Are you saying that you do not need an angle change for flywheels? This shooter is able to shoot full court shots as well as right up against the pipe. I do not think it is possible to just be able to slow down the flywheels enough to lob the ball into the goal. If you want to be able to do both of these shots with a flywheel you also need a system for controlling the shooting angle. The pneumatically controlled power shot system on our launcher is equivalent to slowing down the motors on a flywheel. Both systems need to be able to control not only the power of the shot, but also the angle. An extra motor is not required on our design, however we just chose to put it on so that we can shoot from both positions. We could take off the angle changing system and keep the shooter at a constant angle while still getting the full court shot, just like most flywheels on youtube right now. The results between the shooter with a lot of backspin were not comparable to the pinball shooter. The pinball shooter was much more precise.
Are you certain about that? I have no idea, but I had thought that you could fix the flywheel angle at about 60 degrees and then simply adjust speed, but is there something about the angle at which the ball hits the net that causes it to bounce out or something?
Yes, you need a steep enough angle to be able to not hit the net when you are up close, however it also needs to be shallow (optimal 45º) enough so that when you shoot full court shots, the ball is still able to reach the net. If you try to shoot full court shots at the steep angle, you will be lobbing the balls way to high.
I would disagree that your pneumatically controlled power shot is equivalent to slowing down the motors on a wheel-type shooter. Changing the motor speeds allows a completely variable range of shot, whereas your pneumatic system simply gives a long-range shot and a short-range shot. The motorized angle changer you have allows for a similar variable shot range to changing the speed of the motors on a wheel-type shooter. In order to make a close-up shot as you do using pneumatics, I would simply add a piston to change the angle of the wheel shooter, which I would say is equivalent. I agree with you that it would be difficult to make the close-up shot without changing the angle, but that does not require a motor, it could use a single piston, just like you do for the “power shot.”
I have to disagree here too. The results you showed at 3:46 look pretty consistent for a no-feedback wheel-type shooter (I am assuming you did not use a tuned velocity PID controller during your tests, correct me if I am wrong). Compared to the results at 4:36, I would say they are rather comparable, especially without the use of a speed controller on the wheel-type shooter. The left-to-right variability of the pinball-type shooter is probably the lesser of two evils, but I believe with a well-tuned velocity controller, a flywheel could achieve similar distance accuracy.
I would think that because both systems control the power of the shot, they could be very comparable. We could simply swap the motor on the angle changer, to a piston. You really only need 2 positions anyways. We could keep chasing ourselves in circles however the point is still there, both need a systems to change the angle, therefore you cannot assume that the pinball shooter needs 1 more motor than the flywheel to change the angle.
I would have to disagree with your points. While the left-to-right variability may not vary a lot between the two, the distance greatly varies. Keep in mind that both are using two motors. The reason that the flywheel is not shooting as far is because a large portion of the energy is going into spinning the ball. The pinball shooter does not have to do this in order to achieve similar, if not better, accuracy. This proves my point that the flywheel is a less efficient design. Sure you can throw more motors on the flywheel to get it to shoot the right distance with the same accuracy as the pinball shooter, however my point is that with the same amount of energy, the pinball shooter is more efficient. While this efficiency is maybe not needed for this year, I think that it should still be noted.
My point was that largely variable control is very different from binary control. I believe that only having two launch options would cause quite a few issues for a competition robot. Unless your robot is only designed to score the “match load” balls, it would be very easy to block a robot that could only shoot from a single distance from the goal, and it would be rather wasteful to require driving back to the protected corner every time to make a shot. Except for the single long-range shot position, you would be limited to a very specific radius from the goal with your low-powered shot.
I will give you that this design without a motor to give it variable range for shots would probably be okay for scoring the match loads, and would probably be alright in Skills Challenges, but in a match setting, I believe it would be much less than ideal, which is probably why you added a motor for changing the angle. In any case, again, I have been commenting on this particular robot, on which you did use a motor for this purpose.
I took note that the the wheel-type shooter you built that had the greater accuracy did not have as great of a distance, but mentioned that with a third motor, it would most likely be able to reach the desired distance. I understand how wheel-type shooter physics work, and I have spent quite a bit longer than 15 hours working with them. Again, while a two-motor pinball-type launcher would most likely be more accurate than a two-motor wheel-type shooter, it is my opinion that in order to be competitive, a shooting robot must have more than a binary shot range.
Also, I made note of the fact that your wheel-type shooter did not use any sort of velocity controller, which would greatly increase the accuracy of shots distance-wise, which might even allow a two-motor wheel-type shooter to not require as much backspin to be accurate, and then be able to get the distance required. A velocity controller is most definitely required for a wheel-type shooter to be accurate. If you do not feel comfortable writing such code, then yes, a pinball-type shooter will prove to be much more accurate for you.
I think you are completely misunderstanding this, with the pinball design, you would have much more two places to shoot from on the field. By altering both the power and angle of your shot, the robot is able to shoot from the majority of places on the field. I still do not understand how a robot that has a myriad of shooting positions on the field could not be competitive because it has a “binary shot range”.
