Tractors and wood! Show your pics

[Oldpath05]

Here we go lets do it...........

YouTube

 

[Oldpath05]

We made space dock, one half resting and waiting now lets call it a day.....

 

[hunt4570]

You were probably a bit tired and overheated by the time you got to welding that one, maybe if you had a swimming pool to cool off in between welds, you would've probably been ok!!

WHAT????? Are you jumping on his swimming pool bandwagon too??

The pool is great this time of year though!!

 

[hunt4570]

I'm thinking if I had a pool I wouldn't be fooling around with rebar to begin with......

Hmmm... I know this one guy with a pool.. and I don't see him messing with rebar!

 

[John_Mc]

I think almost all concrete bridges rely more on tensioned steel tendons for holding them up than the rebar.

Yes, it's known as "Prestressed Concrete Strand" - a cable made of high strength steel wires. The steel wire company I work for is not in that product line (we make and heat treat steel spring wire), but some of our competitors are into it (though a lot of the US-based ones seem to have been pushed out by overseas competitors, helps by the strong dollar).

Rebar is used in lower stressed applications, but the bridge girders and precast forms all use PC strand.

 

[John_Mc]

Weight limit would require to much math, not one of my strong attributes but would be interesting to know. The 6x6's are 16', planning on 3' on each end to rest on ground, so that will leave 9' open air to hold a 6000 lb-ish tractor.

The Vermont Dept. of Forest, Parks, and Recreation has been pushing portable skidder bridges for loggers for some time now. They are very similar to what Oldpath05 has built. They have published some designs here: Temporary Wooden Skidder Bridges. Their "standard" design is 20 feet long and built in 3 sections from 6"x8" #1 Grade Eastern Hemlock. It is designed for up to a 14' clear span. The max load rating is for a 32,000# skidder under full load, or a 50,000# forwarder fully loaded. (It should be noted that in addition to the 6 through-bolts, these bridges also connect adjacent beams using 10" flat head log cabin screws midway between each through-bolt. This helps further stiffen the bridge and assure that loads get distributed among adjacent beams.)

I'm no Civil Engineer, but it certainly seems that as long as the wood is sound, OP should have no problem with his +/- 6000# tractor.

Each 3' end will sit on tar paper, that will sit on ground.

When the portable skidder bridges I mentioned above are used, they generally drop them right on the ground. Generally, getting wet isn't what makes wood rot, it's failing to get dry again. Since they are pulling the bridges at the end of the job, they usually have plenty of time to dry back out again. Also, since they are regularly moved, they have easy opportunities to inspect the panels for excessive rot or other damage.

With the light loads and short span OP has described, he should be OK for years. However, It might be worth considering putting some sacrificial wooden footers under each end and making a dirt ramp up to the bridge. If the footers start to go, you can always replace them. If you use something highly rot resistant for the footers, you can get even longer life (Black Locust will far outlast Hemlock in terms of rot resistance. A concrete "jersey barrier" or cast block can also make a great footer.)

I made a little footbridge over a small stream years ago by just free-hand chainsawing 3 hemlock logs into beams and lag bolting them together. I put each end on a short length of 6"x6" Hemlock beam, which was in a wet, muddy area. I had to replace the Hemlock footer after about 8 years. The bridge itself was still fine 15 years later when I pulled it out to replace it with something less beefy, but with better footing (my neighbor's almost completely blind dog had trouble with my log bridge, so they made a nicer plank one so she could still handle their walks).

EDIT - added PDFs of the "Standard Duty" temporary skidder bridge designs. If anyone wants the heavy duty design (uses 6'x10' hemlock beams) let me know.

 

[VroomVroom]

 

[VroomVroom]

This is a rig matt they would lay on the ground or over soft land when doing the hydro transmission line across the province recently. Extremely heavy dense wood. Not sure what kind. Its bolted together similar to OP's. But one section on each end that surrounds the ready rod is removed so they can hook a chain and lift them around if they need to.

 

[Loaderman22]

WHAT????? Are you jumping on his swimming pool bandwagon too?

Nah, just trying to give OP a hard time. He's doing such a great job on that bridge section, I don't want it to go to his head, then he will need the 16' door just for his ego.
"Good" friends of mine just out in a pool. They haven't invited me over there yet either. Hmmm.

 

[Oldpath05]

They use those matts down my way to they are for soft ground and drive trans-verse on them, think they are hemlock and creosoted.