Is lifting worth it?

You can also connect multiple pistons to a single solenoid. I’m not sure what that does to the output strength of the pistons, though. Given enough elastics, you can get away with only one piston, as a release mechanism. You’ll have a really fun time forcing your lift down if you leave the elastics on, and you need to be careful not to put force on the piston perpendicular to the shaft. Also, a motor, since one piston costs 2 motors if you don’t use pneumatics anywhere else, might be a more viable option. If you have enough elastics, you only need one torque motor, geared, say, 1:15, or more elastics geared to 1:7 (make sure your motor can also fight the rubber bands to keep the lift from deploying when you don’t want it to).

Edit: I just saw the last sentence of the post above me. Ignore my first two sentences.

Back in Toss Up, one of the teams from my high school tried to build a mechanism to hang that used one piston as a release and rubber bands to pull the robot up. It was a dangerous amount of rubber bands to say the least–many fingers were smashed and jammed just setting it up for a match and it didn’t work too well. While rubber bands theoretically can store the energy required to lift a robot, it’s impractical to use just rubber bands. When used with either motors or pneumatics, rubber bands are extremely practical, more so with pneumatics than with motors because pneumatics and rubber bands provide a linear force. Not to say rubber bands are not used successfully with motors (most lifts in past years have used rubber bands and motors), pneumatics just seem like the better solution to this year’s problem. The lift has a one-time activation (assuming you’re not trying to elevate in autonomous, which actually might be illegal depending on design because robots can’t expand vertically til the last 30 seconds) that needs to be very fast and strong.

As a VEX U competitor, lifting is worth it. Theoretically, in order to achieve complete, undisputed victory, all you need is to score all your match loads, score 6 stacks, and high-elevate.

Our system is 6-motor drive, 3 shooter, 2 intake, 1 ramp. Like, once the field is clear, what do you do then?

VexU is different.
I don’t think that there’s any way a VexU team could go without a lift and do well.
VexU teams can design their robots to be completely compatible for lifting, so every team could easily make a quick little self deploying ramp. You can’t do that is high school, because a ramp will only work with specific configurations. Our E team made a ramp, but it never got a single lift at the last competition, because everyones bases were either different, or geared to be to fast.

You only asked if it was worth it. I’m not gonna lie, the mechanic is easier in VEX U since you design your 2nd robot, but if you asked if it was worth it, and it is. Ours sits above our bot (which is actually still in VEX HS/MS height vertically interestingly enough) and deploys in 1 second. Scoring all 32 match loads is 160 points, with High-elevate is automatic 210 points, why wouldn’t teams go for it?

As a referee/event partner for several events in Southern Cali, I can tell you that a lot of bots can just throw a ramp on, but designing your bot to lift/be lifted and deciding whether or not the trade-off is worth it happens in the design process. If you decide to do a ramp, remember that you can choose your alliance partner in the finals :smiley:

Having a specialized shooter/drivetrain intake robot with a lifting robot will overpower two robots that can lift. First off, an ideal alliance would only need 1 lifting robot. You only need 1 lifting robot in a match because you can only get the elevation points for one robot. Second, if both robots have a lift system, then one of those robots has motor/pneumatic/elastic power wasted on a lift system that could have gone towards the shooter, drivetrain, or intake

Accuracy is the quality or state of being correct. For example, if you measure the diameter of a 1 inch rubber ball with calipers multiple times by hand, you’ll probably get different values. You’ll probably get 1.1 inches, .9 inches, etc. Each time you run a program, you do the same thing. The program will run, and the robot will do what it is told with the best of its ability. If you are aiming for 45 degrees, the robot will compare it’s current value to 45 degrees. It’s motors will run until it thinks it reaches 45 degrees. How accurately, or how correct it is at getting 45 degrees is not dependent on the power of your drivetrain, it is dependent on how well written the code is. Now of course, this is assuming the drivetrain was physically capable of turning (consider a drivetrain with all wheels pointing towards the center of gravity). As for difficulty, tuning that turning code will vary by the robot. If you have a 30 pound robot that’s turning with a 8 motor drive base at full power, even if the robot tries to stop, the wheels will probably slip, forcing the robot to correct itself again. However, that’s an extreme case. You simply tune the PID values so the robot doesn’t have so much momentum to begin with, making it just as accurate as any other robot in the end, but the difficulty to do so is harder. This difficulty is different from a 10 pound robot with an 8 motor drive base at full power. The chances of the robot slipping are much lower, meaning the difficulty of tuning is easier. This will also apply with other holonomic drives.

Which may be true if there’s no power curve. But what I’m saying is that if you apply the right power curve, then their control becomes identical to their slower counterparts. Are you saying that even with a power curve that can identically copy the speed values of a slower robot for a majority of the joystick values, a faster robot’s control is still worse than a slower robots?

High elevation is above the field perimeter. The perimeter is 12 inches, so people usually think 12. However, People forget the thickness of the foam tiles, making it 10.5 inches plus or minus maybe .25" depending on how robots sink into the foam.

