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The New Hitch
Henry Szmyt, proprietor of Szmyt RV Products, manufactures a hitch for converted Class 8 toters. His hitch has a stack height of 15" compared to the 11" of the TrailerSaver.
In the spring of 2008, I made Henry a deal. I would do all of the CAD work to design a version of his hitch with an 11" stack
height and close to the same footprint as a TrailerSaver TSLB.
I would test the prototype ( You Tube Video of test) with my trailer and toter. He would supply the metal and purchased parts once the design was done as long as I did some
additional CAD work while fabrication was underway.
Hitch Installation
The version of the hitch that I'm getting is a slight modification from the standard lower stack height hitch that Henry
will be producing. I don't have a base plate; I'm using the truck deck (1" plate steel) as the hitch base plate. This requires
that all of the base plate holes be made in place on the truck. After spending the weekend assembling it, this is not something
that will not be repeated. Henry has decided that all future low stack height hitches will have base plates. That's why you
build prototypes.
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| Single Bag Hitch |
Single Bag Design
The air spring is a Goodyear 13,000 lb. air spring. This will allow for an operational pin weight of 3,000-8,000 lbs.
The TrailerSaver, even with the 3rd bag option has a maximum pin weight of 7500 lbs., however, this is misleading, like
most of the RV industry. If you load it up with 7500 lbs., the bags are at 100 psi and acting like bushings rather than suspension
components.
This new single bag design allows even the heaviest of 5th wheels to have the full benefit of an air suspension hitch.
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| Geometry |
Geometry
The geometry of the new hitch design had to maintain the safety aspects of the original ET hitch geometry. Through the
full range of travel, the hitch must maintain a declined articulation angle. This means that if the trailer is pushed from
behind (rear end collision), the forces on the hitch cause the trailer to dive into the toter bed, not be launched up into
the air towards the toter passenger cabin.
The geometry imposes a travel restriction on the new hitch. This lower profile hitch has only half of the travel of the
original ET hitch. However, it has over twice the travel of the best TrailerSaver has to offer.
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| 11" Of Stack Height |
Why is 11" of Stack Height a Big Deal?
The current volume leader in the hitch space is TrailerSaver. They have an 11" stack height in their design. My bed was
designed around that dimension. After talking to a few folks that are experiencing air hitch failures (excessive wear, bottoming
out the limited 1" of travel, bags running at pressure limits, etc.) most are not willing to rebuild their toter beds for
a new hitch, myself included, so 11" of stack height became a design constraint.
I will use one of my newly refurbished binkley heads on this hitch. The refurbished Binkley head reduces the hitch head height by 5/8". This will allow for a bit more air cushion
in the hitch head.
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| TSR Hitch Tail Plate |
Head and Tailplate
As I mentioned above, the version of the hitch that I'm getting is a slight modification from the standard lower stack
height hitch. I also have my own tailplate to keep in line with the "Optimus Prime" moniker.
Receiver Hitch
While Optimus Prime was getting the TSR Hitch installed, I had some spare time, so I had the metal shop install a receiver
hitch. I have a very small travel trailer that neither the WRX or the element can tow, so Optimus Prime will be
put to use. The receiver will also be used to move equipment from my NY property to the MA property as needed. It is
a 10,000 lb. tow capacity, 1000 lb. tongue weight 2" receiver tube welded in directly to the massive ballast bumper.
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| Receiver Primed |
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| Substructure |
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| Gussett |
The receiver hitch extends through the lower plate of the ballast bumper. It is a full 30" receiver tube anchored to
the ballast bumper with a 3" main tube, a 2" support tube, and a gusset to transfer the vertical forces to the main rear
panel.
The receiver tube has a tail plate to further strengthen the joint between the receiver tube and the main horizontal
support tube.
Completed Hitch
The head was installed on 9/12/2008. It was the culmination of 2 separate design elements. The Binkley Refurbish Program and the TSR (Total Soft Ride) hitch design from Szmyt RV Products.
This design was presented at the 2008 HDT National Rally.
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| Don't Shear the Finger |
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| Bed Ver2.0 Complete |
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| Hitch Detail |
The first hitch up was butterfly time. We had several design questions and theories that had to work the first time.
What would the air pressure be (45-55 was the target) ? Would the newly designed Refurbished Binkley mount to the trailer?
Would it dampem bumps properly? Would the hitch articulate like it's big brother? Would the 2-axis rotational joint take the
stresses?
Pictures speak louder than words....
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| First Latching |
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| 52 psi w/ 6200 lbs. |
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| Latched and Tested |
On 9/16/2008, we completed the first pull with the hitch with great success. See YouTube video here.
All in all, everything tested out just fine. The head operated as expected. The hitch performed flawlessly, and the trailer
even passed the egg test. I placed an egg in the fridge on a rigid surface and after a 50 mile test drive, the egg survived.
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