RD4B Chainbar

So been watching some YouTube reveal videos and found few RD4B with the looks a chainbar. Wanting to know how build that chain bar as I already have a RD4B working. This would help me do internal stacking rather than external. Thanks in advance

I think the best explanation of a chainbar comes from this Sack Attack video, but the concepts could be applied very easily for a robot in this game.

OK thanks that helps, so if I’m going to do a chain-bar on a RD4B where most people do it would it be possible to do it with 1 motor speed or torque? And should they have any gearing for it?

My chainbar is currently 1 motor and runs on a 1:5 speed gear ratio. You’ll need rubber bands for it, but it’ll never stall if built correctly.

Ok thanks, Any photos?