keisers1001
Registered User
There is no reason to beat a dead horse; I know that this subject has been discussed in detail, but I have not seen any calculations made. I was installing my bhj balancer and the mustang bolt (it is the same thread length as stock). I noticed that there was only about 5-7 threads engagement into the crank (approx .400”). I read all of the posts on this matter and it seems that there are some people that are not convinced of the potential risk of using the stock length bolt. I decided to run a quick calculation on the potential of stripping the threads out (bolt only):
Bolt size: M14 x 1.5
Shear diameter of the bolt (I used pitch diameter) = .50”
Shear area of the bolt: (.5 x pi x .4)/1.5 = .418in^2
Tensile strength of the bolt: 145000psi
Recommended torque = 130 ft.lbf = 1560 in.lbf
Load on bolt = 1560/(.1*.55) = 28364 lbf
Shear strength of the bolt: approx .5 x tensile (to be safe) = 72500psi
Shear stress = 28364/.418 = 67856 psi tensile stress
According to these numbers, these threads are close to shearing.
Conclusion….use these shorter bolts at your own risk!!!!!!!!
I reccommend a 50mm length.
Bolt size: M14 x 1.5
Shear diameter of the bolt (I used pitch diameter) = .50”
Shear area of the bolt: (.5 x pi x .4)/1.5 = .418in^2
Tensile strength of the bolt: 145000psi
Recommended torque = 130 ft.lbf = 1560 in.lbf
Load on bolt = 1560/(.1*.55) = 28364 lbf
Shear strength of the bolt: approx .5 x tensile (to be safe) = 72500psi
Shear stress = 28364/.418 = 67856 psi tensile stress
According to these numbers, these threads are close to shearing.
Conclusion….use these shorter bolts at your own risk!!!!!!!!
I reccommend a 50mm length.