Attaching tongue extension to an overbuilt NT frame

[drshoe]

So, I need to attach some 2x2x3/16 square tube to this situation - I'm thinking a 3ft tongue length, but I'm not the most structurally-inclined thinker.



That is a 2x4 laid flat 2ft aft to the steel crossmember, I built my cabin out over that.

Clearly, I need to bolt the new tongue into the stabilizer plate, and I intend to use a couple through bolts to attach it to the last cross-member it lays under like so:



My questions, for you engineer-types are these:

Typically you put the tongue under the first two crossmembers. In this case would you go under the wood crossmember and one metal crossmember - or is there much to be gained by going under two metal crossmembers? If you would go under both metal crossmembers, would you u-bolt the wood and/or the extra metal crossmember? Got a better idea that doesn't require a welder or removing the cabin?

[KCStudly]

Definitely 2 main frame xmbrs, not including the wood or that little tie bar at the front.

I would not rely on u-bolts alone; I would want something to positively pin the new member (in this application you will be pulling and pushing on the u-bolts in a sideways direction compared to their intended application).

If passing bolts thru both walls of the tongue tube, it is best to use anti-crush sleeves. This can be accomplished w/o welding by drilling one side of the hole larger to allow slipping the sleeve in place, then having it be captured within the fastened joint...

...but a better solution would be to take your tongue tube to a welder and have them weld bolt tabs on either side where it crosses the xmbrs (or one two hole strap across the top at each xmbr location). Then you can install it, transfer punch and/or drill thru the tabs and bolt. That way the final connection to the trailer does not involve welding near the cabin, but you are still getting a strong clean installation, with just a little drilling underneath.

When compared to the hassle of sourcing, fiddling with and struggling to bodge up some sort of sketchy connection, the effort to find and have a weld shop (or competent friend) make a couple of simple connections seems like a no brainer to me.

[drshoe]

Thanks KC. You're right, for me having tabs welded on is the way to go since there are a few little walk-in welding shops in the area and I would probably be buying the tube from them anyway - seems like something I should have thought of, must be that do-it-all-yourself mindset

[angib]

2x2x3/16 tube is pretty heavy and won't add that much strength since it is only connected to some fairly light cross-members - like anything, it is only as strong as the weakest link and that will always be the cross-members that it is attached to.

3ft is a lot of extra tongue length, and will maybe triple the bending load on the two existing tongue members. As long as your finished trailer will be much lighter than the HF trailer's capacity, that should be no problem.

[drshoe]

Angib it will only be a 2ft extension for a total length of 3ft.

KC - the steel crossmembers each have hole pre-drilled dead center. Do you think it would hold up well if I had threaded rod welded onto the tongue and used a single nut at each crossmember?

[KCStudly]

Threaded rod isn't usually a very high grade. It is available in higher grades, but then there can be problems welding on high grades (cracking/weakening).

Better to weld in an anti-crush sleeve and use a longer bolt.