How to detect a small object in an uncalibrated environment

Hi,

I'm having issues with detecting wire-locks in below images. As it can be seen the environment is pretty dirty and the appearance/shape of the wire-lock vary in different images. My plan is to use HoG and SVM. Therefore, I would like to know whether I'm thinking along right lines or could you please suggest some other feature extraction techniques? Any advice is highly appreciated.

Many thanks.