Frame weight VS Cost, and a couple of other questions

[racermech]

Hey Guys,

After looking at travel trailers, tent trailers my wife and I have decided to tackle a tear drop. And with that comes my first set of questions.

As of right now just about every camp we go to involves some sort of off road driving, so strength and rigidity are a couple of my main concerns. Through my work I have access to welders and plenty of materials, so welding up or adding/cutting something is not a big deal.

I have the option of building my trailer out of 2x2x1/4 tube as opposed to the 1/8 that most people seem to run. The weight penalty is about 2 lbs a foot of tube. About 100 lbs total. But i think I can run 1/4 ply as the base because it will not have to take the same load as it would by using the 1/8 tube and 3/4 ply. The other reason for the 1/4 tube is the cost. I can get "scrap" tube from work for basically pennies a pound, if i go with the 1/8 I will have to order it in and pay full price. With that cost savings and the saving of the thinner ply it seems to make sense.

I have been looking around for a dimension from the ball to the front of the trailer. I believe it is going to be about 3'. If anyone can give me a hand on this it would be of great help.



Last are the axles. I would like to do an axle that runs the same bolt pattern as my truck, and i would like to run the same size wheels/tires (15") I am a bit concerned about 8" or 12" trailer wheels and tires going off road. I am really scared of cutting a tire because of the size and the amount of rocks we tend to run into in the desert. Any feedback on this??? If i need to buy an axle and stretch it to get the correct hub to hub dimension is not a big deal.

Thanks for any and all information!!!

[Dale M.]

Distance from ball to front of trailer (tongue length) should be about 6 inches more than distant from ball to outside end of bumper on tow vehicle, so when you "jack knife" trailer your tow vehicle bumper does not "crunch" front of trailer...

About axles... Check out Norther Tool or etrailer.com or many of the other "trailer parts" suppliers online....

For hubs determine what bolt pattern tow vehicle has and look for trailer hubs that have same pattern... Most popular are 5 on 4.5 inch (Jeep) or 5 on 5 inch for "larger wheels" ( 14 - 15 inch)... IF you can not find hubs with particular bolt pattern then find a appropriate (or blank) set of hubs and have it drilled and have studs pressed in to match TV pattern....

http://tnttt.com/viewtopic.php?t=14918

Dale

[LarryJ]

I suggest looking into 1/8" 2x3 tubing - lighter than 1/4" 2x2 and stronger than the 1/8" 2x2

I believe this is what is used by Little Guy trailers for their off-road tear.

I also suggest this site for info on building an off-road trailer:

Outback Teardrop Trailer

Beautiful, well-thought out trailer - the one that started me on this little adventure.

Make sure you have decided on your rims before you purchase your axle. Auto rims usually have an offset, where trailer rims have none. This will affect how wide your axle must be so the tires won't hit the sides of the trailer (or frame)

[jss06]

I built my frame out of 2"x2"x3/16" for the main rails and the tounge. Then used 2"x2"x1/8" for the cross members and edge rails.

the weight of the materials came in at about 168lbs for the frame not including the axle.

After my last trip I am very happy with the strength of this trailer. I was approximatly 170 miles of ranch roads and cattle guards at 30 to 40 MPH. I did not have any problems with it.

[asianflava]

Since you are building a hybrid tongue, I'd recommend using 2x3x3/16 for the center and 2x3x1/8 for the sides. it can take 13,500 lb-in more vertically, and weighs .36 lbs/ft LESS than 2x2x1/4.

The sides will stabilize the tongue to keep the trailer from shimmying. Most of the stress will still be on the center tongue.

Check this link and it can help you with your decision. http://www.angib.pwp.blueyonder.co.uk/t ... tear84.htm

[Forrest747]

I did mine out of 2x2 1/4 inch weighed in at 400 pounds with axel and wheels

[racermech]

Dale. Thanks for the info, that is what I was looking for.

Larry, that is one of the many links I have looked at, but have yet to really study. Thanks!!!

Asian, Awesome link for working out the weights. The entire tongue will be overbuilt (damn structural steel background!!) But it will be fun to play around and see what i can come up with using what we have in stock.

Forrest. That is basically what I want to build!! But is it an illusion or do I not see any suspension on yours?

