Engine Pulley Cover

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Engine Pulley Cover

Author	Message
Shane1985	Shane1985 posted 8 Years Ago HOT Topic Details
Group: Forum Members Posts: 18, Visits: 175	Hi guys, Planning to make a pulley cover then it dawned on me that I have to take temperature in to consideration. I am planning to make the part using the Epoxy resin infusion process at about 3-4mm thickness finished with a couple of coats of clear coat. I know cambelt covers can get quite hot, so am I okay using this process to make the part? I don't have an oven yet and don't plan to until I am more experienced. Cheers guys Shane Shane -Carbon Amateur- Never give up! Tags Hot part
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Hanaldo	Hanaldo posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	They don't get that hot, it certainly should never see more than 100C. More likely to be around 80C. What resin are you planning to use? Most standard infusion epoxies will take 80-90 quite happily, and exposing them to higher doesn't necessarily mean they will fail. Not having an oven, you won't be able to do an elevated temp cure prior to putting it into service. This isn't a huge issue, but it does mean you will see some print-through of the fibres. Distortion is also possible, but being bolted in place should mean this isn't a problem either. If you go too much hotter than the resin can handle then discoloration and sometimes cracking can occur. The part will post-cure itself in service, so after a few cycles everything will be pretty settled. Side-note, 3-4mm is very very thick for what is essentially a cosmetic item. Any reason for that? Edited 8 Years Ago by Hanaldo
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Shane1985	Shane1985 posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 18, Visits: 175	Hi Hanaldo, I am looking to use standard expoxy for the infusion to start with and as experience grows I'll start looking in to the various other types. What do you mean by print through? Will this be the case even with a couple of coats of clear coat? I may have over estimated the thickness but I was to keep it at the same thickness of the original part, I recall it being pretty thick (I'm on holiday so done have the part with me). As always thanks for your help.. Shane -Carbon Amateur- Never give up!
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Hanaldo	Hanaldo posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	Print-through refers to the effect of the resin shrinking so the fibres 'print' through to the surface, distorting the surface so you get little bumps where the fibres are. The heavier the fabric, the more obvious the distortion is, so often lightweight fabrics are use on the surface as a print-blocker. It can still often occur where heavier backing layers print through to the surface. It is less obvious with coatings, but it is still visible. The only real way to reduce this is to post-cure before coating the part, so that shrinkage is very minimal. Ideally one should always post cure the parts in their mould prior to demoulding so that the mould surface is able to 'balance' the laminate and keep it flat while it cures. It's nothing to panic about, just be aware of it, especially if you are expecting your surface to remain perfectly flat.
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Warren (Staff)	Warren (Staff) posted 8 Years Ago HOT Post Details
Group: Administrators Posts: 2.5K, Visits: 7.9K	3 to 4 layers is probably about right which would be around 1mm thick. Certainly wouldn't expect a simple cambelt cover to need to be any thicker. Warren Penalver Easy Composites / Carbon Mods - Technical Support Assistant
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Walkerhmartin	Walkerhmartin posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 1, Visits: 29	May seem like a dumb question, but is there a limit to the thickness of a part? Or maybe a better question would be, at what point are you wasting money to produce a robust part with similar dimensions to the original? Especially in a part that requires being bolted down? The cover that is being made was probably originally stamped in steel, molded in plastic, or cast aluminum. And while the CF is capable of being much thinner, I can imagine other reasons to keep it the same thickness, for instance if a bracket were to be mounted off the same bolts, and alignment was critical..etc. Is there any merit or detractors to just making the part dimensionally exact to the original? Thank you. Walker Work joyfully and peacefully, knowing that right thoughts and right efforts will inevitably bring about right results
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Hanaldo	Hanaldo posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	The only real 'limit' is in terms of exotherm, which then depends on your resin. That's also very thick solid laminate. In this case there is no real limit, it's just unnecessary. Of course if you have a part that absolutely needs to be 4mm for fitment reasons then you need to make the part 4mm. But the advantage of composite parts is you can be selective. If you have a mating surface that needs to be 4mm, you can make that section 4mm but the rest of the part can still be 1mm. Really it just takes a lot of material to make a 3-4mm part. If it doesn't need to be that thickness for fitment reasons, and it is only a cosmetic part, then it's just a waste to make it so thick.
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