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Discussion Starter #1
Does anyone have any experience with 5/8" D shackles used for a rear recovery point (vs. 3/4")?

The reason I ask is that my cousin and I built a new bumper last weekend, very similar to the Shrockworks bumper with two 1" thick steel tabs welded to the new 1/4" bolt on steel frame. The current pin holes have a 3/4" diameter, which is just large enough to fit a 5/8" shackle (WLL 3 1/4 tons).. the Xterra weighs 2 1/4 tons, so the shackle itself should be fine, I just don't know how much weight I should take into consideration for uphill or extreme recoveries. I could drill the existing holes an additional 1/8" to allow for a 7/8" pin, but I'm afraid that will reduce the integrity of the tabs. Any suggestions or experiences with these thresholds?

(WIP bumper pics to be posted soon :)

thanks!

eric
 

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Here's what I found on the wild wild web...I've never done business with these guys.

A standard 1/2" shackle (5/8" pin ) is rated at 2 ton working load
http://www.1st-chainsupply.com/attachments/misc/shackles/spa050.htm

A 5/8" shackle (3/4" pin) is rated at 3-1/4 ton working load....big difference.
http://www.1st-chainsupply.com/attachments/misc/shackles/spa062.htm

The solution may be a high-strength, all-alloy 1/2" shackle which is rated at 3-1/3 tons. The price seems right.
http://www.1st-chainsupply.com/attachments/misc/shackles/spa050alloy.htm

regards,
 

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Discussion Starter #3
thanks willyswan!

the all-alloy 1/2" shackle does sound like an improvement over the standard 5/8", but will 3 1/3 tons be sufficient for difficult situations? It's still significantly less than the standard 3/4" shackles rated at 4 3/4" tons. Just wonder if that extra ton and a half is overkill or if I should drill out larger holes (the thinnest area of the 1" steel tab is currently at 1/2")
 

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xEDGEx said:
...but will 3 1/3 tons be sufficient for difficult situations? It's still significantly less than the standard 3/4" shackles rated at 4 3/4" tons.
Look at the charts again. You are confusing shackle size with pin diameter. What they call a 3/4" shackle (w/ 4-3/4 ton working load) has a 7/8" pin. That is bigger than what you can attach to a Shrockworks bumper. A 5/8" shackle (w/ 3/4" pin) can be attached to a Shrockworks bumper. A forged 5/8" shackle has a 3-1/4 ton working load.

If you have a 5/8" hole on your bumper, you can attach a 1/2" shackle (it has a 5/8" pin). If you spring for an alloy 1/2" shackle, it has a 3-1/3 ton working load and is slightly stronger than a alloy 5/8" shackle.

I think even a shackle rated at 2-tons working load will be fine. You need to remember, that these are rated for rigging, so the rating is for overhead loads and has a significant safety factor built in. If you find yourself buried to your doors in gumbo mud you can always rig your recovery line to both shackles (assuming you have two on your bumper).

regards,
 

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Good question. At this point, is the tab or the 5/8" shackle stronger? If you drill out the tab, would the 3/4" shackle stronger than the tab? Since the bumper is homebuilt, there is almost no way to know the strength of the tabs or the bumper that it is attached to. Please don't get me wrong, I'm not bashing your fab skills. I have even seen "production built bumpers" get yanked off.
 

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Discussion Starter #6
Thanks again willyswan! yeah I'm aware the pin sizes are an 1/8" larger than the shackle size. I've currently got 3/4" holes to allow for 5/8 shackles. The Shrockworks site says it accepts 3/4" clevis shackles.. I haven't actually compared in person but I assumed that was the shackle size, not the pin size.

Like you said, it probably doesn't make much of a difference over 2 tons.. mostly just wondering what size people were generally using.
 

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Discussion Starter #7
Gerdo said:
Good question. At this point, is the tab or the 5/8" shackle stronger? If you drill out the tab, would the 3/4" shackle stronger than the tab?
exactly! That's my question right there. Unfortunately, like you said, there's really no way to test it. We used the same steel thickness as the Shrockworks and the welds are all professional quality.. so I guess I won't really know until I get stuck :)

here's a pic of the work in progress bumper by the way (excuse the lens flare). I'll take some better ones along with some detail shots when I get a chance.

 

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You could throw a little science at the problem. I'm a couple of decades removed from my engineering degree and I now work in marketing which has turned my brain to mush, but here are a few thoughts.

You are worried about the tabs becoming the weak link if you drill out the holes, so calculate their breaking strength.

Unless you know different, assume they are made from cold rolled mild steel. A conservative yield strength is 25,000 psi...this should be the worst case. Now measure and calculate your cross section area and multiply it by the yield strength. Throw in a conservative safety factor (two?) you should have a ball park strength of your tabs.

If the tabs are 1' wide, the result of drilling out the holes from 5/8" to 3/4" is a reduction in strength of 3125 lbs. Sounds like a big number, but from looking at the pictures, I think you could drill them out with no worries.

BTW, that's a great looking bumper.

regards,
 

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more pics........waiting...
 

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Discussion Starter #10
Jasontamu said:
more pics........waiting...
funny you should ask, that's one of tomorrow's projects :) .. gonna clean it up, throw on a fresh coat of paint and take some better quality pics so my cousin can put them on his upcoming "TimmyBuilt" website.

ultimately, I ended up increasing the holes in the shackle tabs to 1", so 3/4" fit great. The setup was tricky, but once I got the bumper ratchet strapped to the drill press (elevated by 2x4s), it was a piece of cake
 
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