I know many have talked about general strategy for the HUB but I was wondered about reliability of mechanisms. We got a severely deformed ball in our kickoff kit, is this a common issue? Also, I feel the reliability of a dumper is better than the small point gain from a shooter or catapult. Does anyone have any strong feelings one way or another?
Personally, I like the idea of a shooter for the shoot-and-scoot tactic, but my team decided to go for a dumper instead since we were worried about the balls taking a less desirable shape over time. However, if the shooter were a flywheel, you could change the speed of the motor to either dump or to shoot from a distance.
There is also an issue of targeting. The retro-reflective tape is on plastic. This means that, if you use a limelight, you’re going to have to spend a lot of time tuning the limelight to target the small strips of tape. 2 years ago our limelight freaked out just from a little light reflection on the plastic next to the power port.
That’s what I figured, we had issues with targeting last year with flat tape.
Similar to the boiler in 2017, I predict that a lot of upper hub shots will be made from close in with a relatively low velocity “layup” shot. The consistency of the cargo may not be that critical for such a low powered shot. Even teams that can shoot from further away may find that the close in layup shot is more consistent. I expect that the shooter angle for the close in shot and the further away shot may be about the same such that you could adjust the distance of the shot with only a difference in flywheel speed. But still running the math on that…
Our team decided that if we can make a shooter with the reliability greater than 50% then the top goal is worth the point gain.
You probably thought of this, but…
50% reliability on the upper hub will give you the same points as 100% on the lower hub. (10 pts/10 its)
However, 50% reliability on the upper hub will only get you half as far to the Ranking Point earned from 20 Cargos scored. (5 cargos/10cargos)
Our prototype shooter this year has been super consistent, and our balls were not deforming after a solid 100 shots by anything more than the fuzz on the outside. No gouges or scratches. A couple lines where the blue of our wheels rubbed off, but nothing that changed the accuracy or shot predictability. Another thing we noticed was that our shot pattern was LEAPS AND BOUNDS more accurate than 2020
I expect that the shooter angle for the close in shot and the further away shot may be about the same
It depends on how close is “close”
Depending on robot geometry, right up against the fender you need a pretty high angle, like >80 deg.
Personally, my team in 2020 had calibrated the limelight well enough to be within ±3 degrees off of the actual shot angle. We also had a turret that we programmed to stay locked onto the target though, using our kinematics
Based on what? If you are willing to shoot at a high angle and just give it exponentially more power as distance increases possibly, but the higher the apogee of the arc the more likely it is to bounce out. At least I assume, our field isn’t quite yet set up.
I’ve been assuming that the shot will need to enter the “funnel” at a pretty steep angle in order to not bounce out. In 2017, the high boiler funnel was pretty flexible and would absorb a lot of the fuel velocity to prevent bounce out. But even so, we found that you needed either a pretty steep entry angle or a shot that just barely cleared the rim of the funnel in order to limit the bounce out effect. It looks like the hub this year is going to be much more rigid than the 2017 boiler so it seems like the risk of a flat shot bouncing out would be higher. However, the cargo this year may not bounce as much as a plastic whiffle ball so maybe that will cancel out some of the bounce out tendency. So, my working assumption is that the entry angle, more than the apogee will determine whether it bounces out or not. We’ve not had a chance to build a test setup to evaluate this and I am waiting to see some actual test data.
If my working assumption is correct, and the entry angle needs to be fairly steep, then the shooting angle also needs to be fairly steep (darn parabolas). So that is the basis for my expectation.
But, I would love to be proven wrong…
Fair assumption, from what little I’ve seen it might also be that any ball that goes in might just stay in. Another thing to factor in is the agitator, which hopefully will exclusively do its job and not push any balls back up instead
So i actually did the math on this one (no drag or anything just projectile motion) and you need an 80 degree angle to comfortably hit up close. Shooting from the launch pad at 80 degrees would mean the ball would go like 24’ in the air, probably not the most reliable shot.
At what output velocity?
Also, the issue is getting rid of unwanted balls, the issue with the shooter is that it deforms the balls (or at least we can speculate) and a catapult cant release a ball softly.
While I agree that an arcing shot with a 24’ high apogee would be hard to make reliably, I am still not convinced that a shot entering the cone of the upper hub would not bounce out if it entered at, say 45 degrees or even 60 degrees. While I agree that a flatter shot would be more reliable in terms of entering the funnel, at this point I don’t know how flat the shot can be before it bounces out.
Interesting. I would imagine a Lower velocity would be more consistent but of course that’s the gambit of engineering isn’t it?
Thats a good point, I think either way the upper hub from distance is going to be challenging.
Our team is planning on an adjustable angle shooter, this will let us try the upper hub at distance, more importantly it also lets us hit the low hub more easily.