Juup wrote:On gradients, I know most people calculate these as a fraction of unit of rise over unit of length. So for instance 3 cm per 1 meter (100 cm) is a rise of 3/100. Is that then 3%?

Juup

That is the customary usage.

Juup wrote:With such gentle gradients, the measures in degree angle is not a very different number from fraction or percentage (my best guess without calculating is that 3/100 is equal to about 2 degrees. Obviously, with steeper gradients the difference between degrees and percentage becomes greater.

Juup

Yes, the ratio between degrees and percentage is very close to linear linear until past 10 degrees. But the actual equivalence is 2 degrees = 3.5%. So your 1.5° is actually 2.6%.

Juup wrote:I located my sharpest transition (in a hidden section) from 0 degrees (0 percent) to 1.5 degrees (so about 2.2 percent) and this was achieved over about 18 inches. This transition is consistent with about 9 inches per one percent. However, looking at trains negotiating the transition I don't think I passed any limit. So 9 inches per one percent change should be fine even with longer vehicles.

Juup

I don't know what your longest vehicles are, but both in Europe and US, long streamlined passenger cars are 8.5 inches long in TT. The original guideline actually came from 1% per car length - I don't know how that was established, or maybe it was just an off-the-cuff guess, but it stuck. And it seems to work.

Anyway, it seems we are all agreed, and there may be a bit of extra room in the guideline to allow for less-than-perfect trackwork or coupler height settings.

Sometimes you win... sometimes you learn.