[WIP] Small Scale Defender with Brushless Motor (pure Lego alternative)

[gyenesvi]

24 minutes ago, N1K0L4 said:

Awesome little model! It may use RC components, but it's still a clever build with a great looking body :)

Thank you!

24 minutes ago, N1K0L4 said:

Well.. it's not meant for high speed, is it? I think if you gear down at the motor (12:20 instead if 16:16) you could solve the cogging and the too fast top speed issue.

True, and I believe a slower gearing would help with the cogging (actually the current gearing is 20:12, so even a 16:16 would be enough I guess, but then I'd have a large gear sticking out at the bottom in the middle, limiting passability) and also, with slower gearing the slow startup mode of the motor would become too slow and useless. But maybe it would not even be needed, don't knwo, needs more experimentation.

24 minutes ago, N1K0L4 said:

It does! Really liked the shots. Can we see the setup? I wonder how low does it go.

Sure, so this is the piece I printed to attach to the bottom of the transmitter and create a 'tunnel' for the stick:

And it looks like this when put together. My selfie stick is not very long, a bit longer one would be more comfortable, but it's good enough. At least it has a button on the stick to start/stop recording..

[2GodBDGlory]

That does perform very well! Looks very fun!

I guess the more power and speed you get out of the motor, the harder it gets to control. I'm used to Lego models where you just give 100% throttle all the time, but for most of those shots you would have been nowhere near that! It must be harder holding the stick in the right medium position

[gyenesvi]

11 hours ago, 2GodBDGlory said:

I guess the more power and speed you get out of the motor, the harder it gets to control. I'm used to Lego models where you just give 100% throttle all the time, but for most of those shots you would have been nowhere near that! It must be harder holding the stick in the right medium position

Yeah, indeed, most shots were using just a little throttle, I had a similar feeling, that I'm used to less speed and hence less control problems with my Lego models. And the bigger difficulty is keeping the model within the view of the camera for a long enough period of time. When going fast, or just trying to maneuver precisely, I either wander out of the view, or if I look at the camera, I soon crash the model into some rocks.. It takes some practice, but I realized that if I'm at a good distance, and point the camera generally in the right direction and avoid moving my hand too much, then it comes out okay. And of course when it does not, I cut the scene :)

[thekoRngear]

Great! Sadly this year prolly we won't be seeing any C model of an official Lego Technic set from you? 

[gyenesvi]

17 hours ago, thekoRngear said:

Great! Sadly this year prolly we won't be seeing any C model of an official Lego Technic set from you? 

Thanks! Well I only bought the Bronco this year, and I am kind of struggling with a good idea as most have already been done..

[Krxlion]

Great job, Viktor.

I already said few words under your YT video, so I will not double myself. I will just add few comments from my side.

• You don't need to make a separate topic. I would just change the title from WIP to MOC. You can reorganize the first entry, but it is up to you if your topic needs that. ;)
• Regarding cogging effect. The easiest way is to gear down, but I too sometimes feel like there is "jump" between sinusoidal startup and normal motor run. You can tune the behavior in ESC_Config_Tool, but as you don't have PC currently, maybe there is a way for you to do it through Wi-Fi. I didn't dig deep into this topic, but I saw people using the phone to change settings of AM32 device. As you have a model already built, you can adjust your settings to that model. I am not saying though you will have to do it every time you build a new model. ;)
• I need to do something similar with that "Camera holder" under the transmitter. I have a lightweight mirrorless digital camera, so I think I could give it a try. Thanks for the tip. ;)

[gyenesvi]

On 9/22/2025 at 9:12 AM, Krxlion said:

Regarding cogging effect. The easiest way is to gear down, but I too sometimes feel like there is "jump" between sinusoidal startup and normal motor run. You can tune the behavior in ESC_Config_Tool, but as you don't have PC currently, maybe there is a way for you to do it through Wi-Fi. I didn't dig deep into this topic, but I saw people using the phone to change settings of AM32 device. As you have a model already built, you can adjust your settings to that model. I am not saying though you will have to do it every time you build a new model. ;)

