I have a Viaduct

[jamesmantle]

Gradient
I have built a Viaduct with a bed height of 8.5 cm how do I work out the ammount of leadup to it I need in OO. scale any help with the equations needed would be most helpful.
James Mantle

[dmaynard]

The lead up to it would be a grade. Mainline grades are typically less then 2%, or a rise of 2 cm per 100 cm traveled. So to climb to 8.5 cm at 2% you would need 425 cm of run. If you increased the grade to 3% you would need 283.3 cm of run. If you went to 4%, a very steep grade per real railroad standards, you would need 212.5 cm of run. Of course these numbers don't include the transition from flat to grade and back to flat, and you do want those transitions to be as gentle as possible.

My suggestion would be to lower the part of the layout where you want the viaduct, so you can have a much lower grade, or no grade at all. Railroads don't build inclines just for the sake of building an incline. When they build one they have a good reason because it costs them money in materials to build it and fuel to climb it. They build them to get over mountains or obstacles, or because they need to get up on a hillside for some reason.

[jamesmantle]

Thanks
That helps a lot I know it sounded silly but as I have said I am very new to Model Railways and dont want to make mistakes,but I am very good at model building and have also built an engine shed that is very good well my friends think so.
james

[dmaynard]

James, no it doesnt sound silly. I have talked with some people who have been in the hobby for years and they dont understand grades.

Glad I could shed a little light on the subject.