Prophex

I want to buy a shokflyer as my first e-powered plane, but aside from the kit, I have no idea what to get. (I do already own a Futaba skysport radio, which I will use)

I've tried countless times to understand all the terminology and basis of e-flight, but without succes. I don't know which motor to choose for which plane, which esc I need for that motor and which battery.

These are the things I was thinking of getting:

- [link=http://www.hobby-lobby.com/shockflyer-super.htm]Super star shockflyer kit[/link]
- Futaba R-156F 35 MHZ 6 channel micro reciever (I want the extra channels, caus I'm planning to use the reciever in other planes to)
- 4 x Futaba Micro Servo S3108

Now about the rest ...

- What kind of motor ? (it should be one, which I can also use in some more heavy panes, if that is possible and a brushless one)
- Which esc ? (so in this case, one which will work with a brushless motor AND a lipo battery)
- what kind of battery ? (I was thinking lipo, caus they're light weight and have lots of juice)


Also, a stupid question, but don't you also need a seperate battery to power the reciever and the servo's ?


hope you guys can help me choosing a motor, esc and battery,
Prophex

ADRIANjennings

dude me and my dad have the same problem but if you want to go into e-flight fast get a f-27 stryker it is a ready to fly model that is made of a very strong epp foam i got one and flew it with no flying experence and man did it do some crashes and it is still in one peace after about a total of about 18 crashes and if you can fly thay go so fast and out of the box it has every thing to fly in 10 mins.

Mike Parsons

Prophex,
The shockflyer is a great plane. The key to Shockflyers is keeping them light. I have flown shockflyers in range from 6oz to 10oz. And the flight characteristics are greatly effected in those small 4 oz. And no question is a stupid question...you do not need a seperate battery to power RX and servos. The main pack will supply the power needed through the BEC that resides internally in the Electric Speed Controller. The third lead on the ESC provides that when plugged into the throttle channel on your RX.

Here are a couple of my recommendations on the assumtion that this will be flown outdoors (www.atlantahobbys.com carries everything below)


Motor: Torque 34T (outrunner)
ESC: CastleCreations Pheonix 10
Battery: Thunderpower 2S 730mah
(above is what I have in both of mine)

Axi 2208/34 (outrunner)
10x3.8 APC
CastleCreations Pheonix 10
2s Thunderpower 900

For a really light Shocky:
2204/54
9x4.7
CastleCreations Pheonix 10
2S Thunderpower 430

Quite a few people are also using www.littlescreamers.com motors, although I have no experience with them. These setups offer very good power and duration.


-Mike

Prophex

thx for the input, I also thought that a phoenix brushless esc would be a good choice. But how do I determine the amps ? I see you recommend a 10 amp esc, but what's the difference with a 20 amp, 35 amp, ... ?

And I still don't know how to choose a motor ... Is there no general rule for this ?
What is an outrunner motor ?
And what do those numbers 2208/34, 2204/54, ... mean ?


e-flight seems really hard ... [&:]

Matt Kirsch

My Feedback: (21)

Electrics require a different way of thinking. First thing is to get the notion out of your head that "motor == engine." Next is to stop fretting about motor choice. Choosing the motor is the next-to-last step in the process of powering an electric airplane, not the first.

The main thing to remember is that the motor is not where the power comes from. It's where the power goes to. The power really comes from the battery, and that's where you have to start when powering an electric airplane.

It's also okay to plagiarize. Imitation is the sincerest form of flattery. The nice part about this method is you can fly now, and learn about electrics with something that you can hold in your hands, that actually WORKS. Just pick a recommended setup, or one you see in our 3D Electrics forum.

The motor numbers are just designations, like model names for cars and trucks. Technically, they describe one or more dimensions of the motor, but they're useless for determining whether or not a motor is suitable for a particular plane. Just like you have to look at a car's specifications to see if it's something that will work for you, you have to look at a motor's specifications, particularly its maximum ratings for cell count and current. That takes us back to the battery.