I managed to get a Windows PC and connect to the ESC config tool. Even though some settings have weird effects (somehow lowering throttle matching brake seems to ruin the smooth startup for example, even though it seems unrelated), and others don't seem to have effect when they should (sine startup power does not seem to have much effect on the transition to normal mode), I played around a bit and somehow now the transition between sine startup and normal mode seems to be smoother, not that much of a jump, which is good. The cogging is still there, but I realized that it starts cogging after it transitions to slow normal mode, in the range where probably the back-EMF signal is still weak. And even the AM32 tuning tutorial says that more down-gearing might be needed in this case. It's doable in this model at the cost of having a 16T gear sticking out at the bottom :( might try to play around with that a bit though..

[Krxlion]

If you can smooth startup and have low speed control without sinusoidal startup then great, keep it that way. On top of that you should have "cruising" option, so when you let go of throttle it should more smoothly slow down, instead of doing it abruptly. - okay I Just read that you still have cogging effect, geardown for sure will help with that.

I completely get rid of brake functionality in am32 software. I find that enough geardown can often make the model stay in one spot, even on a steep terrain.

Running brake level is always on "1" value, this way It doesn't stop abruptly, but continously slow down.

[gyenesvi]

1 hour ago, Krxlion said:

I completely get rid of brake functionality in am32 software. I find that enough geardown can often make the model stay in one spot, even on a steep terrain.

Running brake level is always on "1" value, this way It doesn't stop abruptly, but continously slow down.

That's what I tried, but then it's acting weirdly. It completely ruins smooth startup (basically it just keeps cogging in the sine range, and then moves when I get out of sine range), even though it seems completely unrelated to that.

[Krxlion]

In the ESC Config Tool, you also have an option to set AM32 to act as "regular" ESC:

This setting is in "Input" tab. With enough gear down, this can offer promising results (low speed control, good torque). I am currently testing a model with two-speed gearbox and this setting on. The brushless motor feels like a brushed one, and on a first gear I have 50:1 gear down(including motor housing and driveline gearing), which is significant, but as I am aiming again both for crawling and cruising possibility the second gear offers 18:1 gear ratio. There might be a case where even on a low gear ESC will send wrong signals to the motor, but it is still up to testing, and you can try it yourself.

[gyenesvi]

16 hours ago, Krxlion said:

In the ESC Config Tool, you also have an option to set AM32 to act as "regular" ESC:

The image does not load for me (on two devices) so I don't know what you are referring to, and on the input tab I don't see anything that could be related to that. What's the exact name of this option?

 

[Krxlion]

17 minutes ago, gyenesvi said:

The image does not load for me (on two devices) so I don't know what you are referring to, and on the input tab I don't see anything that could be related to that. What's the exact name of this option?

 

Sorry, I thought I uploaded it correctly:

It's last option "Car / Basher type braking double tap to reverse, overrides user settings"

Try toggling it and give it a try.

[gyenesvi]

7 hours ago, Krxlion said:

It's last option "Car / Basher type braking double tap to reverse, overrides user settings"

Try toggling it and give it a try.

Well, I saw that option but it sounds like it should have nothing to do with startup, only with braking. I tried how it works, and indeed as the description suggests, when it's checked then pushing/pulling the trigger in the other direction than it was does not reverse immediately but first it brakes and only second push/pull reverses direction.

However, your observation is right that it does change the startup as well, which I would not expect, so it may be a bug? So essentially if this is checked we loose the sine mode startup. I understand that with models with more down-gearing the sine startup would be useless anyway because it would be unnoticeably slow. But still, I don't think this is how it should work, and also I don't like this double-tap setting, it is really irritating when I need to go back and forth.

Also, I tried all combinations of the brake settings, and no matter how I set it it always seem to brake, at least the gearing is enough to stop it immediately, I also tried it with a bare motor (no gearing), and with all braking turned off, and maybe then I see a little bit of coasting, like half a second. Maybe it would be more visible with a heavier model.

