Answer
Iyakar faɗaɗa don zoben waje shine matsakaicin diamita wanda za'a iya shimfiɗa shi ba tare da saiti na dindindin ba. Matsakaicin damuwa yayin fadada shine $\sigma_{exp} = (E \cdot t \cdot (D_s - D_i)) / (D_i^2)$, inda $D_s $ shine diamita na shaft kuma $ D_i $ shine diamita na ciki na kyauta. Idan $\sigma_{exp}$ ya zarce ƙarfin yawan amfanin ƙasa $\sigma_y$ na kayan (misali, SAE 1070), zoben ba zai koma ainihin siffarsa ba kuma zai rasa rikonsa akan tsagi. Wannan shine dalilin da ya sa sau da yawa ana kera zoben karkace tare da juyawa da yawa; Juyawa biyu ko uku na sirara na iya samar da jimillar kauri $T$ a matsayin juyi mai nauyi guda ɗaya amma tare da rage yawan damuwa na mutum $t$ yayin shigarwa, yana ba da damar haɓaka ƙimar haɓakawa da yawa.
