A bit background about the last few months of tinkering:

Some might have seen that a few users, including me, experimented with small non lego/bricks brushless motors and rc parts to build either smaller cars or trophy trucks.
I had my own shot on a trophy truck but sadly at that scale some problems couldn't be solved properly. One of those problems was the wheel mounting, i did use hubs with ball bearings from Zenebricks, but with just pins holding them, they would still come of at higher corner speeds.

But i didn't want to give up on fusing RC components and bricks, as i love rc cars and i love building stuff. So i thought maybe even with reinforcements a live axle/multilink suspension at RC speeds and offroad just won't work as i want.
That's when i thought ok, then maybe some proper on-road or rally car, best with awd or at least 4wd to get more traction and stability.

At that point i only had the Zene wheelhubs with bearings and some might have read the conversation about them, they are not suited for a driven and steered axle. I tried to solve that problem but it boiled down to the fact that i needed at least one custom part, either a shortened/custom u-joint or something else.
And as i knew that m3 screws fit well into pins i figured that RC parts that are mounted with m3 screws might fit the lego system aswell, so i ordered some cheap tamiya parts as those are widly available and it did fit well.

That set the direction for my experiments, fusing RC wheelhups with Lego/Bricks.
But wait..they can't connect to Lego axles, so i needed an adapter. I found someone who helped me with a proper cad design and specs, as some of you might have seen in the brushless post, and i ordered some parts.

I got them 2 weeks ago and it all worked so well and i build a small prototype. The advantages for me were/are huge, for one, except for the custom parts every other RC part is cheap to replace, all 4 wheelhups cost less than 10€ together. I can replace worn out ballbearings in the hub(and i can clean them) for very little money and there is almost no slack at all in the stearing.
Apart from that, by using toe-in/out can be adjusted, left and right wheel steering can be adjusted and the big problem was solved..RC car tires are secured with a proper nut and won't just come of that easy.

Fast forward, after all that text, here are some screens:

More screens here -> Bricksafe gallery

That is my current prototype chassis, currently with on-road touring tires with 82mm diameter. The whole layout is roughtly oriented on most on-road RC cars, except that i choose to center the motor to move it further back and get some weight on the rear axle.


Also i choose to not use geekservos even thou it complicated the steering setup but with all that traction i was worried that the geekservo wasn't strong enough. Also i need them for another project, so i put in a cheaper 15kg servo.
Features:

• AWD
• Adjustable ride height
• Adjustable steering
• Adjustable toe-in/out
• RC shock absorbers
• Aluminium axles
• Zene metal differentials
• Uses common 12mm (1:10 scale) hex mounts for wheels
• Internal gear ratio is 7.95:1 (spur and diffs)
• 3250kv brushless motor on 2s (3s possible)
• 82mm tires

And now for the magic custom part:

That small part provides the connection between how RC wheels are driven and the lego system and are currently made out of aluminium. It offers a 1 stud long axle part so any axle connector can be attached, be it an common axle connector or a u-joint.
The movement range is a bit more than the old lego cv's, i would say about 40 degrees, but that also depends a bit on the RC axle part. A 2mm driveshaft pin needs to be pressed through the hole at the ball end, i designed it that way cause it's easier to manufacture and the pins tend to wear out after some time, so this way i could replace them.

There you can see how it's used an the mentioned driveshaft pin that needs to be pressed in.

They do need some space to move that's why there is an o ring in the RC axle and a small spring that pushes the driveshaft in a bit. That was only neccessary for the front axle as there is more movement.

A first testdrive showed that all the work was worth it. The prototype is fast, stable and fun to drive until a screw(metal 2l pin substitude from a uk shop) got loose cause it was the only screw where i forgot to use locktide :D

Next would be more testing and deciding what kind of bodywork i want to do. From the dimensions it's based on a Subaru Impreza WRC but a Skyline should fit aswell. Think it all depends on whether i can find good 80mm rally tires or not.

Feel free to ask questions and discuss and thanks for all the fish.

Edit:
Had finally the opportunity to make a shot vid. Sadly a 2L axle at the front left drivetrain broke, rendering the whole thing into rwd. Think that was an old brittle part and broke on a 360spin, but then again i added those weakspots on purpose to have cheap and easy to replace points of failure.
So that testrun was on 2S LiPo and abour 50-60% throttle.

https://www.youtube.com/shorts/Cuvu2y7sEfA

Edited May 2, 2024May 2 by Ryokeen
Added short video

Hello , I want to ask you some questions: 

Why do you use so powerful motor? As I see it is probobably 3650 motor. How have you mounted it?

Intresting how you have done the steering. Can you take more photos? I have tried to do something similar but with a 2wd model and up to 30 degrees caster angle. It hasn't performed well.

