Thread: Series recovery points

buy slightly longer bolts for the chassis -spring bolts have a bunch of 3mm plates made up that fit and are about 150mm long, drill a 13mm hole in them so you can fit a 13mm high tensile bolt and cut some 13mmID 3mm wall tubing to act as a spacer.

use a bridal strap and bow shackles BUT put the bow of th shackle to tthe recoery point and the strap on the shackle pin.

try to make the strap so that it runs between about 15-45 degrees and work the nominal WLL of the configuration at the vehicle GVM or the SWL of the bridal straps single line pull rating *1.5 whichever is less.

Thanks blknight I'll look at that.
Nathan

IGH-

Originally Posted by Blknight.aus

buy slightly longer bolts for the chassis -spring bolts have a bunch of 3mm plates made up that fit and are about 150mm long, drill a 13mm hole in them so you can fit a 13mm high tensile bolt and cut some 13mmID 3mm wall tubing to act as a spacer.

use a bridal strap and bow shackles BUT put the bow of th shackle to tthe recoery point and the strap on the shackle pin.

try to make the strap so that it runs between about 15-45 degrees and work the nominal WLL of the configuration at the vehicle GVM or the SWL of the bridal straps single line pull rating *1.5 whichever is less.

Blknight,
I have seen frequent mention of using High-Tensile-Strength bolts for attaching recovery points, but there is something I don't understand about this. Can you explain for me?
Am I right in thinking that the tensile strength of a bolt relates to how much "pulling" or "stretching" force it can endure in the direction of the length of the bolt. I guess that this determines how much tightening torque can be applied to it before either the thread or the bolt-body ultimately fails.
When a recovery point is used, it seems to me that the pulling or "jerking" force will actually be applied in a direction that is roughly at right-angles to the length of the bolt securing it to the chassis.
So isn't the stress imposed on the bolt (by snatching, say) acting to shear through the bolt, and not to put it under tension? If this is the case, why is the tensile strength of a bolt so important in this situation?
Does high-tensile-strength steel inherently also have high shear strength?
Or does the "tightness" with which the recovery point is clamped onto the chassis come into play, so as to prevent the shearing force actually "reaching" the securing bolt/s?
If neither of these, then what makes using high-tensile-strength bolts so important?
Regards,
AndrewMilne

Originally Posted by AndrewMilne

IGH-
Blknight,
I have seen frequent mention of using High-Tensile-Strength bolts for attaching recovery points, but there is something I don't understand about this. Can you explain for me?
Am I right in thinking that the tensile strength of a bolt relates to how much "pulling" or "stretching" force it can endure in the direction of the length of the bolt. I guess that this determines how much tightening torque can be applied to it before either the thread or the bolt-body ultimately fails.
When a recovery point is used, it seems to me that the pulling or "jerking" force will actually be applied in a direction that is roughly at right-angles to the length of the bolt securing it to the chassis.
So isn't the stress imposed on the bolt (by snatching, say) acting to shear through the bolt, and not to put it under tension? If this is the case, why is the tensile strength of a bolt so important in this situation?
Does high-tensile-strength steel inherently also have high shear strength?
Or does the "tightness" with which the recovery point is clamped onto the chassis come into play, so as to prevent the shearing force actually "reaching" the securing bolt/s?
If neither of these, then what makes using high-tensile-strength bolts so important?
Regards,
AndrewMilne

The bolts are made of stronger material, and although they are called high tensile bolts, they are not uniquely stronger in tension. They're also stronger in sheer. When doing up the bolts, they need to be done up in relation to having enough clamping pressure, not necessarily in relation to the tensile strength of the bolt.

So basically, just do the bolt up normally, and they are stronger in tension and in sheer so less likely to snap when snatching. BUT the bolts must also be threaded only down near the nut, not along the full length of the bolt.