Unlimited pneumatics

VEX Robotics Competition Discussion VRC
1

I have been pondering as to why there is a limit to the number of motors allowed on a robot, but no limit to the number of pneumatic cylinders allowed on a robot. There are probably several reasons for this.

  • to encourage more teams to use pneumatics?
  • the weight penalty of pneumatics could be considered the limiting factor, so no stipulated limit is required?
  • the Cortex will not easily handle more than 10 / 12 motors?
  • motors numbers are limited to keep team costs manageable? Not sure why pneumatics would not also be considered in this manner?

The common power sources for motion on a robot are:

  1. Motors
  2. Pneumatic cylinders
  3. Rubbers bands

Motors are limited in number while pneumatic cylinders and rubber bands are not. Does this mean that pneumatic cylinders are considered to be more closely aligned in performance to rubber bands than to motors? :slight_smile:

I am interested as to what people think about allowing unlimited pneumatic cylinders but only limited motors. To keep things simple, I am disregarding the number of pneumatic reservoirs and only considering the number of cylinders as they are providing the motion. Poll options are:

  1. Infinite motors and infinite cylinders (open slather).
  2. Limited motors but infinite cylinders (status quo).
  3. Limited motors and limited cylinders (bring in cylinder limit).
  4. Add motors plus cylinders to a combined limit where 2 cylinders = 1 motor (team decides how to balance between motors and cylinders)
2

I’m for a cylinder limit. Probably 2 would be the right number. Alternatively, there could be a limit on pistons, since a cylinder limit would be similar to the current battery limit.

I think more than a weight penalty is necessary, at this point pneumatics give too much of a purchasable advantage to the wealthier teams.

Sidenote, if rubber band limits begin to be enforced I might just cry.

3

I think it should be kept the way it currently is. With pneumatics, there are real engineering tradeoffs (weight, pressure, etc). I believe it’s been self-regulating. There’s a good reason we don’t see robots pushing the “reasonable” amount of pneumatics. On the other hand, there aren’t nearly as many tradeoffs with motors (other than space, which doesn’t really count).

4

When Torque refers to cylinders he is speaking of the pistons and ignoring air tanks (reservoirs) because the motion isn’t coming from them.

I personally love pistons but their is a trade off. No offense to 12A-G 7033 or other 12 clones but who was in the finals at worlds. If pistons were free power than we would have seen more successful teams using them. In the finals at most teams had 3 pistons.

Adding 4.5 pounds (9 air tanks) to a robot is a huge thing to consider and decreases the efficiency of the whole design especially the power needed to move the robot. Pistons aren’t free power. At most they are

A A lazy mans way to activate mechanisms that rubber bands could do
B A way to break up the power so instead of 10 sources of power we have 16. These 16 can be then sorted into what is required for a mechanism by number of uses and strength.

5

Acting off of impulse, I chose both limitless. Not because of lazy building and I want everything motor powered, but because of the new challenges with electricity that will arise. But thinking a bit longer, I believe this would favor better funded teams, despite the challenges they would face when building.

As for pneumatics though, my team cant afford them. As a result, I can’t give an accurate judgement regarding those systems.

6

I’d rather see a total stored energy limit before match start and leave it up to teams to decide how to spend their energy budget. The game rules could for example define how much energy each battery, pneumatic reservoir (@100psi of course) and #32 rubber band can store. Other energy storage such as part deformation would by rule require documentation to be presented during inspection along with a standard energy budget sheet.

For arguments sake lets say each battery = 1.0, pneumatic reservoir = 0.3 and rubber band = 0.01
If the game rules allowed for a total of 3.0 you could have 3 batteries and zero other energy storage devices. If you wanted 6 pneumatic reservoirs you could only have 1 battery.

Limiting motor count and pneumatic cylinders really only limits the energy output. Capping the energy input would expand the possible engineering solutions available whilst constraining teams to ensure a level playing field. You could probably tweak the limit based on division too i.e. middle school 2.0 high school 3.0 VEXU 4.0 for example.

Interestingly I’ve been advocating for stored energy limits in FLL as teams that start a match with primed pneumatics and rubber bands do have an advantage over those that just use motors and mechanics. IMO teams should be priming these additional storage systems during the 2.5min game but of course this wouldn’t work for VEX!

7

Just to keep the thread coherent when you say cylinder you mean air tank or reservoir right?

8

yeah, too many late nights. will edit the post now

9

No… please not. This would get way too complex way too fast. Any part deformation at all (including a ziptie that brushed up against the floor) will store energy. Also, not all rubber bands have the same energy storage capability, and this capability decreases as the rubber band is stretched out over time.

Regarding the pneumatics specifically:
I don’t think they should be limited at all. The weight and size requirements make them virtually self-regulating. There’s also not much of a safety risk with allowing unlimited pneumatics. However, with motors, there is a safety risk to the Cortex–too much current draw could damage (or temporarily disable) the microcontroller.

10

I agree that pneumatics are basically self-limiting, at least for normal robots. I think that elastics are actually a much better way to store energy, and that pneumatics just allow for additional control. Of course, the real reason I don’t want to limit pneumatics is because I want to see the robot that has 12+ pneumatic reservoirs (think 76’s Clean Sweep super catapult, but capable of firing several times).

