PF L | Thirdwigg.com

Mack Magma

March 28, 2017 5 Comments

I consider myself a LEGO purist. I do not cut parts, paint them, and I do very little with custom stickers. But I confess, I’m bending my purist tendencies as of late with all the great custom tire options available. After getting these RC4WD tires, it was time to build another trial truck.

The full gallery may be found on Flickr.

When I build a trial truck, start with three questions: What functions will it have, how many Power Functions receivers will that require, and how many battery boxes will be needed in what placement. Using these decisions I draw up a basic sketch of Power Functions part placement, and I get to work. This truck would have steering, a 2x PF L motor drive, and a two speed transmission. As with other trucks I make, I started with the axles first. The axles were simple as they required no additional functions. Both front and rear have a knob gear in then center, then a 12t to 20t reduction, and a final 8t to 24t reduction in a portal axle setup. The front as a simple steering setup, and the steering universal joints between the first and second gear reduction.

Both axles are strung together with a frame that houses the suspension and electronics. Both axles have pendular suspension, and are linked together with liftarms front to rear. It is a system that is simple, and incredibly effective. A PF M motor is placed in the front to power the steering, and another M motor sits beside it to power the transmission. Two PF IR receivers and two rechargeable battery boxes are placed with one on each side of the chassis. Both PF L motors are mounted side by side in sliding housing in the rear of the chassis. Each motor drives a set of 12t and 16t gear. These separate axles combine to either a 20t or 24t center mounted gear. When both engines are connected 12t to 24t gear, an overall 10:1 ratio is achieved. When both engines are connected to the 16t to 20t gear, an overall 1:6.25 ratio is achieved. With the power of the L motors, this gives a good low ration, and an appropriate high ratio.

As this was a quicker build, I did not spend too much time on the bodywork. A simple flat bed was installed, and the cab is sparse. I selected a simple America style cab from this design idea to build in blue. The grille is big and square, and the rest of the cab generally follows the idea. Both the cab and the bed can be simple removed.

The truck has plenty of power, and the transmission worked without error. The steering was easily controllable. The larger tires gripped very well, as they are soft with big knobs. They were a little taller than LEGO’s tires, and combined with the softer sidewalls, made the truck a little less secure in its footing. But the truck did not roll over easily, and the soft tires made it grip the ground well. I will be using these tires again.

Until the next MOC, happy building.

Filed under Trial Truck Tagged with 2017, 8878, PF L, PF M, trial truck

Kalmar DCG180-9

March 14, 2016 1 Comment

After doing a lot of non powered builds, it was time for me to do something motorized. I very much enjoyed doing a forklift a couple of years ago, so it was time for another one.

See the full gallery on Flickr and Brickshelf.

The JCB930 that I did a couple of years ago was non-motorized and had some great features. I wanted to build something with all the same features, and since I would need more room for all the electronics, I decided early to model the forklift after the Kalmar mid-sized 180 model. The model would have drive, steering, a two stage lift, and fork tilt. I did not realize how hard this would be. I wanted to keep the boom clear for visibility, and the forks not more than two studs in front of the wheels to keep integrity of scale.

I set the scale and I went to work. After setting the chassis measurements, I went to work on the fork and boom. I knew I wanted to have a two stage boom, and I wanted to keep as much of the boom open as I could. The forks connect through the middle of both the first and second stage booms, and pinch both together. The middle boom is has a gear rack on both sides to lift the forks. This boom has two gears at the top, to route the chain over the top to move the forks. The outer boom is connected to the chassis at the bottom, and two mLA connect to it operate the tilt. After some working, I was able to get the boom to be thin, and just how I wanted.

I decided early that I want to keep the motors out of the boom. So I had to route the lifting function out to the forklift body through the bottom pivot. This required routing the lifting axle under the drive differential. The lifting axle then move rearward, and connected up to a PF L motor. On top of the lifting axle was the drive axle. The PF XL motors was mounted transversally on the right side, and drove and axle forward to connect directly to the differential. To give me some additional space at the front, a portal axle was mounted on its side to move the differential rearward. A PF Servo was mounted in the rear, over the steering axle, and drove the steering function. The steering uses some 2×4 liftarms mounted at an angle to allow for a better steering angle. Finally, a PF M was mounted in front of the Servo, under the cabin to drive the tilt function. None of the mechanics were difficult, but the packaging required a number of drafts.

The final hurdle was the body work. I spend a lot of time early in my MOCs working on packaging placement, so I do not have many body work problems later in the build. Still, some simple SNOT work was needed on the side sills to fit about the battery box, and the XL motor. Oh, and the wires. The cab was pretty straightforward, but still took a little bit of time. Finally, I had some trouble with the rear engine cover and counterweight. In the end it was a simple design that I settled on, but I tried many designs. Again, this took a lot of time.

It took a long time, but I am pleased with the final product. The functions worked smoothly and consistently. The control that was afforded by the fork functions was great. It could lift three AA battery boxes at a time. The steering was quick, and had a great lock which gave great maneuverability. The XL motor provided adequate power, and moved the forklift well. Finally, the bodywork represented the original Kalmar well. I hope you enjoyed as well.

Until next time, Happy Building.

Filed under Construction Tagged with Differential, Forklift, mLA, MOC, PF L, PF M, PF Servo, PF XL, portal axles, power functions, remote control, steering, technic

T-55A

December 9, 2015 4 Comments

The T-72 that a made a couple of years ago is still the most popular MOC I have made; at least in terms of internet analytics. This year, I committed to making another tank, so I figured keeping in line with old Soviet armor would be rather apropos.

The main gallery may be found on Brickshelf or at Flickr. Instructions may be found here.

