[MOC] Polaris RZR (42160 alternate)

[gyenesvi]

 

Hi Folks!

Let me share my latest alternate build, a Polaris RZR buggy built from the Audi RS Q e-tron (set 42160). As usual, I was trying to build an off-roader that is somewhat technically different from the A model, and improves things where I found it necessary. Although the set does not have too many interesting suspension/drivetrain parts (and is also lacking connectors quite a bit), the suspension can be somewhat varied. The model was mainly inspired by the following real world counterpart, a Polaris RZR Turbo S, although it has many variants with some differences in the looks (such as the side being closed in some models).

These buggies have trailing arm rear suspension with radius arms, something I have never seen built in lego form, so I was trying to replicate that, and the new hubs just gave a nice possibility for it. Besides that, the Audi is heavily missing all interior, so I decided to try and build something with full interior :) I believe the root of this problem is the difficulty of the electronics placement in the Audi, most prominently that of the (screwed) hub, so I had to build the chassis accordingly, which this model nicely allowed. I think my alternate model is the first one that does not have any electronics in the cockpit..

Features

• independent front suspension
• independent trailing arm rear suspension with radius arms
• efficient drivetrain with coupled motors
• complete and clean interior with two seats, dashboard, steering yoke and middle console
• lightweight body

Drivetrain

In order to maximize performance, I definitely wanted to couple the two drive motors. It is a very easy to lay out the motors that way, but since with coupled motors the drivetrain must pass through the middle of the chassis, then the battery cannot be placed in the middle. It cannot even be placed above the driveshaft, because then either the lid or the button cannot be accessed (or neither, if the model has an interior). So the hub must go somewhere else, well, the candidates locations are in the back. I ended up placing it upside down in the back, to allow access to the screws, and the turn on button can be pushed through a lever. That leaves the drive motors to be placed on the floor.

Steering

As for the steering motor, I also wanted to put it into the front, not interfering with the cockpit. That's also a bit more difficult if you want your steering to be linked both in front and behind the axle, as in the Audi. I think the Audi has dual steering linkage because it needs it due to its screwed up steering geometry; because of those red connectors on the steering hubs to which the links are connected, the links are mounted half a stud higher than should be, and that would cause significant toe in/out and bump steer; so they solved it by making the linkage symmetric, pushing the wheel hubs in both directions. Actually that half a stud matters more than I thought, the links are quite tight, and are under some stress. Not sure how Lego allows such bad practise, though I can imagine they might even say it is intentional to allow less slack in the linkage. Well, a tight linkage becomes useless if they add a gearing after the steering motor (as in the Audi), and you control the whole thing with the touch screen; it will be unprecise anyway, so the tightness of the linkage does not matter much. It would have been much cleaner if they just designed a proper steering hub with the steering arm in the middle, as in case of the planetary one. Then the whole half stud offsetting could have been easily avoided..

Anyways, I decided I don't want wrong steering geometry (even with the dual linkage, it did have some bump steer, I guess because only one rack is driven by the steering motor), so I just flipped the hubs upside down to allow proper geometry (no half stud offset vertically). Here's the complete driveline and steering geometry. It works like a charm, no toe in/out bump or steer, and it has little slack.

Suspension

The front suspension is a simple independent one with double wishbones, similar construction to that of the Audi. However, the rear one is a trailing arm with radius arms. This seems very similar to an independent one with double wishbones, especially because here I could only implement some of the radius arms with the wishbones. The main difference is that the springs are attached to the trailing arm itself instead of the wishbones. Also, I believe in real life, the trailing arm is the main load bearing structure, and the radius arms only help stabilize the wheel sideways (whereas here it's the other way around). Furthermore, I believe that in real life, the trailing arm and the wheel hub is one solid unit without a pivot. However, in this lego model, I could only imitate this with a pivot at the wheel hub end of the trailing arm. If there was no pivot, then the wheel hub would move non-parallel to the ground as the suspension is working, and then the radius arms would need bal joints on both ends to be able to follow its movement, which I could not implement here due to parts availibility (maybe would be possible with more links). Nonetheless, this simple setup nicely approximates the real thing, and is a somewhat novel suspension technique in lego I believe.

