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Along with getting a new lipo battery pack for my SC, I’d like to swap out the stock 480 motor for something that can handle the 11.1V from a 3-cell lipo pack and provide a little bit more thrust for more daring tricks and the ability to get out of sticky situations a little better. The problem is, where do you start? With no information readily available about the stock 480 motor, you’re kinda in the dark as to what would be a good replacement. A prop RMP meter would be a good tool to have, Tower sells one for $20 that I may pick up soon. But until then I decided to try out a technique I read about somewhere on the Internet for measuring the a motors kV, otherwise know as a motor’s constant – if you put in 1V into a motor and get out 1000RPMs, that means the motor has a kV of 1000. As it turns out if you put in 1000RPMs into the same motor, you will also get out 1V. So with a cordless drill and a voltmeter, we can measure the effective kV of the stock Hobbyzone motor. With that info, we can better gauge picking a new motor, ideally one with a higher kV, hoping that it will yield more RPM’s at the prop, and therefore provide more thrust for our plane.

The trick is that you have to know the RPMs of the drill being used to spin the motor, and it has to be exact. Well, on the side of the drill it’s printed 1300RPMs in High mode, so for starters we can use that. I didn’t feel like pulling the motor out of the gearbox, so I popped the drill on the shaft where the prop would go, and fired away. The gearbox on the Cub is 3:1, so for every single rotation of the drill I got 3 rotations of the motor and the result was a solid 1.420V on the voltmeter. Since we were geared we need to calculate 1.420 / 3 = 0.473V per 1300 RPMs. To get kV we just divide the known RPM of the drill by the voltage that said RPM generated. 1300 / 0.473 = 2746. Voila, the kV of the stock motor for the SC is 2746, or somewhere close to that. As I said, this method is entirely dependent on knowing the RPM of the drill being used to turn the motor. 1300 is what the drill says, it may not be what the drill really is. So as a sanity check, I popped on a Graupner Speed 480 BB Race motor, of which I know has a kV of 3893. If I spin the motor at the supposed 1300 RPMs from my drill I should read about 0.333V. If the drill is actually spinning faster, then that number will be higher, if it’s spinning slower, then that number will be lower. I measured 2 different 480 motors and took the average of 3 readings: 0.308V, 0.312V, 0.296V. There is some error in saying that I know for fact the constant of both those motors is 3893, but I have to start with something that I think I know. Now in order to achieve the intended kV of these motors, I can now calculate the RPM of the drill. As it turns out, the drill is probably only spinning about about 1200 RPMs, not the 1300RPMs as claimed by the drill. Now taking that into consideration for calculating the kV of the stock SC motor, we actually get kV = 1200 / 0.473 = 2536. This is still not exactly right most likely, however it’s probably within +/- 5%. Which for the most part is accurate enough for what I’m trying to calculate.

Some other useful things I measured were no-load and loaded current draw of the stock motor. No load current (no prop) with a newly charged 9.6V battery pack was 0.97A. The loaded current (prop attached) was 9.4A. Of course this is with 100% drag seeing as how I was holding onto the motor/gearbox assembly while the thrust created by the prop was fighting me. During flight the current will drop as the plain approaches cruising speed, and then go up again as you fight through the wind or climb into an impressive loop. But 9.4A is a good amount of current. That’s over 90 watts of power, not bad for a RTF plane. However, the no load current of the 480 BB Race motor is 2.44A, therefore I might can expect the loaded current to be similar proportion as the stock motor or 2.44 * 9 = a whopping 22A, or 211 watts. This is where things get tricky, because there’s a chance that 22A is too much for the ESC built into the one-piece receiver unit in the SC. But then again it might be fine. The other thing is even though the Graupner motor spins 53% faster than the stock motor, it may not actually generate more thrust, since the extra RPMs most undoubtedly come at the expense of torque, the torque required to turn that massive 10×8 prop at several thousand RPMs. There’s a good chance the motor will simply over heat and die, all the while not proving any performance gains over the stock motor. It’s a gamble any way I look at it. I think one of the other Speed 480 motors would work better, one with a lower kV, therefore drawing less current and providing more torque. The other thing to do is just try it, which I might just do. All I need is a 12T, 32-pitch pinion and I should be set. As it turns out the gears in the gearbox for the SC are standard 32P, which I would have thought they’d be metric. (A a metric 0.8 module gear is nearly the exact same size as 32P, so it still could be a metric pitch, however a 32P standard gear should mesh without problems since they are so close). I determined this by measuring the diameter of the spur gear somewhere in the middle of the teeth at each end. Since this gear has 36 teeth, a 32P pinion would result in a diameter of 36 / 32 = 1.125 inches. Whatdaya know, I measured exactly that. So $3.25 should get me a new gear, and we can see what the SC does with a 480 BB Race motor. Hall of fame or hall of shame? We will see…

