Trailer Frame & Pressure Treated Wood????

[stugpanzer]

Hello! I am new to this forum but have been looking into building a TTT for sometime now.

I have a couple questions. I have seen vintage plans where the underlying trailer frame is made of wood (Wanderbug, Popular Science, March & April, 1946 is a great example). What are the views today of using wood to build the trailer frame? Are there any examples that you could direct me to? As for the flooring and underlying wood frame, what about the use of green (pressure treated wood)? Now days, there is no arsenic in the green wood and it seems like a good (and safe) possibility to use there. The major drawback with the new pressure treated wood is that you must use the propper fastners as the new wood will eat away metals that are not specifically treated to be in contact with the wood.

Your thoughts would be greatly appreciated!

[mezmo]

Hi stugpanzer,

First off - Welcome to the T&TTT forum. A great friendly place.

There is one TD on the forum that basically used wood for it's "chassis"
with the half-axle style torsion axles and the hitch bolted to the wood. I
can't recall who did it though at the moment. Hopefully someone else has
a quick link to that build for you.

The Design Library:
http://www.angib.pwp.blueyonder.co.uk/t ... tear00.htm
has a very minimal steel frame in "The Ultralight Chassis" [at the
bottom of the page]. It depends on the 'torsion box' that a well put
together wooden TD becomes once it's all glued together. I don't
know how much of a torsion box a TTT's body would be since it is
larger and generally has more openings. Some of the early TTs from
the 20s and 30s did use wooden chassis, but they were held together
with carriage bolts and such - an extension from horse drawn wagon
and carriage technology/methods etc. so look into that some too.

I'd should think that if you do use wood as some of the vintage plans
have done, it should be oak or ash or some other tough, strong and
somewhat flexible hardwood. Look for the kinds that are also rot
resistant. I don't know if some of the rot resistant softwoods would
be strong enough. You'll have to research the various wood's qualities
and traditional uses etc..

I would stay away from any Pressure treated wood for use in the build.
Even though the "new" style PT doesn't have arsenic it still has other
chemicals you don't want to be breathing, especially in a smaller
confined space like a TD/TTT sleeping area. Don't chance it. Another
HUGE drawback to the new PT wood is that the QUALITY IS TERRIBLE. I
just recently [last year] finished a @13x21ft deck on the back of our
house. The new PT looked OK enough when delivered. But every stinkin'
board - some more than others, but still every deck board and 2x framing
materials either twisted, cupped, bowed etc. w/ huge differences between
PT wood from different lots. God help you if it sits in the sun [especially
the HOT southern sun] before you use it. I do not think it is dimensionally
stable enough for the more precise framing a TD/TTT needs. I had one
12 ft 2x6 joist that was straight for the first 1/3, bowed up 4in off center
the next 1/3 and bowed down 4in from center on the last 1/3! Some did
ease back some when they got wet a little, but I had to use pipe clamps
to force/nudge EVERYTHING into place as I built the deck. Thankfully the
hundreds of screws used to hold it together has kept it pretty much in
place. And this was using the more expensive grade of PT wood! I have
deck boards from three different lots [basically from three different
lengths as purchased] and each has a noticeably different expansion and
contraction rate. Do yourself a huge favor and avoid PT wood for the TD
build. You will be sorry if you use it!

Otherwise, good luck on the build! Ha!

Cheers,
Norm/mezmo

[bobhenry]

The new ACQ treated wood will EAT all but stainless fastners. Borate treated lumber is a good alternate choice and is much more user friendly.

But I must ask why do you think you need treated wood. There is no direct ground contact therefore I do not see a bug infestation problem. If you are determined to have a wood frame trailer just rip good #1 grade southern yellow pine ( usually only available in 2 x 10 and 2 x 12 size most areas).

