Universal 4x4 off-roader

[Zerobricks]

This model (and it's prototypes) are a result of the following topics:

 

Basically the idea behind this project is to make an offroader capable of driving on all kinds of terrain with a simillar perofrmance as the Wildcat 6x6 but having a lower weight

So, why would I want to reduce the weight? While the wildcat 6x6 works great most of the time, it's high weight of 2,5-3 kg has some drawbacks:

• The model requires a lot of expensive electronics (12 BuWizz motors, 6 BuWizz 3.0 bricks)
• High part count (1869 pieces)
• Tendecy of front wheels falling off at hard landings
• High wear and tear of the individual components, which lead to premature failure - planetary hubs, CV joints
• And lastly high wear and tear of the handler due to it's heavy weight

Of course decreasing the weight also means decreasing the power to weight ratio, since there will always be components which are needed regardless of the number od drive motors like wheels, hubs, steering system, suspension and frame.

The first protoype, which I simply call Light 4x4 used only 2 BuWizz motors coupled to a 2 speed gearbox:

While the model worked good in low gear, the high gear proved much trickier. The single gearbox put a lof of strain on the drive axle in high gear, causing it to melt, even with lubrication.

Another issue was the high load of the motors in high gear, resulting in them overheating, while the motor could not even remotely apporach the 15 km/h top speed of the Wildcat 6x6.

But not all was bad, I really liked the free-moving front suspension which acts like a suspended pendular axle, while having a much lower unspring weight. While I could make the rear suspension act like a pendular axle instead off front, i decided agaisnt it, since most of the weight is shifted back when crawling and I wanted to keep the rear stable.

With that knowledge, I went back to the drawing board and decided to up the power for the next version...

Medium 4x4 prototype:

This version used 4 BuWizz motors coupled in a manner simillar to my 1:10 Acura NSX which negates the sideways load on the output axle of the gearbox.

As you can see, this version was quite bigger and it used the reinforced differentials. The increased power drastically improved the performance, the top speed and overall power being simillar to the Wildcat 6x6.

BUT the model had a few problems, main being the exposed gearbox which would get clogged and jam while driving outside. This version was aslo wider compared to the first prototype.

Medium version prototype 2:

This is another concept where the entire front axle is designed to pivot, but I ultimately decided to go agaisnt it due to the higher center of gravity and higher unspring mass.

The final, universal 4x4 model:

I have built and tested the model, but have yet to make any media, that's why I'm using LDD photos for now.

I had to way to make the model more ingress resistant and narrower. This is where I came up with the idea of using the new, reinforced differentials as 28 tooth clutch gears for the high gear of the gearbox:

This way the gearbox's output axle was moved a stud lower, allowing me to cover the bottom of the model with panels which prevent the dirt from getting into the gearbox without sacrificing ground clearance:

The model inherited the front axle from the prototypes which acts like a free pendular axle. This keeps the weight even on both side of the suspension sosimple open differentials sufficed without a need for lockers.

The gear ratios are a bit of a compromise comapred to the Wildcat 6x6, with low gear being 0,89x the ratio and high gear being 0,83x the ratio. Even with these differences, the model still reaches a very simillar speed in high gear, probably due to lower friction losses and lower rolling resistance.

All in all I think this is a worthy successur to the Wildcat 6x6, even though it may not be as flashy, massive or functional (no skid steering).

Final part count is 774 pieces which is 41% od the Wildcat 6x6 and the weight has been reduced to around 1,4 kg - around half of the Wildcat 6x6.

I will be creating a proper in-depth video about the finished models and the protoypes, so I suggest you to watch this space for more upcoming details.

Edited November 24, 2022 by Zerobricks

[2GodBDGlory]

Nice work, that looks like a very fun model!
I do worry about that gearbox though, especially the new differentials being used. I'd imagine they'd wobble a lot because they don't allow for the axle to pass all the way through them, but hopefully it works fine!

[Zerobricks]

10 minutes ago, 2GodBDGlory said:

Nice work, that looks like a very fun model!
I do worry about that gearbox though, especially the new differentials being used. I'd imagine they'd wobble a lot because they don't allow for the axle to pass all the way through them, but hopefully it works fine!

Indeed they wobbled a lot, so I used a lot of half beams to stabilize the transmission rings on the bottom. I will talk about that too in the video.