This is true, we did not use a velocity controller, however I do not see how a velocity controller would magically increase the accuracy and distance of the shots with our test. If you watch the video, you can see that we feed the balls into the flywheel after giving the flywheel more than enough time to come back up to speed, nor are we feeding the balls in minutes later, after the battery voltage has dropped. The velocity controller is completely unneeded, the velocity of the flywheel was the same for every shot. Do you have a video of a 2 motor flywheel shooting as far and accurately as you are promising, because i am very interested in how this velocity controller can magically make the balls fly further and more accurately.
Actually, I think you are misunderstanding. By “range” I am talking about distance. If you take the motor to change the angle of the shooter off of the pinball-type shooter, you lose the large variable range and are reduced to 2 distances from the goal. If you add a pneumatic piston to change the angle, you might have 3 distances, but still not nearly as many as a wheel-type shooter. That was the only point I was making there. Additionally, a 3-motor wheel-type shooter with a single motor to change its angle should be thought of as equivalent to a 2-motor pinball-type shooter with pneumatics, because of the new rules regarding motors/pneumatics.
I believe that using a velocity controller would have increased the accuracy of your first wheel-shooter test, which did not have as much backspin, but shot far enough to make full-field shots. That was the point I made there. Rather than your solution of increasing backspin to increase accuracy, perhaps not as much backspin would be required in order for the shooter to be accurate if a velocity controller is used. I never promised anything, but I pondered that perhaps you could get away with only using two motors for a wheel-type shooter by using the above suggestions. If you were not reading the RPM of the wheels, then you do not know for a fact that the velocities were the same for every shot. Battery voltage and strain on the motors certainly come into play. Saying that a velocity controller is “unneeded” is rather unfounded, since you did not try implementing one, and many others are doing so.
Again, I would like to point out that I am not trying to put this style of shooter down in any way. I am simply pointing out that it probably isn’t significantly better than a wheel-type shooter, at least given the points Griffin and others have made. As I have said, there are certain things the pinball-type shooter excels at, and others that wheel-type shooters are better at. Given that I have not spent time with a pinball-type shooter, I don’t want to be quick to judge, and if you read what I wrote in my earlier posts, I think this design has potential. I only wanted to point out the flaws in Griffin’s reasonings to exactly how the pinball-type shooter is better than a wheel-type shooter.
I agree, both designs have their own separate pros and cons that we could go on forever about. The reason I chose to continue this discussion with you on the forums is so that others looking for good ideas are not turned away from the pinball idea because of some of the reasons you stated. Both the flywheel and the pinball ideas are great, and our testings over the ri3d reflected this. In the end, we chose the pinball idea mainly because we wanted to inspire others to build something other than the most common design. There is always a better design, so by encouraging others to try something different, we will hopefully help them find a better design. In no way did I mean to degrade the flywheel design, over the next couple weeks I am going to be doing more testing, and maybe try to build a flywheel robot. Im glad we had this discussion, hopefully it will inform people about the pros and cons of each design so that they can improve upon them. Nice talking to you
I think we thoroughly ripped the topic to shreds so that anyone who reads this thread will be pretty well-informed on the pros and cons of both designs before deciding how they want to build their robot. Haha, <3 you, Cam. (And Griffin. <3)
I really like the simplicity of the design…
It is also very compact!
The speed of the shooting is a huge plus the way I see it
If this is what you guys could do in 3 days I can’t wait to see a robot that you put months of time into haha! Thanks for sharing!
While forever is a long time, I certainly wouldn’t mind it if the two of you continued debating this for another week or so.
It’s kinda fun to read Jordan’s “Refutations of the Pinball Shooting Mechanism” knowing that, all the while, Team 24 is down in their bunker already building sonic cannons designed to set pinball shooter elastics into an irreparable state of self-destructive resonance.
Is there a way to use the VEX Cam and shorter rubber bands if we used up all the polycarb? I know its possible but I was wondering if somebody had tested it. I’m also a little lazy, so cutting polycarb will probably not happen anyways.
It could totally be possible, however, because the VEX cam is about half the size of the polycarb one, the throw of the piston will be respectably be reduced to half the travel. What this means for you is that the piston will have to accelerate much faster. This can be accomplished with adding more rubber bands. If anyone ends up using the VEX cam for a similar design, please share! I would be very interested in the use of a non-custom vital component for this design.
I used the vex cam for a catapult design and it works really well. I might post videos of it later when I am finished building my robot. My catapult also uses a pneumatic piston to change the launch distance of the ball, but it is connected directly to the launching arm of the catapult.
I got around to making this video: https://www.youtube.com/watch?v=g_Jtw3pm8cY&feature=youtu.be
After adding a velocity control program, I have noticed an amazing change in performance; both the length and accuracy of the balls increased enormously.
I would love to see this!
Would you mind elaborating on what you mean by “velocity control program”? Are you talking about how fast the balls feed into the shooter or is this a modification to the way the cam works, how the motors are driven or…???
It’s looking great!
That’s amazing Cameron. I doubt its as simple as this, but is the limit switch programmed to wait half a second after its activated? BTW, thanks for the tip about the VEX Cam. I just ordered it so I’ll post a video or pictures as soon as I finish.
It is programmed such that the Cam won’t release the energy unless a ball triggers the in barrel limit switch and such that the intake won’t run if both are triggered. Both the barrel limit switch and the “ball ready” limit switch being triggered means a ball is ready to fire and another would run into the ball in the barrel if the intake was to continue.
Exactly what tabor said. I might be posting a video on how it works if there is enough interest in it.