Gearboxes for shooter?

[JVN]

Some considerations that haven't been mentioned:

• The tip velocity of the shooter wheel is proportional to the wheel diameter. Larger wheel = faster tip velocity = further shot. You can't ask us for RPM without telling us your wheel diameter.

• 2 Wheels (top & bottom or right & left) will result in the ball leaving the shooter at double the velocity. (With a 1-wheel system the ball is "rolled out" of the shooter, with 2-wheels the ball is "tossed".)

• Recharge time will depend on your gear ratio. Luckily the CIM has tons of power, so you should be fine if you're gear ratios are somewhat reasonable.

• System rotational inertia will also affect recharge time and will affect how much speed the wheel loses during a shot. More inertia = less speed loss = more repeatable shot. How much mass do you have spinning? Hint: If you don't want a heavy system but still want a high rotational inertia put the mass as far out as possible (make the wheel heavy at the edge.)

• How far do you want to shoot? If you're looking for a short range shooter you might find that a lower RPM wheel will be more accurate in the ranges you want, and will result in a faster fire rate (the wheel don't need to slow down).

• We found that the compression on the ball will affect the shot distance. Experiment. We like 1.75" of compression. Your mileage may vary.

• What type of shot do you want to make? A fast ball? A lob shot? This will greatly determine how fast you need to launch the ball. What angle will your shooter be at?

Overall... the secret is PROTOTYPING! Design is an iterative process. Do some basic design in your head. Build it. Test it. Improve it. Repeat until satisfied. This is the secret to the entire 2009 game. The teams who do really well this year will be the ones who experiment a lot.

Good Luck!
-John

[Rick TYler]

Originally Posted by JVN

Some considerations that haven't been mentioned: (...) The teams who do really well this year will be the ones who experiment a lot.

Aw, John, you just cut-and-pasted this from the Aim High game, right?

[MrForbes]

I think he could have cut and pasted from any year to get the experiment quote

[gorrilla]

well, the farther we shoot the ball, the less accuracy we have(unless we use the camera and everything) so we went for 4ft as our scoring distance, at less than 4ft it works just as well,


we're using two of these wheels bolted together(on the same shaft).... http://www.andymark.biz/08firstwheel.html

not baseball sytle, just the two wheels bolted together on some 2x4's at 8inches tall and 8 inches wide



we used the toughbox because thats all we had to get the wheel spinning fast enough(we dont have the parts for a direct drive off the cim)

[Rick TYler]

Originally Posted by gorrilla

we're using two of these wheels bolted together(on the same shaft)....

That's what we did for Aim High, and it worked great. Should be a winner for you.

[pfreivald]

Originally Posted by gorrilla

we used the toughbox because thats all we had to get the wheel spinning fast enough(we dont have the parts for a direct drive off the cim)

We made some simple couplers by taking some aluminum round stock, drilling out a hole for the CIM shaft, drilling and tapping two side holes for 1/4" bolts (to squeeze the coupler onto the keyed -- or is it flat? -- part of the CIM shaft), and then threading the other end of the hole. Add some threaded rod, and ta-daa! A direct-drive coupler for the price of a few bucks and a bit of time.

Patrick

[computerboi1503]

Although it may be a bit overkill, you could always use FP motors in a DeWALT gearbox, and just limit the output in your code. We used these on our '06 shooter, and it worked perfectly.... although we didn't limit output alot...

[waialua359]

Originally Posted by gorrilla

well, the farther we shoot the ball, the less accuracy we have(unless we use the camera and everything) so we went for 4ft as our scoring distance, at less than 4ft it works just as well,


we're using two of these wheels bolted together(on the same shaft).... http://www.andymark.biz/08firstwheel.html

not baseball sytle, just the two wheels bolted together on some 2x4's at 8inches tall and 8 inches wide



we used the toughbox because thats all we had to get the wheel spinning fast enough(we dont have the parts for a direct drive off the cim)

We also used two AndyMark wheels, but the 2 in. wide ones.
We tried all kinds of configurations, different motor speeds, different backspins, etc.
We came up with one big conclusion.
Unlike the Aim High game when we dealt with just simple Poof balls, these orbit balls comparably are really difficult to deal with. Too much slipping and inconsistent distances, depending on where it makes contact with the orbit ball.
Maximum distance and time that the shooter mechanism can be in contact with the ball prior to release from the robot, really improves the accuracy and grip on the ball.
I'm not going to outright come out and say it, but there is "one" robot in '06 that I think we'll see a lot of this year, much like 121 last year.

[JVN]

Originally Posted by squirrel

I think he could have cut and pasted from any year to get the experiment quote

IMHO - More so this year than any other. Combine a new field surface, new mandatory wheels, new restrictions on size/bumpers with a "weird" game object, and it makes for a lot to learn. Maybe our team is just slower than usual this year...

Let's be honest... it has been a long time since I'VE put any serious thought into drivetrain turning.

-John