Thanks Dave !

[@alanrobison8684]

I am learning. And your definitely HELPING. Thanks

[@Heathfloors]

Fantastic and very helpful video. I watch all your videos but got so much info for me from this one... Thanks you..

[@Hobypyrocom]

i admire your logic power, you just called the rotating part of the motor a "stator" good for you :)

[@matthewfchiera]

This is great information. Very accurate and no bull.

[@ImrePaasen]

Very good information, Peter can explain it very good. thanks!

[@TechDriven365]

Amazing information, this was worth every single second.

[@tczhang6558]

What’s the linear servo at 1:45 called?

[@2891michaelk]

Learn alot from Peter. Great video

[@ppro69]

you guys need to make the plane behind Peter available on the free build plans.

[@cooperandy3]

Fascinating introduction

[@danielmount6928]

I know that Peter is really good and I like his work.