D Hook Hitch Shackle

[DaveInDenver]

The other thing to consider is that your hitch pin is designed and sized to take the load in double shear (i.e. the pin resists the cutting force due to a load right where the hitch and receiver meet). The strap loop into the hitch method works but it does apply a bending moment accross the length of the pin. Does that make sense, I wish I could find a picture to explain this better.

One other thing to keep in mind about these (I use the Smitty, the Warn works fine, too) is the hitch pin. Most people are using a class III hitch pin, which is typically a 5/8" pin made from C1018. This steel is not particularly strong, roughly 60 ksi yield and 5/8" pin has about 0.31 sq-in of area. It's better to use a 5/8" grade 8 bolt, which is 150 ksi. BTW, ksi short for thousands of pounds per square inch, so 120 ksi is 120,000 lbs/sq-in. The rule I remember is to take 50% of ultimate yield in tension and that is your ultimate shear yield. So a 5/8" hitch pin will yield at about 9300 lbs, where as a grade 8 bolt will yield in shear at just over 23,000 lbs.

 

[teotwaki]

I'm curious. What are the pros/cons of the D-Shackle vs. a reciever tow hook, like this one below?
http://store.summitracing.com/partdetail.asp?autofilter=1&part=CHT-D-325&N=700+115&autoview=sku

Your strap will never get out of a D shackle that has the pin screwed in tight.

Let's say you bought the hook instead of a D shackle and are using a recovery strap which is semi-elastic (not a static line tow strap). You set up the strap and give a big ol' tug to someone who is stuck, the strap stretches, the stuck vehicle surges forward and for a moment the tension is off of the strap. The end of the strap on your hook jiggles forward and up, just as your vehicle move forward. The strap either flies off completely or worse, impales itself on the hook and is ruined.

A D-shackle is fool proof in comparison.

 

[teotwaki]

One other thing to keep in mind about these (I use the Smitty, the Warn works fine, too) is the hitch pin. Most people are using a class III hitch pin, which is typically a 5/8" pin made from C1018. This steel is not particularly strong, roughly 60 ksi yield and 5/8" pin is about 0.31 sq in in area. It's better to use a 5/8" grade 8 bolt, which is 150 ksi. BTW, ksi short for thousands of pounds per square inch, so 120 ksi is 120,000 lbs/sq in. The rule I remember is to take 50% of ultimate yield in tension and that is your ultimate shear yield. So a 5/8" hitch pin will yield at about 9300 lbs, where as a grade 8 bolt will yield in shear at just over 23,000 lbs.

It would be nice to get a bolt with the right length of unthreaded shoulder so that it has a nice smooth metal to metal interface with the shackle bracket.

 

[DaveInDenver]

It would be nice to get a bolt with the right length of unthreaded shoulder so that it has a nice smooth metal to metal interface with the shackle bracket.

Yeah, should have mentioned that. You need to get a pretty long bolt with about 3" of shoulder for it to work. My mistake for forgetting to say that.

 

[teotwaki]

Yeah, should have mentioned that. You need to get a pretty long bolt with about 3" of shoulder for it to work. My mistake for forgetting to say that.

Figured it was an oversight but you got me to thinking about hunting down the right bolt. I agree that it might take a hacksaw to get the overall length just right. I would like stainless too in order to minimize oxidation.

 

[asteffes]

Wouldn't you want the pin to act as a fuse in the system to prevent permanent damage to the frame? My Tacoma is rated at 6500 pounds towing capacity, which I figure has something to do with the frame and hitch strength, not just the tranny.

 

[DaveInDenver]

Figured it was an oversight but you got me to thinking about hunting down the right bolt. I agree that it might take a hacksaw to get the overall length just right. I would like stainless too in order to minimize oxidation.

Most hitch pins are made from 304 stainless, which has about the same strength as C1080. If memory serves, 304 is about 75 ksi yield. I agree corrosion resistance would be nice, but you really need a heat treated pin if you are concerned about its strength, which means a graded bolt of some sort. Hitch pins are almost never heat treated and since they achieve their rated strength of about 5000 lbs without it, no one is going to actually grade a Class III hitch pin.

 

[DaveInDenver]

Wouldn't you want the pin to act as a fuse in the system to prevent permanent damage to the frame? My Tacoma is rated at 6500 pounds towing capacity, which I figure has something to do with the frame and hitch strength, not just the tranny.

NO!

The last thing you want is a piece of recovery gear breaking. You'd rather have the frame tweak before having a projectile.

People get killed that way!

Edit: If you are concerned with your truck being damaged in a recovery, then you probably should let someone else handle it. I don't want to sound mean, but the guy in the other truck is putting his trust in you that you are not going to endanger him.

