I have been into R/C for about 20 years. I raced cars and trucks for most of my teenage years (and still do during the winter even now). It has been only the last four years that I have been into helicopters. I have owned quite a few different brands of r/c helicopters and because of the nature of my work, I get a chance to build and fly a lot of models. Part of what drew me to r/c helicopters instead of airplanes was the fact that they were different. Not everyone into r/c flying could fly or had any interest in flying an r/c helicopter. Some brands come and go, some are here to stay. Hirobo is one of those “here to stay” brands. They have been manufacturing r/c helicopters for over 20 years. At this point they have it down to a science. Hirobo manufactures very high end 90 size models expressly designed for the FC3 pilot. This type of “contest” flying is not nearly as popular in the U.S. as it is in Asia and Europe. It seems that 3d flying is really what gets the American market’s heart pumping. As such, I find myself drawn to 3d flying granted, I’m no Alan Szabo or Dominick Haegel I can fly reasonably well, and enjoy putting an r/c helicopter through its paces.
MRC needed a build and review for the SDX, and I was in the right place at the right time. When the possibility of doing a review on the new Hirobo SDX became apparent, I stepped up to the opportunity.
Hirobo has just released the SDX. It seems that while the Sceadu Evolution was very popular, times have changed and people want a more “hard core 3d” designed 50 size machine. The Turbulence D3 marks Hirobo's first 3D specific model, what about a 50? Enter the SDX. It starts where the Sceadu Evolution left off. This doesn’t mean for a minute that the SDX won’t be a great model for beginners, quite the opposite. Hirobo machines are a great way to get into flying, and are easy enough to adjust or slightly modify by adding some light weight rotor blades, and maxing out the control throws. Hirobo has gone a different route than some other r/c helicopter manufacturers. You will not find carbon fiber frames, and a full metal head on the SDX. Hirobo knows that these things are expensive and add needlessly to the cost of an r/c helicopter all while doing very little to improve performance. Hirobo’s SDX is plastic. Plastic in my opinion is the perfect material to make a 50 size helicopter out of. Other companies use a very low grade of carbon fiber that is still quite expensive if you happen to break it in a crash, costing $100 or more!! Also with Plastic head components, they are cheap to replace. Metal grips, will not likely break, but aluminum does bend, and if it bends it still needs replacing. With a Hirobo 50, if you do manage to break the frame it is under $30 to replace. Rotor grips are also inexpensive, and are much easier on bearings. Personally, my 50 size machine is my “beater”. Not that I don’t love the “beater”, I DO! but the “beater” helicopter is the one you’re likely to fly the most, and the one you’re likely to learn new maneuvers with mostly because you realize you are not going to be replacing $100 frames, and $60 metal rotor grips if you smash it in. If you’re familiar with modern Hirobo moldings, you know that it is extremely ridged, light weight, and the moldings are perfect.
Ok, the build…Hirobo manuals are very good. Each step is numbered to a corresponding bag. There isn’t much more frustrating than building a model on step 1 and realizing you need the hardware out of bags 6 and 12. I hate that! Hats off to Hirobo for keeping the absolute minimum number of bags open at the same time. There is not a lot of text to read, but there are exploded views showing where each and every part goes, and exactly what screw goes where. The manual also shows, in detail where thread locker should be used. Much of the SDX build is similar to a Sceadu build, so if you’ve built a Sceadu before you’ll know exactly what I mean. When you open the box containing the unbuilt SDX you first see a canopy that is different than the Sceadu. In my opinion, a welcome change as I was never able to fully “fall in love” with the Sceadu canopy. I did however “love” the SDX canopy right away. The shape is exactly what I was hoping for…no cheeks! For what it's worth, the Canopy will fit the Sceadu, and it is marked for the canopy mounts for the Sceadu.
The SDX is available in a SWM (which means eCCPM) and HPM (which means mechanical mix) You are given the choice to build the SWM SDX version with either a 120 degree OR 135 degree swash plate. All the parts for either version are included. I built mine 135 degree. I feel that 135 is better because you are not relying on the transmitter to alter the speed and travel of the elevator function. All 3 servos move the same amount during an elevator command, and in my opinion result in less unwanted interaction. Unfortunately I only have the lowly DX7 transmitter, but there is an easy way to make a mix so you can use a 135 degree set up. I opened up a “program mix” and mixed pitch to elevator at +30% in both directions. I also increased the swash mix to approximately 20% higher for the elevator function. These numbers may not be exactly what you will need to mix 135 degree, but it’s a start. Essentially I found that if I increased or decreased the total up and down swash plate travel, I had to then also alter the pitch to elevator mix. I set my SDX up with +/- 12 degrees of pitch.