The Department of transportation was a bit more lenient in 1946 now days everyone is looking at safety far too hard and a structural failure could leave you in a bad position. As a 3rd generation carpenter the idea of a wood frame appeals to me and as stated there are 3 or 4 existing here on the forum. The practical side of me knows however I can find an unloved or unneeded trailer setting in someones back yard for far less than the cost of the lumber and fastners. (My 4x8 HF frame was $75 on Ebay and the latest all aluminum 4x7.5 was $60.00) They are out there just walk up to the door and ask. Which ever way you go good luck in your build and welcome to the wonderful world of teardrops and tiny trailers. Bob

[Shadow Catcher]

I will back Norm on this, the pressure treated wood I have used is about a bad as you can get and as an example I bought some 4X4s to replace a porch support. It was WET and took years to dry out to the point it would hold paint.
I do not know that you can find the quality of wood you could back 40 50 years ago with out paying a great deal of money. Old growth trees are hard to come by, and probably should not be harvested.
Tom

[bobhenry]

I will back Norm on this, the pressure treated wood I have used is about a bad as you can get and as an example I bought some 4X4s to replace a porch support. It was WET and took years to dry out to the point it would hold paint.
I do not know that you can find the quality of wood you could back 40 50 years ago with out paying a great deal of money. Old growth trees are hard to come by, and probably should not be harvested.
Tom

There are many back water saw mills that will recommend the lumber species that would be best for what you are doing and custom cut to order from aged blanks that have been down in some cases for years. Quite often the price is very attractive as there are fewer middle men and far less transportation costs. I have a fellow employee here at work that has a portable sawmill and he is paid to remove offending trees by the landowner and again by the lumber purchaser talk about a win win situation.

[stugpanzer]

Wow, wow and WOW! You guys are awesome!

I have been admiring the Wanderbug and like the idea of working the wood. I do know how to weld and could do that as well, but the woodworking side of things is really what I am wanting to do (I think).

So, if I am able to get some high quality lumber and use some of todays technology for fastners and epoxy, I think that would be the way to go.

I will have more questions as I ponder all this.....thanks again!

By the way....here are two excerpts from the Wanderbug article showing the build diagram of the frame and a photo of the assembled frame:

[stugpanzer]

So, if I opt to go with some good quality pine and rip that out of 2x10 or 2x12's, and lets say when the plans call for a 2x4.....do I rip at 4" and glue laminate to make a 2" thick board to have a true 2x4? Or, do I just go with todays 2x4 size (1.5"x3.5")?

I believe I could get a local school to rip the boards, glue some together then plane them down to two inches thick.

Any input on this would be greatly appreciated!

[bobhenry]

I found this fairly complete pdf on the wander pup.

http://www.bobsteardrop.com/Other_Designs/WeekendTrailer.pdf

In it I found out that it's dimensions were 6 1/2 foot wide and 10 foot long. This is the approximate footprint of many, many, pop up camper frames. I can drive directly to two of them setting rotting away within 10 minutes of my office. One has 16 months of garbage and junk piled in it. I am all but certain I could buy either one for less than $100.00. Perhaps you might want to rethink and save yourself a ton of work with a existing frame. They are out there but don't look in the paper look in the back alley ways and barn lots off of the county roads. Maybe a freecycle type "in search of" ad would help locate one. One of this type would be as light or lighter than the larger membered wood frame and I think the cost would be less if you were able to find just that right donor.

LIKE I DID !

I walked up hat in hand and asked about this trailer.......

I was ready to start at $125.00 and was resigned to stop at $200.00.

I told the gentleman I was wanting to know about the trailer. He, without hesitation , said " If you want the damn thing just get it out of here".

Many many many good parts (believe it or not) It is next on my rebuild list.

So perhaps you might look around a bit before you make your "foundation" decision

[gww25]

Good quality wood that is properly fastened is a great structural material. I've been building boats from wood for about 40 years so I can attest to the strength of a well designed wood structural system but the hitch is that good quality wood is now more expensive than steel so a wood chassis doesn't make much sense anymore unless you just prefer to work in wood. There is also the downside of trying to register a trailer made with a wood frame as I doubt any of the agencies have a provision for this type of construction. Weight all of your options and alternatives and then if you want to build in wood just do it using good quality materials and modern epoxy joinery techniques.

[dh]

Just a few thoughts, I know there are still some steel trailers around from the '40s. Anybody have an all wood one that survived +/- 70 years? However, there are wood boats from that era still alive...

If its the look you are after, perhaps a wood clad, or even vaneered steel frame would be a better option.

[angib]

Please note those (metal) diagonal braces on the front of the Wanderbug, from the tongue up to the body sides - it is they that will carry the vertical load from the coupler, not the much more flexible wood A-frame. Leave out the diagonals and I reckon you're good to drive well over 10 feet before the A-frame snaps off......

