Small PoweredUp Lego truck trial pick-up

[Appie]

Some might remember Mahjqa's topic where I made a chassis based on AutoBacon's MOC. This is the finished model:

It's driven by a PoweredUp City hub and 2 L-motors. The truck weighs 752gr (including batteries). It's downgeared with 2x 12:20 gear combinations (1 at the motor and 1 at each axle) which makes it pretty good at overcoming obstacles.

 

 

 

In case you wonder, the choice for knobgears was because I couldn't figure out something else that wouldn't skip in the available space. The half pins which are inserted into plates below the hub help with the structural integrity of the chassis. In the stud.io file I made for the chassis I had a 9L link across the width of the model in that area, but I later found out the front wheels might touch that construction during steering. I'll adjust this in the stud.io file.

 

 

Tried my best to give the model an interior. Below the black tile of the "seat" is the hub and liftarms that give the chassis its rigidity, so I didn't have much room to play with.

 

To turn on the model I need to use an axle to press the button below the "passenger's seat".

 

I would have loved to have a video for you, but I only have 1 phone which I use to control the model through the Brickcontroller app. @mahjqa has made some video's of an event last weekend where I used this little car (with slightly bigger front fenders), I hope he releases a video soon

Thanks for reading and I hope you enjoyed it.

Edited May 28, 2024 by Appie

[gyenesvi]

This is so cute! :) Very tight build, that drivetrain is neatly packed, and the body looks really cool, retro vibes. Can we see more of the inside? For example how the steering is done? It took me a while to find the battery as well, and I have no idea where you put the cables..

Hoping for a video :)

[Berthil]

Nice one @Appie! Hope to see the video soon.

[Appie]

Thanks guys!

50 minutes ago, gyenesvi said:

Can we see more of the inside? For example how the steering is done?

I had to breach a gap of 4 studs for the steering. Normally I'd use 24T gears, but those wouldn't fit, so I used this instead. The bottom goes straight to a steering rack on the front axle through an old style cv-joint. The reason there's a 6L liftarm on there between the motor axle and steering axle is because shorter liftarms could get stuck on edges of the City hub (this is also the reason for the quarter round tiles on top of the hub).

50 minutes ago, gyenesvi said:

It took me a while to find the battery as well, and I have no idea where you put the cables..

Personally quite proud where I managed to hide the cables

At the front I had space left between the 2 liftarms besides the motor:

 

So I could fold it up between the motor and the 6.5L spring and liftarms. To prevent it from going into the steering section I closed that off with a thin liftarm (you can see it on the steering photo).

For the rear I didn't have the luxury of that space, because I needed that space to brace the drivetrain gears. So I used a little bit of the bed:

 

It's basically swirled up below these 2x 3L black axle pins. The hole in front of the 2 pins is where the hub is secured and a little more outwards where the mounting is for the rollbar The final bit has to go over the 3L axle pins due to the mounting points for body work, but I have the space of 1 plate/thin liftarm between the rear of the cabin and the side of the cabin where that wire goes. This is how it sits before the left side bodywork goes on:

 

Edited May 28, 2024 by Appie

[gyenesvi]

Thanks for the photos, that's a neat linkage for the steering (I guess it introduces some slack, but hopefully still okay for the purpose), and good cable management, great compact build!

Wish TLG would cater more for this size of RC builds (both electronics and suspension/steering components).

[Appie]

32 minutes ago, gyenesvi said:

I guess it introduces some slack, but hopefully still okay for the purpose

Not much. Play in the system isn't much different than a few gears in that same spot. The wheels can't wiggle much left and right when steering is in neutral. Also, while the steering motor axle can move 90 degrees, the axle of the steering can't, it does about 75-80 degrees, because the front axle has a 7L thin liftarm below the steering rack (see belly photo) that acts as a steering stop too (touches the liftarm in front the 20T bevelgear there). The 7L thin liftarm is there mostly to prevent negative camber, the steering stop was a sort of bonus. So at full steering lock there's practically no slack. I want to see if I can change the setup to prevent negative camber while unlocking those last degrees of steering angle, but so far can't think of something that I can mount in that area that doesn't compromise ground clearance and still has a positive effect to counter negative camber.

I'd like parts for small RC builds too, but I am already quite happy with the new CV-joints we got for it. Though a dedicated small hub part for it wouldn't hurt

Edited May 28, 2024 by Appie

[gyenesvi]

17 minutes ago, Appie said:

Not much. Play in the system isn't much different than a few gears in that same spot.

Thanks, well, I meant all the linkage and joints together, as compared to a direct steering (motor to steering rack), I imagine it would be similar with gears. For me already the joints introduce quite a bit of play, though true that the whole system is not precise enough to notice too much of it, but still, things add up. Of course at full lock the play can be prevented with physical limiters.

And what introduces negative camber (or did you mean caster)? The linkage geometry?

[Appie]

32 minutes ago, gyenesvi said:

And what introduces negative camber (or did you mean caster)? The linkage geometry?

I looked it up actually, because I always mix them up , but nope, it's negative camber. The front axle has this problem because the parts that hold the CV-joints are only linked to one other part at the top. This causes that part to bend outwards, which gives the wheels negative camber. It's minor, but it's there even with the 7L liftarm there to help prevent it. It's shows itself best on a dusty floor: the rear tyres have dust only in the middle of the tyre, while the fronts have it slightly off center of the middle of the tyres. To (nearly) completely remove it, I'd ideally have to connect the bottom of those parts that hold the CV-joints to each other, but this ruins the ground clearance.

 

Mahjqa and Jovel (see the truck trial topic from Mahjqa I mentioned in the OP) have countered this with not only securing the gearrack with another liftarm below it (like I did with the thin 7L liftarm), but where I used a 3L axle to secure it to the part above the CV-joints, they used a 5L+ axle to add another liftarm above it to counter this effect. That works better, but it's alot of lost space for a small gain, so I opted not to use that.

Edited May 28, 2024 by Appie

[gyenesvi]

40 minutes ago, Appie said:

I looked it up actually, because I always mix them up , but nope, it's negative camber. The front axle has this problem because the parts that hold the CV-joints are only linked to one other part at the top.

Oh, I get it then, indeed, that's common with this approach, but yeah, I would have chosen the same as you did. I have a similarly scaled model that I will publish soon, and in that I do the same as you, only difference is that I have 9 wide axles and hence can use a 9L link for that instead of the 7L half beam, and it's good enough.

[vergogneless]

Wow, I'm thrilled to see a model at this small scale, especially a 4x4. Hats off for the work! I can't hide my irresistible urge to see this guy in action on video 

[Appie]

Mahjqa made a video and posted it in the other topic in which this car has some screentime

Thanks Mahjqa for the awesome video!

 

Looking forward to seeing that 9 wide car in action @gyenesvi I have/had plans to upgrade my previous car (the little yellow/blue Dakar truck) with 9 wide axles.

[Paul B Technic]

This is awesome, well done and thanks for sharing this.