Superlight Torsion Box

[Jiminsav]

Kelsey, you'll notice that the axles are bolted to a piece of oak, the steel is bolted to the oak in back and another up front is bolted to a stringer, and then the tongue is bolted to the steel..works great so far.

[bobhenry]

My very 1st trailer and now my 3rd both have torsion box floors. A 2x4 perimeter with a 3/4 rabbett cut in the top and bottom to accept 1/2" osb.

This post has me rethinking this construction slightly. If a 2x2x1/4 square tube was the center spine front to rear and extended to form the tongue Next drill and bolt 2x4's to each side of the 2x2 tube that have been ripped to fit between the sandwich of osb. The cavity between the floor skins would be filled with styrofoam sheets to help support any load applied to the top skin. You would have 2 torsion boxes bolted to the center tube but the skins would be continuious from side to side. These skins glued and screwed would make a strong and well insulated floor. For the spring perch mounts ( Torsion or leaf) would be a 2x3 angles 3 to 4 feet long bolted thru the side 2x4's. Strength could be added by mortising the angle into the perimeter 2x4. I saw a old farm trailer for sale and looked it over quite closely. It was made with 2x8 floor on 2x6 cross joists and spring perch was a 6" x 3' flat plate and a 2x3 steel tube tongue bolted at each cross joist. It was probably 50 years old and appeared to be reasonably well cared for as it was in good condition but you could tell by the worn floor it had seen a lot of heavy use.

Just the long winded ramblings of a mad man!

[Gary and Cheri]

TinKicker,

Have you thought about Ash?

Morgan cars of England have been made with Ash frames and have lasted for years.


Some woods, I would think, may have fibers that separate as the wood may not be up to the flexing that going down the road is going to put on it. I know several Morgans that are really quite old and the frames are still in great shape. I'm no expert on wood, just know what product Morgan chose.

Gary J.

[dwgriff1]

I don't think there is as much flex in a tear as you might think. The box is not going anywhere, not that size, the tongue won't flex either, but the spot where the tongue meets the trailer is the weak point, as Andrew reminded me early in my design stage.

You can see how I solved that problem.

Some woods are brittle and some flex, no question about that one. I am sure Ash would work fine. Here in the mountain west, where we grow neither one, Oak is more accessible, which is why I went with it.

I laminated a series of oak strips to make the basic tongue, increasing the strength and flexibility in the process.

dave

[TinKicker]

Man, this is a lot of great information, guys!

Jiminsav, who was your source on the axles?

bobhenry, your thoughts are well-taken. That's a design idea I think I'll look at more closely. Sounds very compact and strong.

Gary J, Ash had come to mind, but I know nothing about it either. I was thinking of basswood based on the suggestion of a woodworking friend of mine. I went to this link: http://www.hardwoodinfo.com/species_guide/display_species.asp?species=basswood and found there a chart of the different woods and their strengths. Ash is about 30% heavier than basswood, but MUCH stronger. Time to study up on Ash!

Thanks all, and hope to hear more ideas!

[Gary and Cheri]

TinKicker

I have done some wood carving and bass is what a lot of people use. It is a fairly soft wood from my experience. I question how well screws would hold in it.

It makes for some great birds and fish though.

Gary J.

[Jiminsav]

Tinkicker, I got the axles direct from Dexter axles through a friend of mine who is a dealer for truck axles, which they also make.

[Bernoulli]

My friend the shipwright - (Jensen Boat Works, Seattle) steam bends wood frequently. I have not done it, but it takes a steam cabinet (easily constructed), a zillion clamps and a form to clamp your piece to. When it's done, it's done.

[dwgriff1]

A stem box can be a hunk of plastic pipe or a wood box. An electric teakettle will provide enough steam.

When properly steamed, a hunk of oak comes out amazingly flexible, but as it cools and dries (it happens in a minute or less) it goes back to being Oak.

So the secret is to work fairly fast. It does not take a huge number of clamps, but some how you have to keep the steamed wood against the form till it dries/cools.

It is a lot more complex sounding than it really is.

dave

[TinKicker]

I appreciate all the info guys. Looks like my best plan will consist of different woods for different purposes. Oak/Ash/Hickory(?) for the structural members and something light to fill in all the non-stressed areas. I think I need to get with my cabinet builder friend and actually play with some of these different species to get a feel for them.
And just think--only two million three hundred thousand four hundred and seventy-eight more items on my teardrop builder's checklist to question, decide on, verify, test and incorporate. Piece of cake.