[MOC] SUV Badlander - 1:10 4x4 with gearbox and locking differentials

[Krxlion]

Hi everyone!
Today I want to present you an off-road car, that I've been working for quite some time. There were several attempts, some of it ended up as unpolished models, without all features I initially had in my mind, and some were just concepts of gearbox, axles, etc.
These were my initial assumptions on the model:

• Sturdy drivetrain and gearbox with a wide range of gear ratios
• Remotely lockable both front and rear axles
• Up to 1:10 scale, nothing bigger
• Utility vehicle - it must be able to climb step hills and also provide decent speed on plain terrain
• Removable body (if it would have one)
• Precise low speed control - to provide maneuverability over a variety of obstacles
• Planning the wheelbase and car elements, based on an existing vehicle - to ensure the authenticity of the model
• Using trusted A2212 1000kv BL motor and other RC components to power it

Gearbox

I always try to start with a gearbox if my model would feature one. The idea was to make it simple, yet robust. In order to achieve it, I needed to make sure each important gear will be supported by another. My other goal was to make a gearbox with a wide range of gear ratios, so at least for example 1:1 - 1st gear and 1:3 - 2nd gear. The Gearbox I use worked well in my previous concept model I didn't present here.
Final gear ratios are:
1st gear: 63.787:1
2nd gear: 16.329:1
3.9 times difference between first and second gear! Now you may ask how I achieved this based just on a picture below, but we will get into that later.

Axles

I went through massive amount of research to have a working concept of both front and rear axle, that is driveable, able to turn (front axle) and also featuring locking mechanism somewhere. None of the concepts on the Internet were actually fitting my model. I do not have small technic pistons (I am looking at you Lego Technic Emirates), and it didn't seem I would have a chance of finding something different that will work in my case (rc car). I also knew I would use geek-servo for locking system, so only 90-degree turn must provide option for locking and unlocking mechanism.

Gray 2L driving ring is actually a new one - 2473. It is not yet added to Lego studio, but the existing ring was working for me just fine. With that concept of the axle, I just needed to make sure the upper steering arm is angled, because other way it would collide with the gears. That angle is perfectly calculated, so I could work on finishing the axle, adding steering (for the front) and most importantly - locking differential mechanism.

The finished front axle features: 2x 9.5L hard springs, 3x steering arms to cooperate with springs, 4x steering links, lockable differential mechanism. Did I tell you this was my own first solid axle build attempt?  I guess it may be called multi-link suspension, but you have to correct me on that one.

Locking differential mechanism on axles

As you probably already noticed, this whole model is based around locking differentials functionality. When I was organizing my parts, I came upon instruction of my CADA C61006W, which featured locking differentials in similar scale. The idea of having one gear turning around 90 degree and pushing by it two different gear racks at the same time was splendid. That movement could rotate 6641 Changeover patch part, and thus lock and unlock 2L differential, that was the key of my goal. I went to the drawing board and after some time I created this.

As you can see, If I would rotate 12T black gear to the left around 90-degree, it would push by using 6641 and 64781 parts the 2L 2473 driving ring. I just needed to make sure pivot points are correct, so the mechanism wouldn't move unnecessarily during suspension work.

Chassis

It needed to be as symmetrical as possible, due to previously mention features. I simply wanted it to be robust. I do not focus much on exterior or accessories - it just adds unnecessary weight to the model. The chassis also needs to have all points to attach both axles to.

 

Body

Let me just start with one sentence, I am not proud of the body. I am also not a great body sculptor. The overall design was based on Ford Bronco Badlands from 2021, but I only planned wheelbase and door placement around it. The rest was improvised, simply because I don't like rebuilding 1:1 real cars in Lego. The body is detachable and features opening doors and hood.

Power system and drivetrain

Ah yes, we are approaching icing on a cake. The model is, like I already mentioned, powered by A2212 1000kv BL motor. It also features 3x geek-servos: steering, changing gears and locking differentials. On top of that, I developed some sort of RC-hub (mostly because I want to organize everything in one place). This hub contains 3s battery, receiver and esc. It also features Lego Technic dimensions: 9x9x4 studs. If you want to know more about all of that, check out Brushless motors in the lego world - general topic.

As you can see in the top right corner, there is an A2212 motor directly hooked to the planetary hub. This way revolutions are downgraded to let's say civilized number (from 11100 RPM to about 2000 RPM - similar to buggy motor in fast output). This also provide us built up torque, which we will for sure need in off-roading.

Summary

I am really proud of this model. Especially because it taught me many new things in Lego Technic world. I believe some of you can also learn from my problems and how I approached them. Here are some numbers that may interest you:

Weight: 1.590 kg
Length, width, height: 43x19.4x16.9cm
Theoretical max speed 1st gear: 2.67km/h
Theoretical max speed 2nd gear: 10.44km/h

Soon I will be able to record some footage of all the features of the car and of course playtime! For now, I have more photos and GALLERY for you.

 

 

 

 

[2GodBDGlory]

Nice work! That does look like a really robust gearbox, and it's fun to see a model like this with brushless power

[Aurorasaurus]

This is awesome, I really like the way you're doing diff locks, I was hoping to see something like that on 42177. I also quite like the body, I think tweaking the headlights a bit, or a lot, could get it to look a lot better. Overall though, this is fantastic. For a first time doing solid/live axles, I think you did a really good job!

[Paul B Technic]

Very cool, I love the level of detail in your post.

[gyenesvi]

Somehow I completely missed this topic, probably I was on vacation in the middle of the summer :)

Cool build, I like the use of 3 GeekServos for different purposes, it really shows their potential, and the diff locking system. It's a pity though that it takes up a lot of space and the drive motor and battery had to be pushed up so high. The use of the brushless motor with the planetary reduction is quite interesting though :) And the shape / body is nice too!

[Krxlion]

On 10/30/2024 at 8:00 PM, gyenesvi said:

Somehow I completely missed this topic, probably I was on vacation in the middle of the summer :)

Cool build, I like the use of 3 GeekServos for different purposes, it really shows their potential, and the diff locking system. It's a pity though that it takes up a lot of space and the drive motor and battery had to be pushed up so high. The use of the brushless motor with the planetary reduction is quite interesting though :) And the shape / body is nice too!

Thanks for the kind words, they mean a lot to me. :)
I have modified this model one month after publish or so, but I didn't put it here, as I was busy investigating G500 set and modifying it to work with RC gear. The modified version of this MOC used my 3d printed planetary mount for A2212, so I could attach it directly to the gearbox (which was modified), and I also put the motor more to the front, for better weight distribution. Sadly, the 3d printer case for all necessary RC gear (with battery, esc, receiver) still ended on the upper side of the model, and roughly in the same position. The model performed well, I have even shrunken the space between axles by two studs, but didn't finish the body (I don't like designing this part too much), and thus didn't finish this topic how I would like.

Anyway, I am working on a new model, with very similar functions, but I want to tune everything before presenting, so it will not end the same as with this one. :)