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Lube plate

Heavy duty

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So, since we're talking about lube plates, has anyone else had their plates falling off the trailer?

  Ours has been doing that for a year or more.  My "farmer fix" was to lay the plate on the welding table, and smack the little tabs in the inner circle to swell them a bit.  Seems to have worked so far, but we haven't towed since.....

Newmar X-Aire, VATICAN
Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row
Young enough to play in the dirt as a retired farmer.
contact me at rickeieio1@comcast.net

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I never miss a teachable moment when opportunity presents itself. Incidentally this is the information I recycle every two or three years as new people come into the RVing fold. Let's start with a D.O.T. standard for King pins.


Pay attention to the three numbers here: 3.324" (the overall length of the kingpin projecting down from the pinbox). 1.308 (the length of the upper portion of the pin from the pin box plate to the reduced gripping section). 2.762" (the depth where the gripping section get bigger again)

The picture you see here is for a commercial trucking industry forged King pin which costs about $60 bucks. You do not have one in your fifth. Why? Because Lippert would have a bowel movement if they had to supply these to the RV industry, they supply machined (not forged) pins that do not have that nice flange for welding, the pins are straight like the one you see in the picture below where I welded steel pieces to it to give it the 3.324" overall length.

Having measured scores of RV King pins, majority are at the 3.32" height but I have seen some that were not. The reasons;  welder was suffering from a hangover, welder got served with divorce papers, his girlfriend is now with his best buddy, he can't find the lottery ticket he is sure got the six numbers, etc.  So now that you know the magic number, grab a rule and go forth and check yours.

Now for a bit of math. Subtract 1.308" from 2.762". the difference is 1.454", that is the length of the reduced 2 inch diameter portions of the pin where the hitch jaws grab it. Sounds generous and it is for typical latching schemes on most of the cheap, "pardon" inexpensive, hitches.

Things are different in Binkley head and their latching system has been the gold standard for 3, maybe four by now, decades. If it's so good how come it wasn't used more widely? Binkley had a patent on it, which was good for 17 years and then they got further patents for subsequent improvements to the design. The patents expired by now and I was able to reverse engineer it and others have done that too, B&W is one of them.  Why is it so good? The jaws grip the pin very tightly and precisely for almost the entire length of the reduced section. Couple more pictures and then more math. First the original Binkley jaw


then my reverse engineered cast jaw (not machined yet) and the waterjet machined one.


All are slightly different but they are all uniform in one regard, that gripping portion (numbered 2 in the upper picture) is 1 1/8 (1.125"). in height. Now for more math. Remember that "generous" reduced section 1.454" high, subtract the jaw grip of 1.125 from it and you have 0.329" not even 3/8ths of an inch, divide it into two  (some gap over the jaws and some below the jaws) and you have 0.164", little bit over 1/8 of an inch (0.125"). So if you have perfectly built pin box and perfectly built Binkley an eight inch lube plate will work, it will raise pin but there still be clearance of about 1/32 under the jaws. Quarter inch thick plate, forget it. But the guy smacking these out in his cellar on the outskirts of Shanghai has never seen a fifth wheel, never hitched one up and certainly never has seen a Binkley or knows what I have written. Couple more pictures.



Note how tightly the jaws grip the pin and note how minuscule that gap is above and below the jaws. I designed the Super Binkley so that it "favors" the bottom gap so the pin can come up with slightly thicker plate and still not high hitch.


Edited by phoenix2013
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