Breastlines & Brail Lines

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A short page about Breastlines & Brail Lines

Breastlines are ropes (normally hemp at RCS) which are tied tautly between the flyfloors in order to deviate a counterweight bar up or downstage.

We use them to when there is a clearance issue between flown pieces. It is normal to breastline a static bar, such as LX, in order to let a flown set piece pass cleanly on its way In and out during the performance.

It is possible to deviate a flown piece but this would be done using “running brails” rather than a breastline.

Points to consider

It is desirable to breastline a counterweight bar as low as possible; Ideally, just above the bar terminations.

This is because the greater the distance between the pulley blocks in the grid and the bar the less force will be needed to deviate the bar.

This can be proved with maths

Horizontal Force = Load X (Horizontal Deviation / Vertical Distance from the pulley to the breastline)

Lets assume we want to move a fully loaded 400kg LX bar 200mm upstage using a breastline at flyfloor level

Our Load is 400kg

Our Horizontal Deviation is 200mm

Our Vertical Distance is 8000mm (grid pulley to flyfloor)

Horizontal Force = 400X(200/8000)

So the Horizontal Force required to move the fully loaded bar 200mm is 10kg

Lets run the numbers again but this time let’s try to breastline the bar on the grid

The Load is still 400kg

The Horizontal Deviation is still 200kg

But the Vertical Distance is now 1000mm

Horizontal Force = 400(200/1000)

This time we need 80kg of force to move the bar 200mm


  • Have a think about that next time you are installing running brails ...see below*


Brail Lines

Brail Lines are normally lines tied from the flyfloor to the ends of the counterweight bar.

The purpose is exactly the same as a breastline, to deviate a counterweight bar up or downstage.

They are very common in theatres where the flyman can reach the end of the bar from the flyfloor and in those venues you would normally find a collection of small ropes on the flyfloor, perhaps with snap hooks for this purpose.

The flyman would lean out from the flyfloor, clip to the end of the counterweight bar, pull the line tight and cleat off to the pinrail.

This is not common at RCS due to the fact we cannot reach the ends of our counterweights from the flyfloors


Running Brails

Sometimes it is necessary to deviate a moving (flown) piece and in this scenario neither a breastline or brail will work.

Therefore we use Running Brails

Running Brails are pulleys which are used on the counterweight suspension lines on the grid.

The pulley is then tied off under tension to the supporting structure of the grid (ideally close to the grid floor) and the pulley allows the counterweight suspension line to run while it is under tension

Be aware of the forces that could be applied however (see the Breastline maths above)

This should only be used for small deviations and remember you should always try to move static flown items in the first instance.