[MOC] Unimog U5000 Trial Truck

[Teo LEGO Technic]

Hey everyone! 

After almost a year and a half of working on it whenever I had time, my model of a Unimog U5000 truck is finally complete.

It has the following functions:

• 4x4 Drive with 2 PF XL motors
• Steering with PF M motor and linear actuator
• Remote diff locks, front and back, using pneumatic actuators
• Remote 2-speed high-torque gearbox
• BuWizz power

 

 

 

 

 

More photos on my BrickSafe: https://bricksafe.com/pages/Teo_LEGO_Technic/unimog-trial-truck

The whole idea of this model was to build a truck that could both travel at a fairly fast speed as well as work very well offroad, which meant it needed a gearbox. It also meant it needed differential locks so that turns could be taken smoothly at high speed with diffs unlocked, and offroad terrain could be tackled better with diffs locked.

The main goal of this model was to create a drive train that wouldn't allow any gear slippage or breaking even under tension in low gear. My solution for this was to use @Sariel's heavy-duty gearbox (http://sariel.pl/2011/02/2-speed-heavy-duty-linear-gearbox/), as well as the new differentials from the 43109 Top Gear car. However even those differentials can't take as much torque as I wanted to put on them, and neither can the universal joints leading to the axles. 

For this reason, I decided to speed up the transmission before reaching the universal joints and differentials to reduce torque, then slow it back down afterwards between the diffs and the wheels. This would cause a bit of power loss to friction due to the increased number of gears, but it would reduce the torque on the sensitive components and allow me to send more total torque to the wheels. The result is that the 2 powerful XL motors are sped up  5.01 times or 1.8 times (in high and low gear respectively) before reaching the diffs and universal joints, and then slowed down 11.67 times at the wheels. Therefore the final gear ratios in low and high gear are as follows:

1. High gear - 2.33 : 1
2. Low gear - 6.5 : 1

The result is that the drivetrain is indestructible and never breaks even when run with a BuWizz on ludicrous mode and the wheels come to a standstill. 

The most complicated part of this build was fitting all of the functionality in the front axle - linear actuator steering placed close to the pivot to increase the range of motion, lots of gear reduction, portal axles, and a differential locking mechanism. Although the result is quite good in my opinion - thanks @Zerobricks for the custom portals - the final construction wasn't as sturdy as I would have liked, and this was the main issue with the final model. The steering has less power than I would have liked with the small actuator, and the custom portal axles bend outwards under pressure when steering over rugged terrain. 

Overall however I'm quite satisfied with the final result  Thanks also to @functionalTechnic for the advice, and to everyone else who contributed to the WIP thread: 

Enjoy!

- Teo

Edited April 4, 2023 by Teo LEGO Technic

[gyenesvi]

I like how this turned out, it looks nice and drives well. Great that diff locks are incorporated!

[1gor]

It turned out very good; simple and robust and at the same time instantly recognizable.

[Zerobricks]

I'm a bit late to reply, but what a unit of a model!

How does the sliding gearbox setup work compared to using the usual shift rings? Are there no issues woth gears not aligning and jamming or crunching?

I feel a couple of 7x11 frames might help you reinforce and clean up the axles.

Whey are you not locking the differentials directly?

On 4/4/2023 at 10:36 PM, Teo LEGO Technic said:

The most complicated part of this build was fitting all of the functionality in the front axle - linear actuator steering placed close to the pivot to increase the range of motion, lots of gear reduction, portal axles, and a differential locking mechanism. Although the result is quite good in my opinion - thanks @Zerobricks for the custom portals - the final construction wasn't as sturdy as I would have liked, and this was the main issue with the final model. The steering has less power than I would have liked with the small actuator, and the custom portal axles bend outwards under pressure when steering over rugged terrain. 

How about uisng the ones from the Tiger 6x6?

Their steering pivot point is a stud further offset, but they do use the wheel bearing which should improve the sagging. Also they can be modified to use the new larger CV joints instead of U joints for higher torque and steering angle.

I think this is a good project, but I feel like the chassis/driveline can be done cleaner, stronger and more efficient and I'm willing to help you along if you want to.

No criticism of the bodywork though, it's really smooth and I like the use of classic studded bricks at front sides for more detailing.

Edited April 7, 2023 by Zerobricks

[Milan]

Frontpaged.

[Naturalbornuser]

Final result is great, these tires are very fine :) I know this gearbox from Sariel also from Lugpol.pl and I will probably use it to trial truck Im actually working on. Is it constructed to compete in any race?

[Teo LEGO Technic]

Thanks for all the positive feedback, everyone! It's nice to see the final result is appreciated after all the work that went into it 

On 4/6/2023 at 3:40 PM, gyenesvi said:

I like how this turned out, it looks nice and drives well. Great that diff locks are incorporated!

23 hours ago, 1gor said:

It turned out very good; simple and robust and at the same time instantly recognizable.

Thanks guys!

22 hours ago, Zerobricks said:

I'm a bit late to reply, but what a unit of a model!

How does the sliding gearbox setup work compared to using the usual shift rings? Are there no issues woth gears not aligning and jamming or crunching?

I feel a couple of 7x11 frames might help you reinforce and clean up the axles.

Whey are you not locking the differentials directly?

Thanks, @Zerobricks! The gearbox worked well I thought, the only issue is you have to come to a complete stop between gear changes to avoid jamming gears. 7 x 11 frames would have probably been a good choice as well for the axles, I just avoided them to keep the size down to make them more realistic. I avoided locking the diff directly because, to ensure the best gear meshing and no slippage, I wanted to place the diffs inside the 5 x 7 frames. 

22 hours ago, Zerobricks said:

How about uisng the ones from the Tiger 6x6?

Their steering pivot point is a stud further offset, but they do use the wheel bearing which should improve the sagging. Also they can be modified to use the new larger CV joints instead of U joints for higher torque and steering angle.

I think this is a good project, but I feel like the chassis/driveline can be done cleaner, stronger and more efficient and I'm willing to help you along if you want to.

No criticism of the bodywork though, it's really smooth and I like the use of classic studded bricks at front sides for more detailing.

Those portal axles from the Tiger look much more robust, if I had come across them before I would have used them. I currently don't own the new CV joints, but if you say they're better I will purchase some. And yes, I would love your help on my next project, your models are awesome! I was thinking for my next project to attempt a pure rock crawler, with the one goal of optimal offroad performance in mind.

21 hours ago, Milan said:

Frontpaged.

Thanks, @Milan!

21 hours ago, Naturalbornuser said:

Final result is great, these tires are very fine :) I know this gearbox from Sariel also from Lugpol.pl and I will probably use it to trial truck Im actually working on. Is it constructed to compete in any race?

I definitely recommend using this gearbox design, I found it worked very well. Unfortunately, I'm not aware of any trial truck races around Toronto where I'm from, although I'm trying to find Technic enthusiasts in my area to compete in races with through ToroLug: http://torolug.ca. 

If anyone knows of any Toronto-based Technic builders please let me know, it would be awesome to have some trial truck races like you guys have in Poland and other parts of Europe  

Edited April 8, 2023 by Teo LEGO Technic

[LEGO Train 12 Volts]

Very cool!

[Teo LEGO Technic]

9 hours ago, LEGO Train 12 Volts said:

Very cool!

Thanks!