Answer
Ƙarfin ƙwanƙwasawa na taron ɗimbin ɗimbin karkace yana iyakance da abubuwa mabambanta guda biyu: ƙarfin ƙarar zoben da nakasar tsagi. Ana ƙididdige ƙarfin ƙarar zoben a matsayin $P_r = \ frac {D \ cdot T \ cdot \ pi \ cdot S_s}{K}$, inda $D$ shine diamita na shaft/bore, $T$ shine kauri na zobe, $ S_s$ shine ƙarfin shear, kuma $ K$ shine yanayin aminci (yawanci 3). Duk da haka, kayan tsagi yawanci shine mahaɗin mafi rauni. An ba da damar yawan amfanin gona ta $P_g = \ frac{D \cdot d \cdot \pi \cdot \sigma_y}{K}$, inda $d$ shine zurfin tsagi kuma $\sigma_y$ shine ƙarfin yawan amfanin ƙasa. Idan nauyin turawa ya wuce $P_g$, bangon tsagi zai lalace, yana haifar da zoben zuwa tasa (mazugi) kuma a ƙarshe 'ya fita' daga cikin tsagi. Dole ne injiniyoyi suyi amfani da ƙasan waɗannan dabi'u biyu azaman iyakar ƙira.
