Tongue flex & tongue box to body attachment question

[Galen]

Folks, while I was figuring out what dimension of steel to use for my trailer frame a question popped up.

I am planning on having a tongue box that will share it's back wall with the teardrop body front. It will be attached with epoxy fillets and glass on the sides, inside and out, have a hinged top lid, and will have an internal central wall running fore and aft that separates the battery/electric side from the propane side.

This box will be sitting on an a-frame tongue. At this point I am planning on 2x2 11g steel for the tongue.

My question is this. What happens to my tongue box if the tongue flexes? Will it stress my joints at the connection to the teardrop body?

Because I realized that I am effectively extending the teardrop body with the box, and will also then be shortening the unsupported length of the tongue. So the question becomes how strong I need to make the tongue box if it will be resisting tongue flex?

And if I do make it pretty strong, maybe I can move to 14g steel for the tongue because it is effectively much shorter?

Or it could it be I am over thinking this?

[Darren]

I was also worried about flex on the tongue so I just attached the box to the front of the teardrop and left a space between it and the frame. I had a severe jackknife once backing into my garage and the box came out without any damage. It crunched my bumper pretty good.

Just an option to think about.

[teardrop_focus]

Galen

Or it could it be I am over thinking this?

One can minimize tongue flex by fine-tuning trailer balance...

[madjack]

G, I too build a front box which is part of the body...in my case, the front box is part and parcel of the front bulkhead and as such, it "hangs" off the front of the body, touching the tongue...due to the same concerns as you, I left a small space(about 1/8-3/16) between it and the tongue on the first tear we built...on the second, we got in a hurry and didn't leave that space..so far as I can tell, there has been no problem with that tongue/box contact area so far...the box/bulkhead/walls attach to each other by means of 1x1/16 Aluminum angle cleats, located 3"s in from the front of the body...I made the tongue on the second(a "Y" design) 5' past the trailer frame to allow room to mount the box, a PetCool and a propane tank...the center tube of the tongue is 2x3/16 tube and the side braces are 1x2x3/16 "C" channel...these pieces connect to the main frame 2' back from the front, to the second crossmember........
madjack

[Galen]

Thanks for the feedback all.

I am hesitant to hang the tongue box over the tongue. It seems like a lot of extra trouble, when you have this perfectly good surface to rest it on.

I think I will just make the tongue box fairly strong, which will add support to the tongue itself.

And if it develops some cracks later, I will just fix it then!

Galen

[aggie79]

I had the same concerns and am admittingly overly paranoid about these things.

As far as I can tell by your drawings, your tongue only extends 2-3 feet beyond the platform. On the other hand, my tongue cantilevers about 4 feet. So, I have chosen to have the tongue built out 2"x2"x3/16" instead of the 11-gauge as the rest of the frame.

I don't think there is too much to worry about your design and wouldn't change anything.

[Galen]

As far as I can tell by your drawings, your tongue only extends 2-3 feet beyond the platform. On the other hand, my tongue cantilevers about 4 feet.

Yes, as of right now my tongue is about 3 feet on the drawing. But I am only now figuring out the exact details for the tongue length and box. I want the tongue length to be pretty short, because my trailer body is longer than most tears. But I need to make sure I have room for my tow vehicle bumper on hard turns.

[Gerdo]

One place not to save weight is in the tongue. Mine is an "A" frame design made from 2- 2x3x3/16 steel. Next time you pass a trailer, take a look at the tongue flex. You will be amazed/shocked how much flex there is on commercialy built trailers.

If you have a tire or bearing failure at highway speeds it is a handfull. If the tongue fails it could be catastrophic.

[angib]

Galen, I think 'yes' is the answer to both questions.

Yes, I think you do need to build the tongue box strong enough that it can take some load from the tongue - not to take big loads, just not flimsy. I would be concerned to fix the tongue to the box to avoid there being a fretting action between them, but that may be overthinking too.

Yes, I do think the box will effectively 'shorten' the tongue so reducing the bending load on it. But I also think Gerdo is right about the tongue being the only part of the frame that can be too weak (you never see frame failures anywhere else but the tongue) so reducing the tongue strength to save a few pounds doesn't make sense.

Andrew

[Galen]

...I would be concerned to fix the tongue to the box to avoid there being a fretting action between them...
Andrew

Thanks Andrew.

I have decided to keep with the same steel size for the tongue 2x2 11gauge, but to also make the tongue box fairly substantial and to bolt it to welded on tabs on the tongue (no bolt holes).

Since the tongue box will have three vertical walls creating support between the tongue and the trailer body, (the sides and the internal seperating wall), and a floor, it will actually add a lot of triangulated strength to the tongue, both vertically and horizontally.

Thanks all for your help with this.

[PanelDeland]

You might also consider a "tension rod" under the tongue runner.A simple rod of 3/8ths with a weld at each end and a "bridge in the middle will substancially strengthen the tongue without adding too much weight and doesn't detract too much in the looks department.Sorry I don't have a pic of one but some on here did post one a couple of weeks ago.