Hi instructables so I love biking and decided to build a trail in my back forest area. I planned out the trail and found I need to build a bridge. I thought about using some pressure treated wood and building a ladder bridge, but I went with the awesome looking, fun the ride, natural bridge!
Step 1: Cut Down the Tree
First you want to cut down your tree, obviously. This is pretty self explanatory, if you need a reference here you go: http://www.familyhandyman.com/landscaping/how-to-cut-down-a-tree/view-all Be sure the tree is at least 1' in diameter otherwise it will be really tough to bike across. I recommend around 2' width. For the length of the tree make sure it is about 2' to 3' longer than your gap. You can always cut the tree shorter later. I like to have extra length to ensure that the tree will fit correctly.
Step 2: Drag Into Place
The hardest part of the operation is getting the tree where you want it to be. We had to use an ATV to get the log in place due to its massive size. It was defiantly NOT possible to move without some machinery, unless you had quite a few people helping. First, you need to wrap the tow rope around the tree. Our tree had a fork, this is what we attached on to. If the tree is a straight shaft, you could create a notch with your chainsaw and place the tow rope inside of this. Its pretty hard to move so try and plan where and how you will get it in place. Remember the direction it will be ridden in.
Step 3: Saw It Up!
So this is probably what took the most thought. How are we going to make a horizontal cut? We tried a chainsaw for a cut, but that was really rough on the saw. I remembered a trail that had a natural bridge like this one. It was the one above. **I figured out that they made vertical cuts with a chainsaw then came through with a sledge hammer.** So, You make vertical cuts every 2" to 3" more or less, and come through with a sledge hammer and hit the sides. The wood will fly up in the air so wear eye protection. The tree will not be perfectly flat. This is good for those looking for a more technical ride, but you can come through again with an axe or a chisel.
Step 4: You're Done!
Add ramps before and after the bridge and you're good to go! I recommend clearing out the stuff below, because you're going to fall. Go ride it, enjoy!