Building A Bridge - Take 2

In keeping with solar PV design (reduce you load as much as you can) I now have a small tractor that weighs 900 lbs. Add me and a small trailer and you are at 1,300 lbs. Come back with a few hundred pounds of firewood and I'm well under 2,000 lbs. The tractor width is about 3' and the trailer would be about 4'. The creek I have to span is about 20' wide, but does at time overflow the bank after a heavy rain, maybe twice a year.

I have several trees that I have been told are cottonwood that need to come down. These trees are 18" and up in diameter.

My thinking is to fell 4 trees and debark them and get them spanning the creek. At each end I would get them up off the ground and out of any high flow (maybe setting on a 6" x 6" pressure treated beam). Planing on a 6' wide bridge, I would have two trunks inline with where the tractor wheels would be and two trunks on the outside about 5' apart. The decking would be made out 6' long 2" x 6" boards and I would leave a gap between each one to let water threw.

I'm sure there are flaws in this plan, please point them out to me.

Previous thread on this is here

Thread on the tractor is here

Do you intend to season the wood ?

David

David Livingston wrote:Do you intend to season the wood ?

David

I don't think so. An 18" log would take years to season.

Hi Jerry, et al,

I with you Brother...and in overall perspective sounds really good. You are correct also, seasoning the wood is not needed nor something that really is ever done in Timber framing, or "green woodworking." For the most part the entire concept of "seasoning" wood is a misnomer until you get into "fine woodworking" and thin dimensional lumber for certain applications. Other than that it is all "wet wood" and a Cotton Wood the size you are describing would take close to a decade to season out...if even then. This raises the potential issue for that species...they are wet...and stay wet longer than others in some location of use. Cotton wood is a species used for our "kachina doll" carving and has some many fine attributes...one that is a bit of an issue is that its "free water" is lost easily in dimensional stock, yet in heavy timber the "free water" and "bound water" (even with bark off) can contribute to fungal degradation, and in turn structural compromise of the member.

So...there are ways around this...or at least...to mitigate the effects. Before we get into that (and if I have the time to blow this out for you) do you (or can you) download Sketchup? I can share with you a quick CAD drawing that may address some of the potential design flaws as you have described the planned project to be? Let me know if you have the time...and desire...and I will do a quick model for you to build from.

Regards,

j

Jay C. If you are willing to do something in sketch up I will certainly figure out how to install it and look at the file. I have looked at sketch-up files in the past, but that has been quite some time. Unfortunately I came out of drafting class in school just before CAD became something affordable and I never had a need for it so it is yet another one of those un-learned skills.

Hey Jerry, PM me and the outcome we will post here publicly...

Regards,

j