Gearboxes and return-to-center mechanisms

[JLiu15]

So with the announcement of the 42129 Zetros set, many have been wondering what functions it may have, with some suggesting we may see a 8043-style gearbox to use a single Control+ hub with its 4 ports to power more than 4 functions. I've seen some people suggest that the motors for drive, steering, etc will be connected to a gearbox that can power other functions (e.g. a crane), as well as remote-controlled pneumatics where motors can switch between driving/steering and controlling valves. However, I see a critical flaw in such a system that will make return-to center functions (e.g. steering, valves) very difficult to implement. This would be quite a letdown, especially given that it would defeat the purpose of C+ allowing for servo control.

The first issue is that there's a gap between the teeth on the driving ring and those on the clutch gear. This means there will be some backlash where the driving ring meets the clutch gear, and while it's usually negligible, it won't be good for a return-to-center servo mechanism where precision needs to be very high. In a return-to-center steering or valve mechanism, the "center" that the mechanism returns to will be thrown off by the clutch gear's position relative to the driving ring at the moment they engaged. This might not be as big of a deal for valves, but it will be disastrous for steering as even a small degree of error in the steering mechanism will throw off the direction the vehicle's driving in. Additionally, trying to calibrate the motor would be a nightmare in this scenario.

To eliminate the driving ring backlash issue, we could use a gearbox where a set of gears placed along an axle that slides back and forth engages various gears placed around it. This mechanism has not been used by LEGO since the driving rings were introduced (I believe one of the Car Chassis sets had such a gearbox), so it would be interesting to see it return. While backlash would not be an issue here, the concern here is that you need to make sure the gears line up at the right orientation every time the gearbox shifts (this applies for the driving ring gearbox as well). The mechanisms would ideally also have to return to center and lock themselves when the function is disengaged as well, as otherwise the return-to-center position would be thrown off when it reengages. This would be quite a challenging mechanism to implement. And even if everything were to go well, you always lose some precision with each pair of gears in the gear train as every pair of gears will have some play in them, not to mention adding friction to the mechanism which will make it harder for the motor to do its job.

Now we never know what LEGO may come up with, and maybe they'll introduce a never-before-seen mechanism and/or parts that will make this work flawlessly. Maybe that's what justifies the high price for this set despite having just over 2000 pieces. I'd certainly love for that to happen, as it would mean being able to precisely control a 4W/crab/normal steering system or several return-to-center pneumatic valves without the need for multiple servo motors.

Thoughts?

[Zerobricks]

Quote

he first issue is that there's a gap between the teeth on the driving ring and those on the clutch gear. This means there will be some backlash where the driving ring meets the clutch gear, and while it's usually negligible, it won't be good for a return-to-center servo mechanism where precision needs to be very high. In a return-to-center steering or valve mechanism, the "center" that the mechanism returns to will be thrown off by the clutch gear's position relative to the driving ring at the moment they engaged. This might not be as big of a deal for valves, but it will be disastrous for steering as even a small degree of error in the steering mechanism will throw off the direction the vehicle's driving in. Additionally, trying to calibrate the motor would be a nightmare in this scenario.

Agreed, the steering should have a dedicated motor which does only that with minimum amount of gears as possible.

Quote

To eliminate the driving ring backlash issue, we could use a gearbox where a set of gears placed along an axle that slides back and forth engages various gears placed around it. This mechanism has not been used by LEGO since the driving rings were introduced (I believe one of the Car Chassis sets had such a gearbox), so it would be interesting to see it return.

That will not happen IMO. The sliding geraboxes are very unreliable, need to spin to engage leading to grinding and jams and the gears can eventually slide on the axle locking up the whole thing.

If you want to use several functions with steering and drive with one hub the answer is really simple:

1 motor dedicated to steering

1 motor for drive

1 motor for auxilary drive

1 motor to switch the auxilary drive up to 4 seperate functions with a wave shifter

or

1 motor dedicated to steering

1 motor for drive

1 motor for shifting drive gears (up to 4)

1 motor for auxilary function

or

1 motor dedicated to steering

1 motor for drive

1 motor for shifting drive gears AND auxilary functions, you can have one wave shifter switch low/high drive gears and AUX 1/2

1 motor for auxilary function

Edited January 29, 2021 by Zerobricks

[spongebrickpl]

If You talk about Zetros then I am almost sure that 2 XL motors will be used for driving. So one L motor will be for steering and the last one (propably L) could be for transmission. I think it could have 3 gears:

1st- crawling,

2nd- slow driving,

3rd- winch.

 

[1gor]

And I thought (since this is actually about Zetros) that we have this 

Silly me 

[Scoar Sonander]

Ok, so let me get this strait. WHERE DO YOU GUYS GET THIS INFO FROM?????