Wooden Trailer Frame?

[jwh92020]

I saw a set of plans for a 5 x 10 trailer. The builder said he used 3 sheets of 4 x 8 - 3/4" plywood as the floor. The sheets were cut to 2 - 4 x 5 and 1 - 2 x 5. He laid them side x side and used 3 1/2" strips of the excess 3/4 ply with Liquid nails and screws to join the sheets together. He ran a 2 x 4 frame around the perimeter that was glued and screwed to the sheets of ply. The axle was attached to the floor with 3/8" grade 8 bolts going through a 1/8" thick metal plate, 3/4 ply & 2 x 4 frame, The axle hangers were bolted directly to the 2 x 4 frame. The tongue was made of 2 x 2 steel tubing with 12" pieces of angle iron welded to it. There were blocks of 2 x 4 glued and screwed to the plywood floor in between the 2 x 4 cross members. Bolts went through the 3/4 ply, 2 x 4 and the angle iron. There are 8 attachment points along the length of the tongue. Has anyone heard of people using wooden frames? The builder said he has rolled quite a few miles ( based on his location and the trips he took, it would have to be 5,000+) at highway speed with no issues? Thoughts?

[Redneck Teepee]

Just reading your post the first thing that came to mind was an old horse drawn wagon, most paved roads are smoother than the horse and buggy days (unless you live in California). Read this thread

http://tnttt.com/viewtopic.php?f=35&t=45968

[jwh92020]

Thanks for the link. I didn't get a sense of "NO - DON'T DO IT!" More of a "think it out well, use quality lumbet, reinforce with metal at stress points (which the plans show). I checked with the Oklahoma DMV today. They said there is no issue with them as to wood vs metal frames. As for your thought of roads being smoother now, you haven't driven through the OKC metro area lately. They suck!

[KCStudly]

Rate of speed and dynamic impacts are "a bit" different at 70 mph (car) vs. 7 mph (horse). Just saying, the harder you swing a hammer the more damage it does, so the horse and buggy analogy is not valid.

Can it be done successfully? Yes. Will it be long lasting? Maybe. Are rot, splitting and knots a concern? Absolutely.

[DrewsBrews]

Often ends up more of a unibody type structure than a traditional frame.

I'll be doing something very similar on mine, though it will be more of a small storage box trailer (40"x72"x24") with a plywood divider 18" inside from the front to act as a sort of second frame member. Target weight of under 700lb fully loaded for camping. 3/4" ply floor and front of the box, 1/2" everywhere else. 1x2 hickory to act as fillets in all the corners and be something to bolt to. An 8ft 2"x2" tongue tube will run nearly the full length of the box with 2" angle iron mounting tabs, terminating at a 2" receiver tube for accessories (bike rack, cargo basket, ect). 2" angle iron will act as brackets attaching the axle/springs to the box bottom with bolts, and wrap around the side.

It may still end up a little overbuilt for the size and weight.. less so than a full frame, however.

[aggie79]

[jwh92020]

Thanks for all of your input. It's an idea I'm somewhat kicking around. I have no doubt that I can build a structurally solid platform. I agree that impact at 70 mph is way different than a horse, even at top speed. Even on a metal frame, a trailer is going to be severely damaged, if not destroyed when impacted at 70 mph. I live in Oklahoma City, and we have an RV park that took a direct hit from a tornado a few months ago. Most of the units, from the small travel trailers to the Class A's were destroyed, frames twisted beyond belief. What survived were the floors of some storage buildings that were built in a very basic torsion box style. They may have been 100 yards from where they started, and the building itself was toast, but the floors survived. As for splitting and knots, careful wood selection and proper fastener usage & application will resolve that issue. As far as rot goes, isn't it the same issue with a wood frame on a metal trailer. I would think that if waterproofed correctly, it shouldn't be a problem. All this being said, if the right trailer came along at the right price, I would probably use it. If for no other reason, it would save time in the build process.

