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lemiant
18-01-2012, 01:50
Hey guys,

Today we were prototyping a shooter, and it turned out to be a little more powerful than expected :yikes:. At ~80 feet I'm fairly sure this is the farthest anyone has ever launched this year's game piece:

http://www.youtube.com/watch?v=S6L1LLRHEFM

The contraption uses two kit wheels powered by a CIM geared UP at a ratio of 22:15. This set up is mirrored on the top and bottom (using a total of 4 wheels and 2 CIMs). The shooter takes ~1.5s to recover between balls. Back of napkin math suggests that the maximum surface velocity of the wheels is 200ft/s.

Hope you enjoyed that,

EDIT: When I say kit wheels, I mean 2011 kit.

- Alex
Mk.32
18-01-2012, 02:09
Wow very cool :D

Just wondering how consistent was it? And how much compression did you use on the ball?
lemiant
18-01-2012, 02:17
Wow very cool :D

Just wonder how consistent was it? And how much compression did you use on the ball?

It's not particularily consistent. While it probably stayed within ± 18" laterally, the shot varied almost 5 feet in distance.

We compress the ball significantly (not just in this one, but in all our good launcher prototypes), 3 inches is nothing out of the ordinary.
Mk.32
18-01-2012, 02:23
It's not particularily consistent. While it probably stayed within ± 18" laterally, the shot varied almost 5 feet in distance.

We compress the ball significantly (not just in this one, but in all our good launcher prototypes), 3 inches is nothing out of the ordinary.

Any damage to the balls after that?

This kinda a shooter would make a good feeder bot.
McGurky
18-01-2012, 08:09
Now you face the question that most teams are facing. Do you want to sacrifice two cim motors to use on your shooter?

Great distance, now just control the shot and you are golden!
davepowers
18-01-2012, 09:19
That's impressive, let's see you make a basket from that far.

-D
gpetilli
18-01-2012, 12:30
That's impressive, let's see you make a basket from that far.

-D

For a basket from 80ft, the robot would need to shoot from the pits !!!
Ludicium
18-01-2012, 12:36
If you happened to do research on baseball pitching machines they compress baseballs usually around half there diameter, this is to counteract the slip high speed rollers tend to give.
Dusk Star
18-01-2012, 13:10
That's impressive, let's see you make a basket from that far.

-D
Actually, if their inaccuracy scales linearly with distance, horizontal variation would be ~12in laterally, and 3 feet in distance. with appropriate backspin, I would estimate 1 in 4 would go in. Not bad!
Bruceb
18-01-2012, 13:52
We tried the KOP wheels on a shooter from our lunacy bot using a 1:1 CIM drive and about 2 inch. of compression and it took BIG CHUNKS out of the balls. We went back to smooth wheels.

Bruce
AdamHeard
18-01-2012, 15:15
Now you face the question that most teams are facing. Do you want to sacrifice two cim motors to use on your shooter?

Great distance, now just control the shot and you are golden!

There are EIGHT motors in the kit that are comparable to a CIM in this application.

Sorry to call you out specifically, but I keep reading this on chief over and over.

Keep your 4 CIMs in drive, and use several of our your EIGHT 200+ W motors on our your shooter.

And after you've used 4 CIMs, and 8 200+ W motors, you still have 10 other weak to powerful motors for other systems.

FIRST has given us the most leniant KOP in history, motor allocation is trivial this year.
lemiant
18-01-2012, 15:54
Any damage to the balls after that?

We tried the KOP wheels on a shooter from our lunacy bot using a 1:1 CIM drive and about 2 inch. of compression and it took BIG CHUNKS out of the balls. We went back to smooth wheels.

No significant damage (it does appear to smudge the lines on the balls). When I said kit wheels I was talking about the smooth ones from 2011
fox46
18-01-2012, 16:19
FIRST has given us the most leniant KOP in history, motor allocation is trivial this year.


Agreed- I really don't know what all this fuss is about. CIMs are not jesus motors - they are powerful but the others are not far behind. For teams who are only using two CIMS on their drive- I am sure there are lots of teams who are reading these sort of posts and looking forward to ram-jamming your robots around the field while they go about collect balls. (I know I am) You would be better off running two banebot motors per side or a CIM and a fisherprice.... There are MANY combinations and some teams don't limit themselves to only four drive motors. The two teams I am mentoring are running 6.

