Custom Bumper Project

[PK]

Hmmm, I did not know that, but I was thinking about how Warn bumpers, and Hummers have their tow points on the bumper. My steel is actually almost double the strength of the Warn bumpers, and those D rings are rated to 10K lbs. They are mounted double walled with 1/2" grade 8 bolts, not sure you can get any stronger, I suppose to I could weld a bback plate to the tubing? The other good thing is that I can just disconnect the hooks and move them back to the factory tow points in a few seconds, just 1 cotter pin each

Thanks for the heads up, I am sure Joe Darlington will look at it with great scrutiny when we get to Uwharrie in Oct. If you don't know who Joe D is, he does a lot of fab works for Isuzu, including Tie rods, tie rod shields, bumpers, sliders.....and the list goes on. I am interested in what he recommends as well.
Thanks again PK

Hi Marlin,
I have just gone back through all your photos and would like to offer the following -
The hook bolts pass through your SHS tube without anything to stop crush of the steel tube. You need to weld some steel tube (round) spacers from the front edge of the SHS to the rear edge. This will spread the load over both of the section areas of the SHS. Alternatively, weld a pad, full height of the SHS and about 6mm (1/4") thick, wide enough to pick up both of the bolts for 1 hook.

The lynch pin points do not look man enough or the loads generated on the front and rear of the respective holes. They look as though the holes will elongate. I would either double the number of pins, or weld pads onto the outside of the outer tube, and inside of the inner tubes, to increase the load bearing area.

The bolt point to the chassis looks to be only one bolt per side for your main attachment point. This would bring into question, the strength of the bolts in shear, and again, the load bearing area of the tube to prevent elongation.


Mind you I have not crunched the numbers because I don't have enough information on the materials you have used.
Most snatch straps used these days are rated at a SWL of 8000kg (17,640 lbs). You need to design so that if anything breaks, it is the strap. A flying strap can hurt - even break bones, but put a lump of steel on the end of it, and it can kill.
From a design point of view, we would use a safety factor of 2:1, so your design strength needs to be capable of supporting 35K lbs.

If you had 16 - 17 tons hanging from your arrangement, would you walk under it??

Please accept above points as a genuine attempt to help.

Regards

PK

[Marlin]

Hi Marlin,
I have just gone back through all your photos and would like to offer the following -
The hook bolts pass through your SHS tube without anything to stop crush of the steel tube. You need to weld some steel tube (round) spacers from the front edge of the SHS to the rear edge. This will spread the load over both of the section areas of the SHS. Alternatively, weld a pad, full height of the SHS and about 6mm (1/4") thick, wide enough to pick up both of the bolts for 1 hook.

The lynch pin points do not look man enough or the loads generated on the front and rear of the respective holes. They look as though the holes will elongate. I would either double the number of pins, or weld pads onto the outside of the outer tube, and inside of the inner tubes, to increase the load bearing area.

The bolt point to the chassis looks to be only one bolt per side for your main attachment point. This would bring into question, the strength of the bolts in shear, and again, the load bearing area of the tube to prevent elongation.


Mind you I have not crunched the numbers because I don't have enough information on the materials you have used.
Most snatch straps used these days are rated at a SWL of 8000kg (17,640 lbs). You need to design so that if anything breaks, it is the strap. A flying strap can hurt - even break bones, but put a lump of steel on the end of it, and it can kill.
From a design point of view, we would use a safety factor of 2:1, so your design strength needs to be capable of supporting 35K lbs.

If you had 16 - 17 tons hanging from your arrangement, would you walk under it??

Please accept above points as a genuine attempt to help.

Regards

PK

Great advice, I was already planning on placing another sleeve inside both ends of the tubes for the tow points. That will prevent the crushing of the tubes. I can easily drill another set of holes in order to double pin the outer sleeves to the inner sleeves.
As for the frame bolts, there are two, I used the factory bumper mounting points as well as the factory bumper bolts. I think they are 17mm grade 8? They go through the 1/4" plate that makes up the front of the frame bumper bracket.
I think at that point, the weakest spot on the whole set up would probably be the bolts for the tow points. But as I mentioned earlier, I can move the tow hooks from "my" points to the factory points in less than 10 seconds, I left them accessible on purpose. So if I am buried in mud doing some serious snatching, then I can move the tow hooks. If it is normal, stuck on an obstacle, just need to move snatching, then I can leave it. I plan on going out to the woods when I am done and tying off to a big tree. Then I will slowly back up with a buddy watching to see if anything moves, if it does, that is the next thing to upgrade. This way I can test it in a controlled environment without danger to anything or anyone. Tree huggers may be upset, I will be stressing out a tree.....