Motor Used for Shooting

[JesseK]

We're using 775Pro's through a Versaplanetary, geared to appropriate reductions for the wheel size (still not determined). Other than power:weight as has been stated, I like the open air cooling that's perfect for a high duty cycle use case like what a shooting wheel does. For shooters that use low compression on the ball, it's perfect.

[Ether]

Originally Posted by Nick.kremer

I have seen you posting the same thing in a few other threads. I was wondering if you have a minute to explain/have a link to a thread that explains how operating voltage is tied to using control loops, to someone who knows very little about such things?

What Gus said:

Originally Posted by GeeTwo

The control works by varying the voltage supplied to the motor. The motor controllers cannot put out a higher voltage than they take in from the battery. Without getting into PID theory, essentially if it's going too slow, the voltage is increased; if it's going too fast, the voltage is decreased. If you're running the motor at top speed (giving it full voltage), you can only adjust down. Far better to have your nominal operating speed at say 75% of top speed, especially later in the match when the battery voltage is reduced.

If you still have questions, please do ask.

[roystur44]

Originally Posted by Ether

Reading between the lines, it sounds like you are not planning to control wheel speed, is that right?

Since the target is a hole in the wall and not a hoop. I think getting your shooter to have a fairly straight trajectory is needed. Let the motor rip and throw a fastball into the hole. It's all about aiming.


Roy

[CalTran]

Originally Posted by roystur44

Since the target is a hole in the wall and not a hoop. I think getting your shooter to have a fairly straight trajectory is needed. Let the motor rip and throw a fastball into the hole. It's all about aiming.


Roy

So what's your plan if your battery runs low, or (hopefully not) you forget to switch it between rounds? Pray that it still makes it?

[Ginger Power]

Originally Posted by CalTran

So what's your plan if your battery runs low, or (hopefully not) you forget to switch it between rounds? Pray that it still makes it?

"Letting the motor rip" could still mean controlling for voltage fluctuations. Just gear your shooter such that at 80%-85% speed you're still shooting much harder than you need to.

[billbo911]

We have have exceptional results with our prototype using a single RS 775-18 geared 2:1 driving a pair of 4" wheels. We run the motor anywhere between 8.5v and 10v.

Our intent is to run a pair of 775pro's geared 3:1 (60:19 to be exact) and (This is for you, Ether) Bang-Bang to control the rate of the wheel.
Our plan is to use a single retro reflective section and just measure the period to determine the rate the wheel is spinning. We may end up with two sections to preserve balance in the wheel.

[Boltman]

Originally Posted by Mike Schreiber

For a shooter it really doesn't matter too much. The main thing that matters is your RPM and compression, I'm not convinced torque has a large impact on the shot as much as it has on spin up time / slow down after a ball is shot (which doesn't matter in this game). You want to get the wheels going at a specific repeatable speed to get an accurate shot - generally between 3000-8000 RPM with a 4" wheel(s) and depending on the distance / angle etc.

The advantage to a Mini CIM is that you can direct drive and be at around the right RPM, the disadvantage is that you can't really go any faster than free speed unless you gear up - which is silly. The Bag, 775, or 550 all have high free speeds and require some gearing down, but a versa planetary box makes that really easy. 550s are a little weird this year since you can't get them from VP or AM. Also consider packaging and where your motor / shooter will live inside the robot.

Cool Thanks!

[lark95]

Originally Posted by Mike Schreiber

550s are a little weird this year since you can't get them from VP or AM. Also consider packaging and where your motor / shooter will live inside the robot.

We have plenty left over from previous years so it is not a problem for us. However you can order the 550's directly from banebots.

We have done some more testing of the 550's on a 3:1 with 4 in wheels and are able to get a very straight shot at full speed.

[timytamy]

Originally Posted by popnbrown

We're also looking at using a 775pro at a 3:1 but I'm having trouble figuring out how to attach a longer shaft to the VersaPlanetary Gearbox shaft.

Try http://www.vexrobotics.com/vexpro/motion/217-4008.html

[triumph69]

Originally Posted by popnbrown

We're also looking at using a 775pro at a 3:1 but I'm having trouble figuring out how to attach a longer shaft to the VersaPlanetary Gearbox shaft.

I figure in order to gain efficiency it would be better to drive the shooter wheels directly from the gearbox, without adding a second set of gears, belt/pulley or sprocket/chain set-up. We don't have a lathe, so is our only option to not directly drive the shooter wheel?

Vex Pro has the solution. Hex shaft coupler.

http://www.vexrobotics.com/217-4008.html

[carpedav000]

We are using a miniCIM to power a ratcheting shift-to-freefall gearbox.

[Monochron]

Originally Posted by carpedav000

We are using a miniCIM to power a ratcheting shift-to-freefall gearbox.

Can you describe your reasoning for this? What is the pupose of a ratchet on your shooter? And why the need to shift to neutral?

[CalTran]

Originally Posted by carpedav000

We are using a miniCIM to power a ratcheting shift-to-freefall gearbox.

Originally Posted by Monochron

Can you describe your reasoning for this? What is the pupose of a ratchet on your shooter? And why the need to shift to neutral?

Catapult?

[carpedav000]

Originally Posted by CalTran

Catapult?

Close, spring-powered linear puncher.

[billbo911]

Originally Posted by carpedav000

Close, spring-powered linear puncher.

Shades of 971 in 2014!