The design of the white oak Cube Chair's mortise and tenon joint structure requires a deep understanding of the wood's inherent properties. White oak's hard texture and high density provide excellent resistance to compression and shear, providing a natural advantage for the chair's load-bearing capacity. However, it also exhibits a common characteristic of all woods: slight contraction and expansion with changes in ambient temperature and humidity. The ingenuity of the mortise and tenon joint structure lies in taking these characteristics into account from the outset. While fully leveraging the wood's hardness to enhance structural stability, the unique structural form allows for the wood's natural expansion and contraction, preventing cracking or loosening due to internal stress accumulation.
In terms of force transmission and distribution, the mortise and tenon joint structure demonstrates a sophisticated approach that is perfectly aligned with the characteristics of white oak. The Cube Chair's frame is constructed from interlaced wood strips, with each joint serving as a point of convergence. Traditional mortise and tenon joints, such as the "corner tenon" and "dovetail tenon," utilize a concave-convex interlocking structure to achieve large-area contact between the wood strips at these joints. The hard texture of white oak enhances this joint's tightness. External forces are evenly distributed throughout the frame along the wood's grain, rather than concentrated at a single point. This design fully utilizes white oak's compressive strength, minimizing the risk of localized deformation due to excessive stress, even when bearing the weight of a person for extended periods.
The mortise and tenon joint design closely mirrors the grain direction of white oak, a key element in achieving balanced load-bearing stability. White oak's grain is straight and dense, and its longitudinal load-bearing capacity far outweighs its transverse load-bearing capacity. When designing the connection between a chair's uprights and crosspieces, the tenon is typically cut along the wood's grain, leveraging the wood's high longitudinal strength to resist tension and compression. The mortise, on the other hand, is designed to avoid weak points in the grain, leveraging the wood's dense transverse structure to enhance its grip. This design, guided by the wood's natural character, allows the mortise and tenon to complement the wood's characteristics, ensuring a secure joint while avoiding cracking caused by working against the grain.
To counteract the shrinkage and expansion of wood, the mortise and tenon joint structure provides a unique "buffering mechanism," crucial for maintaining long-term load-bearing stability. White oak shrinks slightly in dry environments and expands in humid ones. Overly tight mortise and tenon joints can easily generate internal stresses during these environmental changes. Therefore, a slight gap is created between the tenon and the mortise during the design, precisely sized to match the expansion coefficient of the white oak. This gap prevents loosening when the wood shrinks, and accommodates expansion when the wood expands, preventing compression and deformation at the joints. Furthermore, some mortise and tenon joints utilize "wedge-nail tenons," which compensate for slight loosening over time through fine-tuning with wooden wedges, ensuring consistent load-bearing stability.
The symmetry of the Cube Chair's overall frame, combined with the even distribution of mortise and tenon joints, further optimizes load-bearing performance. The rigidity of white oak allows the frame to maintain its regular cubic shape, while uniform mortise and tenon joints at every corner and joint ensure balanced load-bearing capacity at every joint. This symmetrical design ensures that when a person's weight falls on the chair, the force is evenly distributed through the frame to each mortise and tenon joint, preventing premature failure of any particular joint due to excessive stress. The uniform material properties of white oak also ensure this symmetrical load-bearing behavior, reducing structural imbalances caused by uneven wood material.
The self-locking properties of the mortise and tenon joint structure complement the elasticity of white oak, enhancing the structure's resistance to loosening. When the tenon is inserted into the mortise, the wood's inherent elasticity creates a certain amount of friction between the mortise and tenon joints. The higher density of white oak exacerbates this friction, creating a natural "self-locking" effect. In daily use, chairs are inevitably subject to shaking and vibration, and this self-locking property prevents the mortise and tenon joints from loosening due to external impact. Furthermore, the elasticity of white oak allows it to deform slightly when subjected to stress, absorbing some of the impact before returning to its original position through its own resilience. This "tough yet flexible" property, combined with the self-locking structure of the mortise and tenon joints, significantly enhances the chair's durability.
In terms of detailed treatment, the mortise and tenon structure achieves a deep integration with the characteristics of white oak by optimizing the contact area and force angle. For example, the "through-and-tenon" structure used in the connection between the chair seat and the frame not only increases the contact area between the wood, allowing the weight of the seat to be more evenly transferred to the frame, but also utilizes the hardness of white oak to prevent the joint from sinking. In the connection between the armrest and the column, the angle of the mortise and tenon is designed to match the direction of force when leaning on the body, distributing external forces along the wood grain and avoiding shear forces at the joints. These meticulous designs combine the physical properties of white oak with the structural advantages of the mortise and tenon, ultimately achieving the perfect balance between load-bearing stability and the characteristics of the wood in the Cube Chair.
