I don't know if it's a forgotten one, but it's certainly one that haven't seen any updates in a long time. And "sadly", it's the only one of it's kind, meaning that if one day, it get incompatible with OpenTTD, there will not be any replacement.
It's the Early train set :viewtopic.php?t=41132
I mean, you can start with minecarts pulled by horses. Something that the 600mm set allows to, but then, by 1804, you get early steam machines.
Two interesting things in this set :
- evolving machines : the first machine "One cylinder experiment" receive upgrades during it's life. So by 1813, it will be faster, more powerful, and even have a different sprite. Those changes are nly if you buy/renew the machine. It's a thing that I rarely have seen used in other NewGRF.
- Compatible rails : you get to built wooden tracks for the horse-pulled carts. Then a light metal railway for the steam machines. The horses can ride on both types, and the steam machines and carriage can ride on the light rail type and the standard type. This allow for a smooth upgrade of the train as time goes by.
There are room for improvement in this set : a first thing would be to merge the two newGRF files into one; a second, to make the vehicles compatible with standard rail with an option, so it avoid cluttering the rail menu with two rail types that will not see a very long use (light rail compatible machines stop to appears after 1850 so you really only use the light rail type between 1804 and 1870 at best).
The horses whistle
Anyway, my main regret is mostly that no one else offers early machines. Even if the UK set offer a Planet by 1830, I still think it doesn't look as funky as those early locomotives with the big red wheel spinning on their sides.