It's all about cell count (Volts) and current (Amps) combining to make Watts. Watts is a measure of power, and every plane needs power. The higher the desired performance level, the more power the plane will need. Depending on how we want the plane to perform, we plan on a certain number of Watts per pound of airplane weight. There is a complete set of rules of thumb for Watts per pound, but the two that most pilots will be concerned with these days are:

1. 125 Watts per pound (or more) for 3D
2. 100 Watts per pound for glow-like sport plane performance (i.e. overpowered R-R-R! )

Hope this helps a little.

Prophex

To be honnest, I still don't quite get it ...

Well, now I know how to choose a motor (with that "Watts per pound-rule") but what about an esc and battery ?


I guess that I will go with this setup then:

Axi 2208/34 (outrunner)
10x3.8 APC
CastleCreations Pheonix 10
2s Thunderpower 900

Although, I would like to know if you can also use that motor in a more heavy plane then the 250 gram shockflyer.

Glacier Girl

My Feedback: (4)

Prophex,
For a good primer on electrics, go to www.utahflyers.org look up Darrens blog, will help get you started on the right foot.
Esc 10, 25, 35 is amount of amps it can handle continuously. What Matt was getting at was pack will determine how many amps your motor can pull safely. Hey, Ive been there, switched to elecs little over a year ago. I know where you're coming from. Get the recommended set up.
Then look at a calc program like Motocalc, 30 day free trial, www.motocalc.com
You can build your planes specs on it, then play around with different motors,props, packs, esc's

Try to think elec in gas terms. The battery is the fuel tank, the motor is the engine, the esc is your throttle servo. Big engine/ motor means high fuel/battery drawl, etc. Might make the switch a little easier.

Mike Parsons

Well written Matt.

The ESC is choosen by how many amps that the setup is known/estimated to put out and how many volts you will use to put through it (3 cell lipo, 4 cell lipo etc.) Manufacturer ratings will tell you what each controller can handle (check www.castlecreations.com for specs on each controller). When choosing what rated ESC you need for a particular setup, there are a few ways to do this.
1- follow someone elses successful setup (I use the search button alot for this task)
2- Use a computer program like Motocalc (www.motocalc.com) or ecalc (http://www.hobby-lobby.com/ecalc.htm) or even a free online calculator like Pcalc (http://brantuas.com/ezcalc/dma1.asp) *note: pcalc does not have a complete listing of smaller setups
3- Trial and error

Since option 3 is expensive, I really like option 1 and 2 .

The battery is choosen in much the same way. Knowing the estimated or actual amp draw of the power system and comparing that to the Manufacturer ratings of the packs. Then choose what voltage (7.4V= 2S, 11.1V=3S) you need to power the motor with by the manufacturer specs on the motor. You are not limited to one or the other, but one can be more ideal than the other and manufacturers will normally have already tested this for you (ie: check the specs of the motor).

Dont expect to learn everthing in a day. I like comparing electrics to parenting....knowledge is general and ever changing as electrics and kids evolve. I have been in electrics for three years from 7oz shocky's to 50cc conversions and I still learn something new every single day.

You can use this in a heavier plane, but realize that something will suffer. Normally performance. If it is ballistic on a 7oz plane, it will be marginal on a 14oz plane. Kind of like taking a 40 size IC engine and putting it on a 90 size plane. It'll fly it, but not as well as it did.

-Mike

Prophex

ok, one final question:

If you want to fly a plane with 2 electric motors ... do you then also need 2 speed controls or can you hook up one esc to both the motors ? (and anything you should keep in mind when doing this ? like maby make one motor turn clockwise and the other one counter clockwise or something ?)

I also did some more looking arround for info and it seems that hobby lobby had a nice explenation on what to get for which motor and such. And it seems that powering the AXI 2208/34 with a 3-cell lipoly pack gives it almost the dubbel RPM. Would it be wise to then use a 3-cell lipo instead of the 2-cell ir will I have weight issues with the small shockflyer ? Also, hobby-lobby seems to recomend low-mah batteries like 320 mah or so, but I would prefer something like 720 mah. but again, will this be a good idea, caus these batteries also wheigh alot more. (or won't it make difference ? I was under the impression that the more mah, the longer your flight time) Will a 3-cell lipo also work with the phoenix 10 controller, or should I also change that, if I would use a 3-cell lipo instead of a 2-cell ?

thx for all the input guys,
Prophex

Mike Parsons

2 motors (brushless) will require 2 speed controllers. There are a few that have been (claim) successful in using one speed controller for two motors, but there are ramifications and side effects that can rear up. Both props can spin in the same direction and there isnt anything special to keep in mind. The two speed controllers controller leads will be hooked up to a Y harness and then plugged into the RX. One battery can be used, but the voltage will need to be higher to run both and the amp rating (on the battery) should be high enough to handle the current.