[bobhenry]

Here is perhaps a meet in the middle answer.

http://www.angib.pwp.blueyonder.co.uk/teardrop/tear57.htm

[jwh92020]

Bob - That is what I was thinking about, but modified a bit. Longer pieces of angle on each side. This would spread the support of the metal out further. 2 x 2 square tube tongue running the length of the trailer with the 2 pieces that form the "A" from just behind the coupler to the pieces on the side (where the axle hangers are). It would look like that pic, but on steroids. I have seen your posts where you have found great deals on trailers. Unfortunately, here in Oklahoma, people want retail $ for old used stuff. I did find a boat trailer at a decent price, but it was only 48" between the wheels. I want to go 7 ft wide, 6 1/2 at the minimum, 6 ft high on the inside and I don't want wheel wells in the trailer. I don't think I can build out far enough for the height to make it safe in a cross wind at that height. Here is a pic of that trailer. Not really sure how to load pics here, so hopefully this will work.

[KCStudly]

I agree that impact at 70 mph is way different than a horse, even at top speed. Even on a metal frame, a trailer is going to be severely damaged, if not destroyed when impacted at 70 mph. <snip> I would think that if waterproofed correctly, it shouldn't be a problem.

Sorry to confuse. I didn't mean 0-70 impact like hitting a brick wall, but rather all of the jostling, jarring and force direction changes that occur going down the road when a moderate mass (the cabin) has to accelerate and decelerate relative to the response of the suspension. This tends to put cyclic loads on fasteners and such. One of the reasons that those old buckboards lasted is because they were so loose and flexible that they twisted and warped under transitions, absorbing energy thru friction at the joints and such. Not such a good thing for a cabin that we are trying to keep water tight. Horse drawn coaches solved this problem by suspending the whole enclosure above the wooden chassis, sometimes using leather straps. Okay for slow speed, maybe not so long lasting w/o a lot of maintenance.

My take on the wood frame over metal frame vs. wood frame only and rot is that a wooden structure that is weakened by rot (as much as we try to avoid this, it still can happen to varying degrees) can still be carried down the road by a steel frame with suspension solidly attached; but a wood frame with degraded suspension attachment is far more likely to sprout trouble, rather than last.

Don't get me wrong, I see the novelty of a wood trailer, and believe it can be done reliably, and you are showing knowledge of the areas that would need to be addressed. It's just that I don't feel that it is a better solution for 99.9/ct of regular builders, and certainly should not be considered as an easy out, just because a builder does not possess metal fab skills (...maybe especially because of this). My reasoning is that the average person who can't solve the issue of working with steel (be it by buying, hiring, horse trading, DIY, etc.), will more often than not also not possess the engineering ability and skills to properly execute a wooden trailer.

Just saying.

(Disclaimer: I have metal working skills and access to metal working tools, so to me there is no logical reason to compromise in order to use wood for the chassis.)

[jwh92020]

I would agree that for most people, a wooden frame is something they shouldn't attempt. I can weld... sort of, but I would not be confident of what I built. (I haven't welded in 25 years, and even then, it was satellite dish mounts. I did make a hitch for a Pinto wagon to drag a Harbor Freight trailer with a dish on it. The car flipped - so did the trailer, but the hitch held. I wasn't there for all that fun). Quite honestly, the idea of building the wooden trailer is intriguing, but not in a "can it be done" kind of way. That attitude is what gets people hurt. Much like the fact that I know I can get 6 1/2-7 ft wide on the trailer I posted the picture of, but can it be done safely with a height of 6 ft? I don't think so. It is 16 ft long, so I know I can get 10 -12 ft in length. Your thoughts on using it? If my wife didn't sleep in a recliner and freak out (claustrophobia) when I had her climb into a Little Guy 5 Wide "to see what happens", I'd build a 5 x 9 on a HF trailer and be done with. Hmmm... little trailer or wife on vacation? Guess I'm gonna build a bigger trailer.