Mechanical Elements: Fasteners, Springs, and Bearings

Mechanical Principles

Lever: $F \cdot d_1 = d_2 \cdot R$

Wheel: $F = (N \cdot \text{coefficient}) \cdot r_1$

Screw: $R = 2 \pi F \cdot \text{performance} \cdot p$

Moment: $M = F \cdot d$

Fixed Joints

Riveted Joints:

Used when joining flat pieces of a certain thickness where welding might cause internal tensions. They are used for riveting or welding parts.

• Lap Joints (Unions coatings): Where the two pieces overlap.
• Butt Joints (Unions for cobrejuntes): Where the two pieces are on the same plane and are linked together by a single plate riveted to both pieces.
• Double Cover Butt Joints (Joints with two cobreguntes): When the pieces are in the same plane and are linked together by two plates riveted, one on each side.

Detachable Joints

Screw (Bolt and Nut):

Features:

• Thread Turn: A furrowed surface that forms a helical fillet wound on a cylinder.
• Inclination (Nut): Right-hand nut (tightens clockwise); Left-hand nut (tightens counter-clockwise).
• Thread Profiles (Geomats the steak): Triangular (standard); Trapezoidal and square (transmit significant forces); Rounded (for sealing); Acme or tapping (for very fine sheets).
• Metric Thread: Triangular profile with a $60^{\circ}$ angle, forming an equilateral triangle (e.g., M8x1.25).
• Washer (Cuff): A ring-shaped piece of mild steel, located between the nut and the piece being fastened.

Keys (Clavet):

A piece located within notches or recesses of a determined geometry in the shaft and the corresponding hole.

They are used to join two pieces when working under cylindrical compression or traction.

Cotter Pin (Pin):

Used to support smaller efforts than keys. Adjustment is much easier.

Taper Pin (Barb):

Allows for axial displacement.

Splined Shafts (Striated axes):

Transmit great effort and are used for gearing.

Springs

Used to absorb energy or shock loads.

• Tension or Extension Springs (Springs tension or traction): Have hook-shaped bent ends. Support efforts that tend to stretch them.
• Compression Springs: Support efforts that attempt to compress them. Ends have a flat shape.
• Torsion Springs: Can withstand extreme traction efforts.
• Leaf Springs (Springs crossbow): Consist of curved steel blades joined in the middle through a flange. The ends of the fasteners are articulated to allow the spring to be stretched.

There are also spiral springs (for clocks) and rubber springs (for machine suspensions).

Bearings

Utilized to minimize friction between two moving parts of a machine and ensure the parts are correctly joined.

Parts:

• Outer Ring: External part of the bearing.
• Inner Ring: Internal part of the bearing.
• Rolling Bodies: Cause friction only through rolling motion in the tracks.
• Separators: Keep the rolling bodies separated from each other.

Types:

• Deep Groove Ball Bearings: Deep tracks, holding axial efforts.
• Single Row Angular Contact Ball Bearings: Can handle radial and axial loads.
• Cylindrical Roller Bearings: Handle large radial loads and can withstand high speeds.
• Tapered Roller Bearings: The best for resisting both axial and radial loads.

Lubricants

A substance capable of reducing friction between the contact elements of a machine when they move relative to each other.