General AtomRC Dolphin help!

jacksrevlimiter

New Member
Hey guys, I'm new here. I've just bought my first electric plane, and I'm very new to this. I was hoping I could get a little help learning about and figuring out what parts I need to finish this plane out.

It's an AtomRC Dolphin. I'm looking at this DYS SunFun 2306 1900KV motor, and a 4S Lipo battery. How do I determine the amp rating of the ESC without having a wattage rating of the motor? And does anyone have any better suggestions on parts? I'm absolutely a noob to this, and I really want to learn how these things are determined, so I can build other things in the future.

I've watched a video on youtube (that led me here) on how to to determine some of this information, but I'm not sure how to put all this information together.

Thanks!
 

RandyDSok

Well-Known Member
That isn't a trainer plane and is not one I'd recommend learning on. That would be for an experienced pilot.

I'd look at a trainer that has a high wing and supports a 4 channel radio in something like a 48" to 52" wingspan or close to that. Larger craft move a little slower and are less affected by wind than a smaller one. The wing should have some dihedral in it, that's a slight V shape and not completely flat. Having a little dihedral helps the plane try to right itself some helping to keep the wings more level.

Had that been a trainer and you were looking for a motor, avoid cheap stuff like the one you linked to. If they aren't providing what the expected amp draw or wattage for a specific size battery and prop, you won't know the info you need to match it to an ESC of any size. In fact, most decent planes will often recommend specific motors, esc, servos etc and for a beginner, that is the best way to go. You'll learn the in's and outs of the electronics after you start getting more familiar with them. Volumes have been written and said about the subject but it will take a little time to learn all of that, so let the model maker of a craft make recommendation and just follow those for now.

We also strongly recommend you start by practicing using a flight simulator such as RealFlight or other. Practicing with one of these helps you learn the muscle memory you need to develop while saving you from having a bunch of crashes with a real RC airplane, heli or quad. In fact, what you save will be more than the cost of the flight sim in the end. The alternate method that also works well but takes longer, is to join a local flying club and let one of the members actually train you. Then if a problem comes up, the experienced member can take over and correct any problems quickly.
 
Last edited:

jacksrevlimiter

New Member
I've flown a few nitro planes, enough to be reasonably proficient at line of sight flight. My dad is a die-hard RC enthusiast, and he taught me quite a bit when i was younger. Would you recommend a certain brand or place to find these parts?

*Edit* I suppose I should clarify: I'm not tremendously new to RC flight. Just to building electric aircraft.

From what I've read, the manufacturer suggestions for this airplane are:
2306 1700kv motor
4s 1300-2200mah battery
30A ESC w/ 5v/3a BEC
9g Servos
5-6" props

What I dont know is the pitch of the props, and how that would possibly affect the motor and ESC selection.

If i were to increase KV to 1900, or decrease it to 1100, how would this affect ESC and battery selection? Most of the motors I've found have been incredibly inexpensive. I dont mind spending money on the build, but most of the motors I've found give no information on wattage. If you've any suggestions on places to find better quality motors, or brands, etc., please let me know. I'm not looking to build a speed demon out of this one. Just something fun to fly that i can dip my toes in on the FPV side of things. I'm just not familiar with parts selection for the electric stuff.
 
Last edited:

RandyDSok

Well-Known Member
I really can't on that motor size... I've always used larger ones and typically a high end brand as well. In addition, I'm starting to think it may be that websites fault for not listing the amp or power attributes of the motors they carry. I looked though most of the ones in the 1700kv range and they didn't once list any relevant info beyond the case size and kv rating.

In addition, since posting, I thought I'd look at what was offered by the hobby shops I used back in the day. The ones I trusted most have gone out of business since. So I looked at some of the large company sites and most were selling BNF and PNP models, not just ARF's. So I'm even striking out on a decent trainer suggestion ( which is what I was looking at ).
 

RandyDSok

Well-Known Member
Ok... I can at least help a little after that last post you made... lol


The 2306 portion is telling you it's a 23mm x 6mm sized motor ... the 1700kv tells you the kv rating which has to do with how fast it rotates. The last one you posted was a 2405 so a little bigger around and a little shorter ( not to mention made for a drone racer ). So unless you know the available dimensions that the plane has for a motor, that last one may or may not fit... you just were not given the info needed to determine that. They did provide a no load current but what you need to know is what is the current ( amps ) pull of that motor with a certain size and pitch of a prop. So again you'd need to guess at stuff you have no info to make a decision from. Another factor which isn't listed... the weight of the motor so you can maintain the proper CG.

The ESC you linked to is for a drone not an airplane type. You can often go up in size ( like the 30a to 40a ) without having to worry too much about the added weight, but any added weight does matter.
 

jacksrevlimiter

New Member
Gotcha. From what I've gathered, there's room for larger motors on these; the as-delivered motors on the PNP and FPV versions seem pretty small on the plate. Does the drone racer thing affect how it would function on an airplane? I didn't know there were differences between the two. I will do a bit more digging.

*EDIT*
E-flite motor
75A ESC

How about these? Hypothetically speaking. Would I be correct in assuming these would make for a bonkers airplane with the proper prop size? Also, would a 6" prop even work with such a setup?
 
Last edited:

jacksrevlimiter

New Member
I'm just dumping thoughts at this point. I've found this on the EMax website. It's their ECO II motor, which fits factory spec for the Dolphin. Shows 36A of peak draw. I'd assume a 45-50A ESC would be sufficient for it? Then, wouldn't I need to determine a sufficient battery to run it? I've found a Graphene 4S 1850mah battery; do you think that would be enough for this?
 

Attachments

  • 2306-2020-10-29-2.jpg
    2306-2020-10-29-2.jpg
    203.1 KB · Views: 1

RandyDSok

Well-Known Member
Those would only make the CG bonkers... flying it ( if they even fit ) would be terrible.

