Motorsport Plumbing Systems: Flexible Hose
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Flexible Hose
08.08
| 00:00 | Flexible hose is the alternative to hard lines and is naturally used where flexibility is required. |
| 00:06 | This could be where part of the plumbing is attached to the chassis or chassis mounted components and another section is connected to the engine, drivetrain or suspension, which of course moves relative to the chassis. |
| 00:19 | Alternatively we may just require some flexibility for servicing to allow fittings to be disconnected. |
| 00:27 | The amount of relative motion or flexibility required at fittings is different for each case. |
| 00:33 | But while we might be able to flex a hard line enough to get a fitting undone, if we use hard lines between the chassis, drivetrain and suspension, we almost certainly will end up with failures, not just from the excessive movement, but also from vibration leading to fatigue. |
| 00:51 | On factory spec vehicles or at the lower end of performance applications, EPDM or nitrile rubber hose is the standard for flexible plumbing because it works effectively while keeping the cost down. |
| 01:04 | In most cases, the hose is reinforced with an integral fibre weave, increasing its strength and helping it to withstand internal pressures. |
| 01:13 | The issue with motorsport applications is that the rubber breaks down when exposed to all kinds of high temperatures seen in racing situations. |
| 01:21 | Motorsport environments are also more abrasive and shorter service intervals result in more external exposure to chemicals and stress, all of which accelerates the deterioration of rubber hoses. |
| 01:34 | In some cases, rubber hose, even when reinforced, will still swell and expand with internal pressure resulting in compliance issues, which we want to avoid for our braking and power steering systems. |
| 01:48 | For these reasons, we usually make the move to a more heat, abrasion and chemically resistant hose that can stand up to the abuse even though they come at a higher expense. |
| 01:59 | The first step up is silicon hose, which is the basic go to upgrade for coolant plumbing but also common in larger diameter variations for our intake plumbing or small diameter for vacuum lines. |
| 02:12 | Silicon can handle much higher temperatures than nitrile rubber as well as offering better resistance to abrasion and chemicals. |
| 02:20 | An important point to make here is that silicon hoses aren't suitable for fuel or oil plumbing as these fluids can permeate through the hose. |
| 02:28 | As we discussed earlier in the course, rubber hose for oil and fuel plumbing needs to be SAE J30 rated with the different R values for different fuel types and applications. |
| 02:40 | R10 for example is designed to be submersed in fluid. |
| 02:44 | If you're hazy on any of the details here, I'd recommend jumping back to the oil and fuel materials modules for a refresher. |
| 02:52 | Moving up, braided hose is more commonly used for motorsport applications. |
| 02:57 | This could be a flexible hose with an over braid that could be made from various materials but most commonly, nylon, aramid, kevlar or stainless steel. |
| 03:07 | The over braid is a fibre weave that retains the flexibility of the hose but provides a barrier to the elements while helping with abrasion and chemical resistance. |
| 03:17 | In saying that, the outer braid, especially when stainless steel is used, is extremely abrasive itself and will quickly wear through anything it comes in contact with. |
| 03:27 | So, routing and support is critical in avoiding this. |
| 03:30 | The neutral weave also functions a bit like a Chinese finger trap. |
| 03:35 | The hose elongates under pressure as the weave limits swelling, but this causes the hose diameter to shrink, gripping down on the fittings. |
| 03:44 | In reality, the over braid is the most simple part of a motorsport braided hose. |
| 03:49 | Flexible braided hose is available in a huge range of different combinations of layers of inner hose, integral braids, insulation and protective layers, as well as various outer braids and other protective layers. |
| 04:03 | The inner hose is usually the most important differentiation as that's what's in contact with our fluid. |
| 04:10 | This needs to have a smooth internal bore for plumbing where flow and pressure are also critical to performance. |
| 04:17 | In some cases, this will have a smooth outer layer over the braid as well, and these are most commonly referred to as push lock hose due to the types of fittings that they're used with but we'll come back to this. |
| 04:29 | CPE synthetic rubber is common in performance applications for plumbing just about everything as it handles high temperatures well. |
| 04:38 | However, the limitation is with certain fuel blends that are common in motorsport, like E85 for example. |
| 04:45 | PTFE inner hose is really the ultimate for most automotive plumbing as it has great chemical heat and permeation resistance. |
| 04:54 | Quality PTFE braided hose can outlast the lifespan of the vehicle if installed and routed correctly. |
| 05:01 | A differentiation to make here is whether the hose is conductive or not, which as you've probably already guessed, means it either conducts electrical charge or it doesn't. |
| 05:11 | As fluid flows through a pipe, it builds a static charge. |
| 05:15 | If we use a conductive hose, this charge is safely conducted out of the fluid and grounded through the fittings. |
| 05:22 | A conductive hose can be more chemically resistant and provide less friction, giving it an advantage for plumbing hydraulic systems like the brake and the clutch. |
| 05:31 | However, it's often argued that it can't be used for fuel plumbing as the build up of static charge could arc through the hose to the outer braid, potentially causing a leak. |
| 05:42 | Leaking fuel and the possibility of sparks are clearly not a good combination. |
| 05:47 | With this said, the likelihood of a real fire risk caused by this is very small, but never zero so it is generally considered best practice. |
| 05:57 | The downside as always is cost. |
| 06:00 | These motorsport braided lines and their corresponding fittings aren't cheap and the expense adds up quickly. |
| 06:06 | Conductive hoses are also typically more expensive, so it's important that we don't blindly take the cheap option and end up with something that'll be useless or unsafe. |
| 06:17 | What's best, and this goes for all plumbing components, is to understand the application and the requirements, including the budget and compare offerings from quality suppliers to find the best option for you. |
| 06:29 | It should also be mentioned that rubber hose is usually easier to bend and work with compared to PTFE which is more prone to kinking. |
| 06:39 | With that said, PTFE hose is usually lighter for the same internal diameter. |
| 06:44 | For rubber or PTFE braided hose, the sizing again for motorsport plumbing is often expressed as dash sizes. |
| 06:53 | Like with hard lines, this number refers to the number of sixteenth of an inch but for hoses, this is of the internal diameter rather than the external. |
| 07:03 | It's important here to understand that this isn't always the case. |
| 07:07 | Different suppliers can use different numbers and methods of expressing sizes and the different constructions of hoses can make dimensions significantly different. |
| 07:17 | The best thing to do is review the supplier's specifications when purchasing materials to ensure that you get what you need. |
| 07:25 | In summary, flexible hose is required to prevent damaging plumbing between components with relative motion and sometimes to allow fittings to be connected and disconnected. |
| 07:36 | There's a lot of variation with flexible hose offerings but rubber hose is the most common and basic. |
| 07:43 | While flexible hose is almost always reinforced with an integral braid, in motorsport applications, the addition of an outer braid helps protect our plumbing from the high demands and brutal environment. |
| 07:56 | Different fluids are compatible with different hose materials, so we need to be careful to choose the right combination, but PTFE lined hose is usually a safe choice. |
