My assumptions are primarily acceleration and deceleration rates associated with takeoff thrust, breaking, reverse thrust, impact with objects, and types of surfaces. For my calculations I used V1=117, VR=127, and V2=137 (although V2 isn't really a factor) all speeds in knots.
Based on those facts and assumptions, I came up with this timeline (all times indicate elapsed SECONDS from start of roll):15 secs. - 80 knots announcement, 1,080' of runway used, 6,682' of pavement remaining22 secs. - V1 (117 knots), 2,277' of runway used, 5,485' of pavement remaining24 secs. - VR (127 knots), 2,700' of runway used, 5,062' of pavement remaining26 secs. - V2 (137 knots), 3,159' of runway used, 4,603' of pavement remaining31 secs. - 165 knots (max speed), 4,464' of runway used, 3,298' of pavement remaining40 secs. - cross over departure threshold into overrun - estimated speed: 146 knots44 secs. - end of paved surface - estimated speed: 126 knots48 secs. - impact with light system before ditch - estimated speed: 95 knots49 secs. - impact with ditch and full stop - estimated entry speed: 89 knots (11 knots slower than what NTSB stated)
I see two critical time periods, both of which are just seven seconds each. First, from 15-22 seconds between 80kts and V1, did the pilots put back pressure on the stick to confirm the elevator was functional? This could have provided the first indication of a problem. The second critical period was from 24-31 seconds after the VR announcement to max speed (at which point I assume they stopped accelerating). They covered over 1,300' during that span at which point they did not have the necessary stopping distance. I don't say this to second-guess the pilots, I'm just pointing out where critical runway distance was consumed and the speeds they were dealing with. The final 18 seconds presumably was used to attempt a full stop.
It will be interesting to see how this matches the final NTSB analysis and report. The bottom line is even though the entire event lasted a mere 49 seconds the actual time that the pilots had to assess the problem and determine a course of action was very much shorter. As previous posts mentioned, pilots are trained not to abort a takeoff after V1, a fact which surely contributed to the second critical time period mentioned above.
Please let me know if you see any glaring mistakes or incorrect assumptions. I'm not always right, but I'm never intentionally wrong.