What makes a Strong RZR Cage?
26-Jan-2012 There are several principles we will talk about that determine the strength, and therefore the safety of a roll cage. This article will seek to discuss some of the importantFactors that will help you determine the relative strength of a cage.
#1 material type.
a bit about roll cage material sciences: All materials are ranked ina variety of ways (maliability, burst strength, shear strength, crush strength and so on) These measures are all done on a consistent and scientific basis. That means it can be compared on vs the other in a large chart or materials matrix. This is a pretty exhaustive method for determining the differences between materials. but there are a few things you can look at to determine which material fits your needs the best. Here at Vent Racing we use DOM for our cages, because we feel it is the best ballance of all qualities for the UTV market. FOr comparison purposes we will consider only a few material examples in the following table (using 1.75 in OD material, same as the stock cage)
| Chromoly |
0.120 |
1.75 |
1.51 |
55,303 |
2.089 |
| Chromoly |
0.095 |
1.75 |
1.56 |
44,453 |
1.679 |
| Chromoly |
0.083 |
1.75 |
1.58 |
39,119 |
1.478 |
| DOM |
0.125 |
1.75 |
1.50 |
44,668 |
2.169 |
| DOM |
0.095 |
1.75 |
1.56 |
34,575 |
1.596 |
| DOM |
0.083 |
1.75 |
1.58 |
30,426 |
1.478 |
| HREW |
0.120 |
1.75 |
1.51 |
24,579 |
1.089 |
| HREW |
0.095 |
1.75 |
1.56 |
19,757 |
1.596 |
| HREW |
0.083 |
1.75 |
1.51 |
17,386 |
1.478 |
| |
= Stock Cage |
This chart begins to explain the differences between available and regularly used cage materials. Since the only measure of strength used here is tensile failure strength, it is not a complete analysis of the materials "real world strength. But for all intents and purposes, it can be assumed that with regard to a roll cage, a rise in tensile is a great indicator that there is a similar rise in other measures of strength. That said to draw a comparason the stock cage on a polaris 800 is made from HREW 0.083 wall steel, whose tensile strength rating is 17,386 PSI, in comparison with 0.095 wall DOM (like a vent racing cage) which measures 34,575, nearly twice the strength of the stock cage without changing the design at all! That said, nearly more important that the material a cage is made from, is the design of the cage, and how it transfer's forces.
#2 Triangulation
The triangle is the strongest simple geometric structure, because it takes force from one point, and distributes it to multiple points, similar to a structural arch, but using an un-compromised member for strength. This means that an attempt to crush a cage that is supported un triangular shape will take more than 3 times the amount of force as a similar material making squared edges. Essentially this plays on two simple principles of physics:
1 Leverage. The greater angular mechanical advantage gained by an epicenter of force, the less resilient a support member will be. in other words, a nail is easily bent laterally with a hammer, but when hit on the head all force is transferred through it. The same applies to Tube Steel. This means that whenever possible you should predict forces on your cage, and line the force's vector with a support member in that direction.
2 Resultant Force Vectors. When you hit a baseball with a bat, the force of the bat, and the force of the ball (from the pitcher) combine to send the ball in a particular direction, at a particular speed. That direction and speed are called a resultant force vector. This principle is used in cage design because when your RZR rolls, the force of the machine, and the ground transfer energy in different directions. By predicting these directions at Vent Racing, we build cages that produce force vectors that are transfered directly to support members, keeping occupants as safe as possible.
This is the beginnings of a run down of cage design for UTV's. Hopefully it has been educational, and maybe even interesting. Stay tuned for more updates.
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