A weird thing that I managed to reproduce consistently is that if I set the Running break level to 1, then the sine startup does not work (only cogs). However, for values 2 and higher it does start up smoothly. That is weird and definitely looks like a bug. Also, for some settings, the sound of the ESC goes away. Weird again..

[Ryokeen]

2 hours ago, gyenesvi said:

Also, I tried all combinations of the brake settings, and no matter how I set it it always seem to brake, at least the gearing is enough to stop it immediately, I also tried it with a bare motor (no gearing), and with all braking turned off, and maybe then I see a little bit of coasting, like half a second. Maybe it would be more visible with a heavier model.

On light models that is to be expected my tiny 1:18 crawler has full bearings and stops from full throttle to stand still in less than a sec just when going into neutral..not enough mass for inertia to overcome the motors internal resistance. Also the mentioned "Running break" might be a problem, commonly it's named "drag break" and applies some break in neutral. Crawlers use that a lot to stay in position without any throttle.

[gyenesvi]

2 hours ago, Ryokeen said:

On light models that is to be expected my tiny 1:18 crawler has full bearings and stops from full throttle to stand still in less than a sec just when going into neutral..not enough mass for inertia to overcome the motors internal resistance.

That's good to know, thanks!

2 hours ago, Ryokeen said:

Also the mentioned "Running break" might be a problem, commonly it's named "drag break" and applies some break in neutral. Crawlers use that a lot to stay in position without any throttle.

I understand, but that's what I turned off.

[Krxlion]

13 hours ago, gyenesvi said:

However, your observation is right that it does change the startup as well, which I would not expect, so it may be a bug? So essentially if this is checked we loose the sine mode startup.

It overrides settings in the first tab, so it will for sure change how it starts (it is not a bug). I don't mind using reverse twice to change the direction where the model is going. It is far better for all the driveline parts that it would free-coast when you let go of the throttle instead of sudden stop.

I am yet to find a sweet spot in the settings, and I think that I agree with you, Viktor that there might be a bug, but with the brake settings.

13 hours ago, gyenesvi said:

A weird thing that I managed to reproduce consistently is that if I set the Running break level to 1, then the sine startup does not work (only cogs). However, for values 2 and higher it does start up smoothly. That is weird and definitely looks like a bug. Also, for some settings, the sound of the ESC goes away. Weird again..

So it is not only me that feel like this :D But on the other hand "running break level:1" is not enough free-coasting. If I for example 50% throttle and let go, I would assume it will slow down in about 3 seconds (similar to situation when you toggle Car/Basher mode on).

13 hours ago, gyenesvi said:

Also, I tried all combinations of the brake settings, and no matter how I set it it always seem to brake, at least the gearing is enough to stop it immediately, I also tried it with a bare motor (no gearing), and with all braking turned off, and maybe then I see a little bit of coasting, like half a second. Maybe it would be more visible with a heavier model.

I don't think, that it will be more visible with heavier model. With heavier model you usually have even more down-gearing, and then it stops even faster (my TRX-4 got "brake on stop" off, "running brake lvl:1", "stopped brake level:0" - as brake on stop is off, this one is on off too). I also think that planetary hubs really push this effect even further, stopping it more abruptly. With brick-built portal hubs(that I currently have in my model), I could see better free-coasting effect.

7 hours ago, gyenesvi said:

10 hours ago, Ryokeen said:

Also the mentioned "Running break" might be a problem, commonly it's named "drag break" and applies some break in neutral. Crawlers use that a lot to stay in position without any throttle.

I understand, but that's what I turned off.

We cannot really "turn off" the running brake. And I believe as soon as we are pushing it to more free-coasting(closer to "1" value) the ESC have a problem with finding position of the motor, and thus creating cog effect. We cannot have both free-coasting and sine-startup, this is something that Alka - master and coder of AM32 software told me. That is why I was waiting and figuring out with him for a 3-4 months a code that will toggle "Car/Basher" setting once you for example push a button on a receiver responsible for channel 3 (for example). It didn't work, and he was busy, so I gave up on this idea.

