Do you want big heli performance in a small package? The Thunder Tiger Mini Titan E325 is absolutely ballistic with the Scorpion power system, and it's a blast to fly. It offers the hover stability and smoothness of a much larger heli while still having the outrageous control authority that more experienced pilots will love. Geared to a lower head speed, it makes a perfect beginner kit for aspiring pilots with a little simulator time.
Thunder Tiger, long a familiar name in the RC helicopter industry, has answered current market demands with a full lineup of electric helis. The Mini Titan E325 is Thunder Tiger's entry in the mini-heli market. When the original Raptor 30 was released over a decade ago, it was highly praised for its durability, low parts count, ease of assembly and excellent flying qualities. The Mini Titan E325 continues that tradition. Just a look at the parts makes it obvious that a lot of thought and engineering went into this kit.
CONSTRUCTION
The main frames are a wonderful example of what talented engineers can do with molded-plastic parts. The entire main frame is composed of only two major parts-an upper and a lower half-and only a handful of smaller parts to complete the entire assembly. Molded into the plastic parts are a number of nice details such as hooks for rubber bands to secure the battery and speed control and hold-downs for the servo and power wires. There are even molded pockets to capture machine nuts, making assembly faster and easier. These details make assembly that much more enjoyable. The fully assembled frames are extremely rigid and should stand up to all but the most punishing meetings with Mother Earth.
The upper main bearing is in its own bearing block and screwed to the top of the frame. The lower bearing sits in a counter-bored hole at the bottom of the frame. Spacing the bearings as far apart as possible minimizes bearing loads and spreads the flight loads more evenly through the structure. This should increase bearing life and minimize frame flex.
POWER OPTIONS
I chose the Scorpion HK-2221-8 motor for power. The motor is attached to the aluminum motor plate included in the kit with two 3mm screws. This assembly is attached to the main frames with another pair of screws. Instead of two mounting slots, the Mini Titan's mount has a single hole and a curved slot. This allows the mount to pivot and makes setting the gear mesh easy. Once you've achieved the proper mesh, lock it down by first tightening the screw over the curved slot and then tightening the fixed screw. The 150T main gear sits about one inch above the bottom of the main frames. It includes a one-way roller clutch for autorotations-for those who are brave enough to try.
The kit includes three brass motor pinions to accommodate various types of motors; there's an 11 tooth for 2.3mm shafts, and 13T and 15T pinions for 1/8-inch shafts. I used the 13T pinion on the Scorpion motor.
The landing gear structure is a single molded piece. Assembly requires only that you attach it to the frame with four small screws and install the included skid stops. The landing gear includes antenna-tube mounts.
RADIO INSTALLATION
The Mini Titan incorporates 120-degree electronic CCPM mixing for the main rotor control. The servos are connected directly to the swashplate to minimize free play and weight. I used Hitec HS-65MG servos for their strength and durability. The stock servo mounts are 22mm wide and the HS-65s are about 24mm wide, so I had to file the mounts to get the servos to fit. There's a small notch in the main frames to allow full travel of the rear swash servo, but the HS-65 servo arm did not line up with the notch. I made a spacer out of an extra servo arm and sandwiched it between the servo-mounting ears and the mount. This fixed the alignment problem and provided full travel without any interference with the frames.
I used to Velcro mount my Hitec Electron 6 receiver in the rear of the frames and just underneath the tail-boom mount. I wrapped the 39-inch antenna around the plastic spool that was included with the receiver to bring it down to about 20 inches. Then I routed it towards the front and then through the antenna tube. A base loaded antenna can give a neater installation if you prefer.
ROTOR HEAD
The molded-plastic main blade grips are mounted on a solid, 4mm spindle with both ball bearings and thrust bearings. I'm always happy to see thrust bearings incorporated in the design of any blade grip, as the forces generated by high-rpm flight can overstress ball bearings alone.
The 4mm-diameter spindle is 33 percent bigger than the 3mm spindles found in other helis of this size. This may not seem like much, but the larger spindle is over three times as rigid! This contributes to the smoothness and stability of the aircraft and to its durability.
The spindle has two fairly hard dampers, The plastic head block is mounted on the 6mm main shaft using a 2mm capscrew. The fit between the head block and the main shaft was a little loose. Since I'm comfortably past the "frequent incident" stage, I used a small amount of Z-Poxy to glue the main shaft to the head block to eliminate any play between these parts.
The washout arms and the bell mixer levers are fully ball-raced for minimum friction. The arms have two sets of holes to allow different flybar ratios. The inner holes slow response for beginners, whereas the outer holes provide faster response. The levers were a little bit more flexible than I have seen on other helis. The Thunder Tiger designers may have done this to build a mechanical "fuse" into the rotor head to protect the servos and other components during a crash.
