[WIP] Lada Niva Trial Truck

[2GodBDGlory]

I don't usually do WIP threads, but after seeing @Teo LEGO Technic start a WIP topic for the truck he's building for this Toronto Trial Truck race we're trying to organize, I figured I might as well document my progress as well!

Anyways, I'm most comfortable with 4x4 off-roaders, and I only have 4 (well, actually 5 if you count my spare one that spent a winter lost in the woods being chewed on by animals) 107mm tractor tires, so I started looking at attractive short wheelbase 4x4 SUVs. My desire to do something I haven't built before limited me a lot, because back when I had less responsibilities/more free time I built a LOT of different vehicles, with varying degrees of  quality! I made a shortlist of models, but wanted to do something a bit oddball, so I eventually settled on the Lada Niva:

I don't suppose this truck needs a ton of introduction in Europe, since I hear they're fairly popular there (Probably more in Eastern Europe??), but for any Americans who haven't heard of it, it's basically a small, very basic, Russian-made SUV that's been in production since 1977, and is apparently still produced in roughly the same form. While this vehicle was never sold in the US, it was in fact sold in Canada, and I can remember seeing exactly one in my life, though that was in a junkyard.

Anyways, I think it looks cool and has an interesting history, so that's what I'm building!

My model will probably attempt to look like a fairly heavily modified example, with larger tires, a solid-front-axle swap, and some accessories.

The planned features are as follows:

• 4WD with 4 PF XL-motors hard-coupled together
• 4-wheel-steering with one PF L-motor per axle
• 2-speed sliding-gear gearbox controlled by some PF motor

The first thing I built, after mapping out the ideal gear ratios in my head, was this gearbox setup:

It looks like the gears should be reinforced well, and I like the large difference between speeds and the efficiency of the setup. I'm not sure how much I trust the small linear actuator to successfully slide these gears along the axle, so I'll likely tweak that, but the other thing I dislike is that I can't get the ball joints I'm hoping to use for the suspension anywhere near the middle, which will hurt my suspension geometry. Nothing obvious presents itself to solve that, but we'll see how this fits with my current wheelbase and see if anything comes to mind.

After that, I built this axle, which I'm quite happy with:

It's got a new custom portal axle design of mine, which gives a steering pivot in about the best possible position, a 1:5 gear ratio, and good ground clearance around the wheels. Of course, this also gives exceptional ground clearance in the middle, with over 8 studs available!

The main axle drive has got the "square" drive technique I was describing in Teo Lego Technic's thread, with 12:20 ratio for better ground clearance than typical gearings. The steering has a PF L-motor driving a 13L rack through two gears individually, one on each side, through a parallel gear setup that goes 8:28, 8:24, then 16:20, for total reduction of 13.125:1, and nice symmetry and strength.

 

Next I'll probably either start thinking about working ball joints into the gearbox assembly or build a clone of this axle for the rear--I've just got to take apart my Land Cruiser MOC to free up those ball joints soon!

[Paul B Technic]

Nice work and I am keen to see how this develops.

[Daniel-99]

Oh man! you made another topic I can not miss! 8 Studs of ground clearance seems to be an overkill to me ;-) I guess such a crazy off-road tuning was inspired by this guys: 

 

[HorcikDesigns]

Nice custom portal HUBs! Looking forward to see the result. Good luck! 

 

[gyenesvi]

Great choice, indeed, those Lada Nivas were quite wide-spread over here, and I also have it on my backlog to be built at some point, though probably a smaller one.

Those portals look really badass, curious how this will perform! Aren't you afraid of those 4 coupled XL twisting axles pretty easily? Or do you expect the massive portal reduction to take care of that issue?

[Daniel-99]

2 hours ago, gyenesvi said:

 Aren't you afraid of those 4 coupled XL twisting axles pretty easily? Or do you expect the massive portal reduction to take care of that issue?

By the way, Nivas are well known for their Low-power engines, moreover, the whole transmission does not allow to overcome an increased torque of a boosted motor! A agree with you that 4 XL motors seems to be very unusual solution here, especially in combination with 5:1 portal reduction. I would use again 2 BM and reinforced open diff at the front with gear combination 12:28 and permanently locked gearing 12:28 at the rear. This would give me a plenty torque without any load on transmission (even Lego U-joints will work here)

[2GodBDGlory]

5 hours ago, gyenesvi said:

Great choice, indeed, those Lada Nivas were quite wide-spread over here, and I also have it on my backlog to be built at some point, though probably a smaller one.

Those portals look really badass, curious how this will perform! Aren't you afraid of those 4 coupled XL twisting axles pretty easily? Or do you expect the massive portal reduction to take care of that issue?

Yeah, I'm quite happy with the portal design! There's a bit of friction against the rim, and a very specific spacing that works for the 3x3 L-beams, but I think they look good and strong.

