[dataway]

Posting this here because it's very 68-69 specific ( I think )

I noticed someone was looking for a 69 defroster duct and Scott Thelander replied that he had one but had a broken tab on it. Made me think ... I've got a very nice 68 example here that I couldn't use because of all the broken tabs .. ended up using one that was chalked up but had all the tabs.

Made me wonder ... would it be worth it coming up with a 3d print that could be glued or riveted on to replace broken tabs.

Probably a limited need for these since it would only be needed by people doing full restorations that had the entire dash apart ... it's not an easy part to get to. So not like many people are going to say ... Hey, think I need to replace my defroster duct today ...

[Scott Thelander]

good idea

kind of a L shape with a tab drill n rivet or glue as mentioned,,,

great idea

used thru 72 on our a body

Scott

[Shiny]

Definitely a need..

But IMO the tabs break because the material used seems to degrade badly ... chalky, brittle, etc.

I think you now need to explore vacuum forming and repro all the ducts for AC cars!

[dataway]

Shiny, don't joke, your jokes become my obsession

I've still got a nice defroster duct with broken tabs sitting on a shelf in plain view to remind me to try to address this problem.

It would be a very easy print to make, only question would be durability, not sure what the originals were made of .. probably ABS which is known for poor UV resistance. Easy enough to print materials these days that are UV resistant.

I'll try to do some test prints in the next few days to see what materials I think would work.

[dataway]

Printing some out now, doing some destructive testing to see what will work before I nail down the actual measurements.

[dataway]

This is what I think they will basically look like ... just from memory ... didn't go down to the shop and get the duct.

Took a few experiments, but now it's plenty strong. A bit stiffer than I had hoped. Probably should be glued and riveted on ... but to rivet it would probably need the duct pulled apart to put a washer on the back side of the rivet. Often with the old plastic the rivet will just split the plastic as it expands unless there is a washer on the back.

I could print them in TPU (Rubbery), it's very tough stuff, but probably too flexible.

This is not to size, just wanted to test the concept. Holes are offset to help prevent a weak spot across the mount.

[Shiny]

Originally Posted by dataway

Shiny, don't joke, your jokes become my obsession

I've still got a nice defroster duct with broken tabs sitting on a shelf in plain view to remind me to try to address this problem.

It would be a very easy print to make, only question would be durability, not sure what the originals were made of .. probably ABS which is known for poor UV resistance. Easy enough to print materials these days that are UV resistant.

I'll try to do some test prints in the next few days to see what materials I think would work.

Joke withdrawn..

But when you start vacuum forming, I still get to applaud.

As to why they get brittle, I doubt it was UV... probably just thermally-driven decomposition.. I replaced my duct when I had the dash out many years ago and the old one was more like a cracker than a polymer. So maybe use a material that is rated for the highest use temperature you can process?

Mike

[dataway]

This is printed with stuff that's good to about 210 F for sure, probably 250 F before it starts having a problem. It prints at about 450 F.

When I was doing my dash I wondered why they made the tabs so flimsy .. then I realized there is probably no situation where these would ever be replaced except a restoration. If you wrecked the car bad enough to need to replace the defroster duct I imagine the car would be totally destroyed

[dataway]

Well this looks like a final product. The opening is elevate a bit from the OEM position ... but I gotta have some meat to have the loop strong enough.

I think I have it at the right angle. One of those deals where you have to commit and see it works to save an otherwise unusable part.

I'll probably end up installing some on my nice spare duct that has no clips at all ... although I no longer need one.

The tabs on the far ends of the duct will have to have the corners trimmed off or they will hang off the ends a bit ... although I'm not sure if some corners hanging off the end would matter.