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

How Part-Run Preroll/Postroll Actually Works, and How to Check It — Explained in Tutorial¶

From tutorial video, added 2026-08-30

Two official Flair 7 tutorials directly demonstrate the mechanism and the exact operator procedure this page's Community Solutions describe only in general terms.

The mechanism (why a part run needs a preroll at all)¶

"30 - The Runtime/Timeline display in Flair 7" demonstrates a part run (e.g. frame 30 to frame 75 of a longer move) and explains why Flair moves before the requested start frame:

"When you do a part run, the move between frame 30 and frame 75 will match exactly as if you had run that from start to finish... but to do that it means that at frame 30, which is where it currently has [to start], it already has to be at the same speed as if it had been running the move from frame 30. So what it will do is it will actually do what's called a pre-roll — when I press shoot it'll actually move a little bit backwards, get up to speed, and then start moving forwards again, and then once it hits frame 30 it'll be at exactly the same speed... similarly when it hits frame 75, it'll do a post-roll." — 30 - The Runtime/Timeline display in Flair 7

This confirms the underlying reason preroll is speed-dependent (as this page's Summary states): Flair isn't padding the run arbitrarily, it's calculating how much run-up distance is needed to reach the exact speed the mid-move frame requires.

The exact operator procedure (Goto Preroll/Postroll Extent)¶

"37 - Goto Menu & Goto Browsing" demonstrates the precise Goto-menu feature this page's 2021-03-27 and 2026-04-08 Community Solutions reference as "Goto Preroll Extents" / "Goto Preroll":

"If your move has a pre-roll... I can go to Go To Preroll Extent, and here it tells me how far that preroll is, and I can — if I want to see where it is — I can actually browse to it or go to it... these prerolls here are quite short, but if you have a high-speed rig, or you're moving very quickly, and it needs to do a very large pre-roll — maybe on the track — and you want to see whether the pre-roll is going to hit something, that can be very useful." — 37 - Goto Menu & Goto Browsing

This matches the existing [CONFIRMED] guidance above almost exactly: set up the actual part run you intend first, then use Goto Preroll/Postroll Extent (not a generic browse) as the last step to see exactly where the preroll will take the rig — with the option to Browse to it at controlled speed rather than letting a full-speed Goto run blind.

confidence_score: 0.6

YouTube 30 - The Runtime/Timeline display in Flair 7 Flair 7

▶ 05:48 — Part run pre-roll/post-roll mechanism: why the rig moves before the requested start frame

YouTube 37 - Goto Menu & Goto Browsing Flair 7

▶ 10:55 — Goto Preroll/Postroll Extent: checking exactly how far a preroll will travel before trusting it, especially on track

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