What's with "hitch pins" for sale that say "not rated for towing"?

[Xfaxman]

Re: What's with "hitch pins" for sale that say "not rated for towing"?

Gents,

I'm not new to the forum, but this is a question that I have in my job.

I design equipment trailers. Not for hauling equipment, but a trailer that has both a hydraulic mast and boom. They weigh about 4000# each and are towed in tandem pairs. For road construction.

Now, I have a new design I'm finishing up, it's got a telescoping tongue so you can stow it on the jobsite.

---------------------------------------------

CM

I would like to see some pictures of the trailer. :thumbsup:

 

[LD1]

Re: What's with "hitch pins" for sale that say "not rated for towing"?

The original CM.

:laughing::laughing:

 

[aczlan]

Here's another reason that I'm not worried about the strength of the pin - these are being pulled most times by a pickup truck with a class 4 trailer hitch, 2" receiver, and a 5/8" pin. These pins are not hardened, cost about $4 and you all trust they won't shear off, and rated to 10,000 load. So we are actually already overdoing it with the pin size, just like everything else on our trailers. They are best in the business.

The difference is that the 5/8" pin has pretty much no offset (the two sides it holds together are pretty much touching) and it essentially has to shear twice to come loose.
With a hitch pin (like on a tractor hitch to an implement), there are 2-3" of space between the tractor side hitch and the top and bottom of the trailer side.
As such, there is a LOT more stress on the 3/4" hitch pin than on the 5/8" pin that holds the receiver in.

Aaron Z

 

[Xfaxman]

Re: What's with "hitch pins" for sale that say "not rated for towing"?

OP, did you read post #13? There is a dot rated pin.

The original CM.

:laughing::laughing:

CM you joined TBN earlier, but the new CM may have been born first.

 

[meos1]

Re: What's with "hitch pins" for sale that say "not rated for towing"?

That is a good point, the speed issue..... But it's only in a crash that it would matter. These things are almost always parked, not on the road.

I think you missed the point sir. I'm not trying to "cheap out" at the expense of safety. I think you also missed the point, that where they are saying "not rated for towing" it isn't because it's an inferior pin, they are just covering their butt, and putting the onus on the buyer if there's a failure. There's a big difference there. In the case of McMaster Carr (the ultimate hardware store) they don't make anything, they only sell it. So they are purposely off-putting the liability. Others do this as well.

The pin that I linked to and complained of the price - yeah, rated for towing 25,000 lbs! We don't need that, I could have a case hardened pin made for less.

I started research today on zinc plated pin, made by a company called redline. I'll find out what the material is and make sure it's vetted before we use it. And it's around $10 bucks.

Here's another reason that I'm not worried about the strength of the pin - these are being pulled most times by a pickup truck with a class 4 trailer hitch, 2" receiver, and a 5/8" pin. These pins are not hardened, cost about $4 and you all trust they won't shear off, and rated to 10,000 load. So we are actually already overdoing it with the pin size, just like everything else on our trailers. They are best in the business.

I hope that I made the point that I'm looking for the right pin, for the right price. Just because the trailers are expensive doesn't mean you can spend the maximum amount on each part and still make money. Truth is, we don't make enough money, so we have to look for ways to reduce cost to stay in business. Blame the tax man for that.

thanks for the replies.

CM

The Good Colonel is looking to source a part sans the "not rated for hiway use" disclaimer that meets his specifications. He wants safety. In fact he wants longevity (Yellow Zinc Coatings)... He is attempting to do the right thing and make sure the pin is not a legal boondoggle should something happen in the future.

My hats off to you sir. You are correct taxes eat up the margin and force lower cost(which often relates to lower quality) parts than you are comfortable including in your design. Stick to your guns.

 

[Renze]

Re: What's with "hitch pins" for sale that say "not rated for towing"?

I design equipment trailers. Not for hauling equipment, but a trailer that has both a hydraulic mast and boom. They weigh about 4000# each and are towed in tandem pairs. For road construction.

I used to, from 2005 to 2008. Here in Holland we have to certify our drawbars according to a formula, get an approval on the brake calculation, before we can go to the local DOT to aquire an individual license plate for that trailer. AFAIK its carried a bit further than what you guys have to put up with.

Lets put things in perspective: You're worried about lawyers getting after you for using a pin that has a disclaimer, while designing the rest of the trailer without hesitation ?

....Just have some pins lathed and galvanised of your own design, it will have the same liability as the rest of the trailer, and no lawyer who only reads labels, will be able to sue you, unless he can find an engineering standard or DOT guidelines on trailer design (if any) which you did, or didnt, keep.

Its quite simple. If there is no guideline, no lawyer can hang you up on it. If there is a label on a 3rd party pin, there is something they can hang you up on.

 

[aeblank]

Re: What's with "hitch pins" for sale that say "not rated for towing"?

while designing the rest of the trailer without hesitation ?

Nothing against the OP, but this point has always gotten me. Sitting in a design review, discussing some MINOR point for an hour... There were THOUSANDS of decisions made about thises or thats that have not even been noticed and are just as important, if not more so.

 

[ishiboo]

Re: What's with "hitch pins" for sale that say "not rated for towing"?

I bet a hitch pin designed for on-road towing is forged, while on implement linkages/etc. it's fine to use a cast piece.

 

[Colonel Monk]

Re: What's with "hitch pins" for sale that say "not rated for towing"?

OP, did you read post #13? There is a dot rated pin.

The original CM.

Just getting back to this after being out of town for 3 weeks with limited access....

Yeah, I did, but the hitch pin I'm in need of is 3/4 diameter x 6 long.....

 

[Colonel Monk]

Re: What's with "hitch pins" for sale that say "not rated for towing"?

The difference is that the 5/8" pin has pretty much no offset (the two sides it holds together are pretty much touching) and it essentially has to shear twice to come loose.
With a hitch pin (like on a tractor hitch to an implement), there are 2-3" of space between the tractor side hitch and the top and bottom of the trailer side.
As such, there is a LOT more stress on the 3/4" hitch pin than on the 5/8" pin that holds the receiver in.

Aaron Z

Yeah, without doubt. But in my application we are using the pin in an application just like a receiver hitch, so as you say, it's practically got to shear twice.

But you might be onto something, they might be stating stating that it's not certified for TOWING using a "clevis" hitch where the clevis could be much farther apart than the 3pt hitch bar or "eye" that it's connected to. That puts a pretty big bending moment on that pin and makes it more likely to fail. I have seen a bunch of bent hitch pins for the reason you describe, they don't have 2 points of contact on each half, only two on one half and one on the other, causing the pin to have significant bending stress.

In that regard, what I'm wanting to use the pin for is a much different application. Pin must shear to let go because of the close fit.

I'd bother with a stress calculation / quick FE simulation if I had any doubt at all that it WILL HOLD. But then again, I'd have to know exactly what the material is for it to be accurate. That information you typically won't find on the sticker of a pin made for farm and fleet.

My only issue with using any old 3/4 diameter pin, is the vendors listing it as "not rated for towing". IF there is an accident and someone is killed, the lawyers will find that and a jury won't understand that it's not negligent, but a cover yer butt for the vendor... Your average anyone doesn't understand what material stress is and what it means. They'd see that disclaimer and you'd be guilty.

That's really what this thread was about.

I think you just explained how and why they might also be using the note, with only 3 points of loose contact in the hitch the likelihood of failure is much much higher.

Thanks,

CMonk