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Custom RHD 90-91 sedan gauge housing

Hey sedan'ers.

I thought i'd post up some progress on a project that i've been working on for a while.

Some of you might have seen my build thread where i replaced my drivers side AC vent with my boost gauge. I thought i'd do a bit of a write up on the project.

I started off with the factory vent, referencing it for dimensions and shape.

You can see its factory clip features too, i mimicked those on the CAD model too  because i wanted it to 'click' into place like the original.

This is what the CAD model was looking like

You can see ive angled the gauge up and toward the driver to make it easier to read.

I did some quick 2D checks to make sure the angles/shape was good and the clip features were going to locate in the right place:

And then i decided to prototype it in 3D. Came out pretty good. The surface finish was a bit rough, but i could've sanded it back. I soacked it in resin too to give it a bit more strength while i was playing with it.

Test fit my gauge that i'd bought:

Looks pretty good so far. Then to test fit it into the dash. The clip features needed a bit of massaging, and