Demco eZ-Latch coupler Upgrade (TAB 320 BD)

sportcoupe

Part Number 14793-81 --- Demco eZ Latch A-Frame Coupler 

eTrailer link ($152)
https://www.etrailer.com/A-Frame-Trailer-Coupler/Demco/DM14793-81.html

Purchased from ($104)
https://www.crofttrailer.com/14793-81-demco-ez-latch-a-frame-coupler-10-000-lb-capacity-2-black/

Factory coupler is a yoke type and can be difficult to unlatch.  Demco eZ coupler is well, EZ to latch and unlatch.

Factory coupler has 4 vertical bolts going through each frame rail. Demco was designed to bold from the side through frame rails.

Demco would require drilling 6 holes in my Tab 320 frame rails, 3 on each side and would put the trailer jack too close to my boondock rack.

Nucamp designed the coupler to be installed with vertical bolts so that is what I did. That required drilling 4 holes in the top of the Demco coupler.

sportcoupe

Disassembly pictures.

sportcoupe

Drilling pictures.

sportcoupe

Assembly pictures. New hardware (nuts) are required for the trailer jack mounting. Not included. 

Chiprchuk

Is there a reason why you would not go with this model? https://www.etrailer.com/A-Frame-Trailer-Coupler/Demco/DM37ZR.html . TIA. 

sportcoupe

Chiprchuk said:

Is there a reason why you would not go with this model? https://www.etrailer.com/A-Frame-Trailer-Coupler/Demco/DM37ZR.html . TIA. 

That one has a 2" drop on the ball requiring me to buy a new TV 4" drop hitch. With the one I bought, I keep my TV hitch ball as-is.

Chiprchuk

@sportcoupe
Very good point! Thanks!

rh5555

It looks like there's a gap between the sides of your coupler and the sides of the frame.  Does that not worry you?  Part of the strength of the connection between the coupler and the frame is achieved by the snug fit which helps prevent side-to-side twisting.

Also, what is the distance from the center of the jack to the center of the ball now?  It looks like it might be longer than with the original equipment (which would be nice).

sportcoupe

Moving aft to close the gap would interfere with rack and require 6 holes drilled into frame.

The gap doesn't bother me. The side fold provided no support. The 4 vertical bolts have all the load, nothing has changed.
Remember, the Tab 320 is only a 2000 lb trailer. The coupler is good for 10,000 lbs.

Center of jack to ball is now longer, a good thing. 

runline

I would like to install this coupler on my 2021 TAB 400 BD, and love the idea of drilling the holes on top to attach like the factory coupler. Does anyone know if the 400 dimensions at the point of where the coupler would attach is the same as the 320? The gap would bother me, although I dont want to drill 6 holes in the sides of the frame.

sportcoupe

Moving coupler towards the rear to close the gap also requires you to remove the lower frame mount plate the factory provided. That's why I didn't close the gap. It also interfered with the boondock rack.

I wasn't afraid to drill 6 new holes in my trailer frame. I wanted to keep the factory boxed frame integrity of the top and bottom mount plate with the 4 vertical bolts. 

I was also concerned that I couldn't get the 6 side bolts tight enough without crushing the Tabs frame. 

Summery: The gap is cosmetic and not noticed till you look for it.

AnOldUR

At the very least, I'd shim the gap. That should be enough to prevent twisting and the lateral stress it would put on the vertical bolts.

sportcoupe

AnOldUR said:

At the very least, I'd shim the gap. That should be enough to prevent twisting and the lateral stress it would put on the vertical bolts.

That is what the bottom plate is for. 

AnOldUR

sportcoupe said: That is what the bottom plate is for.

Not really. All that plate does is distribute the clamping load over a larger area. It does very little to prevent twisting. The side walls of the top plate are designed to cradle the frame. A spacer shim filling that gap would be a MacGyver type fix for a part that's not made for the application. Bottom line is that if you're comfortable with it, that's all that matters. I'm bringing this up for consideration for anyone else who may be considering the mod.

rh5555

I had the same problem when I installed a Bulldog coupler to extend the coupler's reach:

I created 2 fillets to fill the gap and drilled a couple of holes laterally to secure it all.

My biggest problem was that the fillets needed to be wedge shaped because the Bulldog coupler was badly formed.

