Roller Styles
TL;DR: The ideal intake setup for 4476 seems to be hollow tubing rollers that rotate around a full width 3/8” round tube or hex shaft, whenever the intake doesn’t require squishy wheels/mecanum wheels.
Currently in FRC, there are 3 prominent ways of designing an intake roller: live axle, full width dead axle, and separate dead axle.
Live Axle
The term “Live Axle” describes a setup where rotating objects (wheels, arms etc) are fixed on a shaft such that they rotate together. Bearings sit inside the side plates, the hex shaft with wheels on them rotate in the bearings. Extra standoffs are needed
Live axle intakes are quite common because they’re relatively easy to make, and most hardware available have 1/2” hex bores built into them so it’s very easy to slide them onto a hex shaft and call it a day. Live axles also allow for flexibility in plate placement, the side plates don’t need to be on the outside of the axle.
To deconstruct a live axle roller, you’ll need to unscrew the retention screws at the end of the axle, then slide the shaft out of the bearings. This process can be complicated by intermediate plates or wheels that are hard to shift around the shaft.
Full Width Dead Axle
The term “Dead Axle” describes a setup where objects rotate around a stationary axle. The axle is connected connected rigidly to the side plate, and bearings sit inside wheels/rollers which spin around the stationary axle.
Team 4414 has made intakes this way for a few years, they do it with a 3/8” hex shaft (red) spanning the width of the intake. They have a 1.25” polycarbonate roller with end plugs super glued into each end, which each have an integrated pulley and a space for the bearing to sit in. This design is very easy to replicate, and we can even think about using a 3/8” round shaft instead which would be usable with generic 0.375” ID bearings.
If a roller needs to be replaced, simply unscrew the bolts on each side and lift the roller assembly out. The shaft and bearings can be removed and reused if needed.
Screw Dead Axle
This is another variation of the dead axle intake where instead of having a shaft go across the full width of the intake, you just have screws that hold a bearing on each end to the side plate. Additional standoffs are used if rigidity is needed. This style was used by 254 the last two years, and teams like 1678 are starting to adopt this style as it’s completely optimized to save weight.
The roller and end plug design stays very similar, the only change here is both teams mentioned above use bolts to connect their tube to their plugs instead of an adhesive. The end plugs have 2 bearings each to support loads better, and 254 adds a small modified piece of rounded hex for a better fit between the screw and the bearing.
To assemble this roller, the first step is to use a nut and bolt to secure each end plug to the side plates. Then the roller is slid into place and fastened using bolts. These steps are necessary because you need to hold onto the inner nut while screwing the bolt in from the side plate, but that nut is inaccessible when the roller is in place. The side plates therefore need some level of flex so that the roller is able to fit between the two end plugs after they are in place on the side plates.