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Props ‘n Stuff

#1
I’m new to electrics and am confused by prop:ESC/motor compatibilities.
Is there a chart showing min.-max. combinations for FT products? Emax or others?
I keep seeing “slow” props but cannot figure out how to safely get more speed or more torque out of a motor.
I want to build the Viggen but want a pusher prop that will give it quick response.
Thanks!
 

Merv

Well-known member
#2
There is a limit as to how much speed or torque you can safely get out of a motor. If you want more speed select a prop with higher pitch. If you want more torque, select a prop with lower pitch. A higher pitch prop will take more power so you may need to reduce the diameter to keep the prop from exceeding the motor power limit. Likewise a lower pitch prop will take less power so you may be able to increase the diameter.

A watt meter is an essential tool to see if a new prop exceeds a motors power rating. And to see if your motor is pulling more amps than your ESC or battery can safely supply.
 
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sprzout

Knower of useless information
Mentor
#3
What Merv said is all true - you can easily burn up equipment or cause fires by having the wrong matches.

There's a site I recommend for starting out:

https://ecalc.ch

It's $6.50 for a 12 month subscription, and has hundreds of different motors that you can plug in with various batteries, amps, and basic info about the plane you're building, to calculate out and see if your motor/prop/ESC combination is a good match. It's not perfect, as it doesn't have EVERYTHING out there (especially when you start looking at some of the Chinese knockoffs that Banggood or AliExpress sell) but it will give you a good baseline to work from. They have an algorithm that calculates it out, and you can see what's good. I've used it for a number of planes I've built, showing what's going to run hot, what's going to give me good flight times, etc. It's WELL worth the $6.50 I paid to get me guessing right about the equipment BEFORE I buy it and have to put a watt meter to it. The Watt meter that Merv recommends is the true, real world application, but if you're trying to figure out what's comparable in what you can buy at the hobby shop or what you have currently, ECalc is a great starting point.
 

kdobson83

Well-known member
#4
Let me add that a battery also helps determine which prop you should use on the motor you want. Let's take the FT C pack motor for instance. On a 3s battery, the best prop for power and efficiency would be a 1045 prop. This setup will provide roughly 1200 grams of thrust. This is strong torque thrust, you'll have strong fast acceleration but not so much top speed. But say you want a bit more speed. On the same 3s battery, you could move to a 1060 prop producing higher speed. But this added strain on the motor means it will pull more Amos from your esc/battery. You could prop down to a 9060 prop and get the same top speed but loose the torque/acceleration. This is where you increase the voltage. Move to a 4s battery on a 9060 prop should pull roughly the same amperage, maybe a bit more, but turn the 9060 prop faster, giving you more torque and even more speed.
Long story short, unless the manufacturer has done thrust tests, or a community member has tested it and posted their results there is no way for sure of knowing. You can make an educated guess or look at similar motors by other manufacturers that have done tests and posted data or you can buy a few different props, a watt meter, and built a test stand from some wood and a scale and test em yourself.
This is something I e noticed FT has failed to do. They have 3+ new FliteTest branded motors with zero test data for people to see and compare. If I remember correctly they had purchased an expensive test stand and said they were gonna do some extensive testing about a year or so ago but they never did. Maybe someone who knows the guys can contact them and kindly remind that an episode of them testing and going into detail about the performance of THEIR branded motors and ESC's would be a great video. Maybe not big viewer numbers but would be super valuable to people looking to buy their stuff!! 😁 Including me!! Lol
Anyway, sorry to rant. If you find any solid info please post it here for us!
 

sprzout

Knower of useless information
Mentor
#5
Let me add that a battery also helps determine which prop you should use on the motor you want. Let's take the FT C pack motor for instance. On a 3s battery, the best prop for power and efficiency would be a 1045 prop. This setup will provide roughly 1200 grams of thrust. This is strong torque thrust, you'll have strong fast acceleration but not so much top speed. But say you want a bit more speed. On the same 3s battery, you could move to a 1060 prop producing higher speed. But this added strain on the motor means it will pull more Amos from your esc/battery. You could prop down to a 9060 prop and get the same top speed but loose the torque/acceleration. This is where you increase the voltage. Move to a 4s battery on a 9060 prop should pull roughly the same amperage, maybe a bit more, but turn the 9060 prop faster, giving you more torque and even more speed.
Long story short, unless the manufacturer has done thrust tests, or a community member has tested it and posted their results there is no way for sure of knowing. You can make an educated guess or look at similar motors by other manufacturers that have done tests and posted data or you can buy a few different props, a watt meter, and built a test stand from some wood and a scale and test em yourself.
This is something I e noticed FT has failed to do. They have 3+ new FliteTest branded motors with zero test data for people to see and compare. If I remember correctly they had purchased an expensive test stand and said they were gonna do some extensive testing about a year or so ago but they never did. Maybe someone who knows the guys can contact them and kindly remind that an episode of them testing and going into detail about the performance of THEIR branded motors and ESC's would be a great video. Maybe not big viewer numbers but would be super valuable to people looking to buy their stuff!! 😁 Including me!! Lol
Anyway, sorry to rant. If you find any solid info please post it here for us!