A 3 cell pack can easily be used on the same motor that a 2 cell is used on. That is one of the things that make Electric motors so universal. The thing to keep in mind is as you change cell count up or down, something else has to change. Lets use the Axi 2808/34 setup recommended as an example.

Lets say an AXI 2808-34, CastleCreations Pheonix 10, and 2S TP 730 swinging a 10x3.8 produces 8 amps. When you put a 3 cell 730 pack on there, it now pulls 11.5 amps. You are now over the continuous rating of the Pheonix 10 and more amps (16c) on what the 730 can deliver without harming the pack. You now have more RPM's, but while the amps increase. In order to maintain it within spec's, you will have to drop the prop to a 9x3.8. This lowers your amp draw while maintaining the advantage of the extra voltage. This may drop the amps back around 8-9 amps.
The rule of thumb is that as you increase voltage, the prop has to drop (assuming it is running near spec levels on the battery and controller). And as you decrease voltage, you increase the prop diameter and/or pitch. For motors to be efficient they have to run at a certain amp draw. To maintain that amp draw during voltage changes (trying different packs), you juggle the prop to keep it within the window. Clear as mud?

My heaviest shocklyer was 10.5 oz (with 3cell 830 pack). This is a bit of a porker for these planes, and it still flew great. It flew a lot better the lighter I got it though and verticle performance was pretty linear. The 340 packs are great for indoors, but for outdoors, I prefer around 700mah. I fly with 2S TP 730's on my two now. Easy 10 minute flights with power to spare.

-Mike

Prophex

Wait a minute, is the esc not the same as the speed control ? Isn't the phoenix 10 amp both a speed controller AND an ESC or are these two totally different things ?

You say more juice, but how much ? wouls a 3-cell 730 mah be enough to power two 2208/34 axi motors or do you need more then that ?

Also can you not just use a 25 amp ESC instead of a 10 amp one ? (so that the rule is: as long as the amps of your ESC are bigger then the ones the motor needs, you're safe)

thx,
Prophex


offtopic: yeahaaaaaa, 500 posts !!!

Mike Parsons

Prophex,

Typo on my part. Should read "The two speed controllers controller leads will be hooked up to a Y harness and then plugged into the RX". ESC is an acronym for Electronic Speed Controller.

You can run the 2208/34 on a 2 cell or 3 cell. The difference is the size prop you can run to not overamp the motor. The 2208 has a max efficiency of 4-7a. With a max loading of 8 amps. As you go above the Max efficiency rating you begin to generate heat. Heat kills brushless motors. More cells (voltage) above a 3 cell isnt recommended on the 2208 series as it is too much voltage for this little motor to handle. The 2208 is a 2 cell lithium or 3 cell lithium motor. You will have more thrust at a higher RPM with the 3 cell at a weight penalty of a 14 grams. That doesnt sound like a lot, but on a shocky, every ounce counts.
If you are going to fly indoors, go with a 2 cell...if you plan on flying outdoors, I would go with a 3 cell. The power level between the 3 cell and 2 cell will be noticable. However, be mindful of the amps. You might have to drop to an 8X3.8 to keep the amps within the max efficiency levels. You will feel the weight difference of the extra cell the 3S 730 carries, but the extra power will make up for it.

You certainly can run a P-25 in place of the P-10. However, as I mentioned before, there is a weight penalty. Having said that.....I run a P-10 on one Shocky and a 20 amp on the other since it is what I had. Two identical setups with regards to motor, battery and servos and I can not feel the extra weight of the 20a controller.