[HELP] Generic Building Help Topic

[Carsten Svendsen]

  

8 hours ago, m00se said:

Looking for some help: I need a gearing mechanism with one input, one output; if you switch direction of input then not only direction of output changes but also its speed. 

 

Maybe the new One-Way 20T gear (https://rebrickable.com/parts/114913c01/technic-gear-20-one-way/) could help (the back gear of the racing bike); maybe it can be done with differentials, ... I don't know, any idea welcome.

It's simple if you don't need power transmission. Just put a gear on a floating beam, and have two outputs, then link them back together.

 

Otherwise, just use two differentials with a simple directional gear stopper on both (but opposite sides of course)
I wanted to do an illustration with a 3D model, but actually, I forgot how it goes together, so sorry, I can't help afterall. I have no access to my LEGO atm. Also, using Studio is just the worst, I swear that if I win first prize in lotto, first thing I'll do is hire a team to rebuild what Sergio had with SR3D Builder. At least that program was easy and intuitive to use.

Edited July 26 by Carsten Svendsen

[ginger-snapped]

6 hours ago, Carsten Svendsen said:

It's simple if you don't need power transmission. Just put a gear on a floating beam, and have two outputs, then link them back together.

The first 2 sections of this video show a good example of it, especially the one I time-marked. A version of this with some gearing between the outputs should work.

 

 

 

[Carsten Svendsen]

18 hours ago, ginger-snapped said:

The first 2 sections of this video show a good example of it, especially the one I time-marked. A version of this with some gearing between the outputs should work

In all actuality, it's the very last option that he wants to look at. That's what I was remembering with, but it's only one diff, not two. And by default, it has a built-in gear ratio. 
1:1 straight through, and whatever you want on the actual hub, you've got many options

[ginger-snapped]

18 hours ago, Carsten Svendsen said:

In all actuality, it's the very last option that he wants to look at. That's what I was remembering with, but it's only one diff, not two. And by default, it has a built-in gear ratio. 
1:1 straight through, and whatever you want on the actual hub, you've got many options

I thought about suggesting that one, it's where my mind first went when reading his post. It may be more reliable and simpler with built-in gear ratios, but it probably would add a decent amount of friction/resistance from the ratchet, which may or may not be a problem.

[TomSkippy]

Here's the motion I'm thinking of. From the start position, theres a rotation to #1, then it continues to #2. How can I do this with one rotational control?

Note: I'm trying to have a hidden object appear. This will go from start (horizontal) to vertical.

Edited Tuesday at 07:02 PM by TomSkippy

[2GodBDGlory]

Hmm, that's not a trivial question. With a single control, I think I'd be looking at having some kind of rubber band making the second stage deployment more difficult, and then some kind of differential-type mechanism that has the option of driving either stage, but will take the path of least resistance. That way, your rubber band on the second stage makes that the harder option for it, and it will only deploy when the first stage hits some stop. Implementing that still sounds tricky, though. Pneumatics could be a good solution, but might complicate your model more than you want. Otherwise I would look into mechanical differentials, but then getting drive up to the second stage might be tricky

[2GodBDGlory]

You got me thinking, so here's a prototype for ya! @TomSkippy

I had mentioned a rubber band previously, but I was able to get reliable motion with the simpler solution of just using friction pins on the two red gears. The only difference is that it doesn't retract in the same order that it extends; moving to a rubber band would make that happen in the same order, which may be necessary for your build--I just didn't find an easy way to implement that on this mock-up.

Is this what you're looking for? I hope it helps!

Edited Tuesday at 10:22 PM by 2GodBDGlory

[TomSkippy]

@2GodBDGlory Incredible! Exactly what I was hoping for. Going to build around it and see. Thanks so much! 

[howitzer]

I'm trying to make a structural connection with the following parts:

And I was wondering if there are any alternatives to the green part in connecting the grey parts. The bushing-style end in the green part allows for the pink gear to pass cleanly and this particular part was the only one I could think of that had bushing-style end with another pinhole parallel to the axlehole right next to it to allow the connection.

[Lipko]

2 hours ago, howitzer said:

I'm trying to make a structural connection with the following parts:

And I was wondering if there are any alternatives to the green part in connecting the grey parts. The bushing-style end in the green part allows for the pink gear to pass cleanly and this particular part was the only one I could think of that had bushing-style end with another pinhole parallel to the axlehole right next to it to allow the connection.

Are there any space constrains? In what directions the structure needs to sustain pulling, twisting, etc. The problem seems trivial. Can't you use the opposite side of the frame? With a 2x4L beam?

[2GodBDGlory]

3 hours ago, howitzer said:

I'm trying to make a structural connection with the following parts:

And I was wondering if there are any alternatives to the green part in connecting the grey parts. The bushing-style end in the green part allows for the pink gear to pass cleanly and this particular part was the only one I could think of that had bushing-style end with another pinhole parallel to the axlehole right next to it to allow the connection.

That is the only part I've ever come across with that combination of bushing-style axle hole followed by another parallel hole, yeah.