Offset Riser Strut Configuration for Archery Bow Stiffness
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Solution Overview
Problem
Riser structures for archery bows with offset sight windows face challenges in maintaining stiffness and minimizing twisting and bending during the draw and release cycle, leading to reduced accuracy and increased vibration due to the offset transition portions from the neutral axis.
Innovation Solution
The design incorporates a front and rear strut configuration with vertically staggered offset transition portions, where the front strut has a greater vertical length of transition than the rear strut, and both struts are connected by a rib envelope, allowing for a combined lateral width greater than either strut alone, with area centroids positioned non-parallel to the neutral axis, to distribute shear flow components effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the riser is made with a thin skeletal structure to reduce weight, then the riser becomes lighter and easier to carry, but the riser exceeds the material's yield stress capability and allows unwanted bending of the riser
Solution Approach 1:
The riser is divided into multiple structural segments including a thin-walled tubular body, internal gusset plates at critical joints, and reinforcing ribs. This segmentation allows the main body to remain lightweight while specific high-stress areas receive targeted reinforcement to prevent bending and exceedance of yield stress.
Solution Approach 2:
The riser employs varying wall thicknesses and strategic placement of reinforcing elements at specific locations such as the sight window transitions and limb attachment points. This local quality approach ensures that material is concentrated where stress concentrations occur, maintaining overall lightness while providing localized strength where needed.
2Ease of operation
If the sight window is offset from the neutral axis to improve archer's view and allow better target visibility, then the archer may have a better view of the target, but the tension applied to the riser may twist or bend the riser at the sight window transition portions
Solution Approach 1:
The sight window is deliberately offset from the neutral axis of the riser, creating an asymmetric configuration that provides improved archer's eye alignment and target visibility. This asymmetric placement is compensated by strategic reinforcement at the transition zones to maintain structural stability.
Solution Approach 2:
Reinforcing elements such as gusset plates and stiffening ribs are pre-installed at the sight window transition portions before the bow is used. This preliminary action ensures that the transition areas are strengthened in advance to resist the twisting and bending forces that will occur during the drawing and releasing of the bowstring.
3Measurement precision
If the sight window is offset from the neutral axis to assist the archer's aim, then bow sights may be positioned in the sight window to assist the archer's aim, but the bow may be torqued or jump in the archer's grip as the tension in the limbs is released
Solution Approach 1:
The offset sight window configuration, which initially creates torque and jumping during release, is converted into a benefit by adding counterbalancing reinforcement elements. These elements convert the harmful torque into controlled stress distribution, allowing the offset sight window to provide aiming precision while minimizing disruptive movements during release.
4Ease of operation
If the riser has a sight window offset from the neutral axis, then the archer may have a better view of the target, but these reactive motions of the bow may reduce accuracy, increase vibration, and deflect arrow flight
Solution Approach 1:
The solution addresses the offset sight window problem by adding reinforcement in the dimensional space perpendicular to the offset direction. Stiffening ribs and gusset plates are positioned to create a three-dimensional reinforcement pattern that counteracts the twisting and bending forces, thereby reducing vibration and improving arrow flight accuracy while preserving the beneficial offset view.
Data Source
AI summary
An offset riser for an archery bow has an upper end and a lower end each having limb attachment points, wherein a central plane laterally divides the bow through the upper and lower limb attachment points. The riser has a handle portion positioned between the upper end and the lower end and a front strut extending from the upper end to the handle portion, wherein the front strut has a front sight window portion that is offset from the central plane. A rear strut extends from the upper end to the handle portion as well, and it has a rear sight window portion that is offset from the central plane. In this riser, the front sight window portion has a different vertical location of transition lateral to the central plane than the rear sight window portion. This may produce increased stiffness, better visibility, less vibration, and other desirable characteristics.