Possible solutions

After to make the prototype 8-10 we could check that the PVC tubes and the ratchets made with the laser cutter and joined together with glue It wasn't sturdy enough to withstand the weight of a person. 
For that reason we decided to buy other pieces with more resistant materials. 

We will replace the PVC tubes for steel tubes. 

Luckily the measures are similar to the tubes used in the prototype 

The problem to do the ratchets with the laser cutter is that the thickness of the wood is not big enough to do it in one piece so it has to join to the required thickness. For that we will use the ratchet bike because it use the same mechanism to turn in unique direction. 

Other that we saw in the prototype is the tower because it involve the tubes but it slip with the tubes so the solution is to join the tube with the towel with velcro to don't move of the tube and dry wheels better.