 

[asteffes]

I'm not concerned about damaging my truck. My question was really just to bring up the issue, as I've heard it mentioned by others (not here) that they wanted a means of preventing permanent bending or other damage. It does, indeed, sound scary to have anything breaking off and flying about during a recovery.

All that said, has anyone heard of one of these hitch pins breaking during a recovery? Is this a big problem that I'm just not aware of? I understand your concerns. I'm just wondering if this is something that you've whitnessed or heard of actually happening, as I have not.

 

[DaveInDenver]

I'm not concerned about damaging my truck. My question was really just to bring up the issue, as I've heard it mentioned by others (not here) that they wanted a means of preventing permanent bending or other damage. It does, indeed, sound scary to have anything breaking off and flying about during a recovery.

All that said, has anyone heard of one of these hitch pins breaking during a recovery? Is this a big problem that I'm just not aware of? I understand your concerns. I'm just wondering if this is something that you've whitnessed or heard of actually happening, as I have not.

I didn't mean to imply it, just saying it out loud. I am not a professional and hopefully the Tread Lightly! trainers and stuff will correct me. It is my understanding that you NEVER want to knowingly install a part that is not maximized for strength in the recovery chain-of-gear. I don't know what the safe margin for a piece of gear is.

Yup, to be perfectly honest I've never seen a broken hitch pin. It is theoretical in my experience. Still, I personally use a grade 8 bolt. Then again, the working limit on a 3/4" bow shackle is only 4.75 tons anyway...

 

[p1michaud]

Hitch pin.

One other thing to keep in mind about these (I use the Smitty, the Warn works fine, too) is the hitch pin. Most people are using a class III hitch pin, which is typically a 5/8" pin made from C1018. This steel is not particularly strong, roughly 60 ksi yield and 5/8" pin has about 0.31 sq-in of area. It's better to use a 5/8" grade 8 bolt, which is 150 ksi. BTW, ksi short for thousands of pounds per square inch, so 120 ksi is 120,000 lbs/sq-in. The rule I remember is to take 50% of ultimate yield in tension and that is your ultimate shear yield. So a 5/8" hitch pin will yield at about 9300 lbs, where as a grade 8 bolt will yield in shear at just over 23,000 lbs.

Excellent point on material selection.
From the numbers above, you make the assumption that the hitch pin is in single shear. In my mind, the hitch pin is in double shear with both sides of the receiver trying to shear the pin. In that case, the yield numbers will be twice those numbers due to doubling the shear area (i.e. 18 600 lbs and 46 000 lbs respectively). Not trying to cause grief, just making sure that readers get the correct information.
Cheers,
P

 

[DaveInDenver]

Excellent point on material selection.
From the numbers above, you make the assumption that the hitch pin is in single shear. In my mind, the hitch pin is in double shear with both sides of the receiver trying to shear the pin. In that case, the yield numbers will be twice those numbers due to doubling the shear area (i.e. 18 600 lbs and 46 000 lbs respectively). Not trying to cause grief, just making sure that readers get the correct information.
Cheers,
P

That's a good question and I'd think you are right. I have to further qualify by saying I'm just a plain only sparky, so my mechanical is barely passable freshman level. Anyway, my assumption was largely based on the fact that it's a very poor interface fit and loaded off angle quite severely, so the bolt must withstand the force equivalent to single shear because of that. I do think it's actually a double shear problem, though.

Anyway, for clarity, here's what we're talking about.

 

[Xtreme XJ]

Thought I'd dredge this thread back up....
What are the thoughts about domestic vs. imported D-rings?
It's hard to find a domestic D-ring any more.... including the 2 mentioned at the begining of this thread....
American Co. yet both imports.

Curt :safari-rig:

 

[Bayou Boy]

Thought I'd dredge this thread back up....
What are the thoughts about domestic vs. imported D-rings?
It's hard to find a domestic D-ring any more.... including the 2 mentioned at the begining of this thread....
American Co. yet both imports.

Curt :safari-rig:

Try the Crosby shackles as opposed to these Chinese Shackles. THe second you unscrew the bolt you will notice the difference. THe Crosby is like a normal graded bolt while the imported stuff is like a rough generic galvanized olt and nut. An immediate difference. I used to use the Chinese stuff. I bought a couple of Crosby shackles and will never go back.

 

[teotwaki]

Try the Crosby shackles as opposed to these Chinese Shackles. THe second you unscrew the bolt you will notice the difference. THe Crosby is like a normal graded bolt while the imported stuff is like a rough generic galvanized olt and nut. An immediate difference. I used to use the Chinese stuff. I bought a couple of Crosby shackles and will never go back.

Who has the best price on them?