An installation hint: Use the bottom plate as a template for drilling holes in the top of the new coupler.  Just align the holes for the jack tube.

sportcoupe

AnOldUR said:

sportcoupe said: That is what the bottom plate is for.

Not really. All that plate does is distribute the clamping load over a larger area. It does very little to prevent twisting. The side walls of the top plate are designed to cradle the frame. A spacer shim filling that gap would be a MacGyver type fix for a part that's not made for the application. Bottom line is that if you're comfortable with it, that's all that matters. I'm bringing this up for consideration for anyone else who may be considering the mod.

Top and bottom plates create a boxed, triangulated section. There is no "twist" and if it did, the twist would be aft of the Demco coupler mount where there are no top and bottom plates.

Factory coupler has no side bolts, just a folded flange that does not attach to the frame. The flange is quite small also. Its purpose of the folded flange is to provide strength to the upper plate. 

AnOldUR

Nice job @rh5555! The four top bolts that you added are more than up to the task of towing so the main purpose of your side bolts and plates are to maintain alignment. With this in mind, did you also add plates to the inside to distribute the load over a larger area or did you feel that washers behind the nuts were enough? I don't see a problem with either method. Over tightened the side bolts to the point of crushing the rectangular tubing is possible, but that's why they make torque wrenches and nylon locking nuts.

rh5555

On my trailer, the frame is just a C where the side bolts go through.  I used washers to spread the load.  

Another installation hint:  Use anti-galling compound on big stainless bolts when using nyloc nuts.  I had to cut two off when the nuts welded themselves to the bolts before they were fully tight.

AnOldUR

(deleted post)

sportcoupe

Look at my dissembled picture. The frame rails are a two-piece "C" and boxed.  It can easily be crushed even when using a torque wrench. Standard tq on 1/2" bolts is 80 ft lbs.

I do not recommend side bolts with this style frame.

Vertical mounting bolts are way better in this application. Your application may vary. 

rh5555

You're absolutely right, @sportcoupe, I was mis-remembering how I put this together 2 years ago.  It is box-like, not a C.  I fabricated an insert to go inside the box section to support the side bolts.  It was probably overkill anyway, as the side bolts only need to be snug, not torqued down.  Their job is to hold the shim in place.

AnOldUR

2020 320S has gusset around the bolt to prevent crushing the channel. It is open for access where the bolts would be located.

rh5555

I made the mod on a 400.  It all looks very similar, though.

bjn2

@sportcoupe thanks for sharing this! I think I see that you reused the lower plate that reinforces the jack tube and has the OEM's chain mounting bolt holes. 

I followed in your footsteps and today I finished installing a Demco coupler with an Ultimate Trailer Jack. I decided to go with this model coupler and bought from the same source you did: https://www.crofttrailer.com/16854-81-demco-a-frame-2-coupler-with-chain-anchors-10-000-lbs-capacity/

I initially thought I'd mount the coupler with the sides closer to the A-frame, but I couldn't do that and reuse the bottom plate that forms a bolted box, so I mounted it forward where the jack hole on the coupler lines up with the one on the bottom plate. The hole on the bottom plate was 1/16" too small to clear the Ultimate Jack, so my first job was to scribe the target size and enlarge the hole with an abrasive grinder.

I used the bottom plate as a template to mark the hole locations for the four mounting bolts on top of the Demco coupler. I managed to drill the holes using a cobalt stepped drill bit, going slowly and using tapping oil. I painted the raw metal edges of the holes to help prevent rust.

NuCamp welded a panel into the front of the A-frame to create a box structure from the C-shaped steel members.



These images show the installed coupler. The Ultimate Jack normally mounts with its pin shaft pointing back at the trailer. The aluminum platform interfered with that, so I rotated the jack 120 degrees. I had to drill and grind out one of the mounting slots in order to center the jack's mounting plate in this orientation. The Master coupler lock fits the Demco much better than the OEM coupler. My latch lock was fortunately long enough to get through the wider Demco coupler.



The sides of the coupler leave about a half-inch gap, but they didn't fit tight to the A-frame on the original coupler. I do think it's wise to use the bottom plate with the original bolt configuration. And this upgrade is reversible should we even need to do that.



I could never find a specification for the offset difference between the OEM coupler and this cast Demco model. @sportcoupe mentioned two inches, but I think it's more like one inch. Here are profile views of the OEM coupler vs. the new Demco coupler.





