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Pumpkin drop event

Setup Help!! Matching Kit...

#1
At the moment I'm planning on building several scratch builds....
I am in need of some simple instructions for matching Props, Motors, ESCs, Cables, Batteries and Servos etc.
Can anyone help? Maybe just an internet link or a youtube video.

Thanks!
 

Slamazon

Junior Member
#2
At the moment I'm planning on building several scratch builds....
I am in need of some simple instructions for matching Props, Motors, ESCs, Cables, Batteries and Servos etc.
Can anyone help? Maybe just an internet link or a youtube video.

Thanks!
In the Flite Test Store when selecting a model to purchase scroll down and there are suggestions for ESC, Motors, Props, ext. just scroll down a bit and look for recommended electronics. Also you can google Flite Test Power for combo power packs for many of the kits. Hope this helps.
 
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#3
It doesn't really help sorry.
I wanted more of a guide e.g. max amps on an ESC if using a 1300kv motor (I dunno just an example).
Or, which props with which motor?
Which battery with which motor?
etc.
 

xuzme720

Dedicated foam bender
Mentor
#4
Trouble is, it's best to go in the other direction. What kind of thrust will you need, size the motor/prop to that, then everything else follows. Each motor has a maximum rated capacity so you can match that to a prop size, and size the ESC from there, then select battery based on what kind of draw the powertrain pulls and balance that between flight-time and weight(lower mAh batteries are lighter but heavier, higher mAh packs can give longer flights)
 
#5
Thanks I guess that's a bit better.
Where do I find these specs because when I look at motors they show thrust in the item descriptions online, but they don't show anything in the prop's.
 

Jaxx

Posted a thousand or more times
#6
Ultimate_Red,

First, start with the airframe. What airframe will you be building? This will determine how much thrust you will need to make it fly. Like Xume720 said, you can select a motor based on that, and then match the other components. There are usually several power combinations that will work with a given airframe. What's great about the forum is that the members here have probably tested just about every power combination you could think of. To be honest though, a lot of this also comes down to personal preference, and that is usually determined by trying different motor/prop/battery combinations.

To answer your question above. The motor specs often identify the recommended prop for a given size battery (e.g 8X4 at 11.1V(3S)), so once you select a motor that will power your model, it is usually easy to figure out what prop to use. The motor specs also determine the ESC requirement. You must select an ECS that is rated higher than the max current the motor can handle (e.g 25A ESC for a motor that can handle up to 20A) Keep in mind you can have two motors with the same kv rating, but different max current ratings, so don't focus on just the kv when trying to select an ESC. Knowing the specs of your components is important, because helps with matching everything.
 
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Jaxx

Posted a thousand or more times
#7
Thanks I guess that's a bit better.
Where do I find these specs because when I look at motors they show thrust in the item descriptions online, but they don't show anything in the prop's.
Unfortunately, I have found that many online vendors are inconsistent about posting the recommended prop for their motors, and this I assume, is why FliteTest provides recommendations for each airframe. I would encourage you to pick up a wattmeter. This allows you to test each power combination yourself to ensure you have a good match. The key is making sure you don't exceed the current rating on your motor.
 
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xuzme720

Dedicated foam bender
Mentor
#8
Unfortunately, I have found that many online vendors are inconsistent about posting the recommended prop for their motors, and this I assume, is why FliteTest provides recommendations for each airframe. I would encourage you to pick up a watt meter. This allows you to test each power combination yourself to ensure you have a good match. The key is making sure you don't exceed the current rating on your motor.
Very good advice on the wattmeter. If you need a better starting point, and it sounds like you do, try looking at motors here. Heads up has good specs on prop/motor combos with different cell counts and thrust measurements, amp draw, the whole thing. It should at least give you a better idea of what to start with on your own.

Or give us an idea of what you are looking for in performance and model, and we can make some recommendations as well.
 

xuzme720

Dedicated foam bender
Mentor
#10
That is a really tiny motor! The amp rating on this one is listed as "Peak Eff Current: 5.5A". Not sure why it's worded that way, but that is the max you want to pull with this motor. You can use that one with a 10A ESC if you can stand the weight, or a 7A if you need the weight savings. Since it's such a small motor, I'm guessing you are building a micro or nano? Also, that motor is only rated for 2S so make sure you plan on that also. The 2S will also help keep the weight down.

