Lifeguard

a lot of rope twisting can be avoid by keeping the rope path in one plane. all grigri style belay devices i know apply this improvement except for the grigri itself for unknown reasons. they are the edelrid pinch, the camp matik, the mad rock lifeguard, and the beal birdie.

I'll refer you to two websites for curring and historic climbing devices. Probably not a exhaustive list, but: https://weighmyrack.com/belay-device http://www.verticalmuseum.com/VerticalDevicesPage/Belayers.php It would be nice to take a depth look into the history and current belay devices about th