Truck Trial Contests

[paave]

We had a Truck Trial event this weekend, and here's my video report:

 

00:15 Suzuki Jimny

04:42 Chevrolet K5 Blazer 1981

10:43 Dodge Charger Offroad

14:44 Jeep Cherokee XJ

19:33 Suzuki Jimny SJ

22:40 Land Rover Defender 90

27:17 Redneck (my truck)

29:12 Jeep Grand Cherokee

32:55 Hummer HX Concept

Enjoy!

Edited 15 hours ago by paave

[gyenesvi]

Very nice event, thanks for sharing! What were the rules? What scale and what electronics were allowed?

I like the track, what is it made of? It seems realistic and hard enough, despite being artificial.

[keymaker]

I like the looks of vehicles and track itself, but having open diffs in off-road machines? C'mon....

[paave]

18 minutes ago, gyenesvi said:

Very nice event, thanks for sharing!

Thanks!

24 minutes ago, gyenesvi said:

What were the rules? What scale and what electronics were allowed?

Google translate:

Model Rules 1. Competition Description: - The race involves racing LEGO models along a course consisting of various obstacles.

- The winner is the participant whose time to complete the course, taking into account all bonuses and penalties, is the fastest.

2. Completing the Course:

- The participant's objective is to drive along a prepared course from the start, successively through pre-placed gates, to the finish.

- The model can drive through the gates either backwards or forwards. Gates can only be driven through in one direction (passing through and backing out is not permitted). Missing a gate is prohibited. Missing a gate results in a 10% penalty to the overall time.
- Touching the gate is permitted, but breaking the gate results in a 5% penalty to the overall time.
- If your model flips over and doesn't return to its original position, a 5% penalty to the overall time is imposed.
- Moving the model (up to 20 cm) results in a 10% penalty to the overall time. The model may only be moved with the judge's permission.

- Model repairs are permitted; the stopwatch does not stop during this time.

- The total time for completing the course is limited and will be announced immediately before the race. Failure to complete the course in time will result in a technical retirement.
3. Model Layout:

3.1. General Requirements. - The participant's model must be a light-duty SUV. Scale models and original models without a real prototype are permitted.

- The wheel arrangement of the models is 4x4 (if the real prototype has 6 wheels, then 6x6). The body type must be the same as that of a road-going car. The model must have a cabin with at least two seats (driver and passenger). A model engine is optional; if present, it must be located under the hood.

3.2. Model Exterior.

- There must be space for the pilot, steering wheel, and instrument panel. Doors (driver and passenger) are required. The model must have headlights and taillights, bumpers, and a windshield frame. Wheels must be in arches. All body parts must be free of holes; tubular bodies are prohibited.
- Wheels measuring 62-68 mm may extend beyond the arches no more than 1.5 mm, and wheels measuring 75-81 mm may extend no more than 2.5 mm.
- If you are building a real car, your model must be recognizable. A roofless model is permitted only if the real car does not have a roof or if the roof can be removed. For models without a prototype, a roof is required.

3.3. Suspension, Transmission, and Steering.

- Suspension is mandatory. Any type except swing axles. - All-wheel drive only. - Steering is permitted only through knuckles. Steering wheels are front only (fully-steering chassis is permitted for models based on a real prototype with this feature). - A gearbox is optional. Manual transmission shifting is permitted only before the start of the race. - The maximum model width for 62-68mm wheels is 21 studs, for 75-81mm wheels, 23 studs at the wheel edges.
3.4. Wheels and Wheel Arrangements:

- Wheel diameters of 62-68mm are permitted for stock or slightly lifted cars. 81mm wheels are permitted for heavily lifted cars.
- Any tires that fit on LEGO rims without modification are permitted. Solid wheels (all-plastic) are prohibited.
3.5. Power Supplies, Controls, and Motors:
- Power supplies and control units from LEGO, CaDa, BuWizz, and others are permitted (except for replicas of LEGO elements). The use of 3S LiPo batteries and homemade battery packs is permitted, provided their output voltage does not exceed 9 volts. No more than one power supply per model (C+, Buwizz, or PF battery pack).
- Any LEGO motors (except buggy motors), no more than two of any kind per drive (for driving the model). All drive motors must be attached to the model frame (motors on suspension elements are prohibited, except for the steering motor).
- Direct compatibility with LEGO motors is a requirement for using homemade control devices (motors must be connected to your control system via standard LEGO contacts). - Only genuine LEGO motors are permitted. LEGO-branded motors are PROHIBITED.
3.6. Bonuses and penalties for model design features:
- All bonuses and penalties are cumulative.
- Using units with a built-in battery: 15% penalty to the total running time.
- Using RC tires: 5% penalty to the total running time.
- A working and properly rotating steering wheel inside the model: 5% bonus to the total running time. - Engine mockups – 5% bonus to the overall time for each. The number of cylinders, engine type (inline or V-shaped), and its placement on the model must match the real prototype.
- Open differential (center, cross-axle, remotely lockable) – 10% bonus for each.
- Wheels 75-81mm – 10% penalty to the overall time.

4. Prohibited:
- Using parts from similar construction kits.
- Gluing parts together, including the use of stickers on the frame.
5. Rights of the organizers: At the discretion of the organizers, a participant may be disqualified from the race.

25 minutes ago, gyenesvi said:

I like the track, what is it made of? It seems realistic and hard enough, despite being artificial.

