We have been designing a couple of prototypes to test and we were not sure how this year’s game piece is affected by compression. How was your guys’ experience with different compressions and how much was sufficient?
We have used 1in and 2in of compression, 2in was significantly more powerful for us, though that is partially due to a change in shooter design. Id say anywhere from 1-3 is worth testing.
We found two inches to work well. We tested two falcons geared 1:1. We still found the system did not have enough inertia to fire in quick succession, we have to have a short gap of time in between each shot. We will probably add in a flywheel to help solve this problem.
Thanks. One of the biggest downsides for too much compression in our case is that we only want to have one motor for our shooter. Therefore having high compression might mean less distance and increased spin-up time. How many and which motors did you guys use and what were the gear ratios if there were any?
we used two 775 pros at 4:1 reductions. Id really consider using more than 1 motor on your shooter, mostly due the the spin up and inertia that you mentioned.
Hmm. One of the things we are afraid of about two motors is them not spinning at the same rpm. A simple PID loop would probably be enough to get them running at the same RPM but it still seems as if it might cause more issues than it’s benefits. Do you guys keep them at the same RPM with a PID loop? Also, I was thinking of having another set of wheels with higher torque that fed them to the shooter. What do you guys think about that?
Depending on the shooter design RPM difference can actually be a good thing. We intentionally slow down one set of our wheels to add backspin to the ball. If you shooter design has the wheels on the side RPM difference is a bigger issue, but we have had no problems with shooters like that when using two motors. The feeder wheels sound like a good idea, and could probably help you feed multiple balls into the shooter quickly without losing wheel inertia.
We use 2in on our most recent design and use two super heavy wheels and have had no issues with losing wheel speed.
If you connect the two motors to the same shaft then there’s no risk of the motors turning at different velocities, they’d have to be shearing the shaft to do that.
We are actually prototyping a hooded shooter. That’s why we want to make it snug and simple as possible. However, we will probably have another prototype with you guys’s ideas. How far were you guys able to shoot with 2 motors and 2 inch compression?
I am not the best at electronics but I was afraid that two different motors trying to turn the same shaft at different RPMs would harm the motor as one side is technically being stalled. I would really appreciate if you tell me how this works out
The motor is only stalled if the output shaft isn’t moving at all (RPM = 0), which should never be the case for a shooter (yes, technically the motor is instantaneously stalled whenever it starts up, but the duration of the stall is so short that it’s fine). The loads on each motor may not be mathematically equal, but they will be practically equal. You should have no problems at all if you drive two of the same motors to the same shaft.
The only thing to make sure of is that both motors are trying to turn the shaft the same direction, if they are opposing each-other then it won’t be a great time (easy to test by temporarily disconnecting one from power and seeing which way it runs, repeat for the other).
Thanks for the detailed explanation. I was thinking a lot about this issue. My go to way was a PID loop as a programmer but reading that it is ok to only have them mechanically linked is relieving I would also appreciate learning about how was your experience with compression and ideal RPM values
we used a hood shooter with wheels on both top and bottom of the wheel and we could shoot from the trench run into the high goal and the ball was still on an upwards trajectory
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