The quickest way to get off on the right foot when a show comes into your venue is to be able to efficiently call bridles. The last thing a production manager or road rigger wants to see is the house rigger looking up, scratching his head or franticly punching numbers into a calculator or phone.
There are several methods to calling bridles and you have to find what works for you. If you’re lucky someone will be willing to pay for you to lay out the show before hand and, with an accurate overlay, you can pre-figure all of your bridles. I developed a spreadsheet to figure loads and leg lengths. That works to an extent, until you find out that you have the wrong plot or the show moved upstage three feet, and the reality is, most times you are not given this time. I see a lot of people using phone applications to figure bridles lately, this could be a great tool if you knew how to use it quickly and efficiently, but I haven’t seen that happening yet. Bridle charts work well if you take the time to set them up correctly. When I first started to make charts I would do a chart for each bay, figuring off of an even bridle and writing down how many inches each added link gives you. Note: You will find that as you add links and your long leg becomes a larger percentage of your bay size, you will get more movement per link.
Eventually I found that I could make one chart from the center of the room out, again using a computer program, the Pythagorean formula or simply estimating you can figure pretty close to what each link will give you. As you hang points in your venue you can adjust your chart as you find how things hang in the real world. I always adjust the long leg unless there are very special circumstances, I would suggest that you start by doing the same, short leg adjustments get tricky quickly. I have three charts for my room as the bay sizes aren’t consistent from the North end to the South, you may need more charts, in a simple grid you would only need one.
I simplified my chart to approximate every one foot move, link counts in between are easy enough to figure in your head. My chart for the Prudential Center looks like this:
What you will find is that most road riggers will lay out the room with three tapes. Next to the center tape, most will write every point locations measurement from center(the really nice guys write that # in every point). Now you can simply reference your chart to see that a point at 43′ from center will need 7 links of deck chain. At this point you should be able to just look up into the bay to determine which leg to add links to.
I’ve found that the next step to really knowing your room is to memorize some key numbers. The first numbers to get into your head are all of your dead hang and even bridle locations. In the chart above; 6’9″, 13’6″, 20’3″, 27, 33’9″, 38’9″, 43’9″, 51’9″, 60’3″. If you know how many inches of movement you get for every link of deck chain, you can figure a lot of points in your head from these key numbers. If someone puts a point on the floor at 14′, I know without any calculations that, in my room, I need to add one link of deck chain to the onstage side of an even bridle to hit the point.
Once you have those numbers down pat, I like to also memorize where a full deck chain hits, in my case 4’6″,9′, 18′, 22’9″, 31’6″ etc… So now any point within a couple feet of center or within a couple feet of the edge of each bay you can figure in your head so long as you know how far you are from center of the room. It may seem like a lot of numbers but I found I was able to commit them to memory pretty quickly. I rarely have any reason to pull out my chart and I think as you get to know your room the goal should be able to walk onto the floor with a tape measure, laser and some wet chalk and mark the floor quickly and accurately, often only needing the chalk. Checking a chart is a pain in the ass.
If I’m in a new room, or need to figure a point in a bay without measuring from center of the room. I find the quickest way to be simply measuring the bay size and marking center of the bay. Make sure you’re measuring from the center of the beam. Next, measure how far your point is from the center of the bay. Based on the length of your leg and its ratio to the bay size, you should be able to approximate how much movement per link you will get and you can add links appropriately, in my venue I get a little bit more that 5″ of movement for the first link added. If you haven’t read Bridle Dynamics by Fred Breitfelder I highly recommend it. He gives a great perspective on the relationship of your bay size to your leg length and how to approximate link counts. Keep in mind this quote from Plato’s Republic
“The most important part of any work is the beginning”.