Ok, so you want to use a lever instead of a linear lift. However, you did your calculations assuming the force was only 6 inches away. In reality, your force will be located at a robot’s center of gravity. Assuming an 18" robot’s center of gravity is perfectly centered, that would be 9 inches away in addition to your 6, making the real distance 15 inches.

15 inches of a robot that’s at least 12 pounds would be 180 inch pounds of torque, meaning that you would need 15 pistons just to reach 12 pounds. Bringing friction into the equation, delrin and steel has a .25 coefficient of friction. 15 motors*.25=3.75 about 4 pistons to overcome friction. So you need 19 pistons to overcome friction of lifting a robot and the robot itself. Let’s assume the pistons apply 100% of its force since in a lever it would have to be angled anyway. If we don’t you would need even more pistons

However, at this point, you might as well make a pneumatic release, elastic lift

Have you tried this? From what I understand, a solenoid is always drawing current to either stay in position, or move away from a position. The moment you y-cable something you put it in parallel, making it draw twice the current. When you Y-off another Y-splitter you make it then draw 4 times the current. This will go on. Making a single port supply the needed current to run 6 solenoids will probably break a fuse

In the end, I think this is still a convincing argument that it would be better to strive for a specialized shooting robot

Is it better to be prepared to lift anyone or just hope that somebody else will be able to lift you? At regional tournaments, on strategy might be to pick the only other elevating robot at the tournament just so that no other alliances can have them.

Alright. I believe Holonomic drives slip less while turning than straight drives. And you don’t want your robot to take forever turning because you need it to be so accurate.

No, what I’m saying is that even with a power curve, the range of values from the joystick controls a more condensed wheel speed range on faster robots.

I was thinking more along the lines of a 4-bar lift. Also, why is the force located at the robot’s center of gravity? Could you not have supports that stand away from the robot (yet another use for pneumatics)? Also, that coefficient of friction can be reduced with a small amount of lubricant. And you’re forgetting that you can use double-acting pistons with rubber bands. Also, as I explained earlier, a completely elastic powered lift is very, very impractical.

Yes, actually I have tried it before. The robot that I took to worlds for Toss Up had a 5 piston catapult, originally all running off of one port until there was a rule change. Solenoids draw very little current.

Thank you for all of your feedback.
I’ve decided to go for a fast and compact low lift rather than divert resources away from ball scoring; And so that I do have more than just ball scoring.

Getting back to the original question, lifting is actually very easy to accomplish with pneumatics , meaning that it uses very limited resources and it probably worth it. The reason for this is that we are allowed to use an unlimited number of rubber bands, which store potential energy. Then, we can use pneumatics to release the rubber bands in a controlled way and lift the alliance, such as Shaun Weber in this reveal. Obviously this required a large amount of time to perfect, but in terms of raw resources, it only required 4 pistons. Teams can also build ramps that unfold with only 1-2 pistons that utilize the torque of the alliance’s drive base, although obviously they are not 100% compatible with randomly selected alliance partners. For teams that are already using pneumatics, finding the deployment mechanism of the lift is quite easy. For teams that are using 12 motors, consider cutting two motors. There’s really no reason to put 6 motors on a drive base or launcher unless it is designed so poorly that it requires the extra torque. If you are just putting the motors on to allow strafing, increase speed, or increase fire rate, there is a very low chance that this slight advantage will consistently grant you 50 points that lifting does. In terms of the time necessary to build and maintain an additional subsystem, consider having more meetings or working on the robot during a larger portion of your spare time. It’s pretty incredible how fast a dominant robot can be built if the team members are devoted to the robot, much less how fast one system can go up. Given how well teams rose to the challenge of skyrise, even in the first month of the season, lifting is nothing at this point in the season, with as many reveals as there are.

I can’t believe that I hadn’t considered having a completely elastic powered lift with a motorized or pneumatic actuator. That would dramatically streamline the process of making a fast low lift.
Sometimes you really do need 6 motors on a drivetrain. If you have a field ball scoring robot, then having a slow drivetrain is bad, but having a fast stalling one is even worse.
Now that a I’m thinking about elastic lifts, it might be possible to make a completely passive lift. That way, we could use 12 motors for our ball scoring components. Or we could have it deployed by our first intake stage rotating backward.

This is an interesting thread and the answer to the question is quite different at this late stage of the season compared to earlier. In the earlier tournaments, teams could actually win by just shooting their pre-loads and driver loads. That was enough. Then things evolved where after shooting the driver loads, teams went out to score more balls. Now, the best teams are clearing the field first and after everything is cleared, going back and shooting driver loads. By the way, this is the strategy I had predicted would be the go to strategy by late in the season.

We now see matches where every ball is cleared from the field and all driver loads scored with 20 to 40 seconds left in the match. The only thing left to do is lift and nobody can interfere with your lifting. This is why I think that we are at the point in the season where lifting will make a difference.

My guess is that at Worlds, every alliance during eliminations will have at least one robot that can lift.