Cheap Heavy Duty Bridge?

[fraggin]

An oxymoron? I have a creek I need to get a tractor across. The banks are silty, 90 degree drops about 5 ft, water is about 3' deep and 8 foot in width. I have a wood utility pole that was given to me by the power company when they upgraded a pole on my property. It needs to be sturdy enough to drive a tractor across. Sound plausible?
Anyone ever tackled this kind of obstacle in an economical matter?

[peternap]

I had a situation very much like yours and to make it worse, that was the only route to the back of the farm.

Building a bridge as you suggest, is fine but will require some tough planking.

I used steel culvert pipe. Three sections. The first was put in as normal and a couple feet of dirt on it. Then the other two were pit in on either side and above the first in case of flooding. More dirt to slightly above ground level. Water blocks at the entrance of the bridge and exit help eliminate washing since it's at the bottom of two big hills.

I have less than a hundred dollars in it but had to look a while for cheap culvert.

[Squirl]

Here are a few designs.
http://pacifi.ca/assembly.html

Have you ever seen the kids that build bridges for science class out of pasta that can hold hundreds of times their weight.  I am a believer that you can do it with wood for your tractor.

[rwanders]

I built 3 bridges across some creeks at a remote drill site on the coast of Alaska in 1986---longest spanned 40'. I had to bring an 80000 lb rig across and other heavy equipment. Used round logs and green timbers we cut out of the trees we cleared for a three mile road. Looked all over for engineering data for using round/green logs for such a task---finally gave up and just drew up a plan. On the way to the airport I spotted the US forest Service office and made a quick detour since I figured they might have some experience building such bridges on logging sites. Showed their engineer my sketches---he pulled out theirs and I was astounded to find them almost identical. I explained what weight I needed to bear and said I planned on using 2-3 foot diameter spruce and hemlock logs as my base with 4x12 green timbers for the bridge deck-----he said I should have no problem taking the 80000 lb load across----the 40' span didn't even make a sound as I did.

I cut a large notch in each bank and placed a solid mat of 12' diameter logs tied together with steel cables on each ledge. Placed a solid mat of 30" diameter logs across the span bearing on both log foundation mats and tied them all together with steel cables also. Placed 4x12 timbers across those logs and spiked them down using 10" spikes and sled hammers. Then added 8x8 timbers along each side to act as guard rails.

Your load is not even close to that so you should be able to use much smaller logs/timbers----if you have a forest service office near you they may be able to give you some advice. Like building a home---you have to transfer the load to the earth using some kind of footer---could be PT timbers or concrete. Beam span tables would probably provide good data if you are using standard dimensional timbers for your small span.

[Jens]

get an old semi trailer, cut off the underpinnings, or leave them there if you don't care.   

[MountainDon]

I believe using culverts like Peter did could be the easiest and cheapest solution.

[glenn kangiser]

My relatives in Oregon always made big log bridges pulling them in with a D6 or so Cat.  They had to be replaced every few decades.

The logs...... not my relatives....

[cordwood]

 If the span is only 8' you could use just about anything. An old flatbed off of a truck or a trailer that has axle problems. Railroad ties are always an option as well, 16 footers would give you 4' supported on each side. 6 would be plenty, 3,....gap....3 should give enough support and a wide enough track to hit with the tires.

[firefox]

Typically, how much does a 16' railroad tie cost? I am assuming new.
Bruce

[cordwood]

 I've never bought a new one but the hundreds of used ones I''ve used over the years have ranged anywhere from free to $25 for 20' switch ties. With EPA regs. getting worse they may want people to steal the old pullouts just to get rid of them