Yes it is right, i made a slight mistake with the total feet traveled in 1 minute as it was off by 20ft but it was such a small mistake that the answer was still 55.7mph

I calculated the circumference of one revolution which equals 72.3in per revolution, multiply that by the rpm 813.6 and divide by 12in which gives you the total distance in feet traveled in 1 minute or 4,902 ft now that is almost the total distance of 1 mile per minute so you know that it is going to be close to 60mph. now i want to find the percent difference between the distance and the distance of 1 mile so that i can find the speed. The difference would be 4901.94/5280 which equals .9283977273

Now you take that number and you multiply it by it by 60mph and you will get you speed.

RPM = 813.6
Radius = 11.5in
Circumference = 72.3in per revolution
Feet per minute = 4901.94
4901.94/5280 = .9283977273
.9283977273 x 60mph = 55.7mph

The video that i made is outdated and i will be real easing a 2.0 version sometime tonight.

In the video that you can see right now it does not appear to be going 55.7mph probably because its not, it was probably doing 30-40mph

Reason being is that i improved this by greatly strengthening the middle axle as well as reducing the number of spacers i used and i added an optical shaft encoder to measure speed.

It is much much faster now with those improvements and the 55.7mph is very accurate, after i added these things it went so fast i could only see the bar in 2 places and the wheel came off of the ground and started being suspended in the air because of wind resistance, speed, and torque.