Measuring the kV of the Stock Motor – (1.420 / 3) * 1200 = 2536 RPMs per Volt

Double-checking the RPM of the Drill Using a Motor with a Known kV

Measuring the Diameter of the Gear – 36 / 1.125″ = 32P

Measuring the No-load Current of the Stock 480 Motor – 0.97A on 9.6V Pack

Measuring the Loaded Current with the 10×8 Prop – 9.43A Continuous

So I downloaded the demo version of RealFlight G3 and have been playing it for the last hour and what can I say but it is a blast! I thought it would be lame, but it is actually a lot of fun. I remember trying it out at the hobbyshop a few months back and honestly I didn’t get it. The planes’ movements felt fake and I kept crashing and I didn’t know why. Well that was before I actually owned a real plane. Now that I’ve got several hours of flight time under my belt with the Super Cub, I can say that the G3 simulator feels amazingly realistic and acts a lot like my cub does when I’m flying it. The graphics are pretty sweet too, with the mountains and trees in the background. The demo gives you one plane and one helicopter with one playing field, but so far it’s been plenty to keep me entertained. The plane has ailerons too, so I’ve been able to see what it would be like to fly a plane with ailerons. At first it was harder and I kept nosing into the ground, but after several tries I was getting the hang of it. Now I’m doing perfectly straight barrel rolls, inverted flight and other type stunts. I think the plane is easier to fly with the ailerons. If you choose to not use them, and just use the rudder and elevator is actually behaves a lot like the Super Cub, I mean it feels like I’m out in the back flying it around. Except when I crash there’s no harm done, just hit the spacebar and I’m off flying! Cool! I’m glad I tried out this demo, again, since I think with some practice I may be more ready for a plane with ailerons then if I went into it completely cold. Sure you’re using the arrow keys on a keyboard instead of the actual radio, but it’s still good practice. The helicopter is pretty cool too, but what a pain to fly! I think for now I’ll stick to planes. The next one I’ve been eyeing is Parkzone’s Spitfire, due out this February. It’s a warplane, similar to the other two they make, but it’s got a few features that are an improvement over their other warplanes, one of them being a better radio and 3-wire servos. The plane looks freaking cool too, and it has the ailerons so it can do way more tricks. Drop a 3-cell lipo and brushless motor into that bad boy and you’ve got yourself a world-class World War fighting machine. And seriously just playing around with the demo of Realflight G3 Simulator makes me want to get one even more.

I’ve been looking at lipos for my Super Cub, so I measured the battery compartment to see what can fit without mods, and these are the dimensions I came up with: 66.6x36x41 (LxWxH). The 8-cell pack which fits perfectly is 66.6x35x30 (LxWxH). I checked out cheapbatterypacks.com and using their super-cool li-po finder tool I came up with three 1320mAh 3S 11.1V packs that are a direct fit and offer at least 15A of continuous current capability. The most expensive being from Thunder Power costing $55 is a popular choice, the second most expensive runs $48 and is made by Hyperion. However the cheapest way to get an 11.1V lipo into a Super Cub is with the Apex APX1350-3S which runs a cool $35, is a 1350mAh pack and actually offers the highest discharge capability over the other two packs with a 20A constant current capability. That should be plenty to run the stock brushed motor, as well as just about any brushless motor available. Not only that but the pack weighs 1/2 what the 8-cell 2/3A pack weighs coming in at 97 grams vs. 184 grams. The first lipo I bought for my RC18T I couldn’t believe how light it was, I kept think there’s no way this thing is going to power my car, there’s nothing inside! But undoubtedly, it worked out amazing.

