[TC 26] Arctiv ATV

[Plumbum]

Dear fellow Lego-fans,

please find below my WIP-thread for the TC26-contest of my model – a tracked ATV similar to 42139

The first few paragraphs provide an overview of my general „project approach“ to this contest – especially the structuring of my brainstorming to find a suitable model might come in handy for other contestants. From this, I describe my derived building goals and current progress with screenshots of the model & selected mechanisms. I conclude this post with an overview of my next steps.

My project approach:

A little background on my approach: I have observed many eurobricks-contests from the sideline and always have failed spectacularly to come up with a suitable model with a remotely realistic chance to be completed in time. To improve this record, I opted for a structured project-approach with 2 cornerstones: Rigorous time-boxing of my project phases as well as a radical simplification of my entry, relying upon well-established designs & mechanisms. You can see my timeline and must/can-criteria for the model selection & design in the photo below.

In order to identify the entire option space for potential vehicles, I decided to employ a top-down-approach. In this approach, I tried to find suitable dimensions to categorize vehicles (via dimensions in tasks/purpose, the type and the maturity of vehicle design). These dimensions were then supplemented by general factors which influence the operations in an arctic environment and thus influence vehicle design. Based on these considerations, I did some desk-research on various websites and topics. Especially the usage within the wider “exploration”-topic w.r.t. space missions provided much food for thought. You can find my employed structure below.

I quickly ruled out sea- and aerial vehicles, as they weren’t specific enough to be immediately recognizable as artic vehicles imo. I also ditched the idea of some futuristic vehicle, as there are often very few drawings/photos & measurements to base your model upon. I concluded my brainstorming with two potential vehicle choices: A tracked off-road truck with truck bed (similar to 42070 or 42139) or a hovercraft (espc. Due to its ability to operate on both sea and land – which surely comes in handy, when the poles are melting/the ice gets more instable). In the end, I opted for a tracked ATV similar to 42139, as amongst other reasons

• this is imo immediately recognizable as arctic vehicle and fits the bill of a multi-purpose-vehicle nicely
• the 42139 provides a very nice basis
• it allows for a modular building approach (e.g. adding a trailer, if time permits)

 

Goal of build:

The goal is to build a fully-manual tracked ATV which satisfies the following requirements

• Suspended all-wheel drive
• 2-speed-gearbox with fake-motor
• Truck bed with ability to roll-off container (similar to this fantastic MOC LEGO MOC 42108 Roll-off Truck by M_longer | Rebrickable - Build with LEGO)
• Generator on a pallet
• Overall high level of detail (e.g. proper railings & lights, accessories like fire-extinguisher etc.)

 

Current progress:

So far I´ve made quite decent progress, although I´ll have to put in some overtime in order to adhere to my timeline:

The suspended all-wheel-drive is nearly done. Here, I am mainly lacking the connection to the overall chassis, which I have yet to built. For the suspension, this ingenious all-wheel suspended drive MOD of the 42122 (Lego Technic 42122 Jeep® Wrangler upgraded with 4x4, V6 engine and more - YouTube) was a great basis. I mainly had to change the steering mechanism and add some tracks – you can see a close-up of the steering-mechanism below. As for the tracks, I´ll probably opt for the 3-stud wide tracks based on a MOC/MOD of 42139 with 3-stud-wide tracks (LEGO MOC ATV Tracked by LBBDE | Rebrickable - Build with LEGO) - I assume that I will have to replace the currently used sprocket-wheels for some 28t-gears or similar to provide enough "grip" for the teeth to properly engage with the chains?

The 2-speed gearbox with fake-motor is taken from the 42139, although major rework of the surrounding structure was/is necessary – as well as some cosmetic touch-ups.

The truck bed with the ability to roll-of a container/pallet is almost done and requires mainly a few details and marriage to the chassis – you can see the current state below.

This is my personal highlight of the model due to its sequential mechanism to raise the bed and then extending the support rails. In order to achieve this motion, the rotating wormgear first slides along its axle towards the rear-end of the ATV (the axle with half-bushings is fixed and can’t rotate). This in turn raises the bed via a lever-mechanism. After the bed is fully raised, the wormgear can´t slide further anymore and thus engages in a rotary motion with the 8t-gear, which then lowers the gear-racks acting as support rails to the ground. You can see a close-up of the mechanism below, where the worm-gear currently engages with the 8t-gear after having fully raised the bed. I´m very much hoping that this mechanism works as intended, as I yet have to build it physically and it would be a major set-back for my timeline if complications occur.

