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Setting Up Axis Acceleration

[BOTH] Finding the maximum safe acceleration for a rig axis requires a methodical procedure using Flair's velocity and acceleration graphs. This is used when commissioning a new rig, reconfiguring after a hardware change, or when optimising performance for a demanding move. The procedure is described by @peter.

Sufficient travel required

This procedure requires enough physical travel on the axis to reach top speed and hold it for a constant-speed section. If the axis travel is too short, you cannot reach max speed and the measurements will not be valid.

Procedure

Step 1 — Initial setup

  1. Set the camera/move frame rate to something high — 200 fps is recommended.
  2. Set the acceleration figure to something average (not high — you are starting cautiously).
  3. Set Runtime Factor to 1.0.
  4. Set Target Tracking (TT) off.
  5. Set axis fairings to approximately 40%.

Step 2 — Confirm max speed is reached

  1. Run the move.
  2. Open the axis graph — turn on Speed graph, turn off Position graph.
  3. Use the cursor to check whether the axis reached and held a constant top speed (a flat top on the speed curve).
  4. If max speed was not reached, reduce the number of frames (or run the move faster) until Flair finds the maximum speed for you with fewest frames.

Let Flair find max speed

The easiest way to confirm top speed is reached is to use too few frames and let Flair report the maximum speed achievable. You should see a flat plateau at the top of the speed graph.

Step 3 — Read peak acceleration

  1. Turn off the Velocity graph and turn on the Acceleration graph.
  2. Use the cursor to read the peak acceleration value at the ramp-up.

Step 4 — Increase acceleration until the axis trips

  1. Reduce the fairings gradually.
  2. As fairings decrease, Flair will eventually increase the "fastest" frame count — complaining that acceleration is too high.
  3. When this happens, increase the acceleration limit in the axis setup.
  4. Run the move again and read the new peak acceleration from the graph.
  5. Continue reducing fairings and increasing acceleration until the axis trips on the ramp-up (not at top speed).

Trip on the ramp-up, not at speed

The goal is to find the acceleration limit at which the axis trips during the acceleration phase, not while running at speed. This tells you the true mechanical acceleration ceiling.

Step 5 — Back off and set Runtime Factor

  1. Back off the acceleration limit by approximately 5% below the value at which the axis trips.
  2. Run the move several times to confirm it is repeatable and not a fluke.
  3. Set Runtime Factor to 0.95 as a safety margin for production use.

Bolt Fast-Stop Post-Roll

If a fast faired stop on the Bolt causes a small post-roll (a slight overrun after stopping), try one of:

  • Add a second keyframe identical to the end point, held for at least 1/10th the move length (e.g. 100 frames hold at 1000 fps).
  • Use the Smoother Stop option in Miscellaneous Setups.
  • Use the Firm Stop option.

The double-keyframe approach is the most reliable. @Niko confirms both "add a hold" and "firm stop" options work well in practice.

Summary of Settings

Setting Starting value Purpose
Move FPS 200 High rate reveals limits quickly
Acceleration Average Conservative starting point
Runtime Factor 1.0 → 0.95 final 1.0 for testing; 0.95 for production
Fairings ~40% Starting fairing; reduce during testing
TT Off Isolate axis behaviour

Source: Setting up Acceleration on an Axis — talk.mrmoco.com