Explain Motors to Me

[R|M|D Photography]

So I currently have a f550 with naza and stock DJI motors. I have just picked up a TBS Disco frame and a F330 frame to play around with. I really want to put some bigger more aggresive motors on them but I judt honestly dont know what I am looking at! I know some motors are better for heavy lifting, some are better for effeciency..etc. What are the kv's and sizes I should be equating to what performance aspects?

 

[HoverRound]

X2 ^^

I'm very new to all of this but I've been doing a lot of reading over the past couple weeks. It seems that there are really no definitive answers to questions like this. Someone with some smarts about these things should build a graph that shows the relationship of different motor types/sizes. It seems like there are hundreds of different motor manufactures out there and they all list some specs, but it isn't very often that you can compare the specs to one another. It's a hobby that's far to expensive to just start trying different parts until you find the ones that work for you. It'd be nice to get someone's who's experienced to help clear things up a bit.

 

[photobobga]

If you are going to spend time and money on this sport you should try and become an expert using this web site:
http://www.ecalc.ch/xcoptercalc.htm?ecalc&lang=en

 

[HoverRound]

Yea, I've come across that in the past, it's a little intimidating at first glance... and second glance.... and third... and so on.
I've breezed over the help page and it did help a little, but for me I need someone to point me in the right direction. If there were some sample graphs showing different characteristics of different types of multi-rotor copter motors I think that would be of much more help.

 

[Nocteel]

Yea, I've come across that in the past, it's a little intimidating at first glance... and second glance.... and third... and so on.

I agree. I'm pretty up on electronics but that page makes me go cross eyed. I'll bump this since I agree that a few examples with explanations would do wonders. Maybe using a common frame as a base and then building a few MRs in the ecalc tool with explinations as to why certain motors are picked. It might help those of us that are newer to the field and even more-so to those of us (like me) that didn't come to MRs from the airplane or SR world. (I built RC sailboats before this)

 

[RobertsUp]

Lots of good motors won't fit the proprietary holes on Dji arms. It's trouble learning which do and which won't. I decided to install arm extenders having holes arranged so that any motor can be attached.

 

[ponchota]

If you are going to spend time and money on this sport you should try and become an expert using this web site:
http://www.ecalc.ch/xcoptercalc.htm?ecalc&lang=en

Partial +1 to this answer. I say partial because regardless of if you can get all the answers on a forum you should still learn how use and research for yourself. That said, this is the 2nd time in my new membership to this forum that someone replies in a snide way. The first time was more like GTFO if you can't figure it out yourself. This is awful, I know like myself most people that are new to the hobby have redundant questions that many have heard before and many are dumb or simple to more experienced pilots. Isn't that why there are forums like this here? To help each other out? To learn from each others knowledge and mistakes. I have been a member on Helifreaks forum since early 2012 (because I also fly helis) and I am on that site all the time reading answers for questions about just about everything for my own personal improvement and I'm occasionally able to answer some ??? myself which I'm glad to do. It makes me feel good to know I helped someone else out. I have never read a negative reply to a members question there. They are all happy to answer your questions and most of the time you'll get multiple answers.

 

[Nocteel]

Lots of good motors won't fit the proprietary holes on Dji arms. It's trouble learning which do and which won't. I decided to install arm extenders having holes arranged so that any motor can be attached.

I'm running into that too. Your talking about the aluminium plates that bolt on the ends right? I've heard they are heavy versus just getting longer arms is that true? I was going to go with them until someone here said they had heard they weren't good. How are they working for you?

And back on subject: My biggest problem in using the ecalc site is the sad lack of specs on most sites for the equipment they sell. (motors being a some of the worst offenders here) This is complicated by the fact that not all brands are included in the presets. I know that that is just asking too much of the coder, but if you can't find the info to fill it in and make a custom entry for the part you'r looking at, the calculator won't do you any good at all. (Before someone calls me ungratfull I really do apretiate the ecalc site. I'm complaining here about the venders not advertizing their specs.) Again I'm not good enough (yet) to really know where to start, and it's frustrating to spend a bunch of time hunting down specs just to find out that it's not even close to what you need/want.

I'll stop ranting now.

 

[RobertsUp]

I'm running into that too. Your talking about the aluminium plates that bolt on the ends right? I've heard they are heavy versus just getting longer arms is that true? I was going to go with them until someone here said they had heard they weren't good. How are they working for you?

