A tadpole trike is a rather expensive investment and so having it get stolen is a serious concern for many. Trike owners are always asking for advise on forums concerning locking up a trike. Here is a video about securing e-bikes with advise on the matter. It is highly recommended that viewers wear eye and face protection while watching as this video is “shattering”. I noticed one thing they didn’t show concerning cutting locks is the use of a cutting wheel with a battery powered angle grinder. (see video further below.)
Lastly here is a video about various locks …
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So, a good quality D-lock is best. No surprise, but rather hard to use effectively on a trike.