The other option to get lipo power in the SC is to modify the battery compartment to fit a bigger pack, or rather something with more mAh like a 2100mAh or 2200mAh pack. These are available in a 3S configuration (3 series cells, none in parallel) however, you can get even more mAh by going to a 3S2P pack, which takes a smaller pack like the 1320mAh and doubles up on the cells giving you a pack that’s basically twice as big as the 3S version and twice as heavy, since it’s made up of 6 identical cells instead of 3. There are two downsides to this approach in my book: one being cost and the other being if something happens to the pack from damage of some kind (overcharge, under voltage) then the whole pack is done, where as if the extra money were just put into a spare pack, it would still be good.

One downside to li-pos is charge time. Lipos can only be charged safely at a 1C rate but you can charge an 1100mAh NiMH pack at 2C (which would be 2.2A) without damage. At that rate the pack will be charges in less than 1/2 hour. By contrast a 1320mAh lipo will take over an hour to reach full capacity. You can get away with charging a lipo to 80% of its rated capacity, which it can do in about 1/2 the time it takes to fill it up the other 20%. The ICE charger gives off a beep when it’s about at the 80% point where it switches from CC to CV. It’s not the “done” beep though. I like to wait till the charger says the pack is done and not remove it beforehand just because the pack is “charged enough”. Either way, expect to wait for longer charge times for lipos over NiMH/NiCAD batteries.

After tearing apart the stock battery compartment and seeing how it all goes together with the receiver/ESC unit I feel pretty confident that I can modify it along with the fuselage to fit a bigger lipo pack. I’d really like to have longer flight times, it seems like 10 minutes just isn’t enough anymore, and neither is 9.6V. The cheapest pack I can find that would require the minimalist amount of mods is the Apex APX2100-3S which runs 100x34x20, so it’s basically just longer than the stock battery but still comes in under in weight at 158 grams, offers 2100mAh and 31A continuous discharge, well above what we need in the SC, and the best part is it only costs $40. By contrast, the brand name Thunder Power TP2100-3S is $70, almost twice as much for basically the same battery. Is one better than the other aside from just the listed manufacturer’s specs? Only someone whose run both packs could probably tell. I suspect that the Apex pack is just as good as any other, but that’s just my opinion, and based on its excellent price point, I’d be willing to pick one up and check it out. Unfortunately all Mike’s Apex packs are out of stock right now. We’ll have to wait and see…

I decided it was time to move the clevis on the servo link from the outer-most hole to one of the other holes in the rudder and elevator. Hobbyzone recommends using the outer-most hole for beginners and first-time flyers because it offers the most forgiving control by limiting the amount of throw each of the controls in capable of. In the air the plane glides easily and turns and dips in easy smooth motions, even when throwing the stick all the way up or down. Well not anymore, I moved the clevis to the 2nd hole from the inside (two away from where it was) and tested out the throw last night, and what a huge difference! The elevator has a ton of travel now as also does the rudder. So this afternoon I got a chance to fly it and it made an enormous difference in how the plane behaved in the air, so much that I almost crashed it three times (and I was just getting good at not crashing). The Cub is incredibly responsive now, able to turn, drop loop on a dime. Even with the slightest input from the trigger the plane easily climbs, drops or turns. And with a lot of control the plane can get crazy really quickly. I got myself in an upside down spinning stall that I barely pulled out of just before hitting the ground. Overall it makes flying the plane even more challenging to fly which makes it much more rewarding to fly at the same time. I was able to do this stair-step type climb, where it looks like I’m climbing a staircase, going straight up, then leveling off, then going straight up and leveling off over and over, then I could dive straight down for several seconds and then pull out quickly and fly level to the ground from only a few feet away. It’s very cool, and I thought maybe I was growing out of this plane. Well not so, a little tweak on the clevis and the plane is a whole new beast. Hobbyzone did a great job with this plane, making it easy enough to fly for a first-timer, but not so lame you get bored with it after flying it a few times. The 8-cell pack makes a huge difference too. I’m thinking about going to a 11.1V li-po. After all I’ve already got the charger for it, which is one reason most people haven’t converted over yet. There’s no reason not to go li-po in the Super Cub other than the cost of the li-po, and that it’s not a drop in battery, I may need to modify the battery holder slightly. And how long that 480 motor will last on 11.1V remains to be seen. But new motors are $10, so if and when it burns up, I can just get a new one. Or go brushless at that point maybe. I don’t know, but this plane has been some fun.