And every time I see that illustration, the huge notch cut in the two A-frame members where they cross the front of the body make me scream - it's like cutting out a floor joist to get a cable past.

[stugpanzer]

Please note those (metal) diagonal braces on the front of the Wanderbug, from the tongue up to the body sides - it is they that will carry the vertical load from the coupler, not the much more flexible wood A-frame. Leave out the diagonals and I reckon you're good to drive well over 10 feet before the A-frame snaps off......

And every time I see that illustration, the huge notch cut in the two A-frame members where they cross the front of the body make me scream - it's like cutting out a floor joist to get a cable past.

That cut doesn't bother me that much because if using today's epoxy for gluing the wood and treating the wood as you would when building a wooden boat (stitch & glue) then that notch would actually be pretty strong as the cross-member would essentially become part of the notched piece by way of the glue.

[angib]

Yes, with proper use of epoxy, everything changes. I still don't like that notch as it replaces half the along-the-grain A-frame piece with some much weaker (like one quarter as strong) across-the-grain wood, but maybe it wouldn't be a problem.

Just for laughs, I've worked out the trailer weights that the Australian trailer rules would allow for a 2x4 timber A-frame. I've assumed 1,000 psi bending stress (so this is good quality timber) on two nominal 2x4s (ie, actual 1.5"x3.5", right?) with a 10% material margin.

The result is 5510 lb-in bending strength - with the Wanderbug's 32" tongue length from the coupler to the front cross-member, that means a maximum trailer weight of 340 pounds. I believe for the gentle use a teardrop receives, compared to the utility trailer abuse that the Aussie rules are designed for, this figure can be safely doubled and 680 pounds is probably about what the lightly built Wanderbug would weigh. Throw in those diagonal braces and it looks plenty strong enough - without them, it appears to be right on the limit, though not over it.

[stugpanzer]

If I do this then I would use actual 2x4 (read 2"x4" actual size) and 2x2, etc. I talked to a friend that runs a vocational school wood shop and I would take a good quality 2x12 and glue a good quality 1x12 to that making that piece 2.25" thick. Then I will have the lumber planed to 2" thick and then have him rip me my 2x4's and 2x2's. I believe back in 1946 that was the size of 2x4's they would have used and not todays 2x4's (1.5"x3.5").

I do have a query in with my states (Illinois) DMV about guidelines for homebuilt trailers. Years ago, I built a flat-bed utility trailer and the only thing they wanted was the weight and since mine was under (I think) 2000 lbs it did not require inspection.

Also, I have asked about the design in a woodworking forum and those guys seem ok with it. They are having a nice discussion over there as well. Two of them are suggesting the metal frame too. Here's the link to that thread in that forum: http://www.woodworkingtalk.com/f5/wood-epoxy-joint-29541/#post242774

I am finding myself looking around for potential 'donor' frames too, but the idea of making my own appeals to me.

[angib]

Actual 2x4s would increase the strength by 75% so that the Aussie rules rating would be 600 pounds for a utility trailer - so 1200 pounds for a teardrop.

dwgriff1 has done something similar, except that he put in braces in two directions which will carry most of the tongue loads:





This illustrates that a teardrop is a strong enough monocoque to be self-supporting - it just needs some local reinforcement to attach the suspension and coupler to it.

I think imitating a metal frame in wood isn't the best idea. dwgriff1 illustrates one alternative and some time ago I drew a similar idea where I used a deep plywood box A-frame that just tied the coupler straight into the body with no imitation frame at all:



But I think it's still sensible to add some metal (red in the illustration) to spread the load where the coupler and axles bolt on and really it's a lot simpler to use a metal A-frame that just bolts on, like the Superlight:



Here is an old teardrop with a wood frame and metal A-frame that has lasted long enough to become an antique:





It's important to recognise that the only part of a chassis that needs much strength is the tongue/A-frame - all the tough frames under under teardrop bodies you'll see around the forum are just people trying to imitate house foundations. The best example of what strength a teardrop floor actually needs is to look under a wood double bed as they have more strength than a teardrop floor needs - as it's unlikely a teardrop is going to get an 8-year old using it as a trampoline...