O gauge grade

I am in process of designing an O gauge layout. I have experience in HO but am farily new to O. My question is about grade, I would like to operate my train on mulitple levels. Nothing to crazy as far as height goes.

If I took track from table top and wanted to gradually climb up to say a height of about 10 or 12 inches how long of a run would I need. I know there are factors such as number of cars pulled to consider. I have no desire to go above the height I mentioned. We have all seen HO layouts with trains making their way up and down various grades, making things appear more realistic. I just wanted to know if its possible with out.

I am just trying to get an idea how much layout space I would need to accomplice this, thanks for to all for your assistance.

CMS,

Perhaps these links from the FAQ post will help.

What grades should I use?

http://www.trains.com/TRC/CS/forums/328147/ShowPost.aspx

http://www.trains.com/TRC/CS/forums/992970/ShowPost.aspx

General rule of thumb - every 1/8" you climb in 12" is 1%.

1/4" per foot = 2%

3/8" per foot = 3%

1/2" per foot = 4%

I would stay at 2% - or 3% tops. To raise 12" at 2% you need 48 feet - at 4% 24 feet - but if you go too steep, you will regret it later.