Please pardon my using the term "drone" at all... It's only a drone when the aircraft can fly on it's own accord without any pilot input. I got the from the webpage and just used it... without thinking. The "racer" portion is what would be a concern here. The recommended motor spins at around 1700kv .... the one for the racer is around 1800kv. Increasing the flight speed can affect how it handles... again it is one of those you don't know if it would be cool and just fly faster or start getting twitchy and make it harder to fly. This is why I was recommending that you stay within the ( few ) specs they had provided. Staying within the given spec means you are less likely to affect the CG of the plane as well as not exceeding its flight characteristics.
 

RandyDSok

Well-Known Member
Peak current values are the highest they can handle for only a few seconds at most. So with a 36a peak, I'd keep the motor at 30a or lower so you don't burn out the motor. I'd probably go with a 40a ESC just to have a little overhead and nothing bigger so you aren't adding in weight when you don't need to.
 

jacksrevlimiter

New Member
Understood. It's been a long day, and this has fried my brain for today. I'll pick it up and do some more reading tomorrow. Thanks for the help! Hopefully more people will chime in, too. I'm all for suggestions!
 

RandyDSok

Well-Known Member
I know you were asking mostly about how to get a handle on the electronics and determining what specs a motor has when they aren't given specifically. For you to have the info you need, you will have to be given at least 2 of the 3 primary electrical values.... ie voltage, amperage and/or wattage. If you have two of those, the 3rd value is just a simple math calculation using one of the Ohm's law equations. Resistance is a 4th value as well but very seldom used/given in RC motors. Again, take your time on this subject, it's a big one, most of which you'll learn with experience and not so much reading up on it before you start getting a real handle on it.

What is still the more important aspects of any airplane that you don't want to alter much, no matter if it's a glider, nitro, electric or even rubber band powered... Are where the CG is ( center of gravity ), the wing loading ( how much it all weighs ). The other aspects like wingspan, wing type, angle of attack and other things are more on the engineering side of things if you were designing your own. So pay attention to where the CG is located so you don't change that and keep the total weight down so you don't affect the flying characteristics.

Like on nitro's where they often give a minimum and a maximum recommended engine depending on if you want a slower flyer ( trainer perhaps ) or faster one ( sport or aerobatic )... Electrics often just use a single sized motor that instead use different battery voltages and prop sizes to provide the same effect as the different sized engines. If you do go up ( or down ) in motor weight, as long as it isn't too large of an increase, you can adjust the CG by moving the battery forward or backward. Again, the important part is still to keep the CG in the right place and the weight loading in the range the model was designed for.

Electric motor sizes are measured one of two ways... Most are now measured on the outside of the can. Others may be the size of the stator inside of the can. Going to the drawings are probably the only way to tell most of the time.

As I mentioned... don't focus a lot on learning all about the electrical specs... just know what specs are important and how to calculate what they may not list. Focus more on how much the parts weigh and their sizes. Of course always take into account the quality of a part. As an example, the Eflight Power 25 is a decent motor but Motrolfly's equivalent can deliver more power and is around 30 grams lighter, of course it costs more also.

One last thing to keep in mind... this one is if you plan on converting from a nitro engine over to an electric motor. Nitro engines will use a smaller prop size for a given thrust than what an electric uses. So you'll also have to consider the prop clearance so you don't strike the prop when landing or taking off.
 

jacksrevlimiter

New Member
I'll keep all that in mind. For now I'm going to stick to as close to the original specs as I can. The 2306 1700kv motors seem to be kind of difficult to find, but 1900kv ones seem somewhat easier to obtain, so I may just go that route.

As for the rest, I'd really like to try out a flight control board, so would that just go between the receiver and the servos and ESC similar to a drone?
 

RandyDSok

Well-Known Member
The 2306 1700kv motors seem to be kind of difficult to find,


Since the pandemic started... a lot of things have had supply issues.

Just keep in mind that a higher kv means the prop will be spinning faster at a given voltage, which will result in the amps also being higher.

If by flight controller... you actually mean flight stabilization gyro... I don't know actually, once I'd learned to fly I didn't see a need but it would be helpful for a beginner certainly. I can't recommend one but this hobby shop does sell a few different ones... Flight Stabilization - Accessories | Value Hobby

BTW, their airplane selection seems to be from lower quality up to somewhat decent stuff... so may be of interest later if something catches your eye. They had a really nice glider ( I don't have a glider and would think they are fun at times ) that I really had liked but it went out of stock before I could get the funds and just never came back into stock. I normally flew sport/aerobatic planes, but my Dad had several gliders that were great for soaring on cliff sides etc, and I'd like to revisit that at some point. In fact, even some thermal flying would be fun.
 

jacksrevlimiter

New Member
I'd love to give that a try, but sadly the area I live in is geographically pretty boring. I'll check them out. Hoping for GPS return to home and stuff like that if possible. And a little flight stabilization maybe.
 

RandyDSok

Well-Known Member
I don't recall ever seeing any type of return to home features for airplanes... I've only seen that on drone multicopters. Not saying there isn't any now, just haven't seen it before.
 

RandyDSok

Well-Known Member
Ok... just info and not necessarily my opinion... it's also not directly related to the last post, but it did bring this to mind.

The FAA rules forbid flying out beyond line of site in the hobby. If the pilot is using FPV, they must have an observer that is still able to maintain line of site.
 

jacksrevlimiter

New Member
Yeah, i remember when those changes took place. There were a few upset people at the air field I was working at. I've tried to keep up with the rules on all this. Seems like I remember them trying to make people who flew drones and rc planes get a sport pilot license. Bit ridiculous, imo
 
Top Bottom