I'll definitely have to see how the 4XLs perform, but I'm counting on the fact that there's not much reduction prior to the portal hubs to keep it all together

3 hours ago, Daniel-99 said:

By the way, Nivas are well known for their Low-power engines, moreover, the whole transmission does not allow to overcome an increased torque of a boosted motor! A agree with you that 4 XL motors seems to be very unusual solution here, especially in combination with 5:1 portal reduction. I would use again 2 BM and reinforced open diff at the front with gear combination 12:28 and permanently locked gearing 12:28 at the rear. This would give me a plenty torque without any load on transmission (even Lego U-joints will work here)

Huh, interesting! I guess mine will be an even more heavily modified example than I was planning!

That's true that 4 XLs aren't the normal, and it might be challenging to cope with their torque, but I think their form factor is good, and they're reportedly better than buggy motors when high torque is required, though I've never really figured out why.

According to Philo's stats for these motors at 12V, though, 4 XL motors at 12V will give me 12.96 watts, while 2 buggy motors at 12V will only give me 12.32 watts, so I don't think I'm giving up any power there, and the shape is more convenient.

I think that scenario you're describing is a good high-performance setup, but to my ear sounds more optimized for higher speeds than I'm planning on. The primary objective with this thing is to be able to crawl over pretty much anything possible, and then to have as much available speed as I can get, given the crawling ability.

[Teo LEGO Technic]

Great progress! That thing is going to be an absolute powerhouse in terms of its power-to-weight, but as others have pointed out, it will be important to brace everything in the transmission as securely as possible to avoid gear slippage with the torque of 4 XL motors. Usually, I make sure, when using XL motors, to have all gears braced on either side immediately with beams.

On the other hand, your steering setup with 2 gears on the rack and those massive portal axles looks great! The only disadvantage of the massive clearance may be that it can fall over easier due to a higher center of gravity, but overall it looks like I will be hard pressed to come up with a worthy challenger for our truck trial

Edited April 28, 2023 by Teo LEGO Technic

[2GodBDGlory]

I'm back with a weekend update!

I was very happy with both my axle and my gearbox, but unfortunately, they really couldn't work together in a model with as short of a wheelbase as I was building, so one of them had to compromise. I decided to keep the axles and modify the drivetrain, adding bevel gears between the XL motors and the gearbox. This adds a decent amount of friction and complexity, but allows my axles to come close enough together, maintains the gearbox, maintains the power level, and should still be reliable.

I've added the rear axle, which is essentially just a copy of the front one, because I want to include four-wheel steering here. It should allow for tight turns, even with locked differentials, and allows me a decent amount of wiggle control over the independent front and rear axles to help fight for traction in tough spots. The suspension seems quite strong as it is (though I still need to take the other ball joint out of my Land Cruiser), but is a bit lacking in flex. I'm not sure how much of a problem that will be!

Additionally, even though tests showed the gearbox as reliable under torque, I didn't want to take any chances, and so I added a 7L beam in the middle of the sliding assembly that slides along with the gears, ensuring great reinforcement in both gears. I replaced the small linear actuator for shifting with a large actuator (not clearly seen in these pictures I took, apparently), to take advantage of its stronger clutch strength.

Now I mainly just need to hook up a motor for shifting, reinforce the frame a little, and install the electronic control elements, and I should be ready for some preliminary testing!

[2GodBDGlory]

After finishing up those little jobs, I was able to do some basic first tests.

The takeaways are: 

• This is a beast on power! Even in high gear, it's got all the torque it needs for climbing! To make the most of the power, I'm probably going to have to find somewhere to raise gear ratios, so that low gear is actually useful!
• 12T single-bevel gears aren't as strong as I thought. The bevel gears I set up to take power from the XLs to the gearbox were popping energetically when I gave it full power under load, despite having four of these gearings (one per motor) to try to split up the torque, and despite the solid bracing! I'll have to see what I can do about that.

Anyways, it looks like I'll have more work than I was expecting, but that's why I started building so early!

[BusterHaus]

What are the pins you are using to attach the shocks to the frame? They don't have a split. 

[2GodBDGlory]

26 minutes ago, BusterHaus said:

What are the pins you are using to attach the shocks to the frame? They don't have a split. 

Part 77765:

It's fairly new, but rather handy!

[SUPER Max Black]

It seems to me to call a Niva a "truck" is strange. For her, the name "trial car" is more suitable. 

Although in terms of the type of suspension and wheel size, this Niva will look like a monster truck.

 

But I like Soviet lego cars.

Edited May 7, 2023 by SUPER Max Black

[2GodBDGlory]

7 hours ago, SUPER Max Black said:

It seems to me to call a Niva a "truck" is strange. For her, the name "trial car" is more suitable. 

Although in terms of the type of suspension and wheel size, this Niva will look like a monster truck.

