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!
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.
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.
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.
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 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.
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.
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
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.
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.
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).
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.
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!
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!
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.
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.
9 років тому
Eric and Peter are getting really good, they work really well together. At the moment, best presenter duo in the channel.
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.
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.
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.
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
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 .
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!
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!
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.
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.
By making your distance = 1 [inch], it simplifies the calculation. The torque equation is: Torque = Force * Distance (T = F*d). Torque = Force * 1 Torque = Force (force x 1 is equal to force) ** Do note, this is in units of [lbs-in], not [lbs-ft] of torque.**
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.
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).
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!!!
Well done flitetest, very educational, entertaining and simple to understand. As a experienced pilot, i really enjoyed this video. Keep on going guys !!!!
First, it's a rotor, because it rotates. In an outrunner that's a stator, but in an inrunner like a servo motor, it's a rotor :) And it's 1 inch because if you measure the force from anything else, it won't be INCH-ounces. Torque is the force times the distance from the pivot. Inches, feet, meters, whatever.
An analogue servo can actually be driven at much higher frequencies than 50Hz, given the correct signal, because the servo angle is determined by the duty cycle, which at max is about 2ms and the signal period is normally 20ms. I.e. in theory almost 500Hz is possible. I have done this for the autopilot I was developing and it worked great for some servos, but some servos get very unhappy.
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!
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.
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!
Your torque unit of measure is (ounce-inch). Because you are using an (ounce) scale, if you move out only one (inch), that allows you to use the scale reading as an (ounce-inch). Torque= Length x Force.
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 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
@@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.
Great explanations. Learned a lot about servos. Thanks guys. Now, please give us a lesson in picking servos. The price range is dizzying. Are the high priced ones ten times better than the lesser? I know I don't want to crash my plane for a poor servo.
A more expensive servo will be faster, stronger and more precise when centering. As far as reliability in my experience it dosent seem to matter, just make shure you have a proper torque rated servo for your application.
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.
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.
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 😂
Well, they're not wrong. The torque generated by the motor shaft is converted to that rod. The more torque you got the harder it's gonna press of push or pull. Sorry for my bad English
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
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
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!
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. :)
Nerd comment: let's be careful with torque vs. force (or thrust). The torque of the servo is (nearly) constant as you change the moment arm length. That's why the force it produces changes linearly as the moment arm is changed linearly. Thanks for the vid!
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?
Jack Scaling it down is going to be hard. I think foamboard might actually be too heavy of a material at that point, and the motor is also going to be a problem. Of course, with enough money it's possible, but i don't think that they would work on it. The only material flite test has used is foamboard, and i do not think they will stray from it for the sake of consistency.
Jack The problem is, smaller the plane, higher the tolerances You have to meet for the plane to fly well. And for a foldable foamy the Pun Jet seems to be on the edge.The other point is, smaller the plane, the more agile it is. You would need a very good reflexes to control it. Or use an onboard stabilization. But the rule of thumb is, bigger plane flies better. Or is easier to fly, at least.
Will routing the power for the servo's from a separate BEC to bypass the receiver prevent risks of a brownout? I tried it once but I ended up frying my servos. Theoretically it should work right?
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!
you've got torque all mixed up torque=force times radius so the servo will produce the same torque no matter how your linkage is arranged but the farther away from center you are the less force you are able to get but you also get more travel so it is a tradeoff
A linear actuator does not have Torque. It has force. Torque is force at a given radius. In SI, it is measured in N⋅m. Half of the time, these guy's meant force when saying, "torque." Likewise, in other videos, (usually) when they say, "inertia," when really meaning momentum and when they say, "momentum," they mean speed.
I believe in this case that The linear action of the linear servo is driven by a worm/screw gear. The motor driven worm gear is providing a torque force upon the spur gear that happens to be the servo arm.
Special mention: not all lightbulbs fit all in the same sockets, bought some floor lights that sat mostly nonfunctional cus their damn bulbs were harder to find.
Little Bits are great to play with. We had a big box of them last year at Re:Publica in the Maker area and everyone was just creating stuff that made noise in some way or the other :). They are a bit pricey though.
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!
Good job Peter! I learned more about servos in 20 mins than I have in 2 years.
