Hi Alun. Apart from the latest series of Robot Wars it has been generally accepted rule among the Combat Robot community that there is absolutely no entanglement. There was a controversy in the 2015 Battlebots when one team used a net in a fight because they had noticed that there wasn't a "no entanglement" rule but nobody else noticed (although that could have just been TV drama). So I'm afraid even if you found some way that passed through the rules the loophole would probably be closed pretty quickly.

Having said that however it has got me thinking. If you were to use something like a long HDPE rod with steel hooks attached & jammed it into a spinner's drive mechanism with the intention of either grabbing & stopping the chain/belt would that count as an entanglement device (assuming the chain didn't break)?