355 Clear turn signal refurbishment project

Hi all!

I’m excited to share with you a hobby project which has gotten a bit out of hand..

In the past few years, F355 turn signal units have started to become very rare, and especially the European-style clear units are hard to find and are now selling for 4 figures per set. The clear units are certainly favorable to the orange ones, and switching them out is one of the nicest and simplest upgrades for the F355.

I started to research the possibility of replicating or refurbishing these parts. I bought some spares and cut them open... These are not designed to come apart easily!! They are actually made of three parts which are fused together - the housing, the outer lens - and a clear inner lens.

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The initial plan was to 3D print the outer lenses, but quickly it became obvious that the qualities we want in the lens - clarity, UV resistance and shatter resistance - were not well suited to 3D printing. Actually, I found that these parts take very well to being resin cast. By casting these, we can achieve crystal clear parts which closely emulate the properties of the injection molded originals.

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So I started researching resin casting, and buying equipment to start creating prototypes. This was a completely new process to me, and I enjoyed learning about different silicons, resins, clays for creating molds, heating techniques, vacuum degassing, curing etc. The projects was especially though since we’re dealing with clear parts - any imperfections cannot be fixed with bondo!

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So anyway, after many, many months of research and trial & error, I was finally able to achieve the results I was looking for!

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I’ve created 3 additional sets to partly offset the investment I have into the project. They will be listed in the for sale section.

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Please share feedback on the project! It has been a great hobby so far, and a good excuse to buy more cool gear for the garage. If there is significant interest, I’ll consider pursuing this more earnestly and manufacture additional units, or cast other NLA parts the community might be looking for. Currently there are more man hours involved in each part than I care to admit, and to scale up production, I need to invest in a compression chamber, compressor and a few other materials & tools.

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Thanks for the kind comments!

 

I’d love to help out the 348 guys as well. The fog light lens is made of glass on the 348? At least it looks like just the outer lens is designed to be replaced more easily? This might be a lot simpler than the F355 project. If I cast those as a lightweight, more economical alternative, you think there’d be some demand out there?

 

I use a 2-part polyurethane system from a local company called BJB (WC-783). The resin takes a good while to fully cure, but the quality of the final product is great. The material is crystal clear and is resistant to impact, oxidation and UV light.

 

That sounds like a strict inspection process! The lenses have international E markings and indicate SAE standards and DOT compliance. Could you confirm if this matches what you require in Australia?

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The OEM material is PMMA (acrylic). According to Wikipedia, the accepted index of refraction for acrylic is 1.490-1.492. The main component of the resin I use is Dicyclohexylmethane, which has an index of refraction of 1.474, so the delta is just 0.016. The inner lens is re-used. So I'd say the visual impression between the two is virtually identical.

 

Thanks for all the input guys. I'll have a set up on eBay as well. Let me know next time anyone gets a bad rock chip or wants to convert to the clear lenses.