Hi, Nocteel. (the forum disables my enter key so I can't create paragraphs) I installed the arm extenders made by Aerial Media Pros. Those are cnc machined after months of testing at AMP. I'll bet other arm extenders are Chinese clones. Just speculation. I thought they were steel. Their weight is nothing compared to the heavy 770K motors attached to them. My craft hasn't flown as yet. I'm still programming it in Assistant using the DX8. I'm having problems setting up the tx switches to operate correctly. My reply is all messed up because this forum disables my enter key on my keyboard. The AMP arm extenders bolted onto the ends of my Dji arms and made them one piece. Solid. With their supplied nylock nuts too. Those motors are now fixed to my F450 build as solid as a rock. I spun the motors up and there was a low hum from the table. No vibration. No problems. Maybe my craft will maiden in two weeks.

 

[Nocteel]

I will look into the AMP extensions then. BTW I also fly with the DX8 and originally used the programming guide here: DJI Naza Programming for Spektrum DX8, DX18 & DX18QQ - RC Groups . Of course I'v tweaked it a bit to my liking since then but that's a really good starting off point and he even offers the SPM files for DL if you don't want to do it all manually. One modification I made that I highly recommend, once you get comfortable with your rig, is setting a switch to up the D/R and lower the expo. That way you can switch between precise flying and twitchy stunts "on the fly" so to speak. I'd love to compare notes once you're in the air.

 

[RobertsUp]

Yes I hope to compare notes. My DX8 is ready to fly the craft. All the switches are set up and the AR8000 has preset failsafe set. Gains can be changed on the fly with the knob. All the blues light up in Assistant the way they should.

I worked with an off the shelf LiPo and ran it down. Too low. Today I marched out the charger and began learning to use it for the first time. Success. I've more learning to do.

Lots more to learn about the DX8. Your idea as well as finding a way to switch LED's on and off from a separate battery I already have. Already have the Turnigy on/off switch thingy.

Today after all was done I attached one propeller and armed the motors, just to do it and listen and watch. I knew it would be safe at idle speed. The Xoar prop added no noise at all. It was quiet. And ... now I have two three inch scratches on my right forearm to prove that everything worked okay. Lol

I will look into the AMP extensions then. BTW I also fly with the DX8 and originally used the programming guide here: DJI Naza Programming for Spektrum DX8, DX18 & DX18QQ - RC Groups . Of course I'v tweaked it a bit to my liking since then but that's a really good starting off point and he even offers the SPM files for DL if you don't want to do it all manually. One modification I made that I highly recommend, once you get comfortable with your rig, is setting a switch to up the D/R and lower the expo. That way you can switch between precise flying and twitchy stunts "on the fly" so to speak. I'd love to compare notes once you're in the air.

 

[RobertsUp]

>snip< I'd love to compare notes once you're in the air.

Nocteel my craft maidened on Sunday morning and it flew well. Despite poor satellite reception. Upon takeoff it shot up fast. It performed exactly like the hex in AMP's video demonstrating their heavy lift conversion kit applied to an F550. I can't tell if the arm extensions are aluminum or steel. They're black anodized and heavy. The AMP 2814 770k motors are powerful. It flew with 11 inch Xoar beechwood propellors. After landing the motors and the esc's weren't warm. The quad is a beast. (4s battery)

 

[DennyR]

Getting Ecalc to come up with useful information is like Mclarens F1 aero simulations being of any use at the track. The only way that I choose motors is by trial and error based on the the first choice of which prop. I intend to use as the next phase of upgrade. the watts are going to need an increase but probably the Kv will need to come down as you opt. for a larger prop. Be aware that some motors, like the short pancake ones will have very low kv. so if you are working with a big step down in Kv you may simply run out of revs. before the motor achieves peak power. The torque curve of the motor has to match the torque load of the prop.
Some of the TM motors have an unusual magnet to radial gap ratio which can effect the ESC's ability to control the motor speed without some special flashing to change the timing of the EMF feedback signal. Getting the ESC tuned to match up perfectly with the motor is a art form in itself . Autoquad ESC's are about your only option here.

With the DJI motors things seem to work quite well with their own 8x4.5 props and a Kv of 920 (ish) The next upgrade would be to use say the 9 or 10 x4.5 with around 800 kv wind which will also give you more torque, using the same size of 2212 motor and a little more watts. A jump to the larger size motors would be self defeating as the weight gain will offset a lot of performance. Weight gain is a square law so keep in mind not to use too large wire gauge and try to increase your performance by shedding weight.

