FP 2011 (00801-0673) versus 9015 power

[Ether]

Originally Posted by de_

The heating was very apparent when we upgraded our original single motor 9015 to a single 0673 for hopefully improved recover time. The motor direct drove the shooter via the AM 3.7/1.

Ignoring friction for the moment:

20770.....0673 motor free rpm
3.67......gear reduction
5659......wheel free rpm
94.3......wheel free rev/sec
8.........wheel diameter, inches
2.09......wheel circumference, feet

197.6.....wheel tangential free speed, ft/sec

Why did you gear it so fast?

[de_]

Because that was the only remotely appropriate gearbox we had in inventory ! We hoped we could get away with a single FP or 550 size motor to minimize high up weight. We had hoped to reduce chain related losses (and sprocket & chain weights) by direct driving (through the AM). We also had no idea what sort of drop in RPM a largely unloaded motor would incur trying to shoot the ball (drop in RPM means drop in exit velocity of the ball relative to the no-load rpm). Heh I'm not in mechanical But then we found the recover time slower than we would like. Shooting distance was limited to 14 ft which some team members wanted more so we put on a more powerful motor. Unfortunately its KV was higher.

[Ether]

The way to get fast recovery time for a shooter wheel is to use a reasonable gear ratio and control the motor closed-loop at an operating point where it has sufficient headroom to rapidly accelerate the wheel back to that operating point after being disturbed. Some design guidelines were suggested here.

[de_]

Great points you make. We actually do have an encoder and PID on it to set and manage target speeds based on shooting distances. When shooting from any distance that has a reasonable probability of actually scoring (5-12ft), the wheels are not spinning anywhere near full power and the PID code does attempt to aggressively recover the target RPM. So I think we ended up close to what you recommend.

[Ether]

Originally Posted by de_

...When shooting from any distance that has a reasonable probability of actually scoring (5-12ft), the wheels are not spinning anywhere near full power

May I ask:

1) how fast are the wheels spinning under those conditions?

and

2) under those conditions, what voltage is being supplied to the motor (or how many amps is the motor pulling) ?

[de_]

You may ask... It may take me a day or so to get the data. I need to know it for future reference as well. I'm also going to try to get the RPM of the wheels for the 7', 12' and max power off our encoder data, maybe even how much the wheel slows down shooting a ball at the various distances. Did a lot of shooting this afternoon at 7 and 12 feet. Motors completely cool (with fans), recover was 2 seconds or less.

[de_]

Ether: Sorry we still owe you some motor data. We got swapped with camera issues and had to focus on them. Now that our regionals are over, hopefully I can get you the data. I can say that
- with 2 motors, recovery time at reasonable shooting distances was faster than our feeder could feed the ball 8 " to the shooter . Having 2 motors (downside, weight, jaguars, wiring, etc) in the competition was clearly not essential but it did allow us to shoot 30+ balls in a row as fast as we could feed them on the practise field. With the fans, the motors were barely warm.
The fans were there largely to extend the motor life, perhaps in a semi-jam situation.
I will try to get the data in the next few weeks as we need it too. I noticed you don't have a PM email so I couldn't pm you.

Update Oops: Appears I was not logged in when I looked for your PM.

[Ether]

Originally Posted by de_

Ether: Sorry we still owe you some motor data.

No apology necessary. Whenever you get a chance.

I noticed you don't have a PM email so I couldn't pm you.

I have PM enabled.