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.
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.
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.
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.
This is reminding me of ohm's law. Which makes sense because it's a similar 3 variable formula.
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.
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.
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
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.
“Foot-pounds, inch-pounds, inch-ounces, newton-decameters, etc...”
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.
Every question I had as a beginner to understanding what a servo is, was asked and answered in that episode!! Great work!!!!
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).
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.
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!
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!
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.
Not only informative but presented in a fun, entertaining manner
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.
Rav Gupta lots of little bits of misinformation in this video. still really good for anyone with a cursory understanding of physics.
So basically you guys didn't get back to magentic induction servo?
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.
Eric and Peter are getting really good, they work really well together.
At the moment, best presenter duo in the channel.
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.
Peter seems like he was truly in his element in this episode. Awesome presentation!
Great overview - Thanks for taking so much time to put such a comprehensive tutorial together.
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.
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
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.
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
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 .
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!
Good Job Peter!! you really are an asset to the flite test team!!
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!
Hi guys. I was wondering if Josh Scott was coming back?
+flitetest the stator is the part that stays static (no movement) the rotor is the moving part
Excellent video Peter and Eric. Lots of information to absorb and basically love what you guys do!
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.
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.
By making your distance = 1 [inch], it simplifies the calculation.
The torque equation is:
Torque = Force * Distance (T = F*d).
Torque = Force * 1
Torque = Force (force x 1 is equal to force)
** Do note, this is in units of [lbs-in], not [lbs-ft] of torque.**
Outstanding. Accurate, clear, excellent interchange, please consider teaching as a future career.
It's the rotor not the stator :) Technically a commutator but no worries though. Great video as always Guys! Stellar job Keep em coming.
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.
Eric William -MKme Tech The commutator is the part of the rotor that had the contact pads for the motor brushed :)
Eric William -MKme Tech true. and i always thought it's plain simple to remember that stator is static and rotor is rotaiting.
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).
Stators are stationary while rotors turn. If the "rotor" rotates and has a commutator, we call that an "armature".
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!!!
What about using a capacitor for avoiding brown-outs or at least to help?
Learned a lot and am away to check the sizing of my 6 servo speed controller :-)
Well done flitetest, very educational, entertaining and simple to understand. As a experienced pilot, i really enjoyed this video.
Keep on going guys !!!!
Great demo.
First, it's a rotor, because it rotates. In an outrunner that's a stator, but in an inrunner like a servo motor, it's a rotor :)
And it's 1 inch because if you measure the force from anything else, it won't be INCH-ounces. Torque is the force times the distance from the pivot. Inches, feet, meters, whatever.
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.
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.
An analogue servo can actually be driven at much higher frequencies than 50Hz, given the correct signal, because the servo angle is determined by the duty cycle, which at max is about 2ms and the signal period is normally 20ms. I.e. in theory almost 500Hz is possible. I have done this for the autopilot I was developing and it worked great for some servos, but some servos get very unhappy.
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!
Man, I wish they made more informative videos like this nowadays
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.
Extremely educational and illustrative demos.
Many thanks.
Really liking this more technical style of video.
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!
Your torque unit of measure is (ounce-inch). Because you are using an (ounce) scale, if you move out only one (inch), that allows you to use the scale reading as an (ounce-inch). Torque= Length x Force.
Outstanding, glad you guys have done some more tech style videos like you used to do.
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
hi 88buck, have you become a flat earther yet?
@@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
@@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.
@@flat-earther I've been to Antarctica
You can go too. I suggest it. It's not closed to civilians
As someone JUST getting into this, THANK YOU for the tutorials!
That was a fantastic tutorial - really clear and pitched just right. Thanks.
Great explanations. Learned a lot about servos. Thanks guys. Now, please give us a lesson in picking servos. The price range is dizzying. Are the high priced ones ten times better than the lesser? I know I don't want to crash my plane for a poor servo.
A more expensive servo will be faster, stronger and more precise when centering. As far as reliability in my experience it dosent seem to matter, just make shure you have a proper torque rated servo for your application.
Flite test is by far the standard when it comes to RC planes.
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.
I didn't know Scott Bakula was into RC! I'm gonna go watch some Quantum Leap today. 😀
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.
you guys need to make the plane behind Peter available on the free build plans.
