|Apr 17, 2013, 09:26 PM|
Fitting a Bravo SX Fuselage to a GW 9958 Helicopter
Fitting a Bravo SX Fuselage to a GW 9958 Helicopter
This blog post details a scale helicopter project where I attached the fuselage from a Nine Eagles Bravo SX scale helicopter to a GW 9958 pod & boom-style helicopter.
CLICK HERE TO JUMP TO THE FULL BUILD LOG.
(Or if you already clicked here, then just scroll down to the next post.)
|Apr 17, 2013, 09:26 PM|
The GW 9958 is a four-channel flybarred fixed-pitch micro helicopter and was the first model of this type that flew after "graduating" from coaxials. In some ways it shares a lot of the flight characteristics of the Blade MSR, also one of my favorites. Additionally, one of the big reasons that I like the GW 9958 is that it uses the FlySky protocol and binds to the popular Turnigy 9x transmitter which I feel works and feels SO much better than the "toy" transmitters that come with this class of helicopter. Here's a thread at RCGroups devoted to the GW 9958 if you want to learn more about it:
Now, I've always been envious of the folks who fly the attractive Nine Eagles Bravo SX scale helicopter because of how good that helicopter looks. Once I started flying helicopters with the Turnigy 9x, I quickly became pretty firmly wedded to only flying helicopter that would bind to my Turnigy 9x (which can fly my fleet of Blade micro helis thanks to a DSM2 mod by RCG member Daryoon) Thus, I never could convince myself to actually buy the Bravo SX because I'd need to use the "toy" transmitter that came with it. Additionally, I had quite a very large collection of EFlite-style batteries that I could charge in parallel with my Thunderpower AC6 charger. I didn't want to collect a bunch of Nine Eagles batteries as well--also because as far as I'm aware, there are no easy ways to hook those up to the AC6 charger.
Well, back in December of 2012, I decided to go figure out how to get the best of both worlds. I was inspired to install the Bravo SX frames on SOME kind of helicopter that I can fly with my Turnigy 9x. It was either going to be a V911 or a 9958. I first tried installing the V911 RX board into the mechanics of the Bravo SX but I really didn't like how it flew. So instead, I looked into installing a 9958 in its entirety into the Bravo SX fuselage. I was very excited to find this blog posting here:
where the 9958 was installed into the Bravo SX but where the 9958 tail rotor, main blades, and skids were used. I didn't particularly like that approach because I think that the color scheme of the Bravo SX is really quite attractive and the skids are part of the overall package. So, I spent a little bit of time tinkering and figured it out.
Introducing my 9958/Bravo SX hybrid fleet:
These things fly REALLY well. I'm extremely happy with them and love blasting them around my studio.
Here are some side-shots of my fleet. I'm quite pleased with how they turned out mechanically and how well (I think) they look compared to the original Bravo SX.
List of Parts
Here is the list of parts that I used for this build:
Step 1 : Preparing the GW 9958 Internals
The first thing I always do when I get a GW 9958 is swap out its tail boom for the boom of a Bravo SX. The motor on the Bravo SX is MUCH stronger and gives the helicopter so much more tail authority. For this mod, you MUST use the Bravo SX tail boom if you want to follow my instructions. This is because the Bravo SX tail boom is longer than the 9958 tail boom and if you don't use it the frame will sit much further back in the fuselage to avoid the tail blade from hitting the tail fin of the fuselage.
This involves desoldering the wires from the circuit board (or cutting them) and then resoldering the new wires from the boom back onto the board (or splicing them onto the cut wires). I'll assume you already know how to do that. If not, there are lots of tutorials on soldering out there. The boom is not glued into the frame or anything so it's very easy to slide out and slide back in. Just be careful not to pinch the thin tail motor wires when reinstalling the boom.
Note : I strongly recommend this mod even if you don't want to build a scale helicopter out of it. It really makes the GW 9598 fly so much better. (If you're keeping the 9958 looking like stocky, you can even re-use the tail fin by cutting the part of the 9958 tail motor holder off of the old boom and sliding it onto the Bravo SX boom before installing it if you like.)
After installing the Bravo SX tail boom, you can go ahead and install the Bravo SX tailfin of your color. I kept all of my builds exactly the same color scheme (white or black blades) as the stock Bravo SX. Obviously the choice is up to you!
