and if the drums are big enough, it could support the machine across water! seems like alot of stress on a chain-drive system, you would think pulling those 2 sleds of logs if there wasn't drum slippage, the drive chains to the drums would break. wouldn't the safety standards of today have issues with those unshielded sprockets/chains?
I would think if it was built today , it would probably get a little hydraulic motor on each side.