Part Runs and Preroll Extents — Hard Stops, Track Travel, and Safe Checking¶

CONFIRMED SAFETY CRITICAL BOTH

Summary¶

Preroll is speed-dependent. A part run can require a large pre/post-roll move before the visible shot begins, especially after removing beginning frames or starting mid-move. Always calculate the exact forward/part run you intend, then use Goto Preroll/Postroll Extents as the last calculated operation before trusting the extents.

Symptoms¶

Robot moves unexpectedly before part-run start
Track travels farther than expected before shot begins
Robot hits hard stop or disengages during preroll
Goto Preroll Extents does not match actual run
Removing beginning frames changes safety envelope

Stable ID¶

ISSUE-PREROLL-001

First Reported¶

2020-12-15 — part runs and timecode preroll length discussion.

Additional Reports¶

2021-03-27 — browsing to pre/post extent does not replicate actual preroll.
2025-09-12 — Cinebot Max part run caused preroll then hard stop/disengage.
2026-04-08 — Goto Preroll Extents differs from actual run.

Software Environment¶

Both. Several fixes reference Flair Classic menu names; Flair 7 may place equivalent controls elsewhere.

Installation Context¶

All. Highest risk after changing speed, frame rate, sync frames, trigger setup, job type, track length, hard limits, or part-run start.

Possible Causes¶

Preroll calculated for a different speed/run than the one being executed
Dominant axis needs a longer acceleration distance
Track limit/hard limit too close to required preroll position
Low or saved preroll factors from a previous job
Part run starts in a fast section of the move
Operator browsed/goto'd an extent before recalculating the actual run

Community Solutions¶

[CONFIRMED] 2020-12-15 — Users: Julian Hermannsen, Niko, Simon Wakley¶

Lower the preroll factor only for the dominant axis causing the long preroll, and only for the current job. Values such as 0.3 or 0.1 were reported as situational, not defaults. Reset afterward. Starting the part run slightly earlier can give Bolt time to stabilize.

confidence_score: 0.80

[CONFIRMED] 2021-03-27 — Users: Simon Wakley, Julian Hermannsen¶

You cannot simply browse the actual preroll/postroll. Calculate the move at the correct speed, run/cancel if needed, then use Goto Preroll. The rig model should also show pre/post-roll.

confidence_score: 0.78

[CONFIRMED] 2025-09-12 — User: Heiko Matting¶

Before removing track length or changing the move, check pre/post-roll position in the Goto menu. If already in trouble, adjust preroll/postroll factor for the axis that needs the most distance, try Start Quickly / Quick Run Up, or lower move speed and camera frame rate by the same factor. Do not delete waypoints unless you accept that the move changes.

confidence_score: 0.86

[CONFIRMED] 2026-04-08 — Users: Timothy Heys Cerchio, Simon Wakley¶

Set Start as Part Run Up when checking actual preroll extents. Use the exact fwd run or part run you intend, then use Goto Preroll Extents as the last calculated action. Bring speed up gradually; preroll grows with speed.

confidence_score: 0.88

WhatsApp Excerpts¶

2020-12-15 17:12 - Tom D: Hello - quick question regarding timecode triggers if anyone has done some music video experience here. I’m successfully triggering the whole move from a timecode source, as well as part-runs (or sections) of the move as well, and the footage is lining up accurately to the frame as expected. What is NOT expected is that the first few frames of a part-run still contain all the jitter (in the video footage) from the robot gaining momentum into the part-run move, however my understanding was that...
2020-12-15 17:14 - Tom D: I’m allowing lead-in time for the artist of many seconds etc, so this isn’t affecting production, just my understanding of the process is now in question...
2020-12-15 17:14 - ~ Julian Hermannsen: Look for the dominant axis in the preroll and lower the preroll factor. Don't save this but only apply to your job. You want this to be low in general as it can be quite drastic but it'll make it shorter
2020-12-15 17:21 - ~ Julian Hermannsen: You could globally lower everything but this could lead to extremely large prerolls if you're in a fast part of the move at the start so I'd try case by case
2020-12-15 18:38 - ~ Niko: Depending on the move, you can start your part run, a little out earlier too. I use to start the music five seconds before the desired part run starting point, to help singers get into the playback. And the bolt movement, some frame before the desired part run starting point too, with a laser bloop in the real desired starting point. In this way prerolls make their job and I let bolt stabilize the movement a little time