I don't remember exactly, some kind of polystyrene, foam plastic or something like that. It wasn't made by me

[gyenesvi]

1 hour ago, paave said:

Model Rules

Thanks, those are pretty detailed rules! I like that it's precise about many aspects, and also that it expresses penalties and bonuses in terms of time percentages, nice way to ensure those are on a comparable scale to the overall time. At first I was puzzled of the seemingly different wheel sizes, but it turns out those were also factored into the point system in a meaningful way. Also, I like that the models need to have fairly detailed interior and exterior, so people would not build just a chassis with electronics all over the place and a few panels thrown on top. That probably made the entries quite comparable.

1 hour ago, keymaker said:

I like the looks of vehicles and track itself, but having open diffs in off-road machines? C'mon....

Well, it seems there's a 10% bonus for that, so it can make sense. Actually I like the idea, as being able to run on open diffs promotes the need to build better suspension technology, so it is in the spirit of a building contest.

[paave]

5 hours ago, keymaker said:

I like the looks of vehicles and track itself, but having open diffs in off-road machines? C'mon....

Trial with open diffs is called trophy, it exists too as discipline 

[rm8]

On 11/23/2025 at 11:44 PM, keymaker said:

I like the looks of vehicles and track itself, but having open diffs in off-road machines? C'mon....

With closed diffs it is much easier to pass obstacles and no need to work with weight distributionand and suspension (actually it may not work at all)  of model . Also no need to select best route. Less engineering, less driving skills needed.
Driving closed diffs more like a sprint race. We don't like easy ways.

[keymaker]

It seems couple of you didn't like what I wrote about diffs. But hey, having diff with possibility to lock them when needed is even better way to recreate real off-road vehicles. And having them doesn't mean forgetting about other very important features like high ground clearance, suspension with large range of motion, low center of gravity, construction which allows good angle when approaching/leaving obstacles, proper tires and many other things. I would say it is hard to call truck a really off-road machine, if it cannot lock diffs. But locked diffs is not a game changer if other important features in your truck sucks. Nevertheless it is very important feature and I would say, a key feature of off-road machines. That is why I'm mentioning this (not because it much easier to build an axle with no diff than with diff :D). And if your track can be easily beaten just by adding locked diffs (or no diffs at all) then I would say, it is not very difficult track :P

BTW diff with lock can be build even in very small scale, if you are interested, here is one example, 6x6 truck in 1:23 scale, diff locks in all axles ;)

Edited November 24, 2025 by keymaker

[2GodBDGlory]

6 hours ago, keymaker said:

It seems couple of you didn't like what I wrote about diffs. But hey, having diff with possibility to lock them when needed is even better way to recreate real off-road vehicles. And having them doesn't mean forgetting about other very important features like high ground clearance, suspension with large range of motion, low center of gravity, construction which allows good angle when approaching/leaving obstacles, proper tires and many other things. I would say it is hard to call truck a really off-road machine, if it cannot lock diffs. But locked diffs is not a game changer if other important features in your truck sucks. Nevertheless it is very important feature and I would say, a key feature of off-road machines. That is why I'm mentioning this (not because it much easier to build an axle with no diff than with diff :D). And if your track can be easily beaten just by adding locked diffs (or no diffs at all) then I would say, it is not very difficult track :P

BTW diff with lock can be build even in very small scale, if you are interested, here is one example, 6x6 truck in 1:23 scale, diff locks in all axles ;)

Maybe part of it is to make the venue work? If you've got locked diffs, maybe your capability level goes up to the point that it would be trivial to make it through the course they have built, and building a harder course is logistically difficult?

[rm8]

21 hours ago, keymaker said:

It seems couple of you didn't like what I wrote about diffs. But hey, having diff with possibility to lock them when needed is even better way to recreate real off-road vehicles. And having them doesn't mean forgetting about other very important features like high ground clearance, suspension with large range of motion, low center of gravity, construction which allows good angle when approaching/leaving obstacles, proper tires and many other things. I would say it is hard to call truck a really off-road machine, if it cannot lock diffs. But locked diffs is not a game changer if other important features in your truck sucks. Nevertheless it is very important feature and I would say, a key feature of off-road machines. That is why I'm mentioning this (not because it much easier to build an axle with no diff than with diff :D). And if your track can be easily beaten just by adding locked diffs (or no diffs at all) then I would say, it is not very difficult track :P

BTW diff with lock can be build even in very small scale, if you are interested, here is one example, 6x6 truck in 1:23 scale, diff locks in all axles ;)

no offence, It's just our experience. We are driving this event from 2016 or earlier. First we had two groups: with open diffs and factory stock detailed offroaders, and locked diff unimited offroaders. Adult fans preferred first one. 

As for manual locking diffs: whole idea is to pass the track without touching car by hands, because there is a thin line between turn on locker/low gear and help car by hand when it stuck somewhere. Madoka designed self locking diff - but it means it can be adjusted to trun on too early, like there is no open diffs at all.

In real world majority  of 4x4/SUV have only transaxle locker, incuding Land cruisers, and front/rear locker as option: with wide suspensrion travel and weight of car - it's enough (even safer for transmission in lame hands).  So, talking about open diff cars in this event - it is not 100% true. Center differential is missing, so it means its locked. Just add proper suspension travel and correct weight balance.

Here is old video with open and locked diff

 

[paave]

Another event happened this Saturday. Check the video