DLuders

@ Beeman: Welcome to Eurobricks! Could you look through Blakbird's Renders of the 8110 Unimog U400 set, and see if your 4-Cylinder engine looks like this? {Click on it to make it full-size}

Nice! It looks a bit like a Fiat Bravo:

@ Alibaba7: Can you look at Blakbird's 8110 Renders to see if your drivetrain looks like this? The center differential (with the three bevel gears, as you noted) should rotate:

I received the 8081 Extreme Cruiser set, which I plan on motorizing using Louskam's instructions. Maybe I will make it more "extreme" by adding a rocket launcher on the roof or something....

@ Alibaba7: Welcome to Eurobricks! It sounds like your son has made an error with the Unimog's drivetrain. Let's look at this TechnicBRICKS 8110 Review for some good pictures and videos of the innards of the 'Mog. The yellow parts you were talking about are called "Knob Wheels" -- they offer a non-slip gearlike connection. I recommend looking at the many videos posted there on that TechnicBRICKS review, and seeing if your 'Mog is constructed correctly.

Yes, I have this book and have built the Lego Gun shown. You will have to CUT OFF some of the teeth on a 24-Tooth Technic Gear to build it!

@ efferman: I see a mixture of the new and old 2850 Technic Engine Cylinder parts in your picture above. Could you add a picture of the new part to the Bricklink parts datab? The new variant is (seemingly) not listed there yet. OLD PART (with side slot):

@ mezoxr: You can read the reviews of the 8258 Crane Truck (21 reviews) and the 8110 Unimog U400 (6 reviews) on Brickset to determine which one is "better" for you. In regards to availability, use the "Change Region" button at the top-right of this Shop.Lego.com webpage to match your country. In the USA, the 8258 Crane Truck has been "sold out" for months.

In this Wikipedia article about "Mass", it says "Weight is the gravitational force acting on a given body, while mass is an intrinsic property of this body." "In everyday usage, mass is often referred to as weight, the units of which are often taken to be kilograms (for instance, a person may state that their weight is 75 kg). In scientific use, however, the term weight refers to a different, yet related, property of matter. Weight is the gravitational force acting on a given body...." The MASS of the V-22 Osprey does not change, but yes the "effective" WEIGHT of the helicopter is changed by the counterweight. If one looks at ISOGAWAYoshihito's of a Lego solar airplane, it is "flying" horizontally just like the V-22 Osprey according to the Wikipedia definition of "Flight" -- "Flight is the process by which an object moves either through an atmosphere (especially the air) or beyond it (as in the case of spaceflight) by generating lift or propulsive thrust, or aerostatically using buoyancy, or by simple ballistic movement." Yes, Lego models CAN FLY. The V-22 Osprey needs gravity-assist from the counterweight but it CAN FLY horizontally using the lift generated from the propellers to move it forward.

@ Legoroni: ISOGAWAYoshihito's Lego Power Functions "Dog Train" is great! I'm concerned that you said that you are using a "dummy Receiver". The Power Functions (PF) Medium motor must connect to the PF Receiver, and the PF Receiver must connect to the PF Battery Box, like this: Be sure to read the "Frequently-Asked Questions" (FAQ) on the official PowerFunctions.Lego.com website.

Did you get any Lego Technic set(s) as gift(s) today? If so, feel free to tell us what you got so we can be envious....

@ Jakon: Try these steps: 1) Open Lego Digital Designer. Press Cntl-Alt-Delete to get to open your Windows Task Manager. 2) Once in Task Manager, go to the "Processes" tab and find LDD.exe. Right-click on it and look at its "Properties." 3) Once in the "Properties" window, go to the "Compatibility" tab and check-off the box that allows you to "Run this program in compatibility mode for...Windows XP (Service Pack 2)." Press the "Apply" button at the lower-right, then "OK" and back out of the various windows. 4) Close LDD and restart it. If it still doesn't correct your problem, then undo the Compatibility Mode steps and hope somebody else here on Eurobricks has a better idea.