[2GodBDGlory]

47 minutes ago, Zerobricks said:

Indeed they wobbled a lot, so I used a lot of half beams to stabilize the transmission rings on the bottom. I will talk about that too in the video.

Ok, sounds good! I missed the fact that you'd already built and tested it, so I'll assume it's good!

[gyenesvi]

I like this compact design a lot. The way the motors are installed is quite nice, giving way to a simple gearbox and overall drivetrain. Let's see over time how the diff in the gearbox handles all that power. I think 4 motors and 2 Buwizzes are kind of a sweet spot, that's the most I would ever put in one model, both because of not owning more :) and because of considering quite probable wear of parts, but at the same time that seems to give high enough speed and a lot of power to really become fun to drive.

As for avoiding grass to enter the gearbox, what I did and plan to do is instead of covering the bottom with another stud thickness of panels, I just put some duct tape at the bottom (given that the gears don't stick out from the bottom-most layer, which is not that difficult to achieve). This way, I can also use the duct tape (maybe also a layer of cart-board under it) as a skid plate that I don't need to worry about being scratched.

[Jurss]

It is really interesting to read, how and which challenges are solved.

[Zerobricks]

As promised, I took some time during the weekend to prepare more media.

First is a photo of the model on my new vinyl floor, I really like the bright colors:

And a couple of outdoor photos, showing the suspension in action:

The front suspension is inspired by 8475 and acts like a pendular axle and always splitting the weight evenly on both sides of the wheels (important with open differentials):

Tech specs:

• 773 pieces
• 34 x 23 x 17 cm
• 1100 g
• 4 BuWizz drive motors
• 1 PU L servo motor for steering
• 1 PU M motor for the gearbox
• Top speed 13,4 km/h

Lastly here's a very detailed video where I explain the issues faced during the design phase and showcase the performance of the finished model:

 

[Zerobricks]

For the Rolug 2023 Winter Truck Trial I made the Snow Edition. The main idea behind it is simple, just remove the wheels and pop on the tracks with no additional tweeking needed. Here's how it turned out:

 

Edited January 24, 2023 by Zerobricks

[pow]

As the video proofs, we need more orange vehicles with yellow tracks! It is not slow but actually looks way faster in this livery.

[Zerobricks]

1 hour ago, pow said:

As the video proofs, we need more orange vehicles with yellow tracks! It is not slow but actually looks way faster in this livery.

Thanks for the praise. It can go even faster though, this was all recorded in slow gear.

[Zerobricks]

LDD file link:

https://bricksafe.com/files/Zblj/universal-4x4/Universal 4x4.lxf

 

[shroomzofdoom]

I just built this truck from your lxf and, as usual, I am absolutely in awe of your design skills. Every time I put in the effort to build one of your designs, it advances my Technic skillset by leaps and bounds. Thanks for sharing the lxfs and info!

Brilliant work on the transmission! I've never seen the 3.5:1 / 1.25:1 ratio used in a transmission before. (I heard you say you used the same ratio in Wildcat, but I haven't built it yet)

I have a question if you don't mind:
1. the 11214 pin to retain the 28T diffs in the transmission...I can't wrap my head around this. I can only verify that the design kicks megablocks! I just don't understand how this works without being parasitic? Is it magic? :-)

[Zerobricks]

Thank you for the praise, I'm really proud of it too and I'm glad soemone else notices it!

The Wildcat 6x6 uses a smiliar, but slightly faster transmission.

Remember, the 28T diffs in transmission act only as clutch gears, there is not suppose to be any 12 tooth bevel gears inside them so the 11214 pins are there just for support.

[shroomzofdoom]

2 hours ago, Zerobricks said:

Remember, the 28T diffs in transmission act only as clutch gears, there is not suppose to be any 12 tooth bevel gears inside them so the 11214 pins are there just for support.

Ohmigod, I was on autopilot putting it together and placed the bevel gears in the diffs! Hilarious!

OK, so it's gonna be even MORE insane when I go back in and take those out!?!  Don't I feel silly...

[Jundis]

I can't believe how well this thing works!

How would this fare against the wheeled version in trial terrain?

[Zerobricks]

1 hour ago, Jundis said:

I can't believe how well this thing works!

How would this fare against the wheeled version in trial terrain?

Thank you for the praise.

