Motorsport Plumbing Systems: Making O-rings
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Making O-rings
05.01
| 00:00 | With the high regularity of maintenance involved in motorsport, it's easy to damage O-rings with small cuts to their surfaces that will result in leaks. |
| 00:09 | The high temperatures they're exposed to also cause them to break down and while certain materials are better than others, the service life will be reduced regardless. |
| 00:19 | Just like we can make gaskets from sheets, we can also make O-rings from cords and to be clear, the focus here is on irregular shaped O-rings for specific designs rather than the regular circular O-rings, which are usually available in standard sizes. |
| 00:35 | Although, if we're unable to source the exact circular O-ring size required, this method will absolutely work for creating exactly what we need. |
| 00:44 | Again, when possible, it's always best to source suitable O-rings from the supplier, but these aren't always available in our time frame and alternatively, we might just have a custom application that requires a different O-ring to be made to suit. |
| 01:00 | As we discussed in the earlier component section of the course, the important factors are O-ring groove geometry, as well as the diameter of the O-ring and the material. |
| 01:10 | Designing the O-ring groove and specifying the size of the O-ring is out of the scope of this course, but let's assume this has been done correctly and we just need to use an O-ring size that matches the original or whatever the part has been designed for. |
| 01:25 | With that determined, the next step is to choose the material and just like our gaskets, we might not want to choose the same material if the original part wasn't up to the task in the first place. |
| 01:36 | The majority of aftermarket performance parts come with nitrile rubber based O-rings or what's referred to as NBR or Buna-N, which is able to handle up to around 125 degrees Celsius or 250 Fahrenheit safely. |
| 01:50 | Alternatively, we sometimes see FKM used and this can handle closer to 200 degrees Celsius or 400 degrees Fahrenheit. |
| 02:00 | While these are generally up to the task for most street applications or lighter motorsport use, they tend to melt and degrade when used with more demanding applications like endurance racing. |
| 02:12 | This of course depends on where on the vehicle the O-ring is used, with those directly in contact with the engine or close to other heat sources suffering the most abuse. |
| 02:22 | From our experience, silicon O-rings tend to handle the abuse of turbocharged endurance racing applications a bit better and are relatively affordable. |
| 02:32 | So, now that we've sourced an appropriate length O-ring cord in the diameter and material we need, we're next ready to cut it to size. |
| 02:40 | This process involves laying the O-ring in the groove and working around until we overlap the cord with the leading edge to find the desired length. |
| 02:48 | Using small pieces of masking tape here can help hold the O-ring in the groove. |
| 02:53 | We don't want it to be tight around the inside of the groove or loose around the outside. |
| 02:58 | Ideally, it'll be the correct length and sit in the centre of the groove. |
| 03:02 | In saying that, a few fractions of a millimetre off will be fine and the O-ring will still seal, it's just something to keep in mind. |
| 03:10 | From here, we can cut the cord to length with a sharp blade, making sure the ends are square so when we're connecting them, there won't be a kink in the O-ring. |
| 03:19 | Alternatively, for O-rings and grooves around cylindrical parts, we can calculate the desired cut length. |
| 03:25 | To do this, we need to measure the inner diameter of the groove with vernier calipers and of course understand the O-ring diameter. |
| 03:33 | Adding this inner diameter measure and the O-ring diameter and multiplying by pi, being 3.14159 and so on, will give us the circumference of the centreline of the O-ring around the groove and therefore the O-ring length, which we can easily measure out and cut to length. |
| 03:51 | The next step is to glue the ends together, forming a loop. |
| 03:55 | What's important is that we make the ends concentric, flush and inline, so there is no kink and we get a nice smooth seamless transition. |
| 04:04 | Super glue is the go-to here and will set fast so we can hold it in place until it stays and then keep it still until cured as per the glue supplier's specifications. |
| 04:15 | Unfortunately, super glue won't work well for silicon O-rings. |
| 04:19 | For this, we need a silicon based adhesive like ThreeBond for example. |
| 04:23 | With that, we have our completed O-ring so let's summarise the key points. |
| 04:28 | The first step to making a successful O-ring is choosing the right material and that includes diameter. |
| 04:34 | Materials are available with a range of specifications, but the most important consideration for motorsport tends to be the upper temperature limit. |
| 04:43 | Silicon is a good option here if we're having issues with nitrile based or FKM O-rings. |
| 04:49 | With the cord on hand, it's simply a matter of finding our desired length, cutting the ends clean and flat, and joining them with super glue or a silicon based adhesive. |