There appears to be quite a bit of adjustment available when setting up the SDX. I mean there are a lot of places where ball links could go, I’m certain altering the flight characteristics one way or another. I wish Hirobo would advise what each adjustment does, sadly they only instruct to just one setting. I am going to have to do some research to find out how to fine tune this new rotor-head to different flying styles. The FZ-5 rotor-head appears to be a slightly scaled down plastic version of Hirobo’s flagship 3d machine the Turbulence D3's SSZ-4 head. I suspect the adjustment allows for 3d style flying and FC3 style flying as well, why they chose not to include additional instructions for different setups I don’t know.
The only other thing the manual doesn’t really touch on is dial indicating the start shaft. Among those that know Hirobo, this is a no brainer, but if you have never built a Sceadu or Freya you will not realize how important it is to check the run out on the fan hub and clutch assembly. There are numerous discussions about how to properly dial in the clutch and fan hub from the Sceadu, and this is no different. Dial indicating is nothing to be scared of, in fact if you are into r/c helicopters you should really invest in a dial indicator. A helicopter with very true running rotating components is even more of a joy to fly.
The tail control rod on the SDX did have me a little concerned at first. It appears to be a very old design of a wire rod riding in a sheath similar to the old shuttle. BUT in the interest of fairness I was going to fly this helicopter totally box stock to give the engineers a chance to prove their design. After test fitting the wire rod in the sheath, I realized that it’s not simply a plastic sheath…it must be made of Teflon because it is one of the smoothest tail control rods I have ever felt. Do bear in mind that the HPM version of the SDX will have the rudder servo mounted on the boom, not up front in the servo tray like the SWM version.
The servo layout is very similar to the Lepton, and the Turbulence. Hirobo made a VERY nice feature to ensure that your linkages are the correct length. At neutral settings, a 2mm pin is inserted in a hole in the mixing lever; into the blade grip giving exactly zero degrees. Now, all you have to do is attach linkages. Secondly, there is a hole in the aileron levers that you use the same pins in, to show a perfect servo linkage set up. VERY cool.
n my SDX, I used Futaba S9451’s they’re fast, they have a lot of torque, and they are metal geared. I’ve used these servos in several other machines and found them to be very reliable. For the Rudder, I used the Logictech 6100, along with Logictech’s high speed digital servo. I have also used this gyro in several other helicopters with much success. For blades, I chose the MAH 600 g3. They are affordable, and I wanted to try something different. I used a Thunder Tiger Redline 53, and the Redline Hi-flow Pipe. I really like the Redline, it is easy to tune and produces a ton of power.
Out at the field, we were treated to a relatively warm 40 degrees, and very little wind. Quite rare for springtime in Montana. I fired up the Redline, and walked it out to the flight line. A couple tweaks on the needle and the SDX was hovering. Very smooth and locked in hover not unlike the Sceadu Evolution. Transitioning into forward flight was a non issue, also very smooth. Its so cliché to say that a helicopter flies like “it’s on rails” but theres no better way to describe it. The SDX does fly like its on rails. It tracks very nicely, no tendency to pitch up or down in fast circuits. A few loops and rolls and I’ve decided that the lead in the flybar paddles needs to go. I also max out the control throws. Next tank the SDX takes everything I can throw at it. Every 3d maneuver that I’m capable of is done with ease. Snakes, piro-flips, funnels, aileron tic-tocs, even just stationary flips are very fast but predictable. At first, I was disappointed in Hirobo’s continued use of solid plastic fins, instead of carbon fiber, but quite honestly it flew fantastic with the full fins. I’m fairly certain that pirouetting maneuvers could be a little better with skeletonized fins, but for now, I’m keeping the plastic ones on there. I did a full speed backwards hurricane with no problems tracking or wandering problems at all. The stock blue plastic tail blades were excellent as well, with no tendency to blow out, or bounce. They are not the same “bat wing” shape as the old Sceadu tail blades, they are a new shape.
So far, with 5 tanks through the SDX, I love it. I have a new favorite 50. No helicopter is perfect, but I can’t find any glaring faults with this model. The only real complaints I have is that the molded black plastic gears from the Sceadu are carried over to the SDX. They are a bit on the noisy side. The good news is that Hirobo does make machined Delrin gears you can easily upgrade to. Also, the manual doesn’t go into the obvious adjustability of the rotor head. I think Hirobo has a winner on their hands. Customer support is legendary with MRC and this commitment to their products and the people who buy them is not going to change. With the Turbulence D3, and now the SDX, Hirobo has entered the new 3d era in their own style.
Review & Photos by Brian James
