[Moc] - Lego rc car steering problems

[Peter Swinkels]

At the moment I am using a motor  combined with gears to achieve a final ratio of  25:1 (two times 5:1) to drive the final gear directly connected to a steering rack. This high ratio allows the wheels to swivel at a reasonable speed while driving the rc car, but puts considerable stress on the steering mechanism when the the rack has reached its limit. The result is a creaking noise meaning that if the chassis were any more rigid rather than flexible something would break. For this reason I am not a fan of this particular method and used a belt instead of gears at first. This however results in the wheels swiveling randomnly as result of friction with the driving surface and not enough resistance to the rack moving by itself. Apparently, so much power is lost that the wheels will only swivel due to the motor running when they are lifted off the driving surface.

What kind of motorized steering mechanism is powerful but slow enough to drive a steering rack? Without random swiveling introduced by friction while driving. And how do you prevent the whole thing from breaking by trying to oversteer?

Photo's can be found here: https://drive.google.com/drive/folders/1f6BSMj9Mk81Gv7imwdO7v805OrsgUbae?usp=sharing

The motor used: https://www.lego.com/nl-nl/product/technic-large-motor-88013 

Edited January 16, 2021 by Peter Swinkels

[Zerobricks]

Are you using a Powered Up hub to control it? You have to program it so the motor knows when it reaches the limit and this way you also get automatic return to center.

Check RacingBrick's tutorial:

 

[Peter Swinkels]

Yes, apparently I am: https://www.bricklink.com/v2/catalog/catalogitem.page?P=bb0892c01&idColor=1#T=C&C=1 - So I need to install an app on my tablet and program the hub? I will try that.

[amorti]

That's an extraordinarily overcomplicated steering mechanism.

Since you're using the new motors,  just take the axle straight from the motor to the steering rack. You can program it to stop when it feels resistance, and to run slower if it steers too aggressively for your preference.

[Peter Swinkels]

3 hours ago, amorti said:

That's an extraordinarily overcomplicated steering mechanism.

Since you're using the new motors,  just take the axle straight from the motor to the steering rack. You can program it to stop when it feels resistance, and to run slower if it steers too aggressively for your preference.

Okay, I am new to these new technic motors. I am used to having to use gears to get the speed right.

[NikosSprocket]

Hi Peter,

I am in a similar path with my Defender conversion to full RC. I need also to work on my steering as it is not as "responsive" as I would like it but I found a way to make the App. (3.6.0) to calibrate the Angular (SPIKE) position motor so it always start at the center. I created a quick built animation of this configuration below:

 

 

I hope this helps.

Nikos

Edited January 16, 2021 by NikosSprocket

[Peter Swinkels]

Just to be clear, there has been a huge amount of time I didn't build with Legos. The most recent motor I had before buying another one last year is https://www.bricklink.com/v2/catalog/catalogitem.page?P=2838c01#T=C - And the control center was the closest I ever got to programming Lego motors. So I have some catching up to do with these more modern methods.

Edited January 16, 2021 by Peter Swinkels

[Peter Swinkels]

13 hours ago, NikosSprocket said:

Hi Peter,

I am in a similar path with my Defender conversion to full RC. I need also to work on my steering as it is not as "responsive" as I would like it but I found a way to make the App. (3.6.0) to calibrate the Angular (SPIKE) position motor so it always start at the center. I created a quick built animation of this configuration below:

 

 

I hope this helps.

Nikos

I am not sure I understand that construct. While I can build a complex modern Technic model from an instruction booklet my own moc's are at the level of those simple Technic models from the 80's. Once I get to it I will see if I can figure out that app and program the motor with it.

[Peter Swinkels]

Alright, I just had a look at the Lego Powered Up app. What a disappointment! There is no documentation whatsoever, and the supposed long press (some video on the internet suggested it) on an icon to bring up a description does nothing. All I managed is to get one of the preloaded scripts to get a motor attached to a hub to run without understanding how or why. Yes, and I had "fun" looking at the colorful icons and widgets and swiping them around. Okay, now I am done expressing my frustrations, does anyone know of a tutorial for absolute noobs such as me? One that applies to version 3.6.0 of the Lego Powered Up app for the iPad developed by Lego?

Edited January 17, 2021 by Peter Swinkels

[BusterHaus]

Can't help you with PU, but the mechanical solution is a clutch gear. It will still make a noise but at least the gears will be protected. 

[Peter Swinkels]

1 hour ago, BusterHaus said:

Can't help you with PU, but the mechanical solution is a clutch gear. It will still make a noise but at least the gears will be protected. 