All of the balls and ball links are smaller than standard. The links in my kit were all too tight on the balls and needed to be loosened. I usually loosen the fit by using a pair of smooth-jaw needle-nose pliers to pinch the ball link while it is on the ball. This has to be done very carefully with the tiny links provided with the Mini Titan. One link popped off its ball, and I crushed it with my pliers. Fortunately, the kit includes a few extra ball links, and I learned to be more careful.
The kit includes 325mm wooden rotor blades. They are covered, and the root reinforcement is already installed. For extra strength, I cut away the covering underneath the root reinforcements and glued the reinforcements directly to the wood using thick CA.
The tail pitch mechanism has six ball bearings to transfer the motion from the pushrod to the tail rotor blades
TAIL ROTOR
A timing belt transfers power to the tail rotor. I chose the brand-new Hitec HG-5000 gyro and HSG-5083MG miniservo for tail control and mounted the gyro on the main frames just above the tail-boom mount. Two plastic mounts hold the servo on the boom, and a metal pushrod transfers motion to the tail pitch lever. The tail pitch mechanism is one of the nicest designs I've seen: six ball bearings transfer the motion from the ball link to the plastic tail rotor blades. The constant-drive tail provides yaw control as long as the main rotor is turning.
TIPS FOR SUCCESS
If you are just starting out and want to gain some extra flight time, run the rotor head at around 2,200rpm. This will soften the controls a bit and minimize any damage if you have a mishap. You can achieve this rpm with a 10T pinion on the Scorpion 2221-8 motor; it's the smallest pinion that will fit the motor's
1/8-inch shaft. Then adjust your throttle curves to obtain the desired head speed. This will make the motor run more efficiently and it will improve your flight times.
For additional stability, add weights to the flybar to slow the cyclic response. An old trick is to install airplane wheel collars near the paddles for maximum stability and move them closer to the main shaft to lessen their effect.
Be sure to mount the blade-grip thrust bearings correctly with the thrust washer with the larger diameter hole toward the center of the rotor head. If you don't, you'll wind up with rotor grips that do not turn freely when loaded up. Put all the washers on the unassembled spindle, and try to rock them. The ones with the smaller holes will rock very little while the ones with the larger holes will rock a lot.
Initially, I had some problems with the Hitec gyro and tail servo in heading-lock mode. As I centered the rudder stick from a left pirouetting hover, the tail slowed down slightly and rotated another 20 to 30 degrees before it stopped. I reread the instructions and realized that I hadn't trimmed the tail in the gyro's standard rate mode. After doing so, I was treated to a rock-solid tail.
The included manual is excellent and does a great job of explaining how to build the heli and how to setup the radio and servos. It can be downloaded from www.acehobby.com.
Hitec HG-500 gyro and HSG-5083MG tail-rotor servo
Well known for its transmitters, receivers and servos, Hitec RCD recently added the brand-new HG-5000 gyro and HSG-5083MG tail-rotor servo to its lineup.
Weighing a scant 10 grams, the HG-5000 gyro is perfect for small electric helicopters. It offers rate and heading-lock modes, and it yields a performance that equals or is better than that of any other gyro that's available in this class. It can be used with standard and digital servos, but the best performance is realized with the bundled HSG-5083MG servo.
Programming the HG-5000 gyro is easy using a series of LEDs and a button located the face of the gyro. Adjustable settings include servo type, gyro direction, rotation rate and left and right endpoints. When not in programming mode, the LEDs indicate gyro mode (rate or heading lock) and actual gyro gain.
The HSG-5083MG servo is specifically designed for the HG-5000 gyro to obtain optimum performance in micro- and mini-helicopters. It's Hitec's fastest servo to date and has a transit time of 0.07 second/60 degrees and a torque rating of 20.85 oz.-in. at 4.8 volts.
During my flight tests with the Mini Titan, the tail rotor was extremely stable, even in wind gusts. A really good test of a head-locking gyro, however, is how well it maintains a constant rotation rate for a given stick input during forward flight. With some gyros, the rotation rate slows as the tail travels upwind and whips around as it transitions downwind. With the Hitec HG-5000 and HSG-5083 servos, the rotation rate was rock-solid, even in moderately fast forward flight. Those who like to do pirouetting maneuvers such as piro-flips and piro-loops will love this gyro and servo combination. Its performance rivals that of units costing almost twice as much.
The HG-5000 gyro and HSG-5083MG servo package retails for $199.99.
AIRBORNE
It's winter, so it was difficult to get a good day on which conditions were perfect for a test flight. My job takes up my all my daylight hours during the week, so I have to take whatever I get for weather on the weekends. What I got was 30 degrees with wind gusting from 15 to 20mph. At least it was sunny!
Spooling up the Mini Titan and bringing it into a hover, I was amazed by how well it handled the wind. Tall trees surround the field, and there was a lot of turbulence. The Mini Titan handled admirably and responsively. It required only minor corrections to maintain a hover, despite the wind. Subsequent flights on a calm day showed how smooth and stable this helicopter is. It feels more like a 50-size nitro machine than a mini heli. It's that good!