I'll check, but I don't think I'll need more drop on for my hitch's ball mount. It was too cold and late in the day today for me to test the upgrade, so the easier operation I'm hoping for is still hypothetical. I'll report after I've had some time with it. I think I'll like the Ultimate Trailer Jack, but I don't think I can reuse the 7-way connector holder I had mounted to the BAL jack. I doubt that the convenience of the eZ-latch and Ultimate Jack over the years will add up to the time I spent doing this install, but I'm okay with irony. ;-)

AnOldUR

@bjn2 This coupler was designed with side walls for a reason. The original coupler doesn't bolt to the side of the frame like the Demco but does wrap around and contain the assembly. Without that you are depending on the shear strength of the bolts to prevent the plates from shifting under severe conditions. That is not the intent of the design where the bolt tensile strength is their objective. You'll probably never have an issue with your current setup, but you could consider adding shim plates like @rh5555.

bjn2

@AnOldUR I'd agree with you except the OEM's BAL coupler did not fit tight to the sides of the A-frame. It also doesn't overlap very far in terms of preventing a shear load on the bottom end of the four mounting bolts. The shear force is borne across the top and bottom of four bolts, not just one end of a single bolt. Given the difficulty of fabricating shims and drilling through the sides of the boxed A-frame, I'm not likely to pursue that belt to go with the suspenders. 

tphaggerty

bjn2 said:

@AnOldUR I'd agree with you except the OEM's BAL coupler did not fit tight to the sides of the A-frame. It also doesn't overlap very far in terms of preventing a shear load on the bottom end of the four mounting bolts. The shear force is borne across the top and bottom of four bolts, not just one end of a single bolt. Given the difficulty of fabricating shims and drilling through the sides of the boxed A-frame, I'm not likely to pursue that belt to go with the suspenders. 

Is there enough space to put short bolts with nuts as a filler without requiring drilling? Perhaps even reversing so the bolt heads are on the inside acting as shims? Might even tidy up the installation just a bit…. 

AnOldUR

bjn2 said:
I'd agree with you except the OEM's BAL coupler did not fit tight to the sides of the A-frame.

I just took a closer look at mine and it appears to be a bit tapered, snugger at the top. Not perfect, but maybe enough to lessen the likeliness of catastrophic failure. I realize that I'm beating a dead horse. We all have our own comfort levels with this type of thing. I'm just expressing mine.

AnOldUR

tphaggerty said:
Is there enough space to put short bolts with nuts as a filler without requiring drilling? Perhaps even reversing so the bolt heads are on the inside acting as shims? Might even tidy up the installation just a bit…. 

I'm not sure about that, but it's possible. An option might be to make plates like @rh5555 did, but rather than drill through the frame, tap holes in the plate at the mounting locations and use a short bolt to hold them in place.

sorry about all the editing, formatting was wonkey

sportcoupe

First I will say the factory 4 vertical 1/2" bolts are more than adequate alone to tow the Tab. No side fasteners are required.

While bolt shear strength isn't published. It is estimated that shear strength is 60% of tensile strength. A grade 5 1/2" course bolt has a tensile strength of ~17,000 lbs. 60% of that is 10,200 lbs. There are four factory bolts. The Tab is 2,000 lbs dry. 

Now if you are worried about twisting of the frame sections without side support and suspect that is what the side flanges are for, well... read on.
The factory coupler mount side flanges are not fastened to the frame so they provide very little, if any, resistance to frame twisting. Furthermore, there is no structure on the inside of the frame to prevent twisting there either. Nucamp doesn't see a problem and neither do I. 

Twisting frame just isn't an issue. The top and bottom plate with the vertical bolts create a boxed section that is inherently resistant to twisting.

For the OCD folks that don't like looking at empty side couple holes on the Demco coupler upgrade, I have a very simple solution. Get four bolts 1/2"-13 x 1" long and four nuts and four toothed lock washers. They will provide pseudo side frame reinforcement and fill most of those pesky empty holes. There is no frame behind the forward side hole so it must remain empty. The wood pictured has a curve and allowed me to fit the washers and nuts into the skinny gap between coupler and frame to attach the bolts. My fingers were too fat

AnOldUR

Very smart @sportcoupe. Simple, but functional. I apologize for being one of those OCD folks. As only being a retired machinist with too much time on my hands, my "obsessions"  should not be taken too seriously. The quality of your work is excellent. Thanks for sharing.