Tow Dolly Cross Rail Assembly With Positive Camber Against Sag
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Solution Overview
Problem
Tow dollies experience sagging in the middle section under heavy vehicle weight, leading to negative camber tire alignment and increased tire wear, and dynamic shock loading during towing, especially on rough surfaces, due to their susceptibility to weight distribution and lack of length adjustability for varying vehicle sizes.
Innovation Solution
A tow dolly cross rail assembly with a center male bar and outer female bars forming an arched configuration, creating a positive camber effect at the dolly tires, which is achieved through a telescopically slidable relationship and spring-loaded plunger pins, allowing for adjustable length and improved weight distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cross rails are made sufficiently rated to support wide, heavy vehicles, then load capacity is improved, but the cross rails sag in the center section creating negative camber
Solution Approach 1:
The cross rail is designed with a pre-cambered arched configuration featuring a central apex that angles upward between 165° to 179°. This curved geometry counteracts the sagging effect under load, maintaining proper tire alignment and preventing negative camber while supporting heavy vehicles.
Solution Approach 2:
The invention changes the geometric parameters of the cross rail by introducing a specific apex angle (165° to 179°) at the center. This parameter modification allows the structure to maintain its shape under load while supporting increased weight capacity.
2Device complexity
If cross rails are made fixed length, then structural simplicity is improved, but they cannot accommodate different vehicle sizes
Solution Approach 1:
The cross rail assembly is divided into multiple segments: a central fixed section with the apex and adjustable outer sections. This segmentation allows the middle portion to maintain the pre-cambered shape for structural integrity while the outer sections can be telescoped to accommodate different vehicle widths.
Solution Approach 2:
The cross rail incorporates telescopic adjustment mechanisms that allow the structure to dynamically change its length and configuration. This enables the same cross rail assembly to adapt to various vehicle sizes while maintaining the critical apex angle for proper camber.
3Ease of manufacture
If cross rails have sagging configuration, then manufacturing simplicity is improved, but tire wear increases due to negative camber alignment
Solution Approach 1:
The pre-cambered arched configuration with its specific apex geometry is designed to work with the tire contact patch. By angling the apex upward between 165° to 179°, the structure naturally aligns the tires vertically, preventing edge wear while the overall simple bar structure remains easy to manufacture.
4Device complexity
If tow dolly is designed for static weight support, then structural simplicity is improved, but dynamic shock loading exceeds maximum load capacity on rough surfaces
Solution Approach 1:
The pre-cambered apex configuration acts as a structural cushion by allowing controlled deflection and energy absorption. The angled apex design provides built-in compliance that mitigates shock loads from rough surfaces, protecting the structure and load before excessive forces can develop.
Data Source
AI summary
A tow dolly cross rail assembly includes a male bar and a pair of female bars arranged in a slidable relationship, forming an arched configuration that creates a positive camber effect at dolly tires at the outer ends of the bars. The male bar comprises an apex that forms an angle that orients upwardly, forming an angle between about 165° to 179°. The center male bar and pair of female bars are arranged in a slidable relationship with each other. The midpoint of the center male bar forms an apex. The inner end of female bars is in a slidable relationship with free ends of center male bar. The female bars telescopically slide along the free ends of center male bar for increasing and decreasing length of cross rail. The arched configuration of the center male bar slopes the female bars to create a positive camber at the dolly tires.