 

But I like Soviet lego cars.

True, I wouldn't really call it a truck either, but to me "Trial Truck" is just terminology that I slap onto anything I build that's intended for heavy off-road use, and it's especially fitting for this one, since I plan to enter it in a "Truck Trial" event.
Yeah, it will look a bit like a monster truck I think!

[2GodBDGlory]

After determining that my method of bevel gear power transmission was a dead end, I felt stumped for a while. How could I eliminate those bevel gears while keeping reasonable suspension geometry and the gearbox? In the end the solution I struck on was to design a gearbox based on a 5 stud spacing rather than the 4 stud spacing of the earlier design. There aren't many gear ratios that work at this 5 stud spacing, with the only options I know of being 56:8, 40:24, and 36:28. [Well, I just checked and 9:15 (with old, pre-Technic gears), or 6:10 (with splat gears) both work, but are both actually identical gear ratios to 24:40] This was probably the time when I most wished the 48T spur gear from the The Lego Movie version of Emmet's Super Cycle had made it into production, since a 48:16 ratio would have been great! (According to something I read somewhere sometime, it was planned for production, but budget cuts forced them to use a standard 40T gear in the official set) I actually didn't realize 56:8 was a possibility until later, but I'm sure I wouldn't have tried it anyways due to impractical size and pathetic 8T gears. That left 40:24 and 36:28, but wanting the largest possible ratio spread, I opted for the 40:24 ratio and its opposite, 24:40. This meant that my already unsynchronized gearbox would have the added disadvantage of straight-cut gears trying to slide into each other, but so long as the drive motors are turning, it hasn't had trouble engaging. The spur profile also allowed for a neutral gear to exist in between the two speeds, thanks to the two 1/4 stud spaces between teeth and the edge of the gear adding up to the 1/2 stud of the width of the gear teeth, which prevents jamming when shifting. Anyways, this gearbox was able to fit into a space only three studs long, which was crucial, and it allowed the XL motors to be mounted linearly with a three stud space between them--perfect for fitting part of the suspension ball joints between them!

This gearbox is shifted by a PF M motor through a large linear actuator, through a 4-bar linkage, which I found to be the best way to transmit the linear motion of the actuator down ~6 studs to where the gears were without losing motion to part bending.

Redesigning the gearbox also meant redesigning a fair bit of the frame, but other than that not much has changed. The new gearbox has a much lower high gear, though, and it was already slower than I would have liked, so I'll probably have to find a way to add significant upgearing later! It'd be easy to swap the portal ratio from 1:5 to 1:3, but I'll probably have to dig into the axle drive ratio to get the change I desire.
I've already snapped this 8L axle simply by its twisting in the ~1/2 stud space between the 40T gears and the wheel hubs in the portal hub assemblies (in high gear!), which seems like a good indication that I have abundant torque to trade for speed!

Also, I finally took a look at that video you linked, @Daniel-99, and those are some pretty extreme machines! I thought my 8:40 portal axles were the craziest anyone had done, but those 8:56 ones put me to shame! It's a really great idea, though, and one that just might convince me to buy a couple more 56T turntables sometime so I can try it!

Edited May 15, 2023 by 2GodBDGlory

[Daniel-99]

Great progress! I love the new motor placement a lot! Now they dont stick out from the sides of a car. 

I still not understand why one need so much reduction in the transmission ;-) 8:40 reduction in portal axles seems to be enough for me. Moreover I would use planetary hubs instead of brick build portal hubs to keep the transmission from unwanted mud and dust, simplify the build, avoid any potential problems with gear skipping! Brick built portal hubs looks like an interesting development \ theoretical project rather than practical solution for outdoor RC driving. 

[2GodBDGlory]

6 hours ago, Daniel-99 said:

Great progress! I love the new motor placement a lot! Now they dont stick out from the sides of a car. 

I still not understand why one need so much reduction in the transmission ;-) 8:40 reduction in portal axles seems to be enough for me. Moreover I would use planetary hubs instead of brick build portal hubs to keep the transmission from unwanted mud and dust, simplify the build, avoid any potential problems with gear skipping! Brick built portal hubs looks like an interesting development \ theoretical project rather than practical solution for outdoor RC driving. 

Thanks!
Yeah, I realize that I have excessive gear reduction at the moment. I have as much as I do in the gearbox just because I wanted my two ratios to be as different as possible, but now I'm going to have to change my gearing down the line to be faster.
I've built several heavy-duty off-road models with brick-built hubs before (though of a different design), so I'm hopeful these can work, and will provide much better ground clearance than planetary hubs.

