Ever had a tape measure spool stop working because the pin broke inside the case? I did. But why waste money and create waste by throwing the whole thing away?  Instead, why not just design and print a replacement and reuse the tape and spring? 

Thus, this model was born. I used PETG.

When putting it together, you need to make certain that the two pieces of the axel are on opposite sides of the spring so that it can be wound. The spring will try to keep them apart so you may need to finesse them through the hole. I used my fingernail to guide the tip through the hole when I could see it. Once through the hole, put the tape measure spool end ring over the edge to lock it in place. You can then wind the other end of the axel to tighten the spring until you get the correct amount of tension.