Steel used for frame

[Ashleymeadow]

I have searched this site and many others looking for a guide that show the thickness and size of the steel used for the frame. If I had done a 4X8, it would have been easier, but I am building a modified Cabin Car. The frame will be 60" wide and 11' long. The cabin will be 80" x 12'.

I have no engineering training, but it looks like Andrew's charts for tongue considerations, applied to the frame, would work with 2X2X3/16" or 2X3X1/8". The 3" material would make it ride higher than I want. My local welder told me to use 2X3X3/16" for everything, but he likes everything over-built. I think my GVW will be about 1500 pounds.

I will use an A-frame tongue with the straight piece being 2X2X3/16 and the side rails 2X2X1/8.

Any suggestions?

Jerry

[Gerdo]

My frame is over built.

After building my body, I realized that the frame could be built out of much lighter tube. The TD body will add a ton of rigidity.

The tongue should be built strong and where the axle mounts.

It's much different than building a flatbed trailer.

Scroll down on page one of this thread. http://tnttt.com/viewto ... ultralight You will see a "frame" that is just a tongue and axle mounts.

[Ashleymeadow]

I am going to try a construction method that I used in building a reproduction of an 18th century wineglass wherry (row boat). Many of you are familiar with the stitch and glue method. My outer and inner skin will be 3mm thick, stitched and epoxied with insulation between. So the TD should be lighter than most.

I am hoping that someone who knows steel strength will have some words of wisdom on what I should use.

[Shadow Catcher]

Why think steel, why not aluminum? You have the right idea build an aircraft rather than a tank.

[angib]

3/16" thickness for small tubes is a pretty inefficient use of steel (and weight) - it's much better to increase to 3" depth and go thinner.

As a compromise, how about using 2.5" tube? 2.5x2.5x1/8 would do for the tongue if you need it that strong and 2.5x1.5x1/8 for the side rails - though I think 2.5x1.5x1/8 everywhere would probably be fine.

The one consideration is that the Cabin Car has a high tongue weight because its wheels are so far back. This doesn't affect the tongue strength calculation according to the Australian rules, but my gut feel is that it must increase the bending load on the tongue/A-frame. So going a bit stronger would do no harm.

[Ashleymeadow]

I have thought of that! I am using a Dexter #9 torsion axle, which will be about 3.5 feet from the rear. With a 43" tongue, that is going to make it close to 12' from hitch to center of wheel. Not much weight, but I can visualize a lot of flexing. That's why I have so many doubts about using 2X2.

Andrew, your chart clearly shows that the 2X3X1/8 has a good load rating considering its weight.

[48Rob]

I don't remember the exact length of the tongue on mine...something between 3' and 4', pretty long so I can do a hard "U" turn and not hit the trailer.
I used 2 x 2 x 1/4" tube, and decided it had too much flex, so I added another 2 x 2 under it (welded on).
That solved the flex problem.
2 X 3 in 1/4" tube might have been enough.
My trailer has a 280# tongue weight with 2400# overall weight.

Rob

[Ashleymeadow]

Hi Rob, I have studied your picture, so I was happy to hear from you. How did that Cabin Car get so heavy? Was the original that heavy?

Jerry

[mezmo]

Hi Ashleymeadow,

"... the stitch and glue method. My outer and inner skin will be 3mm thick,
stitched and epoxied with insulation between. So the TD should be lighter than most."

Please start a build thread for this! It always seemed to me like that would
be a promising method to use. I don't think it has been used here [anyone?
- let me know otherwise if it has] before so you will be the first here to
adapt the method to TD/TTTs. It will be a very interesting build to follow.

Cheers,
Norm/mezmo

[48Rob]

Hi Rob, I have studied your picture, so I was happy to hear from you. How did that Cabin Car get so heavy? Was the original that heavy?

Jerry

Hi Jerry,

No, the originals were around 900 pounds with a tongue weight of around 215 pounds.
Mine is much heavier due to several things.
The original didn't use a steel frame, and was built with 1/4" plywood.
Mine has a steel frame, 3/4" plywood, and modern amenities that weigh a lot

Here is a page that has a lot of info that may help you.
http://cabincar.yuku.com/directory/defa ... unity=true

Rob

[boomboomtulum]

I used 2x2 x 1/8 for the frame. 2x3 x1/8 for the tongue. No flex, light weight. Most welders or fab shops will want to go overbuilt, spec what you want and they will build it. I built my own frame but like you asked questions to find out between weight and strength. Buld what you think will work for you, but this has worked great for us.
Dave

[Ashleymeadow]

Rob: I have spent a lot of time on your pages. It was your site that made me want the Cabin Car design.

Dave: I received my torsion axle this week. I will now order the steel. I have never worked with or welded aluminum, so I stuck with steel. I am still not sure of which thickness I should use. I'll work on that today.

What is the length and GVW of your TD?

Thanks, everyone.

[Wolffarmer]

Ashley.

I looked at Grants web sight, Lil Bear trailers. And I ordered the same iron he uses in his trailers. I have not started to build this one yet. Have iron, some plywood and insulation and will probably get an axle in the next few months so I can weld up the trailer this winter. Shop is unheated so will not be able to do things that need warmish temps. My first trailer used way to heavy of iron, but then it was free so that was ok. 3/16 is way to thick.

Randy

[2bits]

My build was a teardrop with a home built 2x2x1/8 frame and a Dexter torsion axle. Plenty strong for my purposes. In your situation I would do the same but possibly got for 2x3x1/8