This patent pending project was assigned to me during my co-op at Kal Tire Mining Tire Group. The device uses eddy current technology to scan for surface and near surface defects on haul truck wheels and rims. Following the engineering design process and DFMA principles, I designed key components of the device including the probe holder, encoder holder, front stabilizers, magnet holder and reddy tray unit. The device was presented at the Electra Mining 2022 Expo in South Africa.
Eddy current testing requires continuous contact between the scanner probe and specimen surface. If a "lift-off" occurs, the result of the scan will become invalid. Haul truck wheels/rims are subject to very harsh road conditions that can cause imperfections on the wheel, creating crests and valleys along the surface making it difficult to maintain zero lift-off conditions. As a result, a special probe holder had to be designed to ensure continuous contact of the probe.
The probe holder was designed with an extension spring that exerts a constant pull force, drawing the mounted probe towards the wheel when installed. A dovetail feature controls the tension of the extension spring to increase/decrease the pull force required to maintain zero lift-off conditions. A torsion spring inside the probe holder was added to accommodate for any vertical displacement due to surface imperfections, with an angular pitch of ± 22.5 degrees. Along with a pivoting feature and lock, the probe holder was designed to scan at angles between ± 67.5 degrees.
An encoder is necessary for scanning a wheel so that a position can be marked with every defect detected. Like the probe holder, the encoder holder makes use of a dovetail and extension spring to adjust the spring tension for the same reasons, but without the pivoting feature.
The front stabilizers were designed with the intent to be adjusted very quickly. The winding feature includes fast-travel acme screw and nuts, with a locking feature on the sleeve bearing carriage to prevent back drive of the screw.
The magnet holder is a made up of 3D printed and machined parts. Its main purpose is to add extra stability to the front stabilizer as it contains a magnet that generates a pull force towards the wheel. It includes a dovetail feature for quick installation and an acme screw handle for linear adjustment of the magnet.
The reddy tray is a shelf designed to hold the onboard computer used for scanning. It contains two rotating locks on the sides with ball-nose spring plungers for positioning. The three holes on the shelf bed were created for weight saving.
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