Coast Guard Helicopter


I enjoy helicopters very much, so as it has been some time since the MD600, it was about time to make another one.

The full gallery can be found on Flickr and Brickshelf.

After my last helicopter, I wanted to build one that was more basic. This one would simple, small, colorful, and would make use of the excellent blades from set 9396. I wanted to do something like the Sea King, but with a Fenestron tail. I used a HH-52 as a basis for the scale. I built a mock-up of the scale, and started making the gearbox for the helicopter. The main rotor could be operated from a gear on the left of the aircraft. Two changeovers located next to the landing gear pods could be engaged to drive the land gear (up or down, on left) and the winch (up or down, on right). The main rotor was connected to the Fenstron fan at the rear. Both the landing gear and the winch are driven by worm gears, so they would stay locked when the changeovers were in neutral.

The gearbox is mounted in the bottom of the helicopter directly under the rotor. The landing gear mechanism moves forward with the pilot and co-pilot seats directly on top (I love those new panels). The winch gear moves aft, and drives a simple string spool. The compact driveline keeps enough space for a full cabin. There is enough room to add a battery box, and a M motor to power the rotor.

The body work came together quickly with the exception of the rear doors. I wanted to add two sliding doors with windows, and based on the color scheme of the helicopter, they had a to be white. After six drafts, I finally came up with a solution that was doable. They are not perfect, but all the other designs had windows that were comically small, or too low in on the body. Unfortunate, the design calls for six white rare parts. The rest of the bodywork turned out well. The nose, while a little clunky, looked how I wanted. The top area looked good with the three engine exhausts, and the six bladed rotor, while overdone, fit perfectly. Oh, and with clever pin placement, you can fold the rotor back towards the tail. The tail looked sharp with the ducted fan. The vertical stabilizer looked empty, but that’s a problem for all LEGO Technic aircraft with the exception of 42040 (maybe).

 

The helicopter worked great, though a clutch for the gearbox would have been nice. I was pleased with the bodywork of the helicopter, and the colors worked well; maybe grey and orange would be great on a rebuild. I would have lived to have a cleaner design for the wheel pods, but it worked well enough. It was a good swooshable design, as I found playing with the helicopter extensively. Now I need to make a scale Coast Guard ship on which the helicopter can land. Maybe next year.

Happy Building

Advertisements

MD600N


One of my first memories of a helicopter was watching a Phoenix Police MD520 land in Roadrunner Park, a block away from my house. The high pitch whine of the main prop was incredible, but another sound was missing. I gathered all my seven year old courage, and asked the pilot, “where is the tail rotor.” I got a lesson in aerodynamics that day, and to this day I can still identify an MD520 by sound. It still remains my favorite helicopter, so I figured it was high time for me to honor this aircraft in LEGO.

Full gallery can be found here. Instructions may be found here.

MD600N Front

What excites me about building with LEGO Technic is creating functions that allow motor, movement, and control. Helicopters are mechanically complex, so I find myself drawn to recreating them. I learned about how they work when I built my first helicopter. With this new helicopter I started with the rotor head. I first built Effermans great swashplate design, and figured out what should stay and go. A four blade rotor head seemed not quite right, so after a little work, I managed to get a six blade head. It was with this decision, and discovering in the chosen scale there would be very little internal room, that I decided to switch to making an MD 600N.

MD600N Starboard

I then got to work setting dimensions, and getting the scale of the airframe correct. The length of the rotor blades dictated the scale, and the interior was going to be tight. The major challenge was getting the control functions connect to the cockpit. This is not a new challenge, as it seems to be the case with every large plane I do. I have a lot of experience with it, and so I came up with some solutions. The challenge with a helicopter is the collective. Every movement that is transmitted, must be able to retail its movement while also being effected by the collective. This works well with the swashplate, but at the controls is where this gets difficult. Using the basis of Effermans design allowed for a simple setup where the collective moves an axle on which the the left/right and fore/aft controls mount.

MD600N Cockpit

_MG_2539

Moving the collective moves the other two controls in a way that is independent from joystick inputs, and allows for complete swashplace articulation at any collective pitch. The controls connect to the swashplate above the main cabin and move forward. From there all three fuctions move down to the floor of the cockpit in between the pilot/copilot seats, and the second row seats. The collective is connected here to a lever on only the pilot’s side. The left/right controls connect via an axle to the joystick, and the fore/aft controls connect via a 9L link to the joystick. Both joysticks are linked together.

 

MD600N Chassis

The final control adjusts the yaw of the aircraft. The MD600N uses three methods to give anti-torque to the main rotor. In forward flight the 1)  tail planes give directional stability. The tailboom also has 2) two slits that provide a “Coanda Effect” from the main rotor downwash. Finally, at the end of the boom is a 3) movable jet direct thruster (all are nicely discussed here). This thruster rotates to force more or less thrust against the torque of the main rotor, much like the more common tail rotor. In this MOC, the thurster rotates on a small turntable, and has an axle running through the boom the controls the rotation. The axle connects to the floor petals by way of a flex cable, and a liftarm running below the cockpit. Both pedals are linked together.

Once all the controls were set, I could work on the body. I wanted the helicopter to be blue as I see it in my memory (almost). This presented some parts challenges, but not as many as I expected. The two suicide doors open to the main cabin, though I did not add any to the cockpit. Many liftarms and connectors were used for the rest of the cabin. I wish current Technic parts could facilitate the rather bubbly lines of the MD600N, but I was pleased with how it looked in the end.

As with many of my large aircraft, this helicopter suffered from gummy controls. The range of motion of the controls reflect the scale for the model, but do not allow for great playability or demonstration of features. For something like a helicopter, I am interested in powering the controls surfaces and inputs controls via Power Functions much like this. Next time I guess. But the Helicopter looks great on my shelf, and it brings me back to a great time in my childhood. I hope you enjoy.

Happy building.