Greetings dear fellow FRC makers who are reading this post, I am a coach mentor for team FRC 8067.
I would like to get some advice on choosing the right motor setup for a simple shooter mechanism to shoot the Cargo game piece. I am fairly new in designing a shooter and I have read several CD posts discussing this very topic and would like to get further details regarding this year’s challenge. We would like to shoot to the high goal (2 points) and from the hangar zone, to get immunity.
We tried driving two Colson Performa wheels (4" x 2", 1/2" Hex Bore) that run through a 1/2 Hex bore shat supported by two 1/2hex bearing on each side of the shooter. with a 1,5 inch compression (see picture)
So far, we have tried attaching a 775 Pro with a versa planetary 10:1 reduction and the ball would barely exit the shooter, Our second try was with a Mini-cim (1:1) and was much more successful as we were able to shoot a distance of about 10 feet with the hood angled at 60 degrees and 1.5 feet off the ground) to the high goal.
Now my real question is would the use of two Neo Motors with a 1:1 gear ratio work for our particular shooter?
Does connecting them directly to the spinning shaft a good idea or would it be better to use some belts and pulleys/chains and sprockets?
Finally, is a 1:1 gear ratio a good idea or should we gear it down?
I have never worked with these brushless motors and I see that the datasheet indicates that they run at approximately 5820 RPM with a stall torque of 3.28 N.M
My team has a very similar set up.
We have the same wheels being used 1:1 with a single Falcon500. Although we have a second spot for another Falcon500 in case we determine that another is needed.
2 neos 1:1 with belt/chain/gears should work fine but you need to watch out for bounce out which can be common if your shots are too powerful/too spinny.
A lot of teams are running two falcons/neos and it seems to work including us.
Check out 3636’s open alliance thread for a pretty good shooter design that works and is pretty simple.
I’d recommend allowing for an option to adjust your shooter angle, as 2 brushless motors are pretty powerful and you’ll probably over/undershoot with your current angle.
The short answer to your question is yes, 2 neo’s will be more than enough to shoot into the upper hub. You can likely get away with just one even.
Since you havent worked with brushless motors before, do make sure to be aware of the quirks of either brushless motor you choose (In the case of the neo, you can only use the Spark MAX with it, and it needs that encoder cable plugged in even if you dont use it. For the programming team, they use different libraries compared to CTRE products, and behave slightly differently.)
Always amazed how promptly this community is willing to not only repond but also to provide great advice. Thanks to all for your recommendations and tips. I am definitely going to give the Neos a try while keeping in mind your advice.
Thanks for the judicious info. Speaking about the Neo’s built-in encodr, have youactually tried using it to programm the velocity rate of your motor? I have read somewhere that they only go by a resolution of about 80 ticks per rev and that it might not suitable for a PID controller or some sort - Just asking?
Depending on how the compression is measured (the rails dont exactly touch the ball on the 9.5" dimension) 1.5" could potentially be more than enough that you are not getting optimal energy transfer to the game piece. We found just a little bit less compression than that to transfer energy better, especially when shooting from the purple zone area. Another thing to note that I saw another reply mention is the backspin of the ball which is a good point, with only one set of wheels you will have more energy transfered into angular kinetic energy. This is not inherently bad as the Magnus effect will help “lift” the ball and it will have a more droppy flight path for lack of a better term. It’s just important to note more RPMs are needed to obtain the same linear velocity vs a “two flywheel” design.
To answer your original question a NEO with 1:1 should be enough and some inertia may help keep the RPMs from dropping too much during a shot. More inertia also means more time to spin up the shooter from a stop. Our team currently plans to use 2 NEOs in a 1:1 configuration, with 4in wheels but with a set of 1" wheels opposite to remove some of the backspin. IIRC somewhere around 3000-4000rpms worked well for many of our shots, but this is also from early prototyping without a consistent feeder setup which will be on the final robot. Ymmv.
How? Did you cut the shafts on the Neos? We tried this exact configuration, but there’s not enough space on the inside of the Maxplanetary to accommodate the Neo shaft.
We printed an extra MaxPlanetary outer stage to space the shaft properly. In the past we have just used a hacksaw, clamping the part of the shaft to be removed in a vise.