The T-54/T-55 line of tanks have been produced in greater numbers than any other tank. The MOC represented here is a T-55A, representing types that were assembled starting in 1970. This series included an updated NBC and antiradiation system, an upgraded engine, and also added back in the 12.7mm anti-aircraft DShK on the loader’s hatch that was part of the original T-54 spec.

As with most of my MOCs, I starting scaling the tank before any building took place. I knew I wanted to use the newer, larger track links, and I knew I wanted to use the old mid-sized wheels. This set my scale, so I got to work. Starting with the chassis and the hull I worked first on the driveline and suspension. I used simple 2×4 liftarms to connect the road wheels to a suspension axle which activated a shock absorber inside the hull. Each road wheel has its own shock absorber. Fitting them all in took some creativity, but they are all mounted inside on the left and right sides of the hull. In the end, each wheel has about 3 studs of vertical travel.

In between each suspension bank are the remaining mechanics. After the suspension was set, I worked on the turret functions. Right from the beginning, I knew the tank would have a rotating turret and an elevating gun. It was clear having the elevation mechanics for the gun in the turret would be tight, so I decided instead to have the functions placed in the hull rather than in the turret. Using a vertically mounted mLA, connected directly to the breach of the gun, I was able to develop a method that would elevate the gun throughout the full turret rotation. The turret rotation was driven by a 8z gear connected to the turntable, and reduced by a worm gear. Both motors for the elevation and rotation are placed directly in front of the turret.

Behind the turret are two PF L motors mounted transversely side by side. They drive a 1:1 gearbox which connect directly to each rear drive sprocket. The IR receivers are placed above the gearbox. For those keeping score at home, the internals are (f to r) the battery box, the turret motors, the turret mechanics, the drive motors, and finally the IR receivers.

Working on the exterior of the MOC is what took the most time. The hull came together pretty quickly, with the exception of the details over each track. Most of the finishing time came with the turret exterior. Most Soviet tanks have the distinctive mushroom turret, which considering LEGO’s cube orientation presented some challenges. The turret of the T-55 also has a slight triangle orientation when viewed from the top. Like the T-72, I designed the turret with four side orientations (left, right, front, and rear), and one top orientation. Starting from the rear, I added a basic curved structure. The sides each had a couple levels of slopes, each tapering in toward the gun. The front was a little more complex. There are two “slope blocks” made of 4 curved slope bricks, and a supporting structure. One slope block is mounted on each side of the gun. The support structure is a mess of bricks with a stud on one side, headlight bricks, and plates. The top of the turret is plates on the front, and two sloped plate sections under each hatch. The two hatches are mounted to the turret support under the sloped plate sections. The AA machine gun is placed on the top, and various external mountings are placed in various ways around the turret.

After making a lot of non-powered MOCs, it was nice to get back into Power Functions. I was pleased that everything worked flawlessly. The drive had adequate traction and power. The suspension worked well, and provided good floatation and travel. The turret rotation was smooth and allowed for precise directions changes. The gun elevation worked great, though I had to limit turret rotations to under four before the clutch on the mLA would snap. After a number of smaller builds, and frustratingly long builds, I was nice to finish something that worked well, provided constant entertainment throughout the build, and turned out quite nice.

Happy building.

: T-55

Filed under Military Tagged with 2015, 8878, Independent Suspension, Instructions, military, mLA, MOC, PF L, PF M, power functions, remote control, Tank, technic, Track, Turntable, Worm Gear

Audi allroad

November 8, 2015 1 Comment

There are not many projects I start that I do not finish. I can count a couple. But, sometimes there are projects that take a long time to complete. I either loose motivation, lack parts (read budget), or find something else to do. If I were wise, I would toss the project, and move on to something better. But there is value to trudging through the slog and completing something difficult. The Spitfire is a great example of this. The Audi Allroad has been on The Queue for about 16 months, and it’s finally done.

The full gallery may be seen on Brickshelf or on Flickr.

After completing the OCTAN F1, I thought I could use the suspension for an all-wheel drive car. I was sure I could make the front suspension with steering work at this scale.

I wanted it to have another fun feature, so using a bunch of differentials, I developed a simple three speed transmission. Three power functions motors are connected via two differentials which connect to the drive axles. Each differential acts as a subtractor between each motor. When one motor is running, the power moves through two differentials, and the car moves slowly. When two motors are running, the power moves through one differential, and it’s a little faster, and when all three motors are running the car is running the fastest as no differentials are splitting the power. I got it to work, and within a day, I had a working chassis.

Once this was done, the MOC sat on my desk for a long time. This past fall, Thirdwiggville welcomed another citizen to the village, and this gave me lots of time late at night to get back to working on this project. I spent a couple of weeks working on the body work with the perspective of “finish this.” So the body work could use a little more polishing; doors, mirrors, better lines, maybe an interior. But I was happy to finally get this done.

The MOC worked well. The suspension functions quite well at this scale, and the transmission was simple and effective. It could be a little quicker, but I was not going to make a substantial gearing change after the MOC was built.

Two final thoughts. I need to stop building supercars because they take a lot of time and effort for me, and I find little motivation for the body work; I do not think the body work looks good, and I lack motivation to work on it. Second, I needed to test the driveline earlier in the build process. I spend too much time fiddling with gear ratios after everything was build. But this project is done, and I am happy it is.

Happy building.

: Audi allroad

Filed under Cars Tagged with 2015, 4x4, 8878, Audi, Differential, Driveline, Gearbox, Independent Suspension, MOC, PF L, PF Servo, power functions, remote control, steering, Supercar, suspension, technic

MD600N

August 26, 2015 4 Comments

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.

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.

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.

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.

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.