Compact 4-speed Sequential RC Gearbox

[Sariel]

Edit: a new and improved version of this design which is better in every aspect:

Sequential gearboxes seem to be all the rage these days. With so many brilliant designs around, I wanted one that would be compact, dead simple and robust, and without fancy stuff like Servos, steering links, rubber bands, stepper mechanisms and whatnot. This is what I got. I specifically kept it 7 studs wide for easy integration with the chassis (between stringers), on the downside it's a bit tall. Other than size, the main advantage is that it just takes one PF M motor to operate, the driving rings are being kept locked by catches at all times, shifting works in full cycle - 1, 2, 3, 4 and 1 again, no "ends" - and it can be shifted by ear. No need to watch it, you just need to hear two "clicks".

The only disadvantage I can see is that 3rd and 4th speeds add a lot of friction because of how the gears are arranged. But all in all, I think this is one of my most practical designs.

Instructions: http://sariel.pl/downloads/

Edited April 2, 2015 by Sariel

[Nalyd997]

That is pretty cool! You seem to be having a mechanism stage, but I like it!

[Coola1]

Awesome gearbox, twice as compact as anything I'd be able to make! Sucks I dont have the new driving rings, they make things so much easier.

[Kiwi_Builder]

Looks great Sariel, does this gearbox work with the old driving rings and clutch gears?

[Sariel]

Sure, you just need to add half-stud thick beams as spacers.

[Captainowie]

Very nicely done.

[Kiwi_Builder]

I have created a version of this gearbox using the 2 wide driving rings, and have an LDD file download in topic:

http://www.eurobricks.com/forum/index.php?showtopic=107304

Full credit to Sariel's design and enjoy the gearbox

[DrJB]

Very nicely done, as always coming from Sariel.

If I understand the build correctly, the 'operator' knows there is a gear shift after he/she hears 2 clicks. Then, the operator must be careful to start/stop the motor at the right 'time'. Is there a way to add (maybe a servo-motor) so that every motor actuation does only one complete gear shift i.e., rotates the 24 tooth gear by exactly one fourth of a revolution. I seem to remember a build a long time back where the author did something similar, but the gear shift was manually actuated.

Still, a very nice contraption that opens up many opportunities to build upon ... in my humble opinion only, naturally.

Edited March 23, 2015 by DrJB

[Jeroen Ottens]

Very nicely done, as always coming from Sariel.

If I understand the build correctly, the 'operator' knows there is a gear shift after he/she hears 2 clicks. Then, the operator must be careful to start/stop the motor at the right 'time'. Is there a way to add (maybe a servo-motor) so that every motor actuation does only one complete gear shift i.e., rotates the 24 tooth gear by exactly one fourth of a revolution. I seem to remember a build a long time back where the author did something similar, but the gear shift was manually actuated.

Still, a very nice contraption that opens up many opportunities to build upon ... in my humble opinion only, naturally.

This looks like a solid, well functioning gearbox.

For my Alfa I tried to make some kind of a ratchet mechanism driven by a servomotor. If the servomotor turned right, it would push a knobwheel a quarterturn. When turning back to neutral the knobwheel wouldn't be caught by the ratchet, thus staying in place. I had very little room to build in, so in the end I went for a similar solution as Sariel has chosen: a geared down M-motor to do the shifting. I only added a spring system to have preferential positions for the levers so that you are not too sensitive for the exact position of the motoraxle.

But given a bit more space I am sure it is possible to make a servodriven, ratchet-based RC gearbox.

Edited March 23, 2015 by Jeroen Ottens

[Lipko]

There are plenty of those mechanisms, I'll try to look them up when I get home. I'm also working on a selector mechanism, it's very hard to make it tidy, small and reliable at the same time. I have already given up on the small part, luckily I will have enough space (manual model with middle engine, rear remote gearbox setup, so plenty of space between the two seats without anything else to go there)

[DrJB]

This is the one I was referring to.

In fact, I even built an LDD model of it, that you can get from below

Sequential GearBox.LXF

Not to hijack this thread but, I wonder if Sariel's motorized version can somehow be adapted here.

PS. I do not know who the author of Gearbox is. Certainly it is not mine. I only did the LDD/LXF file.

