Frame plan check before I buy steel....(Revised-please read)

[Cdash]

Getting ready to buy steel in the next week our two and wanted to to run my ideas past those with experience.

I am planning on building a 5'-6" wide x 10' long x 4' tall Jim Dandy shaped tear. I am not planning to build a galley on it. the build is centered around a queen size bed and having room to store stuff between the end of the bed and the front wall, as well as being to enter the trailer without climbing directly into bed. I also pln to run a torflex axle, size to be determined after I figure out weights.I plan to use 2x2 above the frame with plywood on top for the floor and sandwich walls with 3/4 insulation between 3/8 outter ply (thinnest 4 x 10 sheet I can get locally) and 1/8 inside panel.

My initial thought was to go with 2x2 tube for the frame, but after reading, looking at commercially built trailers and thinking about the rigid box, I am leaning towards 2x2x1/8 angle iron. I would size the tongue for the anticipated weight, likely using a 2.5 or 3" tube. I was thinking of running cross members at a 2' spacing. I would use a piece of angle to box out the frame rails at the axle location to stiffen the axle support.

Does this seem reasonable?

I am thinking it is sufficient, and not overbuilt. My biggest question is the cross members at the front and at the end of the tongue, since these two take the tongue load. I can see the front bring ok since it will push up into the box, but the one at the end of the tongue will want to bend down. Should I double up this one, bolt it to the floor or consider a larger member for the end of tongue cross member?

Thanks for any advice you can provide!

Craig[/i]

[bdosborn]

2X2 tubing isn't that much heavier than angle but it's *much* stronger. BUT, plenty of people have made frames from angle.

Here's a link to tubing strength and weight:

Angib Tongue Strength Page

Here's a nice 2X2 angle frame, make sure you make your body good and rigid so it's basically self supporting:


IMHO, an even nicer 2X2 tubing frame where its less important for the body to be totally rigid:


And as always, YMMV.

Bruce

[Cdash]

In talking to my local steel supplier today, I discovered that they carry a section that is 1.5 x 1.5 x 1/8 square. It only runs 2.2 #/ft and is stronger than the 2x2 angle.

I am thinking that I can use that tube and reduce my design to only have 1 interior cross member to terminate the tongue to. I plan to frame the floor with 2x2's for insulation.

Would it be a problem to only have 1 interior cross member?

Second question: any issues with attaching a Torflex axle to a 1.5" tube frame?

Thanks

[Cdash]

Here is my layout:


I have the Axle so far forward due to not having a galley planned and the weight that it brings. This is where the Trailer Balance spreadsheet I found here, suggested to get a reasonable tongue weight while loaded.

Any concerns?

[aggie79]

In talking to my local steel supplier today, I discovered that they carry a section that is 1.5 x 1.5 x 1/8 square. It only runs 2.2 #/ft and is stronger than the 2x2 angle.

I am thinking that I can use that tube and reduce my design to only have 1 interior cross member to terminate the tongue to. I plan to frame the floor with 2x2's for insulation.

Would it be a problem to only have 1 interior cross member?

I framed my floor with 1x2s laid flat to give a 3/4" thickness for insulation between the 1/4" ply skins top and bottom. If you are using sandwich construction you don't really need the crossmembers. The assembly is strong enough on its own.

Second question: any issues with attaching a Torflex road 1.5" tube frame?

Thanks

The mounting flange on the #8 and #9 axles is 2" wide. If you purchase the optional side mount (side bolt) hangars - welding them to the frame - you're probably okay with 1-1/2" tube. I don't think I would want to bolt the axle vertically through the 1-1/2" tube which is what you'd have to do if you didn't use the hangars.

[Cdash]

Thanks for the input!!

I am definatly doing the side brackets. I am going to be holding off on ordering the axle for a while. I want to have a better idea of weight so I don't buy too soft or too strong of an axle. I also want to be able to check balance before I attach the axle. This will make it difficult - I'll have to pull the box off the frame to weld the brackets on, but I think I have that figured out.

Not too many people with my shape and without a galley - so kind of forging off in my own direction. Hopefully my building skills can make it look somewhat like this:


Look for a build journal soon (I hope!!) It's time to get this thing out of the "virtual build" stage.

[angib]

That recent design looks good to me. All the cross-members, except the ones the tongue fixes to, are just added weight, so leaving them out is good.

Axle position looks OK to me also - assuming any heavy loads you carry are likely to be put in the front of the trailer.

[Forrest747]

When it came to axles I went with a 3500lb rated axel. Figured if I went 3 times as much as my projected trailer weight i couldnt go wrong. I know nothing about torflex axels. if your pulling it with your jeep and you plan on any off roading with your trailer go big.

[angib]

Figured if I went 3 times as much as my projected trailer weight i couldnt go wrong.

I don't think that's a good idea. I know big numbers sound like they must be better than smaller numbers, but what you've got is an axle that will have virtually no suspension movement because it's rated for a so much higher weight than you plan. You can expect that it will bounce around a bit like an empty utility trailer, jumping clean off the ground over bumps and that sort of thing. It probably won't come to any harm, but you'll need to everything tied down inside for travel.

Going for an axle a bit heavier than your planned weight is good and even double the planned weight is OK, but three times is a bit too much.

OK - there's a correction on this, as I jumped in without knowing all the facts. Forest 747 has a 3500lb axle mounted on 2000lb leaf springs and that's a very sensible combination particularly for off-road use.

It's the springs that matter for leaf spring suspension and not the axle.