Probably not that well, since the tracks lack any grip on hard surfaces

[pankov]

On 1/27/2023 at 1:59 PM, Zerobricks said:

LDD file link:

https://bricksafe.com/files/Zblj/universal-4x4/Universal 4x4.lxf

 

Hi,

First let me thank you for the the great work - this looks amazing and I'll definitely do my best to build and try it.

Since this will be my first build based on LDD files ... actually this is the very reason I have even installed LDD (v4.3.11 + the latest parts update) ... please bear with my simpleton questions.
And here come the first two:
1. What am I doing wrong in order to get an error message stating that there is one brick that's not placed correctly and was removed from the model when I open the .lxf file... and how can I see which is this brick?
2. Why is there a single yellow piece (an axle connector) at the bottom of the modeling plane (not connected to anything)? Could it be the problematic brick from the error above? And if that's the case then where it's supposed to be placed?

[Zerobricks]

The axle joiner goes inside the ball joint. 

Regarding missplaced bricks, try opening the file with collisions disabled. More info here:

https://www.eurobricks.com/forum/index.php?/forums/topic/151152-ldd-developer-mode/

[pankov]

Thanks,

this solved it.

:D

Looking forward acquiring all parts and having the chance to build it together with my son. 

[pankov]

It's me again with probably another stupid question but is normal that LDD crashes a second or two after switching to Building guide mode (F7) with this project opened ... or it's something wrong only with my installation?

[Zerobricks]

That's a known LDD issue when using custom parts. Even if the Building mode did work, it wouldn't be much help with such an interconnected build.

[pankov]

I see - then I guess I'll try my luck finding out how to build it myself ... I believe it'll be fun ... and a good learning experience.
:)

Of course - I ... and presume many others that attempt to build it ... won't mind getting some hints from you for some tricky moments ... if there are such to begin with.

[shroomzofdoom]

On 2/15/2023 at 2:36 PM, pankov said:

won't mind getting some hints from you for some tricky moments

I'm sure there are more efficient ways of doing this but, when building from an LDD, I use the hide feature to hide things like body panels, motors, and batteries. Then I use the multi-select feature to make a 'slice' like I am cutting with a knife and then I move that section away from the main model to make it a group. Hit the 'undo' to place the newly created group where it belongs.

When doing it like this, you will sometimes notice that various parts didn't get cut off with the slice. If you select the new group with multi select and carefully click the missed parts, you can then create a another new group that includes all the parts you wanted and delete the original which now appears empty. (remember to undo any time you move things away from the model!)

In this way, you create 'layers' of the groups that can easily be hidden later and you'll save a lot of time. The cool thing about the hide feature is that it works on entire groups and when they reappear they appear connected to the correct place but also hide doesn't make a mess of the groups. In this way, you can hide groups to focus on building section by section

Like I said, I'm sure there are more efficient ways. 

Take a look at this LDD and you'll see a version I created to help me isolate the transmission and front end. You may notice that I've deleted some parts, these were parts of his design that I already figured out. At least the groups may help you a bit. When it comes time to build the front axle, I found it easiest to build it forward from the 8L axles with stop around the steering motor.

Part of the fun for me is following a design from a mad genius like Zerobricks and trying to figure out 'why did he do that?' then you realize the elegance of his designs--everything fits perfectly, no excess parts, everything has a purpose. As a guy who still builds his MOCs the old fashioned way (trial and error clicking) it really does advance my Technic skills.

 

https://drive.google.com/file/d/1k1Ud1UVyzOzkajbyu1MvMzLVVYFQAJUJ/view?usp=sharing

Edited February 16, 2023 by shroomzofdoom

[Methes]

I've noticed you have both axles connected without a center diff. Doesn't that cause issues on hard surfaces or especially when climbing over bigger obstacles?
I've tried several times to make a 4WD with axles connected but they always had performance issues and my last offroader even bent a few teeth of the red differential after trying to climb on a matress. Front wheels moved up while rear wheels stayed almost on the spot.

Now I usually resort to one motor powering the front axle and second motor powering the rear axle. Has less power while climbing but no issues with parts broken.

[Zerobricks]

Never had any issues, the wheels can simply slip if there's too much resistance. Besides there is 5,4x gearing after diff and the model is light.

I also took it apart and cleaned the parts after the BuWizz gathering. The closed body really helped with protecting the gears from dust and dirt and there wasn't as much of wear and tear as I expected.

I plan to upgrade it soon to have more functionality and performance, just need the new gearbox parts and the 24 tooth clucth gears.