Cool bridge! Looks like a lot of hard work to make it trustworthy though. Have you considered replacing the old ties with newer, grade #1 used ties? They're available retail for about $12 apiece. Probably cheaper if bought in bulk. They are a bear to handle. I hope your tractor has a front end loader. Large ice tongs can also be handy when handling the ties. You might also consider using steel components instead of wood.
