Joint and bolt strength

[pmganesh]

HI,

I have a particular design of a torque tube to transmit a torque of 650 kg.m , the end of this 65 mm torque tube is welded to a billet of round bar. This torque tube with solid end is bolted to a crank arm. This crank arm then is actuated to move another mechanism. This system is subjected to a high torque, shear stress and tension. The crank arm is diameter 65 and 20 mm thick (SAF 2205) and the end of the solid part of the shaft is 30mm in depth also the same material as the crank arm.

The maximum bolt circle diameter at the end of the torque tube is approximately 48 mm to give a margin of safety of 25 % for an eight bolt configuration using M8 bolts of UTS of 160 ksi.

Could someone comment and tell me if my methodology is correct or whether the arrangement is a reasonable one. Perhaps you might have a better method of analysis. What is the minimum edge distance required from the bolt centre to the edge of the crank arm to ensure sufficient edge clearance also clearance for bearing material between bolt holes.

Would you please be able to provide me with the specifications for a suitable type of bolt for this application.

 

[vonlueke]

pmganesh: For standard, protruding head bolts installed in ductile metals, the minimum recommended edge distance from bolt hole center to plate edge is 2D, where D = bolt hole nominal diameter. For rivets or flat head bolts, 2.5D is recommended. Minimum recommended bolt spacing is 4D.

 

[diamondjim]

I agree with Vonlueke in that the VDI standard does
imply that two times the bolt diameter should be used
unless you have oversize holes in which case it would
have to be greater. This assumes the part are similar
in properties steel and steel etc. and using maximum
forces to clamp these parts i.e. grade 8 fasteners.
If you are using lower grades, I would assume you could
get by with a lesser distance. Most standards are for
the worst conditions.