[Forrest747]

Just leaf springs. Bought the rims and calculated the axle length and then built the frame. came out to be about 2 inches longer than i wanted but its all good, it my trailer. I have more pics of me putting the frame together I can email ya. PM me your email. the tongue was 2x3 1/4 steel which was welded at every point it intersected a crossmember and then bolted just for good measure. Also i purchased an extra set of axle saddles and welded them onto the axleon the top and bottom. THis will make it easier in the future if I ever want to put the axle on teh outside of the leaf spring to give teh tralier more ground clearence, or keep it on the inside the same height as the jeep.

[angib]

If you are going to use 2x2x1/4 (and cheap is good) then you can go pretty much as you like!

The single tongue piece (sticking forward of where the three bits join) will pass the Australian trailer rules at 24" long for a 2100lb trailer or 36" long for a 1400lb trailer. These Aussie rules are strict so those weights are OK for off-road trailers - for on-road or gentle use, you can double those weights.

For the whole 3-piece tongue, from ball to main frame, the Aussie rules allow 72" long for a 2100lb trailer, so you can build almost as long as you want. This assumes that all three tongue members are tied back properly into the main trailer frame, like in Forest747's photo, and are not just welded to the front cross-member.

So for strength, 2x2x1/4 will do almost anything. If you actually built it longer than 48", I could imagine that you might run into a stiffness problem where the tongue was too bouncy. That is the reason that I wouldn't suggest leaving off the two diagonal braces - if you have a long 2x2 single tongue you can run into sideways stiffness problems, where the trailer shimmies because the tongue is flexing so much.

Too much information?

[racermech]

Ok here is a bit more of a solid plan...well kinda solid.







As always feedback is welcome. If it looks good I might start work on the tongue area in the next week or so.

[eamarquardt]

I think you are overkill with your tubing thickness. The tongue maybe 3/16 wall and the rest 1/8 wall.

The rest of the layout looks good. Consider mounting your spring hangers on a separate piece of angle iron with a strap nut inside the tubing to bolt the suspension to the frame tubing. Stronger due to the additional angle iron and it's possible to adjust the placement of the axle for proper balance.



Hope this helps.

Cheers,

Gus

[asianflava]

4x3x1/4 is way overkill, I hope that you're using it because it's free. The rest of the frame doesn't have to be that strong because the body of the trailer will provide a majority of the stiffness/strength needed.

I don't know which profile you are planning, but a 10ft trailer doesn't need a a 10ft frame.

[racermech]

4x3x1/4 is way overkill, I hope that you're using it because it's free.

Ding Ding Ding winner!!!! If it is not free it would still be cheaper then having to purchase a section of tube from any of our vendors(Think pennies a foot versus dollar(s) a foot). It really comes down to what do I have in the yard, or what do i have coming up on projects where we might get stuck with some bad cut lengths. Right now I just happen to have this tube in the yard at this time.

I was thinking about cantilever the galley by about 2', and i know people do it, but my go it makes me a little nervous. Now I have the frame kinda worked out and into 3d, it is time to make decisions on the final design.

[angib]

Even free, 4x3x1/4 is too much - plus it requires you to make bad joints, like cutting the front cross-member in half.

The bigger tongue member doesn't increase the strength much - because the cross-members it's welded to become the weak link in the chain.

Do everything in 2x2 with both the centre tongue and the diagonals underneath the cross-members - so the diagonals will be like your second graphic.

[racermech]

Ok 4x3 is out. That is fine because it was going to look a bit odd. 2x2 will work just fine.

What I dont get is why the tongue and the braces run under the frame header. In structural steel (i know, i building a trailer, not a building) we would never make a connection under another one just help on by a little bit of weld. The braces are not only take any sort of rotational forces out of the tongue, but it is also taking vertical loads as you basically have a giant flex point between the ball and the header. Running the tongue all the way back tot he second cross member pushes loads back to the second member, and the braces going direct to the header will transfer the loads to the header, with he stiffener plates and vertical rotation should be pushed back to the 2 main frame rails.

That along with the fact you are getting 4 sides of weld at ever connection point you should never have to worry about any failure. Running the braces and tongue under the frame you are only getting 2 inches of weld each side, and at that it is only a flare bevel weld with very little penetration at each point. On a light weight build, or one that is not going off road I am sure this works just fine. But as I can see my trailer getting bounced around I am just not convinced running the tubes under the frame is the best idea.

The one thing I will admit to know knowing is if there is a true reason for running the tubes under the frame. If there is one please please please let me know. Nothing is set in stone until i start cutting tubes.