3rd Brake Light Visor prototype by Uncle Mush

Thanks again, Haloruler64.  That is great info to have and I really appreciate the pictures.  I am hoping to get back into my shop this weekend and start tweaking the design with the information I have received thus far from you, Dev and cyclehead.  I'll keep y'all posted. 

If I'm able to carve out enough time, I am hoping to be able to post the results here and send out the next set of prototypes next week.  We'll see how it goes.  If I do attempt to mold the edges like cyclehead has suggested, that will probably extend the timeline a bunch, but I also recognize that would make for a much better finished product.  I've been mulling some ideas around in my head as to how I might be able to do that.  I just don't know if I have the skills or the time to create the mold and apparatus to accomplish that.  It will be a fun challenge, though.  To be continued . . . 

What can I do next? Do you want me to see what temperature we see warpage at? Heat gun + IR thermometer can pull it off.

Posted by: @haloruler64

Drove over 100 miles yesterday, everything from triple digit sprints to slow city driving. Those three tiny pieces of tape held just fine, so it didn't fall off at highway speeds haha. Get home and my engine lid is very hot. The cover itself is cool to the touch. No melting, no warping, no issues. 

I plan to paint mine black and install.   The torture test here will be summer heat and baking in the parking lot.  Unfortunately a cold front is coming through this weekend so 97f weather may be gone.

Hmm, maybe I should hit mine with a few coats of black too. But I don't get super hot weather here anyway. I can only torture test it with hard driving and a heat gun. I do have an autocross event in Sonoma on November 23rd though, but that's a while out.

My problem here is also that the cooler seasonal weather has arrived and we are no longer at triple digit ambient temperatures.  Please feel free to torture test however you see fit but please don't torture your own vehicle in the process just for the sake of this project.   It may be that we have to slow our roll and wait until the beginning of summer before final testing to make certain that the product is good to go to market.  The down side is the potential, due to time-span, that we loose some of our excitement and enthusiasm about creating this new product.  The upside is the increased time provides more opportunity to fine-tune the product and make certain it is ready to release to the marketplace.

However you test the pieces I sent to you, if they get goobered-up, please let me/us know.  I have more HDPE to play with and can send new test pieces to you.  As I mentioned earlier in the thread, I hope to get back out to the shop this weekend to make the next version(s) to send to you.

Thanks again to Haloruler64, Dev and cyclehead for your work on this project.

I’m going to run some of the same tests I have used for the keyhole covers durability and test against it as a control. I generally do it off the car.  I test for weathering heat and impact damage. I push it to its breaking point to get a result.  What I planed to do is cut up the visor into more than 5 pieces and have a few painted  and some unpainted to test. 

Great idea cutting it up Dev. I should do the same if I can think up more tests than just a heat test.

Posted by: @haloruler64

Great idea cutting it up Dev. I should do the same if I can think up more tests than just a heat test.

 What im most concerned about is off gassing of the material and if the material swells from absorbing water and then expanding, contracting and  off gassing once it gets heated up since the underside will not be painted.   You never know what will happen until it happens.  I use to sell the lip spoiler which I was able to get unpainted pieces from a supplier. It was a disaster because the material did off gas and bubbled the paint underneath.  I had to hand out many refunds as a result although some made it. 

I also have a narrow band UVB light device that can speed up sun damage but its not necessary since its going to be painted.   Im just mostly worried about off gassing.  The best way to know is to take it to failure and compare it to the keyhole covers.   

@dev

This HDPE is supposed to be stable up to 178F and should not absorb moisture.  "Supposed" and "should" are important words to take into consideration.   When I vaccuform HDPE I put framed sheets (1/16" thick) into a 350F oven for about 8 minutes befor they are ready to form.   At first there is significant warpage but after about 7 to 8 minutes, the material flattens out quite nicely and forms easily.  Beyond 8 minutes at that temperature, the product starts to sag and can melt,  which is no bueno for the projects I have worked on.  I cannot speak to off-gassing.  I've not done the homework on that. 

Once again,  thank you all for your insights,  tests,  time and support.  

Posted by: @uncle-mush

@dev

This HDPE is supposed to be stable up to 178F and should not absorb moisture.  "Supposed" and "should" are important words to take into consideration.   When I vaccuform HDPE I put framed sheets (1/16" thick) into a 350F oven for about 8 minutes befor they are ready to form.   At first there is significant warpage but after about 7 to 8 minutes, the material flattens out quite nicely and forms easily.  Beyond 8 minutes at that temperature, the product starts to sag and can melt,  which is no bueno for the projects I have worked on.  I cannot speak to off-gassing.  I've not done the homework on that. 

Once again,  thank you all for your insights,  tests,  time and support.  

I did some research into HDPE since I know very little about it.  It would appear that it is very heat and environmental stable. It is often referred to as container plastic because of its durability with various chemicals and its ability to not leach.  This is very good news and I think there should be no problem with any heat issues. 

However I did find two downsides.  

1. The surface can be difficult for primer to stick initially and down the road. There are various methods  to over come this but its important to note. 

2.  Shaping by way of removing material is not the easiest.  I don't think this is a problem since the pieces came out great with no rough or jagged edging. 

This will be superior to fiberglass as long as the primer used has good adhesion either by flaming it, sanding it a little course or using adhesion promotor. It appears that treating it with Krylon fusion paint might be a good sealer before using a flexible primer.   I have done  this with great results with difficult to paint PVC plastics. 

I no longer doubt the material as far as durability because I now believe its overkill but the primer is my main concern and issues don't usually pop up  Immediately so it would be hard to test.  

