whats the tradeoff between a chain drive and a belt drive for an intake, and which is quieter

The provided documentation lists several disadvantages for timing belts, which can be compared to chain. Belts are not customizable in length, meaning a specific length must be purchased, whereas chain may be more suitable for prototypes where length changes often . Belts can also be wider than alternatives like chain . While belts can be expensive, they may save money on pulleys .

For drivetrains, belted systems are recommended, though they can be difficult for new teams . Chain drives require at least one tensioner per side to maintain correct tension and generally benefit from CAD or detailed sketches to visualize the chain run .

The provided documentation does not state which power transmission method, chain or belt, is quieter, nor does it specifically detail tradeoffs between them for an intake mechanism.

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Design Tradeoffs > Spur Gear Gearboxes Planetary Gearboxes

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Note: Spur gear gearboxes are fine for most applications for a rookie team. We are not advocating necessarily having to upgrade to planetary motors, but there are some advantages which may become useful in more advanced use cases such as high-load systems.

Important: Spur gear gearboxes have inherent disadvantages to planetary gearboxes. Spur gear gearboxes should not be used in high-load situations, primarily because the gears can strip and destroy the gearbox.

An example would be a drivetrain that has to change directions repeatedly and quickly. Planetary gearboxes are much better suited for drivetrain and arms, due to the configuration of the sun and planet gears. In addition, spur gear gearboxes are prone to shock loads; therefore, direct drive is not advisable on drivetrains. Refer to the gearbox anatomy section for more complete information on gearboxes. This refers to using spur gear gearboxes which are attached directly to the pinion gear of the motor. It does not mean external ratios outside of the motor gearbox, which will always be in a spur gear configuration.

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Drivetrains > Drivetrain selection

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Warning: It is not recommended for teams to use spur gearboxes on their drivetrain. Instead, use planetary gearboxes, as they are less prone to shock loads and breakage.

Traction/Pushing Power: While this feature is often overemphasized, it is still very important. Pushing power describes a drivetrain's ability to endure defense/engage in defense. In addition, traction will be important if the drivetrain must traverse obstacles or some sort of terrain.

Many factors affect the pushing power of a drivetrain, including wheel type, motor gearing, and overall weight of the robot.

Note: If you already have a very agile drivetrain with experienced drivers, a team can avoid defense instead of having to fend it off or engage in it.

Powering the drivetrain: Generally, there are four options for power transmission: direct drive, chain, gear, and belt. More detail about each option can be found in the power transmission section.

Teams should stay away from direct drive, as gearboxes are prone to breaking, especially under shock loads (for example, if the wheel is hit by another robot, or the wheel slams into the wall).

We recommend belted drivetrains, but realize that belt is a difficult option for new teams. Chain and gears are also great options - chain requires a bit more forethought, as 1+ tensioner per side is required to maintain correct tension in the chain.

CAD or a detailed sketch is generally recommended with chain in order to visualize the chain run (where the chain will be placed). Gears are slightly simpler, and can be a fantastic and easy option, especially when using extrusion. We would advise to stay away from TETRIX gears, and use the gears from other kits such as the REV delrin gears (with hex hub strengthener) or REV aluminum gears.

See the /docs/common-mechanisms/power-transmission/index section for more details.

An important step is determining what you want out of your drivetrain.

Do you want speed?
Pushing power?
Ability to get over terrain?
Do you need to strafe?

All of these questions should be answered before choosing a drivetrain.

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Design Tradeoffs > Passive Intake/Claw Active Intake

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Important: Active intakes (ones with continuous rotational motion) should always be prioritized over passive intakes and grippers.

Active intakes are much more efficient and effective in picking up common game elements such as balls, cubes, and rectangular prisms than claws. This has been a widely accepted rule; many Worlds-level robots over the years use intakes. The exception is that a claw should be used for irregularly shaped objects that would be impossible to control via intake; for example, the relic in Relic Recovery.

Intakes have two major advantages over claws.

Intakes can control multiple game elements at a time.
Intakes are indiscriminate at picking up objects, making them much more efficient.

Claws can only pick up one object at a time, and the driver needs to aim the claw at that specific object to grab it. With an intake, the driver does not need to focus on one game element - instead; intakes will just pick up anything in its path, if designed properly. Claws are also prone to breakage, and thus suffer to defensive robots. They are also generally more fragile than intakes. Therefore, active intakes are as a result much more efficient than claws. Nearly every competitive robot from past years has used active intakes to great effect, so there is plenty of precedent to follow.

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Useful Resources > Mechanical Design and Build > Power Transmission

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SDP-SI Timing Belt and Pulley Handbook (https://www.sdp-si.com/PDFS/Technical-Section-Timing.pdf)* --- A detailed handbook about belts and pulleys. Some of the things mentioned also apply to chain.

SDP-SI Timing Belt Drive Design Guide (https://www.sdp-si.com/Belt-Drive/Designing-a-miniature-belt-drive.pdf)* --- A one-page guide to designing belt and pulley drive systems.

Gears Educational Systems Guide to Chain Drive Systems (https://web.archive.org/web/20191020193018/http://gearseds.com/documentation/deb%20holmes/2.5_Chain_drive_systems.pdf) --- A guide to roller chain, featuring some useful equations.

Gear Efficiency Comparisons (https://www.meadinfo.org/2008/11/gear-efficiency-spur-helical-bevel-worm.html) --- A comparison between different types of gears (spur, bevel, worm, etc).

How Gears Work (https://ciechanow.ski/gears/) --- An interactive visual guide to how gears work.

KHK Introduction to Gears (https://www.khkgears.co.jp/kr/gear_technology/pdf/gear_guide_060817.pdf) --- A handbook covering fundamentals about the mechanicis of gears.

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Timing Belt > Disadvantages:

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Belts aren't customizable. You buy a belt of a specific length and you're stuck with that length until you buy another one. This isn't too bad if you're planning out your robot properly, but chain will work better for prototypes where the chain length will be changing often.
Belts can be wider than alternatives (especially chain). This probably won't have much of an impact, but belt can often be wider than other power transmission methods, so it may not always fit.
Belts can be expensive (but you'll save money with pulleys). While you can buy chain 10 feet at a time, you'll most likely be buying each belt brand new. While this can get expensive, you'll be saving money on pulleys.

(Figure: 7236 Recharged Green, Rover Ruckus)

(Figure: 8417 Lectric Legends, Rover Ruckus)

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Choosing a Motor > Choosing The Right Gearbox

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For regular use, any of the planetary gearboxes will fit your needs. Planetary gearboxes are just a tiny bit more expensive, but boast better backlash and efficiency, higher load capacity, and better capacity for shock loads than spur gearboxes. The tradeoffs, cost and mechanical noise, are almost never a factor.

Tip: Because both gearbox types are so similar in price for similar ratios, we generally recommend the use of a planetary over a spur gearbox.

If you already own spur gearboxes, try to use them in lower-load situations, and use planetary motors on your drivetrain and high-load mechanisms.

For small reductions, it may be more economical to choose a motor you already own and build an external reduction using gears, chain, or belts. It should again come down to your desired output shaft, desired gear ratio, and for the UltraPlanetary, whether you want the ability to swap parts out on the fly.

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