Which type of wheel do you use on your back roller

On this season, l have seen many many teams using a back roller to prevent balls from bouncing out. Would you please show your team’s back roller for others to learn. An additional link will be better!

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We used a pair of blue 2" stealth wheels for our back roller (driven 1:1 off a NEO). Model

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We used an axle directly driven by a NEO motor. The cargo contact area was four 2" AndyMark stealth wheels.

We used 2” stealth wheels as well. 1:1 drive off our shooter with reverse direction.

We used a mix of REV 30A and 45A 2” compliant wheels.

We use orange stealth wheels on the top rollers in the 4414 2021 arrangement and a 3D printed main wheel with black neoprene tread. The surface speeds are matched with gearing.

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We converted from a single wheel shooter. We used 1in andymark sushi rollers in the back and dropped from 4" Fairlane to 2.5" Fairlane on the bottom because of space constraints.

We also converted from a single flywheel hood shooter that we started the season with and dumped because of the backspin problem. Our second iteration shooter was a straight two-flywheel design without a hood. The main flywheel was two 4" x 1 1/2" colsons, belt driven by a Falcon at 1:1.33 while the back flywheel was four 2 1/2" x 1 1/4" colsons, belt driven by another Falcon at 1:2. The shooter frame angle is at 22 degrees. That difference in ratios gave us the ability to use the variable rpms of both flywheels to drop shots from anywhere on the field with no backspin. Here’s a shot of the robot from the business end of the shooter:


The indexer angled up and back to the shooter with break beam sensors to keep the cargo in it until the flywheels were spun up. The Limelight is on arms above and behind the shooter. It worked out very well indeed, giving us a reliable shot from pretty much any position.

It’s important to keep in mind, a back roller helped teams avoid bounce-outs this season. It is because, for this game piece and goal shape, ball trajectory, etc. there was a point where backspin would cause bounce-outs. This is not the case for every year and every goal though. For many types of goals, such as the “chain-and-drop” goals in 2006 / 2016, or the backboard-shots in 2012, high backspin was essential.

There will definitely be shooting games in the future where this kind of roller helps - either for controlling spin or for range or consistency etc. But I just wanted to post this so that future students don’t find this thread and go “oh, a top roller always makes a shooter bounce out less”. The way to find this out for a new game piece and goal is to prototype.

Anyhow, please carry on with sharing and fact finding - just wanted to add this note.

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Two two-inch Colson performa wheels. They work really well too, probably putting 50% or more of the total energy into the ball when shooting.

I’ll get a picture when I can.

Was anyone concerned with backspin for the 2017 goals with the fuel?

We used the same rollers on both sides of our shooters, 4x 4" blue stealth wheels.

Backspin in 2017 would help the balls stay in the goal because it would cause the balls to roll down to the bottom. This year is a weird one where backspin causes balls to bounce out because it causes balls to bounce harder off the bottom and pop out the front.

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Same. 2" blue stealth wheels.

Just a note about this implementation (and to everyone building 1:1 shooters), one side of your axle on the top roller is just supported by the internal bearings inside the NEO motor, which are relatively small and may not respond to the repeated radial loads from a compressed ball passing through the shooter. It’s one of those things that might survive over the course of an FRC season, but especially if you want to reuse the motor over several seasons, finding some way to add a larger bearing connected to the shooter structure on that side of the axle may prolong the motor life.

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Agree on this, but if your going through this effort, just flip the motor or use something like 217-4183 to get yourself a 1:1 belt or gear stage. Added benefit of being able to tweak your ratio, which we did 2-3 times in both 2020 and 2022 to keep the motor in an optimal torque range.

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2 inch blue stealth wheels front and back. Both 1:1 off their own falcon.

We ran a single top roller of 35a stealth wheels geared 3:2 off the main shaft for 3/4 surface speed of the main roller with a 2 inch compression at the top roller and 1.5in compression on the main hood. The light stealth were really nice for getting the shooter wheel back up to speed quickly.

In hindsight we should’ve ran multiple top rollers with less compression as changing ball inflation at DCMP and champs caused us to miss shots we weren’t missing earlier in the season because the change in compression actually affects the shot angle when the rollers are of different size.

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We also use the blue 2" stealth wheels belted up to the main shooter wheel at a 3:1. (We use the 4in blue stealth wheels for the shooter wheel.)

The 2017 balls basically did not bounce at all, so it was not a huge concern. The shape of the goal was also far more likely to keep the balls in - once they actually entered the goal, at least.

In general, when you hit a vertical face with backspin, the backspin helps the ball go down, which is usually desirable. This year was a bit of a edge case with the very bouncy game piece and the wide-open angled goal with a big rigid thing at the bottom to bounce off of.

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Thanks for sharing your team’s incredible design! l have noticed that most teams use a row of top roller. l wonder whether the more rows of top roller, the better effect it will have.