Edited March 23, 2015 by DrJB

[snot]

Wow.

LEGO technic has an extremely niche audience which means most people will never see or appreciate this.

I feel lucky in the nerdiest way possible.

[Tommy Styrvoky]

I may find a use this concept and compact this gearbox in parallel, for a tank.

[Ode]

Quik question for about this changing mechanism:

I have built a version of the gear box using the old style driving rings and I noticed that there is a point in the shifting cycle when both driving rings are connected, thus the gearbox is locked.

Does this occurs with the new driving rings?

Or

Did I did something wrong while building?

[Thirdwigg]

Great contribution Sariel. It's a simple design that works flawlessly. Great work, and thanks for sharing.

[Lipko]

Quik question for about this changing mechanism:

I have built a version of the gear box using the old style driving rings and I noticed that there is a point in the shifting cycle when both driving rings are connected, thus the gearbox is locked.

Does this occurs with the new driving rings?

Or

Did I did something wrong while building?

The main possible issue with this method jugding by looking at it (I haven't tried it), is that the system seems to rely on the double roller mechanism to snap into the discrete positions.

That's why I'm experimenting with a different, but more authentic method, something based on this:

EDIT: I am wrong, the Lego solution can also work, but things have to be perfectly positioned with perfect geometries.

wrong theory:

The main difference between the real solution and the aforementioned Lego

solution, is that a pin is in contant with the pushing/ratcheting part (the

double hook-like thing) all the way through the switching action, making sure

that the gear selector wheel turns perfectly into the new discrete position

(even without a separate discretizer mechanism). With the Lego solution, the pin

has to get out of the way of the pushing part (the double bionicle-tooth thing),

or else this pushing part would rotate the selector wheel back when the pushing

part turns back to its neutral position (or more likely the mechanism would

simply jam: the other bionicle tooth would jam against the pin). So it needs a

separate discretizer mechanism.

I hope that's clear...

EDIT: you do

need a discretizer, because you can still make an intermediate state with the

selector wheel by not pushing the arm to it's end positions during gear

switching. But I hope you get the idea.

But the prblem with your build may be that the system has too large backlash, or you forgot to gear the ratcheting mechanism up with exactly 6:4 ratio (24 and 16 -teeth gear).

Edited March 24, 2015 by Lipko

[Sariel]

Quik question for about this changing mechanism:

I have built a version of the gear box using the old style driving rings and I noticed that there is a point in the shifting cycle when both driving rings are connected, thus the gearbox is locked.

Does this occurs with the new driving rings?

Or

Did I did something wrong while building?

It never happened to me. The position of 2L beams rotated by the 24t gear is crucial - they should be rotated 90 degrees apart from each other. It sounds like you made them 180 degrees apart, check it.

Great contribution Sariel. It's a simple design that works flawlessly. Great work, and thanks for sharing.

Thanks, I'm still trying to come up with some solution to the friction problem. Solving it requires rearranging gears, which in turn would require different shifting pattern that this control mechanism can't handle.

Edited March 24, 2015 by Sariel

[TheNextLegoDesinger]

just what i needed.

Thank you

[Ode]

It never happened to me. The position of 2L beams rotated by the 24t gear is crucial - they should be rotated 90 degrees apart from each other. It sounds like you made them 180 degrees apart, check it.

I made sure that they are at 90 degrees, still did the locking.

I have changed the 2 Technic 2L liftarms with pin and axe with pulley wheels to have more angle possibilities, it still didn't work.

Back to starting point, I will have to redo the whole assembly.

[TheNextLegoDesinger]

I made sure that they are at 90 degrees, still did the locking.

I have changed the 2 Technic 2L liftarms with pin and axe with pulley wheels to have more angle possibilities, it still didn't work.

Back to starting point, I will have to redo the whole assembly.

make sure that the left is full forward en the right full down, if you look from behind the M motor

[DrJB]

The other possibility for one making an easy mistake in the build is that the beams that connect to the gear changers have length 6L. One could use 5/7 by mistake, but in fact they are 2x thin liftarms of length 6L.

Better yet, can you post a photo of what you built? that way we can help you quickly diagnose/rectify the issue.

Edited March 26, 2015 by DrJB