I know im being critical but I have been down this road many times and I just want to make sure there are no issues as paint can be unforgiving.  Its just a mater of strategy to ensure the products success.  

Can't believe I missed this thread.  Great work UM.  I have one of Dev's unfinished TBLV that I finished and installed on my green spyder a long time ago.  Still on there and one of my favorite appearance mods.

As for getting paint to stick to HDPE, I have no personal experience, but have painted a few raw plastic vehicle bumpers as Toyota OEM bumpers come raw.  I always "sanded" with a white scotchbrite pad, used a plastic adhesion promoter, then painted like normal.  For HDPE it seems like it's a 'slicker' plastic than the Toyota bumper material.  I would try light sanding or scuffing with a grey scotchbrite, then using Dev's approach of Krylon Fusion, lay down a sealer, then base and clear.  I would test a little though to make sure the rest of the paint doesn't react and lift or fisheye over the Krylon.

As always, thank you for the input.  I purchased some Toyota OEM mud flaps for my 2018 Corolla and I am pretty sure they are HDPE, but not positive.  I can tell you from personal experience that without adhesion promotor ain't nothing gonna stick to HDPE.  When I did the mud flaps, I was all set to scuff, adhesion promotor, prime, sand and top coat but was so excited to get started that I totally forgot the adhesion promotor until after I laid down the primer.  I thought, what the heck . . . lets see what happens.  I sanded and sprayed the top coat.  I let them cure for 2 weeks.  They looked great, but one simple little flex of the product to install on the car and the paint simply "popped" off the product.  It was a crack-up (and a good educational experience) to see how easily it ALL came off.  The areas where I had sanded deeply (I tried a couple different approaches) had a little better adhesion, but still didn't hold the primer or top coat.  

The top surface of the mud flaps had a texture and they were not designed to be painted, but I wanted them to match the 040 Super White (the fastest color Toyota has ever used, even to this date) of the car.  So I sanded and sanded and sanded.  No matter how much I sanded, I couldn't get rid of the texture without leaving deep sanding marks.  I went t my friendly automotive paint store where over the years they have taught me a lot about automotive paint (although I have lots more to learn!) and they turned me onto a special, two-part filling primer that is basically spray-on Bondo.  It is a fairly expensive product -- $45 a quart, if I remember correctly -- but worth every penny!  Oh my gosh!  It left a beautiful smooth surface and even covered the texture I wasn't able to sand out and all of the dep sanding scratches!  That stuff is freeking amazing.  I had to put adhesion promoter down first, then the primer followed by a very light (600 grit) wet sand and then the top coat.  They came out beautiful.  They have only been on the car for about 5 or 6 months now, but they look as awesome as the day I pained them and they have weathered the hottest days of summer and several long road trips.  I am confident that they will hold-up for years and years.

Although I don't know for sure if the mud flaps are HDPE, the material has all the characteristics I am familiar with, with HDPE.

My plan is to use the same process for the final design of my version of the TBLV so the product will last for years.  I am pretty sure that Toyota OEM bumpers are a different material from HDPE, but again, I thought the process I have described above will work just fine.

By the way . . . the test pieces I sent out did not have the two stage spray-on bondo primer I described above.  They were sanded, sprayed with adhesion promotor and then primed with a high quality automotive primer.  So, in that sense, they will be different from the finished product.

I am still working on ways to add a molding step to the entire process so I can, hopefully, provide a nice and consistent finished edge to the product without having to form the edges myself on each piece by sanding or forcing the end user to have to do that step.  I've got some ideas, but will have to do trial and error until I can come-up with something.  Keep your fingers crossed and say a prayer.  I'll keep you posted here in this thread.

I sprayed my cover with black paint last night.  Today is forecast for 98f so we’ll see how it likes baking in the southern sun.  I wet sanded with some 600 grit, plus tried to smooth the corner radii a little bit.  Then took my best shot at rattle can spray job.  My paint work is never pretty.

I want to touch upon a few things that noocoolname has pointed out as well as UM.  

 My advise is not written in stone as there will always be better methods but I have found what works for me and the mistakes I have made with painting plastic or painting over finished surfaces like carbon fiber.  

1.  Krylon fusion paint is some amazing stuff. It literally inks the plastic and is chip resistant. It also changes the property of the slick shedding film that makes these plastics lose their grip from the primer.  

2. The plastics on our car are made of polyurethane and it is chosen because its ability to flex yet still be stiff before it yields  and be repaired.  It requirers a flexible primer surfactor.  This primer has a flexing agent which is necessary so it resists chipping as the plastics expand and contract. This primer is also a building primer where it will fill standing marks and pits. The reason why it has this building feature is primarily because you need to sand the surface of any plastic to 320 grit  so the primer has traction but in the process it needs to be smoothened out afterwards and that is when you sand the primer with 800 to 1000 grit. It is possible that you could skip the Krylon phase but I will need to test for it.  

https://www.semproducts.com/product/flexible-primer-surfacer/surfacer

3.  The most important part of any paint job goes against what most people are told and that is you need to be very sparing on the amount of primer and paint that is used. The more layers you add to any finish the easier it is for the paint to crack.  You need to lay down the primer just thick enough so it builds on the surface so you can sand it down and even it out.  More primer is bad. 

Thanks for painting tips!   It’s only 88f at lunchtime, supposed to hit 96f this afternoon.   3m tape works fine of course.   Surface temp is only 112f.    At what temp does the cover get soft?