Is it worth it to have a retractable intake powered by pneumatics if we don’t intend on using pneumatics elsewhere? I heard that it isn’t worth it because pneumatics is heavy, but our team isn’t sure how else to do make the intake quickly retractable.
7 Likes
I think the reliability of pneumatics done properly is worth the additional weight.
17 Likes
This is something I have been thinking about recently as well. We haven’t used air on our robot since 2018, but our intakes have retracted painfully slow. I wonder how light we could make the whole air system so we can use it just for the intake.
1 Like
As long as you have the weight and are confident in your ability to setup pneumatics right, then I say its worth it. They’re reliable and one of the quickest linear actuators. So if a retractable intake is important to your design then I say go for it. Plus, it means down the road if you need to actuate another mechanism, you already have the bulk of the pneumatics setup so it leaves you with a lot of options.
That said, don’t feel like pneumatics are necessary for a good robot just because so many teams use them. They can be difficult if you’re new to them and I always find it a pain to charge them before every match.
Really the gist is, do whatever you’re comfortable in your abilities to do and what you think you need for your design to function like it does in your head.
2 Likes
I don’t think there’s an obvious answer here, especially if you found you were close on weight this season. If you have weight to spare (or even if you don’t given you have no more in-season competitions) I would say go for it. If nothing else, it’s a good learning experience if you’ve never done them before. I personally like pneumatics a lot, and so at the beginning of the season usually operate under the assumption we will use them. Knowing ahead of time makes it a lot easier to implement.
8 Likes
Pneumatics are a reliable way of doing that. But, they’re not the only way. For example, you could put a sprocket on the intake arm and use chain to rotate the arm. You could use gears similarly. You could have the intake be spring-loaded. You could use a rack and pinion or a lead screw. You could use gas struts.
Weight is one of the things to consider, but bulk is another – between the compressor and storage tanks and valves and solenoids and the cylinders.themselves, pneumatics just use a lot of space.
3 Likes
In my opinion it would not be worth adding pneumatics for that one function.
To motorize an intake, gear it to be really fast and then use current limiting to make sure you don’t melt any motors. You don’t even need any limit switches or encoder values, just run it full speed out to deploy (limited to 5-10amps) and full speed in to retract (again, limit to 5-10amps).
This is my favorite intake mechanism I’ve worked on in a partially assembled state. It used this concept and worked beautifully. 2020 wasn’t a good year so we never got to use it on a field.
3 Likes
Space is a good point. Especially because not only do you need the space for everything but there are rules about where you can put things. The most annoying is that you need a release valve and pressure gauges in an easy to see and access place, otherwise you won’t pass inspection.
2 Likes
AND so you can troubleshoot your robot, which should be an even higher priority. Please note that your robot doesn’t need to “work properly” to pass inspection.
2 Likes
Rather that use pneumatics for our retracting intake this year we used a motor. To drive it we used poly-cord belts. Tensioning is a key part of that strategy. Just enough so that it won’t slip when doing the normal actuation but enough so that it can slip during an impact to prevent damage to the drive mechanism.
A single motor turns a jack shaft near its middle and a belt on each end of the jack shaft drives the intake arms so they stay in sync.
Much lighter and more compact than a pneumatics system.
1 Like
The “easy to see” standard is maybe not as hard as you think. You can see one of our gauges in the lower right of this photo just above the front wheel.
We had so much woe from our previous robot’s motor&chain positioned intake that we switched to pneumatics this year. It turned out to definitely be the right choice for us. Impacts that would have easily broke the previous intake have been shrugged off time and time again. Plus when we found we needed a locking mechanism for our climber having pneumatics already on board made that super easy.
3 Likes
Whatever your decision on implementation, please be sure your intake is retractable and that it can be done quickly. You want to avoid G204 penalties.
1 Like
We managed to accomplish the same thing through a custom friction clutch, on an intake that looks very similar. That’s one of the things I love about FRC - there are a million ways to accomplish a simple task like actuating an intake, and none of them are “right” or “wrong”.
Personally, I wouldn’t do pneumatics for a single actuator, but if I can use it in multiple spots, and can make some things simpler!
3 Likes
Thanks for your response! What makes pneumatics more durable than a motor and chain?
Thanks for your reply! Does the custom friction clutch use pneumatics? Also, are there any good resources on how to use one?
What would you say is the best way to make a fast retractable intake? (given that the robot won’t be overweight and has plenty of space?)
Nope, no pneumatics. A sprocket with a thunderhex bore (13.75-ish mm… our lathe doesn’t have a good readout for that) squeezed between two metal shaft collars. The shaft turns the shaft collars, the friction between the shaft collars and the sprocket turns the sprocket (and, in turn, the intake). Adjust the bolt on the end to increase/decrease the friction to the desired point - it helps with the PID loop for raising the intake (encoder on the rotation shaft, not the motor shaft), as the clutch starts slipping when the intake moves too high, and it lets the intake fold in when hit (and the PID loop then sends it right back out).
Pictures below are for a “demo” unit we made for talking to judges. We ended up putting a thumb bolt on the end instead of the regular socket head bolt, making it easier to adjust the tension by hand and feel the difference in friction!
8 Likes
We included pneumatics to actuate our intake and also to switch on/off a climbing winch versaplanetary ratchet. The latter ended up not being reliable, despite efforts to tune it, so we went a different direction… leaving just the intake.
It worked well. Beyond that, the biggest benefit to us is probably just that we re-learned how to do pneumatics again and gained confidence. If I could go back in time, I’d probably do it again. But I would like to try the motor power option to compare/contrast now that our season’s done…
Question to those using motors to actuate their intake: I often see a common axle with that approach. Necessary?
It entirely depends on the design. Our 2020 robot had one - the same axle used to pivot the arm had wheels on it that spun independently to help move the balls. Our robot this year did not.
Necessary? No.
Advantageous? Often. Kills two birds with one stone, saves a little weight, and let’s students learn the meaning of “co-axial.”
1 Like