Cat 315C L – Broken thumb

I rented a Cat 315C L with a hydraulic thumb for lot clearing job I'm doing. We've had a good couple days, down to about 15 mature trees left to flop when I hear a loud pop and notice the thumb is dangling. I had just flopped a 20" Red Oak and it was partially hung up in another tree. I couldn't quite push it down from my angle, so I rolled the thumb to stow position and tried to hook the root ball to pull the tree back some. The tree with root ball was more than the hoe could pick, so I readjusted and tried again, and that's when I heard the pop. Some of the discoloration is from foliage from me moving the tree out of my way after the cylinder broke. It just dangled in the way while I was working the debris out of my path. The brownish discoloration on the eye near my hand might be rust. I scrubbed it with a wire brush to make sure it wasn't dirt.