Grip Minutia: Speed-Rail®
Time for another closer look at some of the things we use every day. Today it's Speed-Rail® or more precisely 1 1/4" schedule 40 6061 aluminum pipe. It's interesting to note that we use pipe and not tube. Pipe is designed to carry fluids(and gasses) so it's inner dimensions are more important than it's outer dimensions. Tube is designed for structural applications and is classified by it's outer dimensions. So while it would seem illogical to use pipe for our structural applications, it turns out that price is the determining factor as pipe is much cheaper to produce than tubing.
Because Speed-Rail® is pipe it's dimensions depend on it's "schedule." Pipe schedules are an engineering thing that I don't fully understand, but basically each NPS(nominal pipe size) has a different wall thickness depending on what schedule it is. Because Speed-Rail® is 1 1/4" schedule 40 it actually has an ID of 1.38" and an OD of 1.66" with a wall thickness of 0.14". Speed-Rail® also comes in 1 1/2" but that is also schedule 40 and at least here in Los Angeles is much rarer than the 1 1/4" you're probably used to seeing.
Now the last bit of that description is the 6061 designation. That number is a designation for the alloy that Speed-Rail® is commonly made out of. I'm not that well read on specific alloy properties so I'll leave that to Wikipedia.
Now that's all fine and dandy, but what would Speed-Rail® be without fittings and clamps? Well funny you should ask that, because the standard fittings we use are actually handrail fittings. That's right even the name Speed-Rail® is technically a registered trademark of the Hollaender Manufacturing Company. If you look at the Hollaender website you'll see lots of fittings that you recognize and lots that you don't, mostly because there are a lot of handrail fittings that aren't very useful in the context we work in. Now there are also a ton of Speed-Rail® clamps and accessories that are made specifically for our industry. Speed clips are a perfect example. Also, a large majority of what Modern Studio Equipment makes is intended to be used on Speed-Rail®. The other major clamp we use for Speed-Rail® is the cheeseboro. Those are actually made for a range of pipe sizes and likely came out of the scaffolding industry.
What about weight? How about strength? Well the first is pretty easy to nail down, at 0.8 lbs per foot or 16 lbs per 20' piece it's pretty stinking light. Strength is another matter entirely. I don't have my engineering degree yet so I'll just link you to Hollaender's "Mechanical Properties of Pipe" PDF and let you figure it out.
Hopefully armed with this information, you'll be better prepared to tighten down some grub nuts, which just happen to be 3/8" - 16 thread set screws and should be tightened to 10 ft/lbs of torque.[4(PDF)]
*note- If you're wondering why it's "Speed-Rail®" with every instance, it's a legal thing.