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WES-Technik Helistar LH35 Nano E-Helicopter

Micro helis have steadily grown in popularity in recent years. Technology developed for other markets like cell phones, pagers and lap top computers have been used by ingenious designers and innovators to advance micro, indoor, hovering, radio controlled flight. The growing popularity of the Ikarus Piccolo and Model Sports Hornet has led others to consider even smaller e-helicopter platforms than these 280-320 gram wonders.

Splash


Prototype data
Rotor Diameter: 350 mm
Length: 310 mm
Airborne mass: 120 g
Flying time: up to 20 min
Receiver: R4P-JST

Servos:

2 x LS-2.4 or LS-2.1
Gyro: PG03-JST
Controller: HF100 - twin
Battery: 3 x Li-Ion 450mAh


Introduction
Micro helis have steadily grown in popularity in recent years. Technology developed for other markets like cell phones, pagers and lap top computers have been used by ingenious designers and innovators to advance micro, indoor, hovering, radio controlled flight. The growing popularity of the Ikarus Piccolo and Model Sports Hornet has led others to consider even smaller e-helicopter platforms than these 280-320 gram wonders. Successful smaller versions of the Hornet (Gnat) and Piccolo as well as the MIA HouseFly went in the direction of shorter main rotor spans and tail booms but really didn't penetrate into the 100-gram size RC heli. Now from Walter Scholl (WES-Technik) in Germany comes the Fixed Pitch Helistar LH 35. In box stock form, with the recommended components, the Helistar will weigh in at 120 grams ready to fly. With a little extra effort the heli can come in under 100grams. Let's take a look at the principle characteristics:


Construction

The on-board electronics selected for this review were those recommended by the manufacturer except that the WES-Technik 3.0 micro servos were used. Although .9grams heaver than the 2.1 suggested, the response time of the 3.0's were just a little faster at 150ms as compared to the 200ms for the lighter servo. The fact that there were a pair of the 3.0's in bench stock in my shop did have a little to do with it also. Walter Scholl said that the 3.0's would work and I found this to be quite true.





2.1 Micro Servo


Other Prototype data
Max deflection: Now 14mm
Time to full deflection: 0,15sec
Max output force: 150 g
Operating voltage: 3-5 V
Load current: 100mA


The other exception was the batteries. Although three 450mah Li-Ion cells in a series hook-up are recommended, the new Lithium-Polymer packs available from Bishop Power Products (http://www.b-p-p.com/) seemed a better choice, due to more amps and less grams. A three cell 560mah Kokam Li-Poly pack was used at first and then a two-cell pack was found to be adequate but lighter. There are 450mah Kokams on the way, that reportedly handle the 4-5 amp draw even better than the 560's, while being even lighter still. These will be tested on the Helistar when received and results posted on the Zone. The flight duration with the 560's was in excess of 15 minutes, but we followed the designer's recommendations and did not exceed 8-minute flights after the one maximum duration test. This regimen is suggested to prolong motor life of the main and tail drive motors.

The included instructions are clearly written and do not suffer from translation as has been the case with some other imported products. The steps are ordered in the proper sequence and have quality pictures illustrating the steps with both sketch renderings and photographs. When building an E-helicopter, weight and balance are all important. As an example, the CA adhesive used for this kit should be applied with a straight pin one drop at a time just to minimize weight (and control the mess). All moving parts should be statically balanced to minimize vibration. Bad vibes wreak havoc with gyros and servos, so smooth running main and tail rotor mechanics are essential.

GRP is used for the chassis and some of the main rotor head components, while ABS plastic is used for links, main shaft housing, skids, swashplate and the anti-rotation arm. Tail boom tubing, landing gear struts, flybar paddles, and the tail rotor are fashioned from carbon fiber. The main rotor blades are pre-crafted in Germany from balsa and plywood then covered with black heat shrink covering. There are a number of finely crafted, machined fittings and nano-hardware fasteners provided. Ball bearings are fitted for the main (upper and lower) and tail rotor (inner and outer) shafts as well as the swashplate. The parts count is low considering the complexity of the machine. One requirement to be aware of is the need for a method of mixing the main and tail rotor motor ESC outputs. This is the "REVO" function on most helicopter radio transmitters. Another possibility is the use of the new CSM Head Hold (HLG 200 uncased) gyro and it will handle the mixing function. To date I have not had the opportunity to verify this claim by the CSM vendor (ANX Solutions, Ltd.) that I have dealt with in the UK, however it should work as claimed.