Step 2 : Modding the 9958 Skids
The first thing to do is to sacrifice the 9958 skids. The reason for this is to be able to use the skid frame as an internal spacer that will let you re-use the Bravo SX skids. The 9958 internal frame sits MUCH higher in the Bravo SX fuselage than the stock Bravo SX does so you need this to help brace the 9958 frame.
All you have to do is take a wire cutter or something and clip the landing skids off of the frame like I've done in the picture below:
then you can attach the skids back to the frame like you see in this picture here:
Step 3 : Installing MCX Blades and MSR Flybar
In order to match the Bravo SX color scheme, you need to install either solid black or solid white blades. The 9958 blades are white but come with stripes on them. Now you have a few options here. You could do what I did and install the lower head and lower blades from a Blade MCX since those blades come in solid white or black. The MCX head is required for use with the MCX blades because the feathering shafts are different lengths from the GW blades (see paragraph below).
You could also install the solid black blades from a GW 9998 coaxial or the solid white blades from a GW 9988--rebranded as an Ares coaxial that you can buy in the US at HobbyTown USA. If you use the GW (or rebranded GW) blades then you don't need to install the MCX head.
Now, as an aside, when I used the white Blade MCX blades, I had to swap a few around until I got a matched set. When I first tried it, I got a lot of vibration and the blades did not track very well. I think the white blades tend to be a little more likely to bend and so they'll be more likely to not track as well out of the box. Fortunately I had a few spares so I swapped them around until I got the behavior that I wanted.
As you can see in the picture above, I also installed the MSR flybar. I like how the helicopter flies with the MSR flybar better than the stock flybar. This will obviously be up to you and how you feel it flies. Try both and see which one you like better!
The nice thing here is that you can re-use the stock 9958 links. They fit a little loosely on the MCX and MSR parts but they stay on and fly just fine!
Step 4 : Securing the Screw Mounts for the Nose
I only used four small fuselage screws to hold the Bravo SX fuselage together. They were found at the end of the tail, under the point where the tail meets the body of the fuselage, and then two under the nose.
To make the screw mounts, I used the searchlight piece that comes with the Bravo SX. I didn't have anywhere to connect the wires since the 9958 doesn't seem to have any place to hook up LEDs (as far as I know...) so I didn't bother keeping the search light attached. The LED part of the light pops out of the little ball socket as seen below:
I then used a single short fuselage screw to attach the mount to the fuselage. Note, the mounting hole is keyed and so it should only attach one way. For now, only attach a single side. See below:
Step 5 : Cutting the Fuselage to Fit the 9958 Servo Links and Swashplate
The process of preparing the Bravo SX fuselage involves cutting a little bit of material off of the top of the helicopter to make space for the different-shaped 9958 head and servo arms. Here is the left side of the canopy before I started cutting:
Here are the approximate cut lines, marked in red, that you can use as a guide to see how much to remove:
Now obviously, you can trim to your taste and your satisfaction for how well the helicopter fits into the fuselage, but I found this combination to work pretty well for me. Below, you can see what the canopy looked like after I finished cutting.
And then you can do the other side of the canopy in exactly the same way. Here's my right side canopy piece after cutting.
Step 6 : Making the Upper Canopy Mount Holes
The first set of canopy holes are ones that can be made directly with a pin vice or other small drilling implement. You could use a needle, I suppose. Here, I just popped a hole in the center of this part of the canopy. It's pretty small and pretty easy to find the approximate center. I started a hole with a pin vice and then used a punch with a wider diameter to increase the size of the hole until it was big enough to fit the canopy mounting rod on the mainframe. See below:
Then you can do the same to the other side.
Step 7 : Making the Lower Canopy Mount Holes
This part is more challenging because now you have make sure that everything lines up properly and you don't have holes that are twisting the helicopter frame or are putting unnecessary stress on the helicopter fuselage. You also need to take both measurements for the second set of pins at the same time otherwise you end up with a helicopter that has its internals mounted kind of crooked on the inside (ask me how I know!!!).
