wood chassis or trailer

[Mary C]

Has there been any real discussions on the trailer being built out of wood and other materials. I know of one TD but have there been more than one built? so can we open this up to cover the subject? Do you have had any experience or have any Ideas or Pictures diagrams or any real ideas that we can discuss? I know of a wood chassis TD with over 4000 miles on it so I know it is possible. I think the time is now because I know I am not the only one who has thought of doing it. What about other types of materials? Lets brainstorm without getting too technical and turning this into "it wouldn't work" type backlash but open it for discussion. if it wont work why lets know your experience and detail why it wouldn't work. Lets discuss ideas. I am looking for light weight and less expensive. any Ideas? Remember in GA you have to have lights , a safe hitch, chains and some type of suspension in order to get a license tag. So perhaps you can't in your state but transfers are usually ok and acceptable by other states.


Mary C.

[angib]

I see two ways of doing an all-wood tear:

1) The 'dumb' route which is to duplicate a metal-framed teadrop in wood. I have not looked at the numbers, but my gut feel is that something like 6x2 oak would make a good A-frame frame. With wood you get the problem that joining it isn't as simple as welding, so I think I would go for a simple triangular frame, something like the Ultralight frame. This is just a base on which a self-supporting teardrop body can sit.



2) The 'smart' route is to recognise that a self-supporting teardrop body doesn't need any frame under it - though it does need a secure axle mount plus a tongue. I see no problem in building enough strength into the base of the sidewalls to allow an axle to be bolted on, so that just leaves the tongue. This can be built in box-section plywood to connect to the front of the teardrop body.

Here's a design I did a long while ago, showing a nearly-all-wood Ultralight. Blue is wood, red is the few bits of metal needed (though with care even those could be eliminated and replaced by some oak) and green is the purchased hardware.



But building an all-wood tear is a lot, lot harder than building a metal-frame one, so no-one should think it was an easy alternative to some welding. And I'm not convinced that it would be safe to do this, unless the builder had wood-epoxy boatbuilding experience.

Oh, and doing this without using epoxy strikes me as nearly impossible - this would not be just woodworking in the normal sense of cabinetmaking - a different skill set would be required.

[CarlLaFong]

The idea of building a wooden trailer to save weight and money seems good, at first thought. The majority of homebuilts, that I see here, have grossly overbuilt frames. I mean some have 1/4 inch wall, square tube frames. My 3500 Dodge truck doesn't have a frame that thick. The simple A frame, shown here, is more than enough for any traditional teardrop. All of this worry about having battleship underpinnings supporting every square inch of the trailer body is paranoia. A properly constructed body is strong enough to support itself and won't sag. Look at it this way. If you build an A frame and hitch it to your TV and pull it all over the country, whats going to happen? Nothing, that's what. Now take the same A frame and put a small box on it. As long as the suspension is adequate now what is going to happen? I propose that, again, nothing will happen. You will have a well built and very light and strong unit.
If I were to build a wooden trailer, I would NOT use oak as stressed members. Ash or hickory would be a better choice. Oak is brittle.

[pchast]

I like Ash better than Hickory. I believe its significantly lighter.

[cleburnescv1937]

The reason we used oak is that what we found in Old wagon building books. But as a former home builder ash or hickory would work fine.

[bonnie]

I see two ways of doing an all-wood tear:

2) The 'smart' route is to recognise that a self-supporting teardrop body doesn't need any frame under it - though it does need a secure axle mount plus a tongue. I see no problem in building enough strength into the base of the sidewalls to allow an axle to be bolted on, so that just leaves the tongue. This can be built in box-section plywood to connect to the front of the teardrop body.

Here's a design I did a long while ago, showing a nearly-all-wood Ultralight. Blue is wood, red is the few bits of metal needed (though with care even those could be eliminated and replaced by some oak) and green is the purchased hardware.



But building an all-wood tear is a lot, lot harder than building a metal-frame one, so no-one should think it was an easy alternative to some welding. And I'm not convinced that it would be safe to do this, unless the builder had wood-epoxy boatbuilding experience.

Oh, and doing this without using epoxy strikes me as nearly impossible - this would not be just woodworking in the normal sense of cabinetmaking - a different skill set would be required.

I am at this cross roads now. The box is self supporting and has 2x4 or 2x3 box sides. The axle is fine. The tongue needs moved out of the interior and either lowered to under the box or attached in some fashion. Looking at your drawings I have a question about the top one. Is the front tongue box built into the cabin to the dotted line or is there other support? I had been toying with putting a shortened A frame type arrangement under the front edge to beef up the tongue part and allow me a small storage platform on front. I was thinking of having said A frame welded. I like the look of the wood tongue arrangement better. Could you expand your thought? The box on bub is a foam fiberglass composite.

[angib]

As you say, that is something like a giant tongue box that is stuck on the front of the body. There would be no extra structure except the top, sides and bottom (which is the trailer floor continued forwards all the way to the coupler - just as the top is in effect the roof continued to the coupler). Bending loads from the coupler are reacted into the floor and top skin - so the strength of the joints between the tongue box and those skins are absolutely critical, as are the joints down the side panels onto the front of the body, which carry the shear loads from the coupler.

If you have foam/fiberglass composite sandwich panels, you need to work out how to join the inner and outer skins with more than foam at the joints - the loads must be carried into the inner cabin skin as well as the outer.

None of the external 'tongue box' panels can be cut out to make access to the space inside, but maybe half of the bulkhead between the cabin and the tongue box could be a doorway to access the box.

If you go to a welded A-frame, then none of this is relevant. It may be tempting to think of a short A-frame, but why bother? For the sake of a couple of feet of tube on either leg, you can connect the A-frame to the front of the axle as shown in the Ultralight chassis above.

[Larry C]

I don't think using wood for the chassis will save weight over using steel. The 5X8 A-frame pictured weighs 45#
The cross piece that's included in the 45# weight is just a temporary brace till the axle is attached.

If you really want to use wood, why not get the closest thing to real iron that grows from the ground?
Ironwood; Eastern Hop-Hornbeam. I used to cut fire wood, and this tree was by far the heaviest, most dense wood in the forest. While cutting, sparks would fly from the chain saw chain

[grantstew8]

For a motorcycle trail the uk law states it not wider than 1 meter 3'(ish) and not longer than 2.5m 8'(ish) from the rear axle of the bike. Most importantly it's total weight is 2/3 of the bike or 150 kg 330lb max. Im looking at every alternative to save weight and not having a chassis makes a huge difference. It's a monocoque rather than a traditional. chassis.
I've yet to finish my td before I start on the bike td so I've time to do some research.

[pchast]

Grant,

I've been thinking about light. Wood i-beams of 1/4" Baltic birch and thin hardwood rails are very sturdy, same as c -channels of sheet metal. With either method the trick is to fasten them so that they will not twist. With the appropriate bracing and foam that weight goal should not be an issue.

IMHO solid wood studs will never be lighter than steel at the same strength level.

[grantstew8]

Yup I think your right about solid wood vs steel.

The forces will be much lower on the coupler on a 330lb bike Td than on a "normal" 1500lb td. Using a really basic F=MA they should be 5 times less.

The duct tear made from dictator and plastic pipe has shown my current design is way over designed. I'm in that really early design stage of the bike td and considering all options.

I'll bounce my design off you when I've got something to show.