[2GodBDGlory]

So, the first thing I did after my last update was to start changing gearing to make this truck faster. I added an extra stage of gearing in the axles after the ball joints, with a 20:12 ratio being the largest I could fit in. This gearing also allowed to keep my axles flatter, with the advantage of giving me neutral castor angle and even ground clearance, rather than backwards castor angle and uneven ground clearance. The second gearing I was able to change was switching the portal axles from 1:5 to 1:3, with 12:36 gearing. This was a bit disappointing to have to do, since portal axles are really where you want to keep as much reduction as possible, but I didn't see anywhere else where I could change gearing without compromise. If I decide I need it still faster, I'll probably have to find a way to increase the drive ratio of the bevel gears in the axles, but that would either require a lot of rebuilding, weaken the components a lot, or introduce unevenly operating knob wheels.

After getting that done, I moved on to bodywork! I had decided that I wanted to use these custom-painted 1:8 car wheel arches, but mounting them normally in the front would result in them sticking out two studs farther than the front, because my Niva has the wheels pushed out to a non-stock location in the extreme front. Rather than forget the wheel arches and bore myself building another 4x4 with basic beam-stacked sides and slope-brick wheel arches, I decided to mount the wheel covers at an appropriate angle to still cover the wheels. It looks a little odd now, but it allowed me to use some panels to fill in gaps, which looks fairly nice, I think, and at least different from my usual! I've started trying to find a place to mount the rear wheel cover, but my rear-wheel-steering system is complicating this.

After getting these wheel arches figured out, I moved on to the front. I'm super happy with how the orange/white secondary lights turned out, fitting nicely into some black System panel pieces to provide a realistic black rim around them. The grille wasn't too complicated, but the bumper unfortunately couldn't reach the full width of the car for fear of colliding with the wheels at full steer and suspension travel. I'm quite happy with how it's looking so far, though, and I think this should become something that's both fun to drive and fun to look at, which isn't something I could say about a lot of my off-roader models!

[2GodBDGlory]

I'm a little tardy in posting this final update, but I got the bodywork finished up last weekend, and added LEDs and an old Canadian flag piece from my Dad/Uncle's '70s Lego collection.

Spoiler

(My memory is that it came from the 565 Moon Landing from 1976, but Bricklink thinks that set only came with a US flag. We have lots of other flags as well, some that seem to match supplemental sets like 939, but the only similar Canadian ones on Bricklink come from 575 and 357, neither of which I have any memory of. I guess it's irrelevant)

I'm pretty happy with how it looks!

I also reinforced the portal axles, and added skidplating on the bottom, so really all I have left to do is add some bumper stickers, and then test it out and make whatever changes are necessary!

[gyenesvi]

Cool, it is getting recognizable :) The only part I find messy is around the front fender. Maybe, if the angling of the fender piece was not so aggressive, you could make its angle match the bottom of long wing panel above it and simplify that area a bit by removing the short panel?

Curious about the performance, it seems huge!

[2GodBDGlory]

14 hours ago, gyenesvi said:

Cool, it is getting recognizable :) The only part I find messy is around the front fender. Maybe, if the angling of the fender piece was not so aggressive, you could make its angle match the bottom of long wing panel above it and simplify that area a bit by removing the short panel?

Curious about the performance, it seems huge!

Thanks! It's true that it could look better with more normal fender placement, but I had a really hard time finding any placement that would work with massive tires, a fair bit of steering offset, and lots of suspension travel, all without sticking the fender out past the front of the car, so I'm not thinking that would be an option.

I'm looking forward to doing some off-road tests, but right now I'm just waiting to get my real car on the road so I can get it to places more easily!
 

[Daniel-99]

A serious progress here! Congrats! I have not seen a Niva made with Lego in such big scale! Are you planning to share the driving tests, or you want to keep them in secret until the Event?

[2GodBDGlory]

26 minutes ago, Daniel-99 said:

A serious progress here! Congrats! I have not seen a Niva made with Lego in such big scale! Are you planning to share the driving tests, or you want to keep them in secret until the Event?

Thanks! I do plan on sharing video of it at some point, but I haven't actually done much testing yet, so I don't have any film yet.

[Paul B Technic]

That has come together really well :)

[2GodBDGlory]

Well, I finally got around to taking an outdoor test drive, and immediately some major problems came to light. For one, the 11L axle in the gearbox is getting extremely twisted, and there isn't really anything I can do about it, other than scrap the gearbox. Additionally, the 20:12 upgearing in the rear axle began skipping like crazy, ruining the 12T gear. I'm not sure what I'll do at this point, but it seems pretty clear that I'll have to make some dramatic changes to the drivetrain...
Removing the gearbox would really be too bad, but I'm starting to think it might be required in order to safely run the amount of power I'm wanting to have.

It also has a worryingly high center of gravity, and worse traction than I'd hoped. That'd be harder to fix without essentially building a new car, but it would be good if I could come up with something to do about it.

Anyways, I'll be thinking about what needs to be changed on this going forward!