There are different types of Bowtie antenna as mentioned below. Due to its structure, it is known as butterfly antenna. The links to other antenna calculators are also mentioned.įigure-1 depicts typical Bowtie Antenna. It mentions Bowtie Antenna Calculator and mentions formula or equations used for Bowtie antenna calculations. Sag is definitely less if the shelf ends are attached to the case, so if the shelf works ok supported by a couple of bricks or paint cans, it should work even better if it's attached to the case sides or back.Bowtie Antenna basics | Bowtie Antenna Calculator Check sag (deflection under load) and creep (permanent deformation under load) with the materials and design you plan to use. A 1x2 used as edging vertically is 4 times as effective than if it's attached horizontally if I can believe my calculations, a 1x3 would be 11 times better.* As always, your mileage may vary. That cube relationship means that going from 3/4" to 1" thick means that the sag decreases by a factor of 2.3. A workable bookshelf design at 30" will probably perform like crud at 36" wide, and don't even think about 40" without additional support.* Thickness also matters. The short, mostly math-free version:* For creep (permanent set) resistance: Solid wood is vastly better than engineered wood of the same thickness, and the farther you get from solid wood, the worse it gets.* Length really does matter. Unfortunately, the beam deflection is proportional to the cube of the length as well, and the resulting deflection is proportional to the 4th power - a 20% increase in length means that the sag will more than double.Calculations get even more complicated, of course, but this should help.
If you're storing books, the weight is proportional to the length, so going from 30" to 36" increases the weight by 20%. This is why I-beams work so well, and why you can get a substantially stiffer shelf by using 1" thick shelves instead of 3/4".The other tricky part is the load and length of the shelf. If you look at the moment of inertia equations, it's clear why: resistance to deflection is proportional to the cube of the distance from the center of the cross-section. Fully loaded with hardcover books, there's little or no measurable deflection.The best edging is wide and attached on edge. The latest shelf project has 30" spacing, fixed ends, and 1-1/2" wide edging in white oak. We have about 7000 books in the house, so I've built a few bookshelves, and I've seen what happens over time. Too many of us have seen what happens to plywood, even 3/4-in thick, when it's not supported right during storage - if it can creep under its own weight, it's definitely going to creep in use unless you design around this.Creep resistance for engineered materials (plywood, etc.) is going to depend strongly on the glue used to hold everything together.One of the reasons that I like wide edgings on plywood is that the edging is both stiffer than plywood (less deflection) as well as largely creep-resistant. In fact, for long term book storage, my opinion is that MDF and particleboard are essentially useless unless the shelf is supported on three edges. MDF is worse, and particleboard is even worse.
Plywood tends to creep under load and shelves will develop a permanent "set" that persists even when the load is removed (hint: make plywood shelves removable so you can flip them if this happens). The single biggest difference between reality and the equations is the contribution of creep, or deformation over time. The standard equations are available from a variety of web sites - look for "beam deflection."Even if you understand everything I just wrote, you can still get into trouble.
Angle on bow calculator free#
Basically, you need to calculate the moment of inertia for the shelf's cross-section, determine how it's loaded (even load over the length, or concentrated in the middle), and whether it's fixed on the ends or free to move.
0 kommentar(er)