Just FYI. The "Product Config Table" below the description can sometimes be a better source of info than the description specs...
 
#11
Thanks xuzme your a great help. Also then where did it say 2S? Can you make a guide that other users and myself can look at and say "Right I know that, therefore that must be less than that, so I'll pick that ESC" whilst their looking on the internet.
This would be very useful. Thanks
 

rcspaceflight

creator of virtual planes
#12
If you're going to order from Hobby King, the best section to look for a motor is to go to "Electric Motors":"Outrunners By Size":"Bell Type" or "22 to 27mm" if you want the 'blue wonder' sized motor. Then go to "28 to 34mm" if you want a little more power like 'the beef' set up.

But technically you start with the plane you want. The estimated flying weight of the plane and the power ratio that you want. Then you use a static thrust calculator to figure out what sized prop at what rpm will produce the amount of thrust you're going for. Then you find a motor that can handle that prop at that speed, which a good thrust calc will estimate how many watts are needed. Then you use the motor specs to know the amp draw and use that info to choose ESC and battery.

All complicated stuff.

It's better to be overpowered than underpowered because you can always use less throttle. But you don't want to go too crazy. You can also always put a smaller prop on an electric motor but a bigger prop will burn out the motor or ESC. You do lose efficiency when you have a big motor with a little prop. or by having too big of a motor on a plane, but that only has to do with flight time and isn't the biggest concern.

I'm not sure what you're building, but a motor from the "28 to 34mm" section has some great motors for a 30" wingspan to 60" wingspan foamie. A bit overpowered for a 30" wingspan light foamie. Maybe a bit underpowered for a 60" wingspan. But I think that is about the size motor for those sized planes. But it really depends on the plane. I'm just trying to simplify it and make it easy.
 

Justin

Senior Member
#16
A lot of this is personal preference. If you want your scratch build to have a long flight time, then you would go with a larger battery, which would require a larger ESC and the larger battery would also require a larger motor. If you want a fast plane, then you need a higher kv motor, which could effect the type of ESC or battery you get. You should think of what size plane and how fast of a plane, FPV plane?, then once you have an idea of what plane you want, then electronics will start to fall in place.
 

Justin

Senior Member
#17
Sorry, didn't see you plans, looks like a higher speed plane. My first, most recent and only scratch build was a quadcopter. I fly planes too. I like to get big ESCs because you don't have to worry about heat, or new ones for upgrades.
 

rcspaceflight

creator of virtual planes
#18
I really like your design. Especially the dual prop slots.

A few things that might need to be changed:
- The bigger the slot the better in order to keep the noise down. And noise is wasted energy.
- The rudder should be bigger for better stability.
- The elevator should be larger too.

I have this motor and with a 5x5 prop and a 3S battery it fairs pretty well: http://www.hobbyking.com/hobbyking/store/__18198__Floater_Jet_Replacement_Motor_AXN_2208_2150_.html

That motor is practically useless with a 5x5 prop and a 2S battery.

Since you'll be using two motors, it should fly with two of those motors and two 4x4 props.

I actually think the CG on your design will end up right about where the motors would be mounted, assuming they're before the slot. So putting a 3S battery in the nose should balance it all out really well and I think it's an excellent design.

I wouldn't worry too much about weight if you're making it out of dollar tree foam board. You shouldn't need any extra weight for proper CG. So that will keep it light.

Be sure to do glide tests to find the appointment CG before you fly it.
 
#19
If I just double the size of the design it should fit most props. at the moment it has a gap for up to a 5" prop. but doubling it will mean I can get better motors and props.
Doubling it would mean it's wingspan would get to 30"!

Also: if you can see the green dot on the model is CG, the red dot is CoL. (CG is in front) (they're on top)
 

xuzme720

Dedicated foam bender
Mentor
#20
Think about doing the slots in a "bow-tie" cutout. It can be added(cut) later if you seem to be getting a lot of noise when you test.