@ mezoxr: You can download PDF Building Instructions for Jurgen Krooshoop's "Ultimate 8043 Motorized Excavator" at the bottom of this webpage on the JurgensTechnicCorner website. Discussion of that model is on this webpage.

If you want to add LED lights to your Lego Technic 8110 Unimog U400 set, Artifex Creations has his Brick Lights kit available. There are 11 pictures showing the 22 Brick lights installed in this Mercedes-Benz Unimog: - 12x headlights - 2x mirror - 2x roof lights - 6x taillights Light installation guide/instructions are in my Website Gallery. Custom Mercedes-Benz Unimog Light kit available in my Web store and eBay store."

Let's draw an analogy between the V-22 Osprey and this crane below, which can lift 1000 grams at 100 cm. It could lift more (up to 9 kg at 20 cm) if the boom angle and counterweights are just right. The relationship between the LOAD and the COUNTERWEIGHT is the "mechanical advantage". The crane is truly "lifting" all of that weight via its onboard motors. The Osprey provides LIFT and is FLYING in the vertical-->horizontal direction under its own power. Sure, it uses the "mechanical advantage" of the counterweight but IT IS FLYING HORIZONTALLY via LIFT from its propeller blades. It is "flying" as much as that crane is "lifting".

No, the wooden counterweight does not "Effectively it reduces the mass of the plane" -- the Osprey and the wooden counterweight are BALANCED and can stay in equilibrium for as long as the Osprey's batteries hold out.

The counterweight provides a measure of CONTROL, and the rotating mobile arrangement allows the helicopter to "fly" in a circular pattern. We're not talking about fantastic, 100%-CONTROLLED FLIGHT here -- it flies just as well as this toy does if it were attached to the same mobile: Whether it's rubberband power (in the balsa plane), or the Lego V-22 Osprey (with its onboard motors and battery boxes), energy is transfered to the rotating rotors to generate LIFT. They both "fly" in the strict definition of the word.

Yes, this V-22 Osprey is "flying" under the definition in this Wikipedia article about "Flight" -- "Flight is the process by which an object moves either through an atmosphere (especially the air) or beyond it (as in the case of spaceflight) by generating lift or propulsive thrust, or aerostatically using buoyancy, or by simple ballistic movement." "Mechanical flight is the use of a machine to fly. These machines include aircraft such as airplanes, gliders, helicopters, autogyros, airships, balloons, ornithopters as well as spacecraft." "Because the craft is heavier than air, it must use the force of lift to overcome its weight." The non-Lego rotors are generating the lift. The inaminate string and wooden counterweight is not generating the lift. For those "Lego Purists" out there, I wonder how much lift could be generated by the white 89509 "Propeller 1 Blade 14L with Two Pin Holes and Four Axles" parts that come in the 9688 Lego Renewable Energy Add-On Set, if they rotated at the same speed as the rotors in the video?

Kymera76 posted this of his modified Lego Technic 8110 Unimog U400 set with a "Full Pneumatic Stabilizer System":

UniverLiber posted this of his 5-Speed Manual Gearbox (which makes a nice display for kids to understand how gear SIZE relates to wheel SPEED):

[bUMP] Itchy4000 posted this of a Lego Bell-Boeing V-22 Osprey FLYING under its own power. He wrote, "This video is for all the people they say it is fake and I am a liar. Here you can see how it works. It give no external touch, only a lever with a counterweight. Powered by 4 Lego XL motors and controlled by LEGO ® Power Functions IR Speed​Remote Control (8879)."

A week day ago, Conchas/ Conchinhas posted this of the 9395 Lego Technic 9395 Pickup Tow Truck (which costs US $69.99 at Shop.Lego.com):

m43photo posted this of his Lego Technic 4WD Skid-Steer Loader. The last 1/3 of the loader shows its construction details. It uses "Wheels from 8264, electronics and bucket from 8043. Four Power Functions motors."

Well, here's another one of Alasdair Ryan's recent YouTube videos regarding a Lego Technic Linear Actuator:

Here are Alasdair Ryan's YouTube videos of his Lego Technic custom Linear Actuator: (showing it in action): (showing it being assembled):