 You can find the current status of my digital model also as a Stud.io.file in my bricksafe. Link:231113_Status Post - Bricksafe

As for the next steps:

Until end of this week, my priority is to finish up the chassis to connect the undercarriage and the truck bed to achieve a prototype which can be build physically. And obviously the generator has to be built as well – here I´ll probably draw some inspiration from this great MOC of a Diesel mud pump (LEGO MOC Diesel Mud Pump by Nico71 | Rebrickable - Build with LEGO). After ordering missing parts on the coming Monday, I´ll in parallel start with some touch-ups.

 

I hope that this write-up was helpful and interesting to you. I´m very much looking forward to updating you shortly with some decent progress as well as the entries of other forum members for this cool contest. Please don’t hesitate to contact me in case of any questions or feedback.

Kind regards

Plumbum

 

[2GodBDGlory]

Welcome to Eurobricks!

I really like the idea for that sequential bed operation, but it's hard to know how it'll work in practice. I'm pretty sure that at minimum you're going to have issues with the worm gear interfering with the LBG connector at the end of the axle next to it, though you can probably redesign it to avoid that problem relatively easily. Is the idea with that long axle next to it with bushes on it to have the worm gear engage with the bushes?

I also think it might be quite a challenge to prevent the force of that shock absorber from making the worm gear skip over whatever it's engaged with (I'm not sure if it's the 8T gear on the bed or that axle, or both)--you might want to look into a more robust way of bracing the worm gear, or a weaker shock absorber maybe.

Edited November 13, 2023 by 2GodBDGlory

[Plumbum]

On 11/13/2023 at 10:18 PM, 2GodBDGlory said:

I really like the idea for that sequential bed operation, but it's hard to know how it'll work in practice. I'm pretty sure that at minimum you're going to have issues with the worm gear interfering with the LBG connector at the end of the axle next to it, though you can probably redesign it to avoid that problem relatively easily. Is the idea with that long axle next to it with bushes on it to have the worm gear engage with the bushes?

Hi, 

thank you very much for this assessment - you are indeed correct, my intial design was flawed w.r.t. to this aspect - I redesigned it, however testing is postponed until my missing parts order arrives here :(

And yes, the idea is, that the wormgear travels along the long axle with half-bushes and "pulls" the casing (Part # 87408) along with it - which in turn raises the bed . Once the wormgear reaches the end of the axle and can´t move further, it should cause a rotation of the 8t-gear at the underside of the bed, thus moving the long gearracks downwards. In order to reverse this motion correctly (e.g. first retracting the gearrack via the 8t-gear, then lowering the bed), the casing will be held by some rubberbands, pulling it towards the rear of the subframe - I hope that this causes enough resistance to the whole contraception in order for the wormgear to first rotate the 8t-gear and only after fully retracting the gearrack, moving along the half-bushes and thereby lowering the bed.

 

Progess since last post:

Obviously I´m lagging behind with my model, but I am nonetheless confident to be finishing it in time, if the digital model transfers flawlessly into a physical model. You can find the screenshot of the (hopefully) final digital model below (give or take some missing parts in digital model like  rubber-bands, springs and ropes).

 

Key changes:

• Finalization of ATV
  • Updated mechanism of bed-raising/gear-rack extension/kneeling of undercarriage. Currently I´m not entirely convinced if the whole assembly will be strucutrally sound, but let´s see 
  • Updated track & supension design, taken from here (Lego Technic 42122 Jeep® Wrangler upgraded with 4x4, V6 engine and more - YouTube) and here ([TC25] 42069 Extreme Adventure - 2/3 Scale - LEGO Technic, Mindstorms, Model Team and Scale Modeling - Eurobricks Forums)
  • Detailing of ATV, e.g. proper colouring, adding of engine-details, side-mirrors, implementation of winch-mechanism from Set 42139
• Creation of mobile launcher for small UAV
  • Mechanical launcher, using pullback-motor to pull sledge with UAV via a rope. UAV will be placed with its wings in red slids atop the sledge
  • Launcher is foldable (see third picture above) and has designated spaces for storage of dismantled UAV during transport - again I´m not entirely convinced if the launching-rails will be strucutrally sound when extened, but let´s see

Current WIP of Stud.io-file can be found in my bricksafe: 231226__Status Post - Bricksafe

 

Next steps:

1. Build physical model as soon as parts arrive
2. Modify build if necessary
3. Take pictures and videos
4. Write entry-topic

 

 

Edited December 26, 2023 by Plumbum

[2GodBDGlory]

Looks nice! I hope you can get that sequential worm-gear mechanism working, because those are always cool!

That UAV launcher also sounds very interesting!