Hello I’m curious around what RPM different teams intakes were spinning and what motor teams were using on their intake. If you chose that speed for a specific reason what was that reason?
A general rule of thumb is to run the intake such that the speed at the tip of the roller intake is 2x your robot’s max speed.
I don’t want to speak for most teams, but the motor selection comes down to making sure that you don’t stall your motor out when intaking a ball. Consider the worst-case scenario where the ball gets jammed.
These two considerations can help guide you in figuring out a motor/gearing combination that you are comfortable with. But, if in doubt, go with the new 775Pros.
775 pro all the things
front intake was 1800 rpm about 11 FPS surface speed
50 percent of our shooting speed, theoretically 65 ft/s, but I know its less.
Our intake wheels are the same as our shooting wheels (six inch wheels mounted to to mini-CIMS) with two outrigger wheels to avoid a tangent point. Heres a picture.
This is true for “ball” intake systems, though more so for previous robots that drove a bit slower.
The reason for this is a rolling ball has zero surface velocity at the point of contact with the ground, and 2X its center rolling velocity at its upper surface. Thus the 2X multiplier so the ball rolls into the robot instead of the robot rolling over the ball (which can cause the robot to climb a ball).
As robots are getting faster and faster top speeds, this metric makes for higher and higher surface velocity of the rollers which in turn makes risk of stall much higher.
I think a more accurate target should be 2X the speed with which you expect the robot to be traveling when you acquire a ball. In 2014, this was possibly a very high ground speed. In 2016, due to sprint distances, the actual speed robots saw was quite a bit lower.
For non-ball objects, target should be at or near robot speed, but the likelihood of dealing with stall is much higher.
Two keys to powering a good intake:
- Throw power at it
- Make it go fast
We ran a BAG motor at 9:1 on our 1.5" rollers. You can do the surface speed math. It was pretty good. A smidge faster and it would have been able to shoot into the low goal from the bottom of the batter, which is sometimes useful. If possible I would have just left it at 9:1 and put a 775pro on it.
We briefly tried a mini-CIM direct into it, but that was clearly ridiculous, not enough torque.
The 2x robot’s max speed rule is also only valid if you are intaking the ball from one side. If you have top and bottom rollers (or left and right), you’re pulling in the ball instead of rolling it, so 1x max speed is fine. And as robots gear themselves ridiculously fast, 2x max speed just might not be all that practical.
1800 rpm with a 1" diameter intake roller so we had a surface speed of about 8 fps. We were originally worried about stalling out the intake and burning the motor so we didn’t go for the 775pro, opting instead for a bag motor. As it turns out though, the stall torque of a bag is almost the same as a 775pro’s optimal power output torque, so going 775pro is almost always the way to go. We switched to the 775pro for champs.
Edit: I failed at math: 8 fps, not 400 fps
you may want to check your math. I get closer to 8 fps…
(1800 rpm = 30 rev/second, 1" DIA = 3.14159" circumference, this equals about 94 in/sec which is about 8 fps).
I thought I was doing something wrong… minutes != seconds
We used upper and lower Bag Motors on a 10:1 VP with a 1:1 9mm belt from gearbox to 2.375" Banebot wheels. Theoretical RPM on those wheels is about 1300rpm. Robot ground speed was max 15fps (though I don’t think we were ever near full speed when intaking). The belts were fit slightly loosely on 3D printed pulleys to create a “slip-clutch” to prevent motor stalling. The plastic pulleys held up just fine all year, no broken teeth, and even took quite the beating from impacts of robots and walls. Never had a single issue with belts from ratcheting over the pulley teeth either. We’ve done this a few times for these very low load type of applications - I would NEVER do this setup on our drive (though I know as our wheel axles got bent over the course of the year, we did quite a bit of ratcheting on those belts…but again, no issues).
We ran a 775 at a 7:1 ratio with a 1.75" roller. That’s roughly 2600 rpm.
One 775 pro at 9:1 on 2" diameter rollers. About 17ft/s. The rollers were 1/2" ID polyurethane pressed on to a steel round shaft with a 1/8" key in it. They acted like a clutch when a ball was captured instead of stalling the motor.
We started with two 550s, but then we switched to two 775 pros because they kept smoking halfway through a match.
We ran 2 775’s through 3:1 gearboxes at 0.4 speed. That comes out to about 2400 RPM.
Maybe not 2x, but gearing a linear speed of an intake faster than the drive allows you to intake while the robot is moving in any direction. Just gearing faster than the drivetrain is a better rule of thumb.
I don’t think you’re asking the right question.
The RPM of any intake is not a good measurement, because the same RPM on different rollers provide for different performance.
The most important factor of the intake is the Linear Speed, as Adam described in the quoted post. The linear speed of an intake is independent of the roller diameter, and is a better way to measure intakes across other robots.
As for motors, the 775pro is bomb.
I’d echo making sure that you have enough power on it.
469 in 2012-2013, and most of 5188s intakes were a 2" roller on a 550 or 775 motor at roughly a 5:1 reduction. The power of a 775Pro makes it great for this application.
We used a BAG motor on a 9:1 Versa Planetary and switched to a 10:1 for champs. This gave us a wheel speed of about 13fps on our 2" wheels.
I would not run this setup again. The BAG motor tended to stall out when intaking the ball from the side (we ran 2" mecanums on the outer rollers), and the intake was a little slow. A 775pro would have been much more beneficial, as well as faster (speed was the big issue since stalling was fixed by tuning compression).
A handy tip for anyone looking to increase the performance of their mecanum intake: set the intake to have about .75 to 1" of compression, and allow it to be pushed up by the ball when intaking. We achieved this by using an in line pressure regulator to limit the extension side pressure of our pistons on the intake. Although it could be done with code adjusting your Kp value in PID (while intaking == true && the intake position is in a certain range with the lower bound being full extension and upper bound being 0" of compression) if you’re using a motor with an encoder to move your intake.
I’ve attached the intake calcs for my teams robot this year. Our robot was geared for 14.5 fps so our intake was geared according. We spent weeks upon weeks testing on what intake was the fastest and best and came out with 6, 4" mecanum wheels (3 on each side) and 2, 4" stealth wheels in the middle. Our intake was very very quick. We took inspiration from 118 and worked with them a bit to understand how theirs worked.
As stated earlier in the thread, 2x your robot’s ground speed is a good start for your intake speed. We then also threw power at it. We used 2 versaplanetary each with a 775pro to power our intake. We put about 1.75" of compression on the ball to grab it but when the ball came into the robot it would compress down from about 10" to 4" to get into our catapult. We had no issues with jamming or anything all season.
Here is some video of it in action.
You’re right my bad
Our intake, which was also our shooter, ran a 775pro on a 5:1 versaplanetary at full power on both top and bottom rollers. To shoot high goals from the batter they were at something like 80%. rollers were 2inch blue andymark wheels. It was FAST. the ball just disappeared from where it was into the intake. made the whole assembly jump a little when it sucked one in:)