[MOC] Compact gearbox with reverse

[BrickDesignerNL]

I'm working on a small model that needs to revers it's pattern when it hits the end, and again when it's at the start (like auto-reverse in an old cassette deck).

This is the first concept draft I made using only pieces from 51515-1 and no clutch gears and driving ring, and utilizing the "double bevel" feature of the gears.

Resulting in a 2.5L instead of 5L gear width.

How it functions

The long axle turns, the 12 gear double bevel on the yellow axle can be pressed in two sides, press left and it turns in the same speed and direction, press right and it will turn in the opposite direction of the black axle.

Part list and building instruction can be found here: https://rebrickable.com/mocs/MOC-65251/BrickDesignerNL/easy-push-to-reverse-gear/

TODO

I would like the reverse to turn in the same speed as the forward. - so size will change

Edited February 6, 2021 by BrickDesignerNL

[rasikaa]

Nice and compact design. Love the use of the new parts.

However, coming from a GBC background, I hate to see gears that are not re-enforced and prone to slipping out. The free 12T gear on the top middle enabling the reverse can easily slip off the pin-axle when you keep moving the yellow axle back and forth. One suggestion would be to use a 4L axle with stop and have a bush on the outside to keep it from pulling out.

Rasika

[higgins91]

something is wrong, there is a 20T on one side and a 12T on the other, how can the mobile 12T engage in the right 12T?

[rasikaa]

There is another 12T gear that allows the reversing. The instructions show it.

R.

[higgins91]

ha yes, with the angle of the image I had not seen the other 12T!
sorry

[BrickDesignerNL]

On 2/7/2021 at 1:22 AM, rasikaa said:

Nice and compact design. Love the use of the new parts.

However, coming from a GBC background, I hate to see gears that are not re-enforced and prone to slipping out. The free 12T gear on the top middle enabling the reverse can easily slip off the pin-axle when you keep moving the yellow axle back and forth. One suggestion would be to use a 4L axle with stop and have a bush on the outside to keep it from pulling out.

Rasika

Thank you Raskia for the feedback.Would the 3L axle with stop and a 1/2 bush give enough stability as well, in your experience?

And looking at it differently; would the pushing of the yellow axle to the right help to enough re-ensure the 12T gear into it's position on the axle pin? Or your experience is that such would not be sufficiently in durable operation?

 

Thank you very much for the suggestion and feedback.

 

On 2/7/2021 at 6:05 PM, higgins91 said:

ha yes, with the angle of the image I had not seen the other 12T!
sorry

Thanks for that feedback, I'll look for better angles next posts!

Edited February 8, 2021 by BrickDesignerNL

[Horologist]

Great idea, I have one question: If only the bevels are meshing, then wouldn't the 12T gears feel a force pushing them apart along their axles when rotating?

[BrickDesignerNL]

19 hours ago, Horologist said:

Great idea, I have one question: If only the bevels are meshing, then wouldn't the 12T gears feel a force pushing them apart along their axles when rotating?

I think you've nailed it!

 

This is an extended model; just adding a 1/2 bush between the 12T & 24T gear (it becomes wider, so fixation and yellow axle changed as well)

This introduces the "free gear" in the middle: 

When put on a flat table no-matter in what position the gear on the red axle starts, when you start spinning the 8L axle, the gear gets to the center and stays there, the faster you spin, the faster it tries to move away from the other gears.

And then re-tested with the first build; evolves to locking.

So in short; you have to continuously keep pressure on one of the ends of the red (yellow in the initial post) axle to keep the gear in place.

 

So the ends of the red (yellow) axle acts like a switch: when the axle is pressed it starts moving until the pressure on the switch is gone or weak enough to resist by the rotational energy that wants to move out the gear.

Building instructions can be found on rebrickable.

Edited February 9, 2021 by BrickDesignerNL