[gyenesvi]

On 9/26/2025 at 9:12 AM, Krxlion said:

We cannot really "turn off" the running brake. And I believe as soon as we are pushing it to more free-coasting(closer to "1" value) the ESC have a problem with finding position of the motor, and thus creating cog effect. We cannot have both free-coasting and sine-startup, this is something that Alka - master and coder of AM32 software told me.

That is interesting to know - I did think that something like that might be the happening, because precise speed control and coasting (no speed control) sound like technically opposing things. However, I'd expect that free coasting would be happening when the trigger is released, hence, when speed control is not happening, so they might not be opposing after all. But then one thing could break this reasoning, namely that as I am releasing the trigger, the speed control might react so fast that it is continuously slowing down the motor already, and hence by the time I actually release it, it is too slow and does not coast.

But even then, I think that the fact that it only cogs at brake level 1 is kind of an inconsistency with itself for all other levels, so whatever the phenomenon should be it should at least not behave very differently for this one value than all the others, hence I suspect it is a bug. Also, I think free coasting is something that is not actively done, it is something that only happens naturally, so by that, it could not be opposing some other process that is done actively (the speed control). So still weird..

[Krxlion]

I know that we are getting slightly out of your topic, but wanted to share a small discovery. So you said that you don't like the way you need to double-tap to go reverse, etc. If you could replicate my settings from below, you can have cruising experience with instant reverse functionality.

The key is to uncheck the "Complementary PWM", and uncheck of course "Car/Basher" function as it overrides "Settings" tab. I have sinusoidal startup checked, but It doesn't work without "Complementary PWM", so you probably can uncheck that as well. On top of that, I noticed that indeed "Running brake level" seems weird on 1 value. It makes my car *beep* sound significantly quieter, and sometimes if I open the program again it changes itself to 0 or 10 value (I don't remember which one was it, but definitely not 1). I might speak to Alka, but I also don't want to trouble this man so hard. I know he is probably busy. :D

Oh, and the version I am running is 2.19 with "ramp" feature, but to be honest I couldn't find any benefits of moving around those sliders, but I might have not dig enough.

[gyenesvi]

2 hours ago, Krxlion said:

So you said that you don't like the way you need to double-tap to go reverse, etc. If you could replicate my settings from below, you can have cruising experience with instant reverse functionality.

So what you are essentially doing is turning off the sinusoidal startup :) Indeed, it could be an interesting setup to test.

To go back on topic, I have made a PF/PU/Buwizz version of the chassis, just for the sake of seeing if it could be done and how it would behave. I used a PU angular small motor for steering instead of the GeekServo as it is almost the same size, so it fits. I have always wanted to test this motor for a steering alternative. It is somewhat weak, but it kind of works on not so sticky surface. For the drive I used a PF L motor, the PU version did not fit. The speed/torque ratio is quite okay actually, but of course slow speed control is not so much. Because of the mix of PF and PU motors, a Buwizz 3 had to be used for power, which fits into the bed.

[N1K0L4]

Nice! Were any major chassis modifications needed to fit the motors?

If you tested it outside already, are there any other drawbacks other than throttle and steering control? (weight distribution?) 

How well do the bronco tires work offroad? Maybe you could compare them on this model as from what I can tell it fits all 56 mm tires for 30.4 mm rims.

[gyenesvi]

56 minutes ago, N1K0L4 said:

Nice! Were any major chassis modifications needed to fit the motors?

No, only around the mounting points of the motors / Buwizz.

56 minutes ago, N1K0L4 said:

If you tested it outside already, are there any other drawbacks other than throttle and steering control? (weight distribution?) 

I haven't tested it off-road yet, so I don't know. Not sure if it's worth it due to the weak steering..

56 minutes ago, N1K0L4 said:

How well do the bronco tires work offroad? Maybe you could compare them on this model as from what I can tell it fits all 56 mm tires for 30.4 mm rims.

I don't know, maybe I'll test with Bronco tires, but they seem hard and expect them to be slippery. This bodywork would probably not work with small tractor tires as they are wider and get caught up in the fenders easily.