Al-Ko Trailer Tongue failure

Uli,

Use of bearing vs. friction for bolts in shear depends on which industry you're operating in. For building structures it's quite common to use bolts in bearing since often the loads are relatively static. Friction bolting is advantageous in applications where the loads are cyclic and fatigue is a concern. It's also advantageous for applications that require accommodation of loose field tolerances since the bolts can be tightened to clamping friction and the bolt holes can be oversize or slotted.

I agree the ALKO tongue connection is subject to cyclic loads and fatigue and would benefit from a properly installed friction bolted connection. A compression bushing between the inside walls of the square tube is needed to develop the proper clamping force. Drilling a larger hole for a bushing and pushing it through the square tube won't accomplish the goal.

Craig
7Q

Hi Craig - point taken! I didn't even think about static applications. I designed mining and tunneling machines and now I engineer around wind turbines. Think high vibrations and dynamics in both cases, so in my world, stuff is constantly trying to fall apart while I desperately try to keep it together - with bolts as long and tightly torqued as the materials allow ;-)

Uli
AS

On Thursday, July 21, 2016 at 6:42:04 PM UTC-7, AS wrote:
Uli,

Use of bearing vs. friction for bolts in shear depends on which industry you're operating in. For building structures it's quite common to use bolts in bearing since often the loads are relatively static. Friction bolting is advantageous in applications where the loads are cyclic and fatigue is a concern. It's also advantageous for applications that require accommodation of loose field tolerances since the bolts can be tightened to clamping friction and the bolt holes can be oversize or slotted.

I agree the ALKO tongue connection is subject to cyclic loads and fatigue and would benefit from a properly installed friction bolted connection. A compression bushing between the inside walls of the square tube is needed to develop the proper clamping force. Drilling a larger hole for a bushing and pushing it through the square tube won't accomplish the goal.

Craig
7Q

Hi Craig - point taken! I didn't even think about static applications. I designed mining and tunneling machines and now I engineer around wind turbines. Think high vibrations and dynamics in both cases, so in my world, stuff is constantly trying to fall apart while I desperately try to keep it together - with bolts as long and tightly torqued as the materials allow ;-)

Uli
AS

Hi Uli,

I can absolutely see why clamping force is king. Lots of other things to consider as well I'm sure. I remember being fascinated by the use of tapered studs to control shear lag / bond stresses in the bonded steel fasteners for the FRP blades. Interesting industry.

Cheers,
Craig
7Q