It would be nice to understand better how it works in reality, so if anyone understands this better, let me know in the comments. One thing I don't quite understand is that the radius arms introduce sideways movement of the wheel as it moves vertically, and I don't get if there's a trick to make the trailing arm follow that sideways movement, such as being placed at a slight outward angle..

Interior

Many people complain about the Audi lacking any interior. I think the reason is a mix of two things; cost saving, and the inability to place the electronics outside of the cockpit (due to the screwed hub). So I decided to make a full interior just to show it's doable even with the mighty screwed hub and only using the Audi parts :) Besides the two seats and dashboard, I added a middle console with a gear stick and built a steering yoke.

Bodywork

With the bodywork I simply tried to roughly replicate the lines of some variation of the real buggy, for which the many panels proved useful (especially the roof is a nice match). I definitely wanted to reuse the stickered curved panel with the front lights, and because of that the nose came out a bit blocky, so that's a compromise. Also, the nose is about a stud too long anyway due to space requirements for the front axle and the steering mechanism. But otherwise, the shape is quite okay I think. Here are some more renders and photos.

More renders and photos are available on my Bricksafe.

Building instructions are available on Rebrickable.

Let me know how you like it!

Cheers,

Viktor

 

[Jurss]

Nice one. 

Cool, that you used front sticker in the same place.

[Zerobricks]

Well done! Nice to see such a good replica of the rear trailing / A-arm suspension.

[Lixander]

Nice......you did a great job!

One question though - how do you managed to get the tires in the Studio program?

I tried files from 2 sites and both of them cant be used because of some errors in the file or because the program doesnt recognize the files.

Edited November 7, 2023 by Lixander

[1gor]

That could be even official set; perhaps cheaper than Audi. It looks great; simple, light, rubust

Edited November 7, 2023 by 1gor

[Celeri]

I love cool buggy's and your MOC really does not disappoint. I will definitely consider building it — provided I get the set one day ;)

Great work!

[langko]

Cool looking model and great write up as always!

My workplace is currently designing some aftermarket accessories to some Polaris Rangers at the moment… So it’s very cool to see this LEGO rendition of the more sportier version. 

[Timorzelorzworz]

Good alternate model. I really like the idea with the sticker for front-light. It looks like this sticker was exclusively made for this model, probably the best reuse of sticker part ever seen. 

Good job! 

[gyenesvi]

Thanks for all the positive feedback!

On 11/7/2023 at 12:25 PM, Lixander said:

One question though - how do you managed to get the tires in the Studio program?

I used Philo's package, that he recently made. What I usually do when the program does not recognize the custom parts is that I open/import them in part designer and then export them to Studio :)

On 11/8/2023 at 8:10 AM, langko said:

My workplace is currently designing some aftermarket accessories to some Polaris Rangers at the moment… So it’s very cool to see this LEGO rendition of the more sportier version. 

That must be a cool workplace :) I like these kind of buggies, so it can easily happen in the future that I'll make other version of this without limiting myself to a single set, and maybe with more power :)

23 hours ago, Timorzelorzworz said:

Good alternate model. I really like the idea with the sticker for front-light. It looks like this sticker was exclusively made for this model, probably the best reuse of sticker part ever seen. 

Thanks, well stickered parts are often hard to reuse, and so I rarely apply stickers, but this one is a fairly generic one, so I decided to apply it just for making this model more detailed.

[Lixander]

2 hours ago, gyenesvi said:

I used Philo's package, that he recently made. What I usually do when the program does not recognize the custom parts is that I open/import them in part designer and then export them to Studio :)

I tried with the Part Designer too, but the same things happens.

I will see what I can do with the file from the Philos site. Thanks anyway!

Edited November 9, 2023 by Lixander

[flappybird906]

I wish there were instructions for  Polaris RZR on different websites than rebrickable.com

[gyenesvi]

2 hours ago, flappybird906 said:

I wish there were instructions for  Polaris RZR on different websites than rebrickable.com

Why do you wish that, what’s wrong with Rebrickable?