Hey!
I have been working on a design and it needs a reversal on the monition of the pneumatic piston. If the piston is out, I need to have have a way of converting that motion backwards as simple as possible. Same thing if the piston is retracted, I need to have to motion going forward.
Essentially, I was wondering if anyone knew of a relatively simple mechanism to make a standoff l move in the opposite direction of where the piston is moving.
Well, the “piston” is inside the air cylinder. If you can post a quick sketch showing an air cylinder along with a depiction of the motion you need, perhaps the group can help a bit.
bro, nobody cares if someone calls it an air cylinder or piston, it gets the information across.
Hey Bro, as both an engineer and educator for nearly 35 years, I think that students should learn proper technical terminology, even while in school. Once they leave the little bubble-world of VEX robotics they’ll see that in all of industry, air (or pneumatic) cylinders are proper terms for these actuators; therefore, I will continue to use proper terminology in my postings.
I do, and I agree with @kmmohn. Getting the correct terminology will help in the long run. It’s a good initiative to use proper terms, especially taking it into perspective when you’re speaking to judges or writing/typing this down in to the notebook. Yes, it may get the information through, but it’s good practice to get the information through correctly. I by no means want to argue disrespectfully, but I am just saying that correct terminology is a good thing and it is a good habit to build.
While the proper-terminology speech from kmmohn was appreciated, it did little to answer the OP’s question. One way to do so would be through the use of gears and racks. Racks are the linear gears. Below is a screenshot of what I mean.
One of the racks could have a pneumatic cylinder, whereas the other could have the standoff.
That’s a cool application, but there is a simpler way.
Gears and linkages are both great ways to do this. I want to know why the OP wants this. Is it because they think they need to start retracted for example? Is the true problem wanting to invert the direction of motion?
I need to start extended and then retract to close a claw. I also need to be able to open and close it as needed. The claw just has to have the Air Cylinder starting extended and have the claw close when it is retracted.
If you have double-acting cylinders, you can start with the cylinder either extended or retracted: just swap the air lines. Double-acting cylinders are always pressurized during operation.
If you have single-acting cylinders, you’re stuck with “retracted” as the “off state” (which is why we like double-acting better!)
Ya you can just switch which tube goes to which end of the cylinder and it flips the default state of the cylinder.
That’s exactly the answer I was expecting and makes the other posts obsolete.
I agree with this post in general, however I will say that some of my teachers have used the word “piston” and “air cylinder” interchangeably in classes. Also, as a counter-point, we still use the term “flex wheel” instead of “compliant wheel”. Flex wheels are VEX-branded compliant wheels (although they are a relatively niche product).
@LEVIathan Are you using a single acting or double acting air-cylinder? If you are using a single acting cylinder, you should consider using a double acting cylinder that can both extend and retract, or consider another method to retract the cylinder, such as rubber bands. Since you are using a claw, I would recommend building your robot such that when you extend the cylinder, the claw opens, and close the claw with rubber bands (If using a single acting cylinder).
See this article for more information about pneumatics that should help you see what type of cylinder you are using, and to double-check that you have connected your cylinders correctly.
I am using a double acting.
Yes, I would be using double acting.
Crank and slider mechanism?? this would work similarly to a car engine. To make it spin more consistently, add more air cylinders firing periodically but asynchronously. To make it spin further, use one. Then, this rotary motion can be converted to linear using a rack and pinion. The correct term for the air cylinder motion is Reciprocating. Essentially, what I am saying is Reciprocating → Rotary → Linear.