Clevis Mounted in the Second Hole for More Performance

Needless to say I’ve been having a lot of fun with my new plane. I’ve gotten a little more confident in my flying abilities, so I’ve begun trying out some tricks. I have no real idea how to do any actual tricks other than doing a bunch of loops but today I tried flying upside down. Now I don’t believe this plane is designed to fly inverted – one, because it doesn’t do it very well, and two because I haven’t seen anyone else mention ever trying to do it. Since it has no ailerons, it’s almost impossible to achieve this unless it’s by means of just coming out of a loop too soon, which is what I tried doing. I’d fly the plane nice and high, then when I go into the loop, at the top of the loop I throw the stick all the way forward, the elevator forces the plane to come out of the loop while its inverted, and then with some control, but not much, I’m able to fly around inverted for a few seconds. Some of the longest inverted flights I’ve had were when I was out by myself with no camera around. But wow it felt cool! And as far as I can tell there’s only two ways to come out of the inverted flight, and that’s by throwing the rudder all the way to either side and eventually the plane just straightens itself out, or by throwing the elevator back down which basically throws the plane downward finishing off the rest of the loop that was started earlier. The problem I have is the plane gradually decends while inverted even with the elevator all the way up, so maybe it’s time to move the servo linkage to one of the other holes to give me a bit more movement. I believe the reason this plane isn’t designed to fly this way is due to the shape of the wing, it’s not symmetric, so it’s always creating an upward lift all the time (so when it’s upside down the air above the wing is pushing the plane down, into the ground, with only the elevator to counteract it). That’s my lame attempt to explain it. I think I need a new plane…

So this is the video me trying several attempts to fly inverted, with some loops and random crazy flying around thrown in. Not to mention the sweet tunes in the background. Yes, RAD is one of my all-time favorite movies, and it just so happened that this song was the exact length of the video clip, so I had to use it. Just imagine Crew Jones and that chick from Full House hopping around on their BMX’s at that cool dance while you watch the Super Cub do its own set of rad tricks.

Hobbyzone’s Super Cub comes with a 7-cell 1000mAh battery pack, and the only thing it really has going for it is that it’s probably lighter than any other 2/3A NiMH pack available (not talking about lipos). Even though I was consistantly getting over 1100mAh on each charge and over 10 minute flight times, I still wanted more. So I was anxious to pick up an 8-cell 1500mAh pack to replace it, since it’s a direct replacement and perfect fit for the battery compartment on the SC. Well it arrived today, and me being the patient person that I am, hooked it right up to my Intellipeak Digital Ice Charger (best charger ever invented BTW), discharged it at 10A and quickly went into a 2A charge cycle. After waiting what seemed like forever, I bumped up the curent to 2.5A (not recommended) and it probably went another 10 minutes or so before it finally peaked. I only got 1360 or so mAh into the cells, most likely due to it being their first charge, and it was a quick one. Subsequent charges at 1.5A and less have shown the pack can charge up to 1520mAh without problems. It usually takes cycling a new pack a few times before it shows its true potential.

True potential or not, the first run on the pack was awesome in the Super Cub. It had so much stinking thrust I could pull out of almost any maneuver without concern. I could pull hard into large loops and do loop after loop without loosing altitude. Man it was sweet! The plane becomes a whole new animal with the extra voltage, and power for that matter. I believe the Elite cells are quite a bit better than the stock cells, meaning they have less Vdrop and less IR (internal resistance). Whatever it is, they make the Cub take off like a rocket (yeah, even for a park flyer with a 48″ wing span) I could climb to several hundred feet in only a few seconds. It felt nice, anyway I’ve got some more video that my brother shot with the new battery pack. So here it is. Some of the slower-moving shots are with the motor either off or at 50% throttle.