Motorsport Composite Fundamentals: Measuring & Mixing Liquids

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Measuring & Mixing Liquids

07.20

00:00	In this section of the course we're going to be discussing all the tools and consumables required for the construction and finishing of composite parts, including mould and pattern making as well.
00:11	As we'll only be covering the practical skills for wet layout construction, we'll limit our discussions to the tools and consumables used for this process, and not be covering those specific to vacuum bagging, resin infusion and prepregs.
00:25	There is some crossover though.
00:27	We'll try to cover the tools and consumables roughly in the order that they're used.
00:31	But of course there could be some that are used for different jobs at different stages of our project.
00:36	For each tool we'll discuss when, where and how it can be used, as well as any special considerations, keeping in mind that the practical skills will all be covered in the coming sections of the course.
00:48	Also while we'll discuss alternatives, just keep in mind that there's an endless amount of options available and always more being added to the market.
00:57	So, what we're discussing are those key items that are commonly used.
01:01	The intention is that you'll be able to come back and reference the relevant module in the section when you're looking at purchasing that specific product.
01:09	In terms of our discussions around consumables, this won't include the resins, reinforcements, gel coats, adhesives or core materials that make up the finished part, as we've already discussed them.
01:21	More so we'll be looking at the supporting equipment, materials and ancillaries.
01:25	With that out of the way, let's get into the tools and consumables used in one of the first stages of our project, which involves measuring and mixing our liquids.
01:33	This is where we combine accurate amounts of resin and catalyst or hardener and mix them thoroughly, which is critical to successful construction.
01:42	To start, we'll pour resin into a mixing cup.
01:45	The basic option here is a paper cup.
01:48	These are available in small, medium and large sizes and what's important is that they're contaminant free, so they don't spoil our resin.
01:56	The main consideration here is that they're single use and disposable, but they're very cheap and can also be used as a catch pot for any excess resin that drips from the part.
02:05	A slightly more expensive but arguably more useful option is a calibrated mixing cup.
02:11	These feature markings on the side that allow us to measure the volume of the contents.
02:15	They're made from a sturdy polypropylene plastic, which is non-stick and resistant to the resins we'll use.
02:22	As such, they're reusable, after cleaning of course.
02:26	This can be done with a solvent like isopropyl alcohol, or more simply by letting the resin cure in the cup and then flexing the cup so it cracks and breaks free, without cracking the cup of course.
02:37	An alternative that's suitable for working with small volumes, like that of catalyst, hardener, pigments or additives, is a syringe.
02:45	These are also graduated with markings to measure the volumes, and are usually disposed of after use.
02:51	The final type of container we'll discuss in this module is a catalyst dispenser.
02:55	While these are typically used for MEKP catalysts, they can of course be used for other relatively small volumes of liquids.
03:02	These reusable dispensers can be filled easily by removing the lid and have a flute which is calibrated to a specific volume, usually 15 The flute can be filled by squeezing the bottle, and then the volume in the flute can be tipped into our mixing container.
03:17	Before moving on, it's worth noting that many of the containers that resins or hardeners are sold in, feature or can work with dispensing pump lids.
03:26	If we're using products from the same suppliers, we can be fairly confident that a full pump from one dispenser will equal that to a full pump from another, and therefore we can mix our components based on the pumps from each container.
03:40	That's if we don't have graduated measuring cups on hand of course.
03:43	The methods we've discussed so far allow us to do our measuring by volume.
03:48	The alternative is to do it by weight, and this is where scales come in.
03:52	Measuring by weight with scales is generally going to give more accurate results as it takes most of the human error out of it when reading measurements on the cups and relying on dispenser pumps.
04:02	A quality set of scales is a worthwhile investment for any workshop if we're serious about getting quality results for high performance parts, and nowadays the scales will almost always be digital.
04:14	There is some variation in what's available that we need to consider though.
04:17	Often we'll see scales with fine resolution, so for example being able to measure in 0.1 gram increments but a relatively low maximum capacity of around 2 kgs.
04:29	The alternative is generally less resolution at 1 gram or so but much more capacity, usually around 10 kgs, and this can make it difficult if we're working with very small amounts.
04:40	Although in practice for car parts this isn't usually an issue.
04:44	We'd recommend scales with at least 2 kg capacity and capable of measuring in 1 gram increments.
04:51	Anything past this isn't typically necessary unless we're working with huge parts or extremely small parts.
04:57	It's possible to buy both highly precise scales with fine resolution that also have a high capacity, but as you'd expect these come at some extra expense.
05:06	And saying that, kitchen scales are perfectly adequate here, as long as they're good enough quality and able to provide accurate measurements.
05:14	They're not really any cheaper than the more industrial items sold in tool shops, but the chances are you already have a set at home.
05:21	When we're confident we have the perfect amount of resin and hardener or catalyst, the next step is to mix them together.
05:28	For this we use mixing sticks, either disposable wood like popsicle sticks or reusable plastic.
05:35	The plastic items are usually much sturdier and easier to hold making it easier to mix larger volumes in bigger containers.
05:42	It's imperative that our resin is thoroughly mixed with the hardener, catalyst or whatever other pigments or additives we might be using.
05:50	Failure to do so will almost certainly cause voids, inconsistencies and weak spots in the final part and likely areas of resin that don't cure.
05:59	A good rule of thumb here is to mix vigorously for about two to three minutes, being sure to continuously scrape the sides of the inside of the container until the mixture appears consistent and uniform color and viscosity, and then mix for another 30 seconds for good measure.
06:14	Mixing will introduce air bubbles into the liquid so we'll often let the mixture degas for a few minutes to remove these as we want to minimize any air in the laminate, although throughout any of this work we always need to keep in mind the resin's working time.
06:29	Let's leave it at that for now as we'll be covering the practical skills separately soon.
06:33	To summarize, one of the first steps in our project will be measuring out the required volumes of resin and additives and mixing them together.
06:41	Contaminant free paper cups are the most inexpensive option and are also great to use as catch pots but aren't reusable and don't provide any form of measurement.
06:51	Calibrated mixing cups are a more sturdy plastic option that's reusable and allow us to measure our liquids by volume.
06:58	The alternative weight measurement from digital scales generally provides a step up in accuracy by minimizing human error.
07:05	The correct amount of each component needs to be completely mixed by using a disposable wooden stick or a reusable plastic mixing stick, which will most likely make the task a little bit easier.