Mechanics and Construction > Mechanics and Construction

Using two servos for two DoF but the strength of both...

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Fredrik Andersson:
I got this idea about a year ago for a science fiction drawing i was working on, and now when i got into robotics i started to wonder if it works, and if it works well in reality. Not sure if it is already done, but thats why im asking.

The main feature is that you can use the strength of two servos for two different directions. The mechanic also allows an 2 DoF arm to be completely in water, if you can work out to keep the two servos outside the water.

Ok, lets get to the picy picy:







So, if the servos roll in different directions compared to each other, the middle pin will roll and if the servos roll in same direction compared to eachother the whole mechanics in the midde will roll... meh, i hope you can see how it works...

I tested it in LEGO, and it seems to work well, the only concern i have is that the coggs on the gears will have to hold all the weight of whats connected to the middle pin...

Gertlex:
I like this :)

You'll probably want to find some good bevel gears somewhere... It might be tricky to find some that can easily be connected to the servos though.

HDL_CinC_Dragon:
I can easily see that the servos moving in opposite directions will indeed help each other disperse the workload between them thus be able to hand higher loads... but what dont see is "if the servos roll in same direction compared to eachother the whole mechanics in the midde will roll"

What do you mean by that? Based on your CAD design there, it looks like the servos would just battle each other and fry themselves...

And I also agree with Gertlex, you would be best off if you found some Bevel gears. Im sure you would be able to find some in a google search fairly quickly. Maybe even try ebay! And about attaching them to the servos you could probably just super glue them to one of the servo horns that hopefully came with your servos... or maybe just order some from the manufacturer of your servos... would probably only cost you shipping...

But the setup your CAD design shows, if your servos traveled in the same direction relative to eachother, they would probably fry themselves...

Ro-Bot-X:
I understand this design easily, because I have used it many times with Lego.

The thing that is not obvious at first glance, is that the U shaped piece is NOT fixed to anything. Actualy it should be fixed to the top, big U piece. So, the pieces can rotate around the servo's shaft. Now if both servos rotate in the oposite directions, they will be blocked, so all movement will be transfered to the U shaped pieces and they will rotate around the axis going through both servos shafts.

Try Servocity.com for servo (external) gears and sprockets.

HDL_CinC_Dragon:
Im just not seeing the room for movement... are there then slots in the |_| shaped component behind the servo horns that allow it to move away from the shaft?

Sorry im not understanding what you mean :-\

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