Originally Posted by
Connedrod
2000 rpm to 1586 rpm big difference. Please explain as you said it hit at 2000 rpm simple math you said. Difference is one being governed and one not. Nearly 25% not worried about a any ones elses reading as its not a point im trying to make. With out accurate measurements and not some pics its impossible to get it right. Its pure speculation as to prop speed. If it was simple maths we would not have 3 different answers aready.
You're new here so, I'll be nice. It's not speculation, it's estimation.
And the maths
is simple, it's year 7 level. We have two different answers (not three) because we have two different estimates of the distance between the prop strikes. I think megan now sees that her original estimate was on the low side because her reference measurement was on the high side; that means that you can discard the original estimate of 1586 rpm. So now you have one estimate that is within 6.7% of 2000 rpm; that's not bad given the method of estimation, moreso when we can see that the prop speed is retarding at about 4% per completed rotation as it chewed its way along the roof.
It is worth noting that 300mm between the roof cladding ridges is the largest distance likely and based on that we get an average left prop rotation of around 1866 rpm. That speed is in the green arc. If the ridges are closer than 300mm then the estimated rpm goes up, not down.