2020 Intake Compression and Speed

Our team is currently in the CAD process of a rebuild for Infinite Recharge. As we do not have access to our workshop right now, we can not prototype. Therefore, we are trying to minimize the prototyping process by learning from other teams’ best practices.

One of the areas that we lack experience is intakes. We could not find good resources to design efficient intakes. We could not find what compressions teams used in the 2020 season. Could you share the compression levels you found most successful picking up balls from the floor? Also, how did you guys keep the compression throughout the intake? Some teams like 118, 2471, 1678, 987, 3847, 6328 and a bunch of other teams did a great job at this and we would love to learn from them!

Another question we have is about different roller speeds. We are planning to have a 3 roller intake. We are planning to use compliant wheels on the first shaft and polycarbonate tubes for the other rollers. We are concerned if different roller/wheel diameters would cause any problems?

Looking for your insights!


I would suggest watching some of the build videos for the RI3D. A few of them go into what they found from their testing. And pretty much all they discuss is valuable to know.

A good insight I got by reading 254’s tech binders is that the tangential velocity of your intake has to be greater than the velocity of the robot, otherwise you will be unable to collect game pieces while in movement


I’m pretty sure the ideal intake is to be a constant speed, but about twice as fast as your drivetrain. Constant speed all the way so the game pieces are steadily flowing, twice the drivetrain so you can pick up while the robot is moving.

And for compression our mounts were “compliant” to facilitate the powercells getting into the storage

It should not cause any issue.

Be sure to make your intake go fast! Speed = good.

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These game pieces require minimal compression for an intake. Basically they move if you touch them. So it comes more down to spacing between rollers than compression.

If the rollers are different diameters, but have the same gearing, the surface speed of the rollers will be different (specifically, with two rollers spinning at the same rpm, the larger one has a faster surface speed)

That’s alright if the rollers increase in speed as they enter, but can cause problems if the lead roller is faster than the roller behind it (balls enter the intake from the floor faster than they exit it into the robot).

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I would be comfortable with 1/2" - 2" of compression in an intake, maybe even more where the bumpers are involved. In general the surface speed of the intake should be 2x the max speed of the DT

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Here is a link about selection of gears & motors to build robust robots
by 971

Can you elaborate on why this causes problems? I’ve seen teams do this before, most notably 254 in 2020 so I figured it was a good way to put less strain on motors but still have a lot of speed on the leading roller for pickup while moving.

You’re trying to compress the skin of the ball which is in contact with the two different-surface-velocity rollers. This can lead to inefficiency in the best case, and squeezing the ball through the two rollers and out of the robot in the worst case. Also, the possibility to jam multiple balls against each other as you’re intaking them (since the first ball may not get out of the way fast enough).

If you independently power the two different speeds, this is probably less of an issue (as they can vary and speed and ‘match’ each other during the handoff) but probably still problematic.

We saw a bit of this on our intake which used 2" diameter PVC tubes as a set of rollers. at week zero we had 4" wheels on the end… switched to 2" for week 1; much more seamless handoff.

I’d wager similar problems exist on an intake that increases in speed as it goes along- you’d be putting the ball skin in tension as it rolls.

(This isn’t to say there’s never a case where you want different speed rollers in a series… friction feeders (YouTube) operate on this exact principle to separate objects :wink: )

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On a really basic level, if you have things coming in faster than they’re coming out, you can end up with multiple balls touching each other and multiple rollers in your intake, which is an easy way to end up jamming

Also, as Thad mentioned, you can have the ball pop out of the intake between the two rollers.

This would be the argument to have the later rollers be faster than the lead roller.

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