To do this, I assembled the 9958 internals and put them into the mainframe as much as possible. I started with the tail, secured the end of the tail with a small fuselage screw, then moved to the back of the helicopter and attached the back end with a screw. Finally I had the picture that you see below:
At this time, I GENTLY squeezed the black window plastic of the helicopter body against the lower canopy mounting pins with my fingers at the same time. I applied an even amount of pressure to both pins so that a small dimple appeared in the black plastic window. You can see the dimple below:
and then again on the other side:
Then I removed the fuselage pieces, used a pin vice to start the hole and then used my punch to increase the size of the hole until it was large enough to fit the canopy pin.
Step 8 : Prepping the Bravo SX Skids to Use 9958 Batteries
Since I started with a 9958, I have 9958 batteries and chargers. I wanted to keep using those rather than investing in Bravo SX batteries. To mod the skids, I found that I could use a set of pliers and gently pull out the metal contacts and plastic battery holder pieces from the front of the skids. A front-view of the skids can be seen below:
and a side-view.
This lets me slide the 9958 battery in back-first just like as if I was installing it into a stock 9958. The battery cable of the 9958 mainboard comes out the back of the helicopter as well.
Step 9 : Final Assembly of Fuselage
The final assembly is kind of tricky. You need to make sure that the skids are properly inserted into the fuselage as you close it up. There are two pins in the front of the skids that fit into mounting holes in the fuselage.
You also need to make sure that you are gentle when you push the two halves of the fuselage together as the little mounting pins are kind of fragile and can easily break off inside their corresponding sockets if you're not careful!
Here's a picture of what the final assembly looks like from the underside. Note the rear of the skids are held in only by the fuselage. You could potentially secure it with a little wire or glue or something to the 9958 skids but I found that this wasn't necessary.
Step 10 : Go Fly!!!
The last thing you'll need to do is to re-trim your helicopter to get it back into a neutral hover at center stick. This means that you'll want to CAREFULLY pop the servo link rods from the swash plate and lengthen or shorten them as needed to achieve neutral trim.
I recommend reading Daryoon's blog here about how you do that:
Also, because you'll be using the Bravo SX tail boom, you will probably need to use your transmitter to trim the rudder channel some. It won't stay centered at center rudder--at least in my experience.
Thanks for reading! Let me know if you have any questions.
|Apr 18, 2013, 08:30 AM|
Thanks! I ran out of time last night before I could finish any of the written descriptions. I will work more on this tonight and hopefully finish!
A least I have most of the photos uploaded.
|Apr 18, 2013, 07:34 PM|
Just did a few more updates to post #2. I'm only about half way done with the written description of how to assemble the parts.
I wanted to save it so that I wouldn't accidentally lose my place! Will be back with more updates.
|Apr 18, 2013, 08:39 PM|
Okay! Done with my updates to post #2! I'll probably post another picture or two later to show which screws I used.
|Apr 20, 2013, 11:25 AM|
I flew my 4 birds a few times last night and I think that they're a little too tail heavy. I have a tendency to tip backwards when landing. Normally that's not a big deal because the tail fin keeps the tail blade from hitting the ground but it could hit something if you're landing on an uneven surface.
The solution may very well be to put the LED spotlight back into the nose to give it a little more forward weight. I've tried pushing the batteries as far forward as I can and it helps but that extra weight with the LED might be good.
Of course, the really cool thing would be to figure out how to wire up the LED spotlight so that it actually works like the original Bravo SX...hmmm...
|May 15, 2013, 07:43 PM|
It is not very clear how the Bravo SX skids attach to the frame. Everything else is nicely detailed. I was shopping around for a fuselage and was almost ready to buy the Bravo SX, when I came across this: HK 189 Coax, which is GW9xxx (dont know which model exactly).
Same size as the GW9958. With everything needed for the swap, it was 15 GBP as opposed to 31 if I went with Bravo SX fuselage.
Of course the quality and the details of it are not going to be Nine Eagles levels, but its a small heli and who the hell is going to see.
Why am I posting here: I need ideas from a man that has already done this. The only thing that bugs me is the battery compartment tray of the HK189. It can be opened and its designed for a wider and shorter 220mAh battery. How do I go around fitting the 9958 narrow and longer battery?
All these, plus the Blade MSR flybar and MCX lower head and blades are coming on Friday. I need this figured out by then.
