Thanks. Yeah the wheels in Carcinus are set 120° apart and the idea is that the robot is able to strafe i.e. it can go diagonally and sideways. There's supposed to be a third wheel at the back to complete the setup but I've been having trouble trying to find a wheel that's slippy enough to be pulled along when the robot is moving forward/back, but grippy enough to turn the back end when needed.

The robot is also front-heavy due to the claws so there's not much weight pushing down on the back wheel, which doesn't help matters. But I've got a homemade wheel idea in mind that I'll try and see how it goes

Regarding the claws, I think I've actually made the robot a little compact to fit an effective enough actuation mechanism into. Either that or I need to consider more compact custom options. But the drive uses three channels so I think my dad would struggle to cope with having four channels to operate!