Do you mean https://www.brickowl.com/catalog/lego-gear-with-24-teeth-and-internal-clutch-76019-76244 this?

[NikosSprocket]

6 hours ago, Peter Swinkels said:

Alright, I just had a look at the Lego Powered Up app. What a disappointment! There is no documentation whatsoever, and the supposed long press (some video on the internet suggested it) on an icon to bring up a description does nothing. All I managed is to get one of the preloaded scripts to get a motor attached to a hub to run without understanding how or why. Yes, and I had "fun" looking at the colorful icons and widgets and swiping them around. Okay, now I am done expressing my frustrations, does anyone know of a tutorial for absolute noobs such as me? One that applies to version 3.6.0 of the Lego Powered Up app for the iPad developed by Lego?

Take a number! I am also disappointed with the release of PU (Powered Up) code without any documentation. I was greatly helped by https://racingbrick.com/powered-up-code-block-guide/.

Using the older system PF (Power Functions) the best motor for steering is the Servo Motor (88004). No need for any programming.

[BusterHaus]

2 hours ago, Peter Swinkels said:

Do you mean https://www.brickowl.com/catalog/lego-gear-with-24-teeth-and-internal-clutch-76019-76244 this?

Yes. 

[Peter Swinkels]

15 hours ago, NikosSprocket said:

Take a number! I am also disappointed with the release of PU (Powered Up) code without any documentation. I was greatly helped by https://racingbrick.com/powered-up-code-block-guide/.

Using the older system PF (Power Functions) the best motor for steering is the Servo Motor (88004). No need for any programming.

I will have a look soon. Thank you.

13 hours ago, BusterHaus said:

Yes. 

Good, I will try how that works when I get to it.

[designer-han]

On 1/17/2021 at 12:36 PM, Peter Swinkels said:

Alright, I just had a look at the Lego Powered Up app. What a disappointment! There is no documentation whatsoever, and the supposed long press (some video on the internet suggested it) on an icon to bring up a description does nothing. All I managed is to get one of the preloaded scripts to get a motor attached to a hub to run without understanding how or why. Yes, and I had "fun" looking at the colorful icons and widgets and swiping them around. Okay, now I am done expressing my frustrations, does anyone know of a tutorial for absolute noobs such as me? One that applies to version 3.6.0 of the Lego Powered Up app for the iPad developed by Lego?

Your absolutely right. The link to Racingbrick helped me a lot either.

But still the PU-App is sometimes weird in functions NOT available. If you create your own controls (choose controller type with the BLUE sliders on it; e.g. not the predefined controller ones)..... it is NOT possible to invert the slider input; as the code block WHITE functions do miss the +/- code block. And, on the Slider itself you can only choose return-to-zero, nothing else but fancy colors for your slider.... So, using sliders for drive/steer may result in opposite directions than expected based on your motor position or even/odd gears in the drivetrain.

I turned the diff, and it works now okay..... but hey, that's weird.

Now the strange thing: IF you selected and EXISTING control (the most right one, within the building scene as background).... and you switch to the coding layout... the +/- code block DOES exists..... Why o Why does LEGO makes it so hard for MOCs......

Another thing what strikes me - already mentioned by Sariel - is the fast overload protection kicks in on the Control+ hub by normal use of a L or XL motor.....

I am still in on the fence.... Make a new MOC with PU (as this should be the future!!) or just stay another 1-2 years with PF, even when discontinued on their site for purchasing.... My view is that LEGO is not focussing on the PU-App for MOCs, neither has the IT knowledge to do so....? In the end the sales do not come from MOCs, but from predefined sets with predefined controls. That this rules out the creativity for kids to add their (simple) MOCs with PU motors without having the app shouting 'wrong connection, wrong motor used'.... is probably acceptable for LEGO nowadays.

 

[Peter Swinkels]

Two things I would like to mention:

1. I tested the clutch gear, and it looks like a neat solution to preventing a motorized steeringrack from grinding itself to pieces. I haven't gotten to building  a motorized rack using it yet though.

2. I built another rc car https://drive.google.com/file/d/1LMs6sLBzrkx2vt5WfU8QkTSXbw9qga--/view?usp=sharing - I dare you to call it overcomplicated. :-) It moves and steers decently for such a simple design too.

Edited January 19, 2021 by Peter Swinkels
fixed an embedded url

[Peter Swinkels]

Okay I build a new rc car with a motorized steering rack. This time I used the clutch gear: https://drive.google.com/file/d/1rv4YGIrqt7lZ4NKg0bDTSuaJIAmMGPkV/view?usp=sharing How does this look?