This is a small tow truck with simple motorised winch and spring-snapping ramp built mostly with stud-less Technic pieces.
The core of this concept is the possibility of fitting steering and drive motors in between the front and back wheels and placing Technic HUB between the axles. It's also about making a set that has motors with controller and reasonable amount of bricks and gears to play with, but not a huge one and based on IP like existing kits with multiple motors and Technic hub.
I'm generally not fond of making full showcase videos - I like building mechanisms with Technic, but making a video composition with good timing, music and descriptions feels like a chore/work to me. Below you can find feature footage so you can take a look at what interests you instead of scrolling through a lengthy showcase.
The model is built with powered up/control+ motors and a Technic hub which neatly corresponds to the truck's aesthetic. Here's the drive test within the photo scene where I experimentally run it on a moving photo turntable:
The reverse speed is set to 50% and that's why there is more control when backing up on such small area. The Control+ app would enable virtual switching gears - starting slow and increasing speed, but due to optimal cable connector location, I wasn't able to use it (you can only use the predefined configurations on Control+ app currently).
The drive motor is positioned between the rear wheels and the differential connected to it is actually slightly behind the rear axle due to the size of differential gear being comparable if not slightly bigger to the wheels used and this could pick up/get stuck on uneven ground. back wheels are connected to each other on the sides, so all four of them use single differential as pairs.
The steering motor in the front is fitted between the driver and passenger seat where in the truck you would have the engine cover. The cab has working doors with frames and there are detailed seats with armrests inside as well as steering wheel.
There is a third motor attached behind the rear axle that potentially could have been used to motorise the ramp like in previous models using this kind of ramp, but making a rigid transmission for this requires some space and it would break the near-ideal proportions of this model.
Because I couldn't motorise the ramp being low on the space to fit it, I made the ramp spring-locked so it snaps into either position, open or closed and is held in it by the spring.
Finally, I decided to make a simple winch that is working well enough to pull up a model fitting on the tow truck with the motor that is located behind the rear axle and forward the winch cable to the fake/decorative winch mechanisms at the back of the cab.
The model should generally be easy to build, although there are places where cable ribbons are tightly routed and because of that the final model could potentially need to be two or three studs longer to make more space in front of and behind the Technic Hub for better arrangement of wiring.
- mostly built with stud-less Technic pieces (except for mirrors)
- detailed cab interior with steering wheel, steering motor in place of engine cover and seats with armrests
- open'able cab doors with window frames
- neatly fitting motors and Technic Hub inside the truck base
- radio controlled movement and steering
- working differential shared by two rear axles with wheels smaller than differential body
- detailed rear end with tail lights, ramp motors and pushed back safety bar under rear bumper
- simple motorised winch
- spring-locked two-stage ramp
- details around the sides that are hiding the winch motor and Technic Hub
- fake winch mechanisms at the back of the cab
Why does it make sense as a LEGO Ideas set:
- has balance between fun gear mechanics, interior/exterior details and making enough structural integrity to support the weight
- contains multiple wheels, gears and motors so it could be a new go-to RC set for MOC creators community
- the amount of bricks is similar to medium sets in contrast to other motorised sets with more than two motors which are really big
- does not base on IP/trademark so again it won't require to license the IP
The model in a final kit could be made slightly longer for better routing of cable ribbons to the Technic Hub. It also doesn't necessarily need to be a tow truck, it can be any truck with even just two motors. This is about showing the possibility of building around and using the shape of Technic Hub as structural and visual piece in a small scale mode, thus final model could be a simple container truck or a box truck with tarp/canvas etc.
The Wheeled Excavator in the winch video is not a part of the set, it's just an example of how the load for this kind of truck could look like on it.If you like it, you can find in my other submissions.