Has your model got caster angle?

To me it looks too complicated, do you think to simplify it? 

You use rc wheel hubs, won't the wheels stick out a bit behind the bodywork, or vice versa? 

 

Anyway, nice rc car!

Edited April 9, 2024Apr 9 by Krzychups

4 hours ago, Krzychups said:

Why do you use so powerful motor? As I see it is probobably 3650 motor. How have you mounted it?

No particular reason, other than i knew how to mount 540er brushed motors and 3650 motors have almost the same mounting points.
This is what i use for mounting, just some short m3 screws through the part 32814 holes and half liftarms to fill to a gap of 5 studs. The pinion gear then rests at pinhole level so everything that can mesh to a mod1 pinion gear(12 tooth or 16 tooth works best) can be used.

 

4 hours ago, Krzychups said:

Intresting how you have done the steering. Can you take more photos? I have tried to do something similar but with a 2wd model and up to 30 degrees caster angle. It hasn't performed well.

Has your model got caster angle?

I wouldn't recommend doing the steering like i did or how real rc cars do it as frictionless pins have way to much slack. I get away with it cause i use some metal pin replacements that sit very tightly and reduce slack a lot. So using a gear and rack might be better if you don't have such metal parts.
At first i thought about adding caster angle but it would make the suspension way to complicated, because either one have to tilt the whole axle along with the steering mechanism or(and that should be possible) i would have to use RC Hubs with a build in cast angle. But from my experience on-road RCs hardly have caster angle, or if only a few degrees. 30 degrees sound way to much and makes steering way to hard.

 

4 hours ago, Krzychups said:

To me it looks too complicated, do you think to simplify it?

Honestly i don't know where i could make it more simple, but i misunderstand what you mean with that. The cassis itself is quite simple, it just might look a bit messy with all those cables.

Thats's the brick build chassis without the rc components and stub wheelhubs and motor, around 470parts

4 hours ago, Krzychups said:

You use rc wheel hubs, won't the wheels stick out a bit behind the bodywork, or vice versa?

Well depends on the bodywork thats build ontop :) So far with tires it's 28 studs in width. And if you mean that the wheels might stick out during steering, the pivot/rotation point is actually only half a stud further towards the tire edge as when using the defender wheels.

16 hours ago, Ryokeen said:

But from my experience on-road RCs hardly have caster angle, or if only a few degrees. 30 degrees sound way to much and makes steering way to hard.

Well, 2wd normal rc cars have got about 30 degrees caster angle, I'm not sure what caster angle to use. I drive more on straight lines than on curves. Using Zene's motor and differential its only possible to build 2wd rc car. 

By the way I am also building an onroad lego rc car (because its easier than an offroad car) and I'm curious if rc onroad oil shocks are worth buying.

Edited April 10, 2024Apr 10 by Krzychups

8 hours ago, Krzychups said:

Well, 2wd normal rc cars have got about 30 degrees caster angle, I'm not sure what caster angle to use.

Yeah but that's mostly on offroad(buggy) cars but i would add as much cast as needed for stable driving as caster for an onroad car is more about self centering and keeping the line than smoother suspension.
I have an older nitro RC that is pretty fast and that thing got 2 degrees of caster angle(negative) and that is more than enough.

I mean 30 degrees is a lot, never seen that on any onroad car.

8 hours ago, Krzychups said:

I'm curious if rc onroad oil shocks are worth buying

From my experience, if you go faster yes it is worth but you don't need super good ones. Main point is, just springs tend to bounce up and down a bit after they got compressed. That will lower your traction and at higher speeds that's bad for steering and breaking(breaking puts more tracton at the front where a 2wd can't break).
Even cheap non oil springs have most of the time at least a friction dampening build in to reduce the bouncyness.

At this point it’s starting to get closer to 3D printed RC projects. Which is great. But in that case I would rather try more “RC looking” arrangements 

2 hours ago, NoEXIST said:

At this point it’s starting to get closer to 3D printed RC projects. Which is great. But in that case I would rather try more “RC looking” arrangements 

Valid point but even with 3D printed parts you tend to print more and more specialized parts. I wanted to see how close i can get to onroad hobby grade RC-cars with using a minimal amount of aftermarked/custom parts.
what i did here is more of a proof of concept and it allows me to make any chassis i want but still having proper driven and steered axles along with all bearings.
And with the speeds i can drive that thing it actually shows very well how durable and versatile lego technic is. I only use screws for the shock absorber and wheelhub mount as there is just no other way. Apart from that the whole chassis holds only with pins and interlocking parts. And it holds very well, nothing came loose so far.

Btw, that experiment does not contain a single 3D printed part :D