Let's talk about hydraulic fittings. And pressure drop in a hydraulic fittings. So I want to explain why a fitting causes a pressure drop. And show you the equations for the pressure drop in standard fittings. Here's a typical hydraulic fitting, which is a 90 degree elbow. And you would use this if you want to bring a hose and connect it up to, say, a cylinder, and have the hose run alongside the cylinder. So one of the things about this fitting, it's convenient because it allows you to take the 90 degree turn. But as we saw earlier, because of that 90 degree turn, the fluid flow is going to become turbulent and the fitting is going to offer resistance to the fluid flow. So anytime you have an abrupt change in direction. Or in an abrupt change in diameter, you're going to get a turbulent flow, and you're going to get some pressure loss. Precise predictions of exactly how much pressure loss you have requires computational fluid dynamics. But there are some approximation equations that are useful to allow you to calculate the overall pressure losses in your hydraulic, system. So here's the key equation. And, it shows that the pressure loss Delta p is a function of k, which is the loss coefficient. And the density of the fluid and the velocity of the fluid. And again because [UNKNOWN] fluid power systems you're working with flow rate. And over here on the right we've got it in terms of the flow rate. So you can see the pressure loss goes to the flow rate squared. The area is the, area of the fittings, so that would be the, the, the, the, the area of the circular bore. And then this K, this loss coefficient, is one that you can look up in your textbook, or in vendor catalogs for particular fittings. So a couple of examples, that 90 degree elbow has a K factor of 0.2. Or that tee fitting that you saw earlier in a video. Has a K factor of about 0.9. So let's take a look at some fittings on a excavator. And so if you, you know, really wanted to analyze what's going on in the flow of the fluid of these excavators so starting here is a smooth, gently changing diameter conduits, so you can probably take this as a laminar flow and calculate the pressure drop across its conduit based on its length. Then over here, once we get up to these pipes when you're going way up over here and, getting to the cylinder, you've got a, two 45 degree bends here, so you want to take into account fitting losses. You get into the cylinders, this is the 90 degree bends, so you want to calculate the losses there. And, as I mentioned before, these losses can be significant. So, for example, we're working on some systems in my lab where we're putting eight hydraulically powered, ankle that you can wear. And in order to run the fluid to that ankle, we wanted to use that small bicycle pump, or bi, bicycle break line that we showed earlier. But because of that 2.2 millimeter inside diameter, and because the losses are so sensitive to diameter, if when you look at the amount of fluid that we had to push down through the one meter length to go say from your waist down to your ankle. It turned to be too much of a pressure loss. So we had to go with the motorcycle brake cable instead, which is a little bit bulkier than we wanted. But the, is much more efficient for pushing the fluid power through. So now you've the knowledge to model any or most of the parasitic losses in the hydraulic systems that are due to conduits and to fittings. [SOUND]