Frame front crossmember question

[jjlevek]

80 views on my other post, and no responses!?! Maybe I have too many questions in one post? So, here is one question:

I want to modify a frame from a folding trailer I wish to widen. What I am thinking of doing is butt joining 2 C-Channels by placing a half hat channel over top of them as in the picture below. The C channel would be cut off to nest in and bolt to the side rail hat channels. This would be about 6" as you can see on the left side of the picture. Same thing on the right side and the 2 channels inside meet in the center above the tongue. Then on the front and rear vertical sides of the crossmember, there would be 12 bolts to join them together--3 bolts into each lapped piece, front and back, on both sides = 12. I know, ideally I should get some new metal, but I want to re-use the original metal as much as possible without spending more money.

My concern is about the strength of this if I do it. When I look at it and think about it, if the butt joint in the center wants to move up or down, the outer ends would want to move the opposite way, but they would be inside the other channel and this would transfer some load to the bolts, but the channel around them would also contribute a bit to limiting movement as would the joint being right above the tongue. And once the box is on top, that would help limit movement, too, BUT, I don't know if this could survive the dynamic stresses it would experience by being over the tongue, if the bolts could handle the shear loads from any tension and compression on the cross member, if I should use grade 5 or 8 bolts (the trailer was originally assembled with grade 5), if this could be dealt with by extending the A frame angle further back on the side rails (how far?), or if a bulkhead above that crossmember inside the TD would help much or not. And I don't know how to calculate any of these things.

Aren't there a few of you out there who can chip in with your thoughts on this? Even if you don't know how to calculate these things and think it is not a good idea, or if it might work, any kind of feedback/comments would be appreciated. I've read a lot of posts and responses on this forum and have not come across anything like this and would really like to hear some comments.

Thanks!
joe

[bobhenry]

O.K. IF YOU INSIST !

I was about to comment Monday ?? when I saw your other post but did not want to throw cold water on your plan. Spend the $40.00 for a 2x2x1/4 steel tube for the tongue and run it the full length of the frame. first crossmember to the last. Use the current tongue for your 1st crossmember since it is the heaviest member. Triangulate the tongue as you have shown in your picture



I just replaced a factory installed tongue that was fastened to the 1st and 2nd crossmember on a 5x8 flatbed trailer that I used under my " barn" trailer. The 2nd crossmember was badly bent downward about 3 inches.
Most frames built as you pictured are prone to having this problem. Having it triangulated will help greatly but all end on the same member.


I am not able to give credit for this picture but I snagged it off of the forum for my use later. I would love to build this exact same trailer. Notice the tongue member extends almost 1/2 way down the side rails and is reinforced with the checkered plate. This is a frame ya gotta love!



If ya gotta go cheap that's cool but the frame and especially the tongue is not the place to scrimp. You are talking about your safety and the safety of others out there on the road.

[jjlevek]

Thanks for the input bobhenry. I'll give it some thought and see what other responses come. I don't know if the tongue really needs to go all the way to the rear, but, if I use the current tongue for the front crossmember, I still have part of the same problem since it is about 4' long and I want to go to about 58" wide frame.
joe

[jjlevek]

I decided (hopefully wisely!):

I partially took bobhenry's advice and added it to other info I've read here over the past year as well as knowing that other than overloading my original 1190# axle and ruining the hub (probably because I figured I could make an overloaded 400 mile trip without repacking the bearings!), the original frame and tongue carried 1500# plus many times, many miles without breaking or bending over the past 19 years I've owned this. So, I just spent $69.10 including tax for some steel. 20' of 1/8" 2x2 angle (cut in half for free so I could fit it in my F150) and 3 useable remnant drops of about 5.5' of 2x2 almost 1/8" (13ga, same as the original; $11.06 each). I'll have to cut off 7-8" to get the width I need.

I think this looks much better and will be stronger than my original idea. Hopefully others think so too.

I now have to calculate the exact width I need as well as the frame length. I may bolt it together as it originally was since I have not done much welding for 25 years or so and only have a 90amp 110v flux wire feed welder, though I may weld it. If I do weld it, I'm not sure if I should weld every place where the metal touches or just select places. Any thoughts on this anyone?

Whether or not I bolt or weld, I may bend the angle (I guess this would mean I would have to weld the top horizontal leg to join the part I would have to cut out to bend it) and run it down the side rails-Does anyone have thoughts on this? Is it better to do that, or run the angle back as far as it will go (almost to the rear of the frame (though this would put it over the axle and with an underslung axle might require notching the vertical leg--not sure if that is a good idea or not).



Here's a rough layout now; new metal clearly sticks out from the cleaned and primed original metal.



I'll start a build journal in the next week or two once I get this done and put some pictures up. I may be able to get some of it done this weekend, but I have to work outside (my 1 car garage is filled with other projects) and it looks like rain is due tomorrow, for sure.

joe

[bobhenry]

Well done!

That down force on the 2nd crossmember is now carried by both "vee" stabilizers and the tongue is reinforced for up and down and side to side as well. I think it look great ( but what do I know )

[jjlevek]

Thanks for the response bobhenry!

I've read a lot during the past year on this site (though I would have preferred to have had money to do stuff with!)--many of your postings as well as many by many others--I respect all of the experience you all have and I am glad to hear that.

Now, if I can just get some feedback on bolting vs. welding, particularly as it pertains to whether or not I can or cannot bolt or weld through the horizontal legs, I'll be one tiny step closer to moving on with the build.
joe