In normal mode, the motor draws 13 amps with the main rotor at 2,600rpm. This is a nice head speed for normal flight and basic aerobatics. The rotor disk is solid and does not show any tendency to pitch up in forward flight.
Next, I moved on to basic aerobatics. Loops can be as big as you want them. Rolls are extremely axial, no doubt due to the high CG. The Scorpion motor is a powerhouse! Transitioning to full throttle and pitch, you hear the motor just bear down and handle the load without any problems.
Wanting to test the limits of the Scorpion motor's 500W continuous power rating, I set up my idle-up-2 throttle curve to provide full throttle throughout the ±12-degree collective-pitch range, and replaced the stock wooden blades with a set of 325mm SAB carbon-fiber blades. I also increased my aileron and elevator swash mix to just below the head binding point to get the maximum rotation rates.
With the Mini Titan in a stable hover, I took a few steps back and then flipped into idle-up-2. The rotor head raced up to about 3,300rpm and the real fun began! I pushed the left stick all the way up, and the heli shot up like nothing I've ever seen. I wasn't able to keep the power there for long, as the heli quickly became a tiny dot in the sky. Bringing it back in closer, I followed up with a few effortless rolls, loops and flips.
All this power doesn't come without a price. Predictably, flight times were short; I get about 4.5 minutes of hard 3D before the battery shows that it's losing power. Beginners and intermediate pilots who don't need that brute power can switch to a 10T motor pinion; that should bring the head speed and current down for flights approaching 10 minutes.
I did notice that fast collective pitch response was a little soft; I suspect this is caused by the flexing of the plastic mixing arms. Hardcore 3D pilots will want to replace them with rigid metal arms.
During 3D flight, my Eagle Tree flight recorder logged an average 22A current, a max current draw of 53 amps and peak power at 513 watts. With all this power available, any 3D maneuver you can think of is possible. You'll definitely want high C batteries to feed this monster!
Scorpion Power System from Innov8tive Designs
When I heard from my Fly RC editor that he had the Scorpion motor and speed controller to power my Mini Titan, I immediately raced over to the magazine's offices to pick it up. This power system has been all the rage on the Internet forums, and I was really excited to have a chance to see what all the fuss has been about.
The Scorpion HK-2221-8 is a brushless outrunner motor. It is beautifully made and has gold-anodized endbells and a black main body. The Scorpion logo and the motor's number are nicely engraved on the main body. A series of holes have been drilled at an angle to the face of the rotating endbell to provide a propeller-like effect to increase the amount of cooling air that passes through the motor. Very ingenious.
The motor is rated for a whopping 475 watts of continuous power and 45 amps of continuous current. This is an incredible power rating for a motor weighing only 79 grams. With a 3595Kv, the Scorpion HK-2221-8 is a perfect match for 450-size helis such as the Mini Titan E325 or the T-Rex 450. For pure power freaks, Scorpion also offers the HK-2221-6 motor. With a 4400Kv, it is rated for 525 watts!
Scorpion also offers a full line of brushless speed controllers to complement its line of motors. I used the Scorpion Commander 45A ESC. It is rated for 6 to 15 volts, and the built-in BEC is rated for 4 amps maximum current. Included with every Scorpion speed controller is a fully featured programming card that's used to set its parameters. Adjustable parameters include battery type, cell count, low-voltage cut-off level, power cut-off type, current-overload protection, braking level, acceleration time delay, PWM frequency selection, timing advance and motor rotation. Both of these components are a great value: the motor sells for $49.99 and the speed control for $59.99. Both are backed by a 2-year warranty against defects in materials and workmanship, so you can buy with confidence.
CONCLUSION
I love this little heli! The Scorpion power system and Hitec gyro and servo make a perfect setup for extreme 3D performance. They never missed a beat and really brought the Mini Titan to life. Even though I focused on its fantastic 3D performance, a pinion change and a throttle-curve adjustment give the Mini Titan a stability that rivals that of much larger machines. It also makes this machine suitable for beginners who have a little simulator time under their belts. Give the Mini Titan a try; you won't be disappointed.
Links
Thunder Tiger, distributed by Ace Hobby Distributors, www.acehobby.com (949) 833-0088
Hitec RCD USA Inc., www.hitecrcd.com (858) 748-6948
JR, distributed exclusively by Horizon Hobby Distributors, www.jrradios.com (877) 504-0233
SAB Rotor Blades, distributed exclusively by Miniature Aircraft USA, www.miniatureaircraftusa.com (352) 383-3201
Scorpion Motors, distributed by Innov8tive Designs, www.innov8tivedesigns.com, lmiller@innov8tivedesigns.com
X-Caliber batteries, distributed by Innov8tive Designs, www.innov8tivedesigns.com, lmiller@innov8tivedesigns.com
Z-Poxy, manufactured by Pacer Technology, www.zapglue.com
For more information, please see our source guide on page 169 of the March issue of FlyRC.