I know that Peter is really good and I like his work.
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 😂
The item you referred to as the stator is actually the rotor. The stator stays stationary and the rotor rotates.
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
So if I were using 18-20 analog servos, what type of power supply should I use?
Probaly a good BEC in your ESC, bufferd with 4-5 nimh cells
Or a separate BEC, but still bufferd
The ratio of the distance you move is the same as what we call in engineering as a moment, basically the same thing as torque
8 years on and still relevant in 2024. Thanks for explaining
Great explaination of how servo's work. Thanks
Great video Guys. Well done Peter, very intuitive.
wow, listening to them not knowing anything about torque was painful.
Yeah I’m lmfao
Well, they're not wrong. The torque generated by the motor shaft is converted to that rod. The more torque you got the harder it's gonna press of push or pull.
Sorry for my bad English
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
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
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
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!
Great stuff! Thanks for the knowledge Peter! I have been flying for a few years now and never knew this stuff.
Enjoyed this video very much. Thank you for the information.
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. :)
The best show this year!
You guys are awesome. I am ready to start playing with netduino, I will be doing servo projects. This episode helped so much...
Nerd comment: let's be careful with torque vs. force (or thrust). The torque of the servo is (nearly) constant as you change the moment arm length. That's why the force it produces changes linearly as the moment arm is changed linearly. Thanks for the vid!
Those gears are Delrin, polyacetal, nylon is slightly yellow in the raw state. Delrin is even stronger.
I like the Flying Squirrel Multirotors sticker on the computer at 8:06!
i admire your logic power, you just called the rotating part of the motor a "stator" good for you :)
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?
very informative, peter if you see this please make a pun jet for the mico cargo, biplane?
Jack does anybody think its possible
Jack Scaling it down is going to be hard. I think foamboard might actually be too heavy of a material at that point, and the motor is also going to be a problem.
Of course, with enough money it's possible, but i don't think that they would work on it. The only material flite test has used is foamboard, and i do not think they will stray from it for the sake of consistency.
Jack The problem is, smaller the plane, higher the tolerances You have to meet for the plane to fly well. And for a foldable foamy the Pun Jet seems to be on the edge.The other point is, smaller the plane, the more agile it is. You would need a very good reflexes to control it. Or use an onboard stabilization. But the rule of thumb is, bigger plane flies better. Or is easier to fly, at least.
Will routing the power for the servo's from a separate BEC to bypass the receiver prevent risks of a brownout? I tried it once but I ended up frying my servos. Theoretically it should work right?
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!
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!
Can you do a video on choosing the right motors? KV, Watts, etc.
Pete Always has awesome projects and knowledge👍🏻
New drinking game: take a shot every time they say “basically.”
you've got torque all mixed up
torque=force times radius
so the servo will produce the same torque no matter how your linkage is arranged but the farther away from center you are the less force you are able to get but you also get more travel so it is a tradeoff
Can we get a video on flaperons? I never see them used, but a real pilot told me there were few disadvantages to having them.
I liked this. It was more informative than most of the videos I've seen here.
A linear actuator does not have Torque. It has force. Torque is force at a given radius. In SI, it is measured in N⋅m.
Half of the time, these guy's meant force when saying, "torque." Likewise, in other videos, (usually) when they say, "inertia," when really meaning momentum and when they say, "momentum," they mean speed.
I believe in this case that The linear action of the linear servo is driven by a worm/screw gear. The motor driven worm gear is providing a torque force upon the spur gear that happens to be the servo arm.
+David Allen
This is true. However, if that's how linear servos give specifications, it's not very useful.
Special mention: not all lightbulbs fit all in the same sockets, bought some floor lights that sat mostly nonfunctional cus their damn bulbs were harder to find.
Are the metal gears solid?
+LAHegarty lol
ahahahhaha XD
Yeah, when I heard that I instantly said "Metal geeeeear"
*!*
The metal gears are made from mercury,so they flow around the servo.Takes up less room.
Little Bits are great to play with. We had a big box of them last year at Re:Publica in the Maker area and everyone was just creating stuff that made noise in some way or the other :). They are a bit pricey though.