Chains and ratios

Time to think what speed I wish to ride on TT, that's why I need to calculate gear ratios. I think that 50km/h is very good top speed, and to make some calculations I end up doing Exel sheet of graphical diagram of how the speed will vary in different ratios. Wheel size, cadense, and all gear teeth's can be added and put into diagram.

A picture how I will put my chain go thru into front wheel is here.




Here we can see a diagram with a candence of 80 rpm. Gear ratios are 12-27, main ring is 44T to keept it small. Still I have to figure out does my feet bang into derailleur, then I have to go with my plan-b.
Speed increment is very linear as they usually are, which is very good. Speed starts from 20km/h to be able to start from launch wheels and topping to 50km/h. Hopefully I need to change gears to suit better to 60km/h ;-)