 

[AboveAllAP]

Hi All

I am running a F550 with the AMP motors and arm extensions with 11x5 props. I am still learning but have had a number of flights and it just works. I have nothing to compare it too other than other posts. My recommendation is stick with vendors whom have proven records and have invested their own time and money into their own products.

 

[HoverRound]

As far as I can see DennyR is so far the only person to offer up anything close to an explanation of motors. I had started another thread and asked kind of a broad general question about motors and got absolutely no replies. I think a lot of us (or maybe just me) that are new to the sport were hoping we could come to a friendly forum and pick up some useful information that would get us started on the right track to building a flyable Multirotor. While "trial and error" would be fine for people who have a lot of disposable income, it's not practical for people like me who need to budget their money carefully.

Maybe this hobby is just too new and no one (except for a few professionals in the business with loads of inventory at their disposal) really knows what their doing. I find that hard to believe. I see a lot of nice flying multirotors in videos here, so someone must have a formula as least started. I am getting the feeling that those who know want to make the rest of us struggle and waste money because they did at one time. I don't really think that's the purpose of a forum.

Denny, thank you for that glimmer of insight into motor choices. It's a great start.

 

[SMP]

All righty, I'm new as well but heres a couple of things I've played with on our smaller birds.

TBS Disco
Flew awesome w 2814s (no extensions) and 9" Graupners. Would likely have flown better w 8" Graupners but cant find any. Slight forward back wobble at highest fast forward flight (FFF)

Flies ok with Stock DJI motors and 10" Graupners. Slight forward back wobble at highest fast forward flight (FFF) Definitely less powerful and responsive than the 28144s.

Flies like **** with stock DJI motors and 9" Graupners. HUGE wobble at FFF
Conclusion - Will likely go back to 2814s and add brushless gimbal

DJI 550 - I'm a huge fan of this guy as he's soooo configurable, that said its got limits!
Flew the best w stock dji motors - 10" graupners - Iris Aerial Legs and batwing and hardmounted GoPro 3. Able to do flips rolls etc. Very little effect from legs but susceptible to jello. Everything must be balanced perfectly.

Flew very good w stock dji motors - 10" graupners and gotheli RC legs (taller than the Iris legs) which allowed a wire rope isolated gopro 3. best combo for toss in the car go flying with Fatsharks. Able to do flips and rolls but buffets slightly due to legs in FFF.

Flew ok with stock dji motors - 10" graupners and Aeroxcraft landing gear. Starting to get heavy here but allowed the addition of small servo gimbal. NOT able to do flips or rolls and FFF required a delicate stick. Wobbled a ton on descent but new Naza FW seems to work better for descents across the board. Still a good size for backseating in the car but starting to creep in size and footprint.

Flew great but worked like **** with AMP motor extensions, tmotor 2814s, 12" Xoars and Quadframes LG and Musky Gimbal. This is where the limits of the frame start being felt. TONS of friggen power - rocket ship power in fact and no worries hauling everything plus the two 6000mah batteries. Unfortunately this COMBINATION resulted in so much vibration the frame was unusable with this gimbal. I suspect this is due to two reasons. one the Quadframes Landing gear lets a ton of vibration through and the motors are simply too powerful for the arms resulting in twist. At this size its just as big as the AD6 and you've lost any footprint advantage. Considered moving everything onto one of the new Tarot folding frames for 300 bucks as Components this good deserve a better frame. Ultimately, just created a quick release rail system and moved this gimbal/LG onto our droidworx framed coax 8 which works much better. Moral of the story here is...if you're lifting anything other than a gopro or small pointn shoot a better frame is probably in order. Conclusion; Will take this guy back to its 550 stock"ish" configuration w small brushless gimbal and decide on Iris or Gotheli legs or aeroxcraft LG based on how much clearance is required.

 

[aerorynamic]

All righty, I'm new as well but heres a couple of things I've played with on our smaller birds.

TBS Disco
Flew awesome w 2814s (no extensions) and 9" Graupners. Would likely have flown better w 8" Graupners but cant find any. Slight forward back wobble at highest fast forward flight (FFF)

looks like gotheli has some 8" CCW, just not the CW right now. ^^ and great info above btw!
http://gothelirc.com/shopdisplayproducts.asp?id=156&cat=Graupner+Props

 

[15crewdawg]

I think what the OP is asking for is a listing of motors and all of their specs - Brand, model & KV, Watts, etc, etc.
Along with suggested prop range for each application. With a practical lifting capacity breakdown.
And possibly a graph of torque curves for motors/props.