Uses

Chains transmit power across a long distance. Movement is transferred between two parallel shafts which are any distance apart. Chain is flexible in one dimension, meaning that it cannot elongate or twist side to side.

Chain is typically run at relatively low speeds, up to about 800 ft/min (Chain Speed). At higher speeds, gears are preferred as chain becomes quite loud.

Advantages

• Simpler & Lighter than gears for longer distance runs.
• Require less precision than gears.
• Easy to change reduction ratios by changing sprocket sizes and re-running chain.

Chain Terms

One Chain Link is one individual unit of chain.  The chain contains alternating inner and outer links.

Rollers are the round pins which act as pivots between chain links.

Plates are the metal plates holding the rollers together.

Pitch is the distance between round rollers on a chain.

Sprockets are profiled wheels with teeth which chain wraps around.  The teeth allow engagement between the chain links, with the teeth pulling directly on the rollers. Sprockets can be on a live axle or can be bolted to a wheel in a dead-axle configuration

Designing for Chain

When designing for chain, it is usually important to design in some sort of chain tensioner.  Team 254 prefers using a cam which shifts a bearing block to tension the chain without adding any additional friction to the chain.  Other options, such as placing idler sprockets or low-friction plastic blocks in the chain run are other possibilities.

The calculator in the blue box below can be used to calculate the distance needed and the number of links needed for a certain chain run.  Simply fill in the boxes and the remaining boxes will be filled in automatically.

Chain Sizes

The two most commonly used chain sizes used in FIRST Robotics are ANSI #25 and #35.

ANSI #25 Chain

• Pitch: 0.250"
• Roller Diameter: 0.130"
• Tensile Strength: 781 lbs
• Working Load: 140 lbs

#25 chain is more than strong enough for most robot applications, and is used often by Team 254. However, due to its small size, #25 chain is very sensitive and must have proper sprocket alignment and tension to function properly.

ANSI #35 Chain

• Pitch: 0.375"
• Roller Diameter: 0.200"
• Tensile Strength: 1758 lbs
• Working Load: 480 lbs

#35 chain is often used by Team 254 for raising large arms and other high load bearing applications. Furthermore, #35 chain can handle much greater forces and much looser tolerances than its smaller counterparts. For teams who are not confident about achieving proper alignment and tension, #35 chain is often a better solution.

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Bandsaw

A bandsaw is a motorized saw which uses a continuous sawblade moving in a circular path to cut.  Typically powered by electric motor.  On a horizontal bandsaw, the piece is fixed in a vice and the blade moves down, using gravity to cut.  On a vertical bandsaw, the saw is fixed and the piece is pushed towards the blade.  Team 254 uses a horizontal bandsaw to cut metal stock and uses a vertical bandsaw to take rough cuts on all sorts of materials.

Drillpress

A drillpress is a fixed drill mounted on a stand.  The piece is placed on a table, and a lever is actuated, causing the drill spindle to move downward towards the piece, drilling into the piece.

Mill

A milling machine is a machine used for the manufacture.  A tool is held in a spindle which can move up and down along the Z axis.  The piece is typically mounted in a vice, but can be held to the table in many ways.  The table can be moved along the X, Y or Z axis by rotating handles.  In opposition to other types of machinery such as bandsaws and drillpresses, milling machines allow for very precise work.  Team 254's manual mills are precise up to about 1/1000 of an inch.

Lathe

A metalworking lathe is a machine tool which spins a block of material to allow for various operations upon the block.  Cutting ools are placed in a tool holder which can move in the X and Z direction.  Many lathes also feature a tailstock, which can be used to drill holes concentric to the piece, or to support the end of a long piece.

CNC

"Computer Numerical Control" refers to a class of machinery that can be controlled by computer "G-Code".  It allows for faster and more precise operations than a manual machine, as well as allowing more advanced and complicated cuts.  Many different types of machines can be controlled by CNC technology.  Team 254 has one CNC Milling Machine, which is very useful for fast and precise cutting.

Waterjet Cutter

A waterjet cutter is useful for cutting virtually any material.  It cuts using a high pressure water stream mixed with an abrasive.  Waterjet cutters typically feature CNC control, and consist of a head that moves over the work piece along the X and Y axes.  Sometimes the head can tilt, allowing for more advanced cuts.  Although team 254 does not own a waterjet machine, we often have sponsors who will waterjet parts for us.  In robot construction, waterjet technology is most useful for cutting plates.

Laser Cutter

A laser cutter features a laser that can cut many materials.  It is often used for cutting sheet metal.  Laser cutting on aluminum is approximately 3x slower than waterjet cutting.  Laser cutting can perform extremely precise cuts.

Shear

A shear is a tool used to cut.  It is often used in robotics to cut sheet metal and plastic.  Team 254 owns a foot powered shear in which a foot lever activates a break which holds the workpiece, followed by a blade that comes down to cut the piece.

Brake

A brake is a sheet metal tool used for creating bends in sheet metal or plastic.  It features a press that presses the piece down into a groove.  Team 254 has a hand break in which a lever is actuated by hand to cause the press to press the piece into the groove.  After the lever is actuated, another lever is actuated to cause the piece to bend to the desired angle.

What is an Aluminum Tube Stock Frame?

Tube Stock

A frame constructed from Aluminum Tube Stock Team 254 typically constructs robot frames using aluminum square and rectangular tubes - Usually (1" x 1" or 1" x 2" Tube Outside Diameter and 1/8" or 1/16" Tube Wall Thickness) Team 254 welds tubes together to create a frame, but it can also be built using gussets, bolts and rivets as well. Some teams cut "pockets" into tubes, but pocketing tubes reduces strength greatly while not reducing a ton of weight. It is usually stronger and lighter to just use tubing with a thinner wall thickness.

Applications of Tube Stock Frames

Applications of tube stock frames can include drivebase, superstructure and manipulator frames: Team 254's Drivebase frames typically consist of two side rails connected by two or more ladder bars connecting the rails.  Some robot drivebases are closed (have ladder bars at very front and back of frame rails), while some have open fronts, as in the example at right.  Most drivebases have more than two ladder bars, with some bars in the middle to provide additional structural rigidity. Team 254 has built numerous superstructures and manipulators out of tube stock, including arms in 2004 and 2005, elevators in 2007 and 2008 and conveyor frames in 2006 and 2009.

Example Tube Stock Drivebase Frame

Advantages & Disadvantages