11

I fully endorse not limiting the pneumatics, only because our 24" cubed robot at Worlds this year used 9 pneumatic reservoirs and was an adapted 12A bot.

But really, pneumatics in VEX have natural limitations from a variety of different aspects.

12

Theoretically 10 energized pneumatic solenoid valves is the limit for current on the 5V supply.

The rules are what they are and there has been no suggestion that they will be changed anytime soon, however, I would like a limit on pneumatics just as a way of keeping costs down, perhaps 2 kits max, 4 pistons and 2 reservoirs. That’s over $400 and more than the cost of all 10 motors and controllers.

13

Thanks Tabor. Sorry if I have confused with using the term cylinders, but this is what the pistons are called in the Vex Store. Cylinders = pistons and Reservoirs = air tanks.

I don’t think you can say that robots using multiple pneumatics systems were inferior in Sack Attack because none of them reached the final. In reality, among all the robots at Worlds, there were very few that had more than 1 pneumatics kit fitted (probably because cost of doing this is quite prohibitive), so by shear weight of numbers plus the large amount of luck required to reach a final, these robots had little chance of doing so. If 12A had not made an error in over farming, which lost them a qualifying game, things could have gone very differently for them. Interestingly, of the six robots in the High School final, 5 had pneumatics kits fitted and the one that did not, 2941D, would have had if the budget had been somewhat larger.

Yes 9 air tanks is a lot, but what about 2 or 4 air tanks? 1 reservoir is quoted at 0.68 pounds weight, so it is slightly lighter than a 3000 mAh battery. Again, it is interesting that batteries are limited to 2, but reservoirs are unlimited.

Due to Toss Up including hanging as a reasonably well rewarded endeavor, the weight penalty of using multiple pneumatics in this game is much greater than it was in Sack Attack or Gateway (no hanging required). In Sack Attack or Gateway, the optimum weight was probably around 18 pounds (still run 1.6:1 drive but lessen being pushed around) so a reservoir or 3 was probably ideal ballast (if you could afford them) :slight_smile: and opened up a lot of possibilities.

For example, in Sack Attack, 2941A post APAC was fitted with 2 pneumatic cylinders to assist the lift. The lift was then able to use 3 motors at 7:1 ratio, which allowed a second motor to be moved to the intake conveyor, which allowed the conveyor motors to be changed from torque gears to speed gears, which made a massive difference to how the robot picked up sacks.

After sleeping on this one, I have decided to vote for the combination limit. I think the limit options could be:

12 motors + no cylinders or
11 motors + 2 cylinders or
10 motors + 4 cylinders

So no more than 12 motors (if no cylinders) and no more than 4 cylinders total. I think this would help to lessen the advantage that teams with unlimited budgets currently have.

I see no reason to have a different motor limit for VexU. Having more motors allowed, makes designing easier - it should be harder for College teams!

Cheers, Paul

14

After giving this a lot more thought I have slightly changed my viewpoint. Pistons are free controllable power BUT not as much as one might think. They give a big benefit for a considerable cost. This is only true when used in “worthwhile” applications. Some teams that used pistons when rubber bands could have been used could have had better robots if they had used rubber bands because of load on the drive motors.

I try to use the names off of the Vex Store as well but just wanted to make sure the thread was coherent for people reading this thread later. :smiley:

The piston/motor limit you suggest would be very very interesting. I would be so scared building a robot. It would force all of us to use our power as efficiently as possible. Teams that used a piston to deploy their intake once would be outraced by robots with more motors on the drive train.

I have a question for you Paul. If motors were unlimited how many do you think you would use?

15

I’ll answer the unlimited motors question. This year I would probably end up using 14 or 16. I could see 8 motors on the lift being feasible since a full load would rarely be drawn because you wouldn’t be driving while hanging.

6 motors on the drive as well. I wouldn’t go any faster than 1:2 (favoring speed) on a drive with the zones being so small and some power being needed to go over the bump.

16

:eek::eek::eek::eek::eek: Why in the world do you need 8 motors?

17

5:1 hanging with a 6 bar/chain bar? One of our teams is using 8 motors to hang, but thats with a transmission from the drive and about 20 pounds to lift.

Also, Tabor’s question is kind of a perfect world scenario. I can’t really see any arguments besides power draw and added weight against using motors to effectively replace torque. You should need about half the gear ratio if you double up motors.

18

Clearly you can’t use more pneumatic parts than you can fit into the robot’s size limits (so they’re limited by volume if nothing else).

I think a rule limiting pneumatics would be really annoying, like the rules in Round Up and Gateway that limited us to using 4 393s. Pneumatics are incredibly useful and there is so much that can be done with them if the teams are smart enough.

As for the funding issue, a lot of high-level teams are able to fundraise and/or get businesses to sponsor them. And if you want to limit parts because they are too expensive for some teams, imagine if robots were limited to a small amount of aluminum… :frowning:

19

Think bigger mwuahahahahahahahaha
I would probably cap off after having about 20 motors on my robot. Maybe a few more if I really tried.

20

I mean… we could always go the FRC route and limit the total cost of your robot to $4000 :p.

All jokes aside, that’d be fun to see the resourcefulness and how teams respond to the challenge with their design skills and engineering ability, but I personally wouldn’t enjoy it for our team.