Parts Diagram


The following pictures illustrate the Helistar as it came from the box and progressed through the construction sequence.





A small box for a small helicopter



Parts bagged by assembly sequence



WES-Technik next to a Hitec HS-50 servo






Initial assemblies go together quickly



In the interest of keeping it light, building with the scale at hand



Beginning to take a familiar form



Fixed pitch head, flybar and main rotor blades.



High tech balancing fixture - two single edge razor blades.



Balanced main rotor installed.



The main machinery plant.



Tail rotor motor and pinion mounted.



On-board electronics.



Magnum PI Island Hopper at 115.6 grams.





Ready for charter


Flight testing
The Helistar was fitted with training gear made from 1mm CF rods with small Styrofoam balls fitted to the ends. A dimension just slightly larger than the rotor span works well. Check the Crafts area in your local discount outlet for the Styrofoam balls. There was nothing remarkable about the first flights. It responds much the same as an FP Hornet or Piccolo. Once out of ground effect and it's own downwash, it hovers with a fair amount of stability. It is very responsive to cyclic control inputs and like all FP helis tends to pitch up in FFF. It is definitely an indoor flyer or outside only in the calmest of wind conditions.

The nice thing is, that when you have it trimmed and you are used to its responses; you will be able to take it for a walk through your home or office. I do recommend that this be done only when the premises are not occupied. Although diminutive in size, the rotor head speed is adequate to eject a failed part at a velocity sufficient to do harm to your person. Wear safety glasses and treat this as you would any helicopter - a complex machine not a toy.

A failed flybar control arm caused one main rotor blade to eject and whack me a good one in the face. You would be surprised what a strawberry a 3 gram, heat-shrink covered, balsa rotor blade can leave at these velocities. Thank goodness for safety lenses. The failure has been reported to the manufacturer and the USA distributor. The response was most responsible and immediate.

The following is posted on David Lewis's web page for Homefly.com.... Quote "01/09/03 Airworthiness Directive: An in-flight ball separation failure of the flybar control arm has been reported. Ground the Helistar until this part has been tested, reinforced or replaced. I will send reinforced flybar arms to current owners as soon as parts arrive from Germany. Warning: When the helicopter malfunctions or crashes, parts can be ejected at high speed, creating a hazard. Safety glasses are a good idea, and spectators should be alert whenever the heli is operating. "End quote.

The modified flybar control arm replacement part is expected a week from this writing. Current Helistar owners should contact their dealer for the replacement part. Of course when this happened the little heli tried to eat it self, but surprisingly only three items had to be replaced. One main rotor blade, the flybar control arm and one servo spur gear (that came adrift and has not been seen again) were required. I am pleased to say that David Lewis had the replacement parts in my hands within 48 hours at no charge. You will also find that his pricing is slightly more affordable than buying directly from WES-Technik (not including the shipping). Conclusion - Even with the failure of the flybar control arm, I would still recommend this kit to anyone who has mastered building and flying micro helis like the Piccolo or the Hornet. The product support service is outstanding and due in no small part to the efforts of David Lewis (http://homefly.com/) backed up by Walter Scholl at WES-Technik in Germany. Do I think that a CP version is coming? Well the folks at Stanford University in California are working on nano-UAV's that will be dispersed in swarms to collect audio and video intelligence and these will be fly sized............so what do you think? 3D in a phone booth?? Only our imaginations will limit the possibilities.


Conclusion
Going from this project to an E-conversion of a Century Hawk SE V II, made me feel like I went from being a brain surgeon to being a lawn mower mechanic. It's all great fun no matter what the size. Cheers.

View a video of this heli, provided by HeliHobby.com
HeliHobby.com advises us that LH35 hop-up parts, including Carbon Fiber fixed pitch blades and an aluminum swashplate, are coming soon!

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