What have I done, this will never work...
|May 15, 2013, 08:25 PM|
The Bravo SX skids attach to the Bravo SX fuselage the way that they're supposed to if they were actually being used on a Bravo SX. That is, there are two "canopy pins" that stick out to the sides on the front of the Bravo skids and these fit into two little sockets on the inside of the Bravo SX fuselage. The rear parts of the skids just hang loosely out of the fuselage. The little fuselage slots that the skids poke out of in the rear are pretty much sufficient for keeping the skids in place.
They will pop out in the event of a crash though, so one thing I've thought about was to tie the back of the Bravo SX skids to the underside of the modded 9958 skids. If I ever disassemble one of my birds, I'll try to take some more photos to make this more clear.
|May 15, 2013, 08:34 PM|
The HK 189 is actually a rebranded GW 9988. That's right, this is the same company that makes the 9958. Here's a link to the GW 9988:
but yeah, it's pretty much the identical machine. I have a HK 189 AND I've got another one of these that I bought at a HobbyTownUSA (a hobby store franchise in the US) that is ALSO identical internally but it's called the Ares coax and it's orange. Looks good though.
If you look at the 9958 thread, I believe someone has used this fuselage with their 9958 already. Check out the postings here:
Some modding info here:
A video here!!!
MORE modding info here:
So yeah, you should contact the guy who did this for more info. let me know how it turns out!
It CAN be done!
|May 16, 2013, 01:43 PM|
Hey man, I`d like to get you a beer if we werent on different continents. Love your enthusiasm.
Even if those guys didnt write a build tutorial like you did, I still have no idea what is the best thing to do with the battery tray. Keep the 9958 batteries and modify the 9958 tray to fit the 9988 canopy, or just simply get a few 9988 batteries (220 mAh) and be done with it.
I think I`ll ruin the 9988 canopy to accomodate the 9958 batteries this time, and if flight times are too low, than just order 3-4 9988 batteries and a new canopy (the canopy is really cheap, but the extra bits like screws, skids and windshield triple the amount).
Anyway, at least I know it can be done.
Thanks a lot RoboHeli. I have the confirmation from Heliguy sending out the canopy and the rest of the bits by first class next day delivery so I should have them tomorrow morning. Nothing from Wheelspinmodels (Im expecting the Blade flybar, lower head and rotors from them).
I will do a build thread with pictures for every step.
Too bad that I`m a little late for the party and by the time I bit the bullet and bought this cheap heli (I`m very skeptical about cheap stuff) most pilots have lost interest in this heli. But I feel this heli will be on the market for a quite some time to come, and new people will find our picture documented mods helpful.
Btw, what are your flying times for this bird with the Bravo SX canopies, that is if youre running the stock batteries? How much did it drop?
|May 16, 2013, 01:52 PM|
Hey, that sounds awesome! Drop me a note when you start your build thread so I can follow.
Regrding flight times, I only ever fly to 4min as a rule but the performance of my heli at the end of those four minutes is not significantly lower than stock. Mind you I fly 160mah turnigy and nanotechs. I don't use the stock batts and have given them all away anyway.
Regarding the battery door, you can muck it up all you want and buy a replacement of just that part. When you bought the fuselage did it come with windshield, tail, and battery door? I've had to buy all those parts separately.
|May 16, 2013, 02:06 PM|
Nah, the canopy comes butt naked. It doesnt even include the tail fin/wing. Even that is a separate part. The windshield is also a separate part, as are the skids. And then you need screws. The battery door is also a separate part, but I didnt order that one, I didnt see it in the parts list, and only when I saw a picture of the helicopter with the door open, I realised Im not gonna have a second delivery cost of £7 for a £0.98 battery door. Pretty much as things are with the Bravo SX canopy.
Oh so you`re running aftermarket batteries. The man to ask then. What type of connector do those Turnigy batteries use? I`ve been looking at them, but can`t order since I dont know if they can be connected to my 9958. And then what charger? I havent got a clue what are the standards with these micro connectors, or even if the 9958 uses standard connector or proprietary ones. I also ordered a new 9958 battery. So now I`m going to have 4. Just to find out that pretty much everyone uses aftermarket ones. Neat.
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