It'd be kinda nice to see the numbers on them! I mean, specs of continuous amperage

I wonder if they haven't done it because they might be rebranded from another manufacturer, i.e. Emax makes them but puts FliteTest on the motor? (I don't know if that's what's happening, mind you - I'm just making a wild guess LOL)
 

Wildthing

Well-known member
#6
If you really want to test and tune motor, prop and esc combos not only get the watt meter but also invest in a thrust stand. You can now test all combinations and come up with a winning one for whatever your build is. Props are all over the place for performance between brands even though they are the same size and pitch.
 

kdobson83

Well-known member
#7
It'd be kinda nice to see the numbers on them! I mean, specs of continuous amperage

I wonder if they haven't done it because they might be rebranded from another manufacturer, i.e. Emax makes them but puts FliteTest on the motor? (I don't know if that's what's happening, mind you - I'm just making a wild guess LOL)
Don't you know the guys or at least a couple? Give em a call/email and tell them to put that test stand TJ got a year or so ago to work and do a testing video! 😋😎
 

DamoRC

Well-known member
Mentor
#8
I agree with pretty much everything said in the responses thus far but I have a slightly different take on it.

I have a thrust stand and a watt meter and various batteries and motors and props (when you do this for a while you will end up with a collection) and so I can pick and choose what I might consider an optimum setup for a plane and my experience with these components informs any further buying decisions I might make.

But when I started - no motor, no prop, no ESC, no battery and little knowledge - and wanted to come up with the best possible option for a power setup for the least number of dollars, I trawled through the internet. One post I saw on RC groups basically said "find out what other people are using and start there". "No way" I thought. I was going to do the research and math and more research and get the best possible option. After hours comparing setups using online tools, comparing prices online, and reading about how all this works, I eventually settled upon an NTM 2826 1200kV motor, 3S battery, 25A ESC and 9x6 and 10x4.7 props. And you know what? This was basically the original C-pack power configuration that FT used. I could have saved myself a lot of effort by simply going with "what other people are using".

It's good to do the research and learn and gain the experience but you can't test components with watt meters and thrust stands unless you have already bought them. So I would start with what is a good recommended setup to get into the air. For the Viggen, get the C-pack motor (either the Emax or FT radial version) , an 1800 - 2200mAh 3 cell, A 30A ESC (4S capable) and some 9x4.5 SF props. This will get you into the air and give you plenty of punch-out (quick response). Then you can start to expand your collection of props (9x6 APC, 10x6 APC) and see how you like the additional speed (with some sacrifice in punch out) or invest in some 4S batteries and satisfy your need for speed (if you have one). This motor / ESC / prop combo will pretty much cover you for any 25-40inch wingspan weighing up to 2.5 pounds.

If you want to see some of the performance data for the FT Radial C-pack I have posted my test results here. (although it would be nice for FT to start running and publishing their own data as suggested by @kdobson83
 

sprzout

Knower of useless information
Mentor
#9
Don't you know the guys or at least a couple? Give em a call/email and tell them to put that test stand TJ got a year or so ago to work and do a testing video! 😋😎
Maybe we just flood Stefan's forum name and beg? LOL Actually, I haven't ever met the FT guys!!! One day, I will, but until that date, I'm a lowly forum member like most others here. :) LOL

As DamoRC said, there's a lot to be said for "go with what others use" because it's already been tested, in a sense. That doesn't ALWAYS work, though. For example, I have a little 3D foamie that I bought for $15 at the AMA Expo West a few years ago. It says to use a T1806 motor with a specific kv and usage on it; when I looked up the info on the internet, it points to a VERY specific motor - one that has been discontinued. So I started searching around, and found a couple of replacements based on what eCalc's data had, and I'm going to end up getting it in the next few weeks (I have a gift card for Amazon, so I'm trying to go through them to buy it).

But, if there are a bunch of people using a specific type of motor for the plane, and it's readily available? Use that motor. It's a LOT less of a headache to do so.
 

Wildthing

Well-known member
#10
Proven and safe combos is one thing and you will find tons of it on the internet but now to find that little extra is another thing. Besides different brands of props and motors what about changing the timing in the esc and which esc performs better at which ever setting?
 

sprzout

Knower of useless information
Mentor
#11
Proven and safe combos is one thing and you will find tons of it on the internet but now to find that little extra is another thing. Besides different brands of props and motors what about changing the timing in the esc and which esc performs better at which ever setting?
While that CAN be done, I'm leery of letting the "magic blue smoke" out. I'd much rather have a fudge factor on any of my numbers to fly in a safer manner (i.e., nothing smoking and catching fire in midair) than pushing it right to the very edge...And that's my personal opinion, mind you; if you want to try it, feel free to try it. I don't want to, myself. LOL