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ET Hitch Problems


Overthinker

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Just cannot resist an "opportunity" to conduct a KING PIN UNIVERSITY  lecture.

First the kingpin. Installed on millions of commercial trailers and RVs. Industry standard, not to be deviated from regardless whether the pin is forged or turned to size on a lathe. Grab your micrometer and check the numbers.

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Dimensions you should be "mightily" interested about. Did they weld it in the pin box and protruded it down 1.308" from the pinbox plate to the 2.00" reduced neck area. With the forged pin like the one you see above there are no "options". RV pins are typically turned on the lathe and don't come with a flat bolster plate, which means that how it's anchored and how the welder achieves the 1.308" distance relies on his welding skills and the anchoring methods. I've seen those methods inside the pinboxes and they range from unique to bizarre.

Now for some math. Subtract 1.308" from 2.762" and the difference is 1.454". The cast jaws on the original Binkley heads are 1.125" thick where they grip the kingpin in the reduced 2.00" section. I originally had these cast to the identical 1.125" Binkley dimensions. The new redesigned ET head manufactured by Young's now utilizes rolled steel jaws waterjet cut. The steel plate they use is also 1.125" thick. More math again.

Subtract 1.125" from 1.454" and the difference is .329". In an ideal world the pin is welded perfectly with an equal gap above and below the jaws. .329 divided by two equals .1645. So the bottom gap is .165" before you start raising the pin to insert a glide plate. I found half a dozen plate vendors, they tell you the overall size, nobody wants to tell you how thick they are. Found one on Amazon who did.

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3/16" is actually .1875 already more than .1645. Some wit decided to measure the actual thickness which is even more than that. 

So if you pin is welded low, you might be OK, if you find a thin plate you might be OK, Otherwise the math says that you are SOL. Being SOL is not a good thing, product that results in SOL is not very attractive. I am currently working with Young's to eliminate the SOL situation, more on that in my next post.

 

 

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2 hours ago, GeorgiaHybrid said:

Being SOL just means you use grease on the top plate.

Wise statement containing perfect solution. More UNIVERSITY.

Original Binkley fifth wheel latching mechanism was patented in 1977 (49 years ago) Patent # 495,706. Good ideas are timeless. Few years into the production cycle Holland patented additional improvements to the jaws in the area where the two spurs project into space when jaws are open (the little reliefs you see) to control better the jaw motion when the pin comes in and closes the jaws around the pin.

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Holland would not sell me the jaw sets to go into my (competitive) head design (can't blame them) and since they did not maintain the patents beyond the original 17 years protected period, I reverse engineered the crap out of their original design and had a casting house cast me a bunch.

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Those who work with castings know that these are only at a starting point. These required about 45 minutes machining on various jigs I developed.

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and additional 45 minutes of hand fitting on each head to make these work right. The main reason why these are so massive compared to jaws in other hitch heads is that these were cast from the beginning and casts don't have the same strength characteristics as rolled steel. But there is no documented failure of these (that I know off) in 50 years of their existence. I knew there was a better way than the two hours of machining and hand fitting. I found out from Jack Meyer that he knew about a nifty waterjet outfit in Kansas. Bit more engineering and this is what I got from Kansas.

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No machining, no screwing around with hand fit. The only machining requires was to remove steel in the interlocking areas in both jaws and welding on spacer rings for the jaw mounting pins (spacers were cast in the originals).

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I was blown over when the prototypes did these.

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Young's Welding started using these pretty early in their production after we attritioned the last of the cast jaws they "inherited" with the company. So why this change didn't do away with the SOL problem? Any guesses? Let me know and I'll let you in on the solution on the way.

 

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One solution would to machine a relief into the head and put nylon pucks in, held by countersunk screws.  These could be retro-fitted to old heads too.

KW T-680, POPEMOBILE
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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11 hours ago, Larry Burkett said:

I believe I saw a Teflon plate screwed to the hitch plate on Suite Travels Comfort Ride hitch.

Comfort ride hitches do have one screwed down to them. The only problem Iran into with that is when I am picking up old campers for salvage. Some of the old mid 70s and older 5th wheel trailers had a shorter pin. I had to take the plate off a couple times when puling those old trailers.

Farmer, Trucker, Equipment operator, Mechanic

Quando omni flunkus moritati-When all else fails, play dead
I'm a man, but I can change, if I have to, I guess.

 

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  • 4 weeks later...
  • 3 weeks later...

In "perfectly" built head the jaws should grasp the pin completely around with no gap. There is a lot of welding (on the jigs) to build a head, about 3 1/2 hours. With that much welding each head is slightly different. Sometimes the jaws are tight around the pin sometimes there is a little gap. Even with the gap the jaws are securely locked. I know how to make "perfect heads", requires about 1/2 to 3/4 of an hour screwing around, mostly grinding here and there, before you send it to paint. Perfection is a sworn enemy of good enough and "finished". In manufacturing finished and shipped is a sworn enemy of perfect. 

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