I just wanted to comment on the steering system of the wood go kart using ropes. In the books I mention the pro’s and con’s of the rope steering.
Number one, you don’t want to use a low quality rope but should be using a higher quality nylon rope. Use of a clothesline rope is not going to cut it.
Secondly, the rubbing joints on the rope and wood can be quieted down with grease. The whole system is quite sound and low cost. Ships have been and still use ropes that are basically made out of weeds. Bottom line is that the interface points between the rope and the rubbing surfaces should be non-abrasive and damaging to the rope in question. This makes it cheaper to assemble and does not require pulleys to keep it running .
Thirdly the use of wire cables can be used, however, pulleys will need to be used and conventional tackles found at the local hardware store will not hold up, seeing they are rated for only around 25 pounds.
Fourthly, the positioning of the ropes on the steering system is important too, because if you mount the ropes internal the forces required to move the steering system get to high, and then will over stress the rope. But, with the rope mounted externally, the load forces for the rope are well within the rating of the rope.
Also, the braking system does not require more than 50 pounds of force to actually lock up the rear wheels, so a rope is more than adequate for this application. The interfaces of the rope to the body and the brake system should be rounded partially to keep the sharp edges from cuttting into the rope.
Rounded, or cam style surfaces are used all the time in boating and sailing for holding sails in place. The sharp edge is the no-no, not the rope.