Furthermore, why do you need to shoot 80ft? Sounds to me like you just threw reason to the wind and "Tim Taylor"ed your shooter.
TheAthlete
18-01-2012, 19:06
Hey guys,

Today we were prototyping a shooter, and it turned out to be a little more powerful than expected :yikes:. At ~80 feet I'm fairly sure this is the farthest anyone has ever launched this year's game piece:

http://www.youtube.com/watch?v=S6L1LLRHEFM

The contraption uses two kit wheels powered by a CIM geared UP at a ratio of 22:15. This set up is mirrored on the top and bottom (using a total of 4 wheels and 2 CIMs). The shooter takes ~1.5s to recover between balls. Back of napkin math suggests that the maximum surface velocity of the wheels is 200ft/s.

Hope you enjoyed that,

EDIT: When I say kit wheels, I mean 2011 kit.

- Alex


Last night we had our prototype launch the first shot a measured 100ft across the parking lot. After that it averaged a little less than 80, but was very inconsistent, probably because it was 10 degrees out and the basketballs were noticeably different in the cold. And the way we fed the ball into the launcher was inconsistent.

Our prototype was just a wood mock-up at a 45 angle with two cims directly attached to a single wheel(several years ago gray rubber wheels) aligned so they touch the largest circumference of the basketball, and spaced with a gap of about 4 inches for the ball to compress through. However, it did leave large black streaks across the ball, so...

It was definitely not what we were expecting, and not necessarily our goal to accomplish, but it was pretty darn neat.

For our actual design, we won't use cims, for a good reason as there is an extensive range of other motors, and we plan on using all 4 cims for drive train. And going toward a pitching machine like design, it will take some experimenting with compression to achieve a design that wont leave giant black marks during the match and actually fit in a reasonable range for the field. But overall, I think we know what path we're going down this season!
greasemonkey
16-05-2012, 09:09
using a cim anywhere but on the drive train is a waste of torque that could be used on the drive train so i agree with you 100%
KevinGoneNuts
17-05-2012, 12:58
My rookie team got our shooter to shoot 100+ feet (I dont remember exactly how far it was. During a few practice matches in Sacramento we shot into the upper stands. (actually got in a lot of trouble from a reff.)

When we were at 254/1868's lab we got a full court shot at I believe around 30-40% power. At 100% we were shooting high above the hoops and at one point i think we hit one of the heat lamps attached to the ceiling. I felt really bad. Lol

We used 4 banebots 775, and we're probably not using those motors in the future. They are anyting but Reliable and consistent.

Here is the video of our full court shot:
http://www.youtube.com/watch?v=5t4xUBL0-XU&feature=youtube_gdata_player
Mongai
17-05-2012, 13:04
using a cim anywhere but on the drive train is a waste of torque that could be used on the drive train so i agree with you 100%

You can always have one cim moter power each side and gear it up so the torque is made up for. It would be slower, though.
Steven Sigley
17-05-2012, 14:32
My rookie team got our shooter to shoot 100+ feet (I dont remember exactly how far it was. During a few practice matches in Sacramento we shot into the upper stands. (actually got in a lot of trouble from a reff.)



I remember this clearly, me and the some of my teammates in the stands watching the practice matches were like :eek: that's a strong shooter!!!
PAR_WIG1350
17-05-2012, 15:49
You can always have one cim moter power each side and gear it up so the torque is made up for. It would be slower, though.

I believe he meant to say "a waste of power." the same torque can be achieved with one CIM, but it would be slower since the power from the second CIM is not available. I don't think it a waste of either. The amount of power provided. By a CIM would have been reasonable for the application. I do however believe that it is a waste of a CIM. CIMs are big. Big motors can disipate thermal loads far more efficiently than small motors like 550s and other similarly sized or smaller motors. 775s are also big, but CIMs are bigger. This makes them the most appropriate for applications in which they will stall, or come close go stalling for extended periods of time or applications where they are required to run for the entire match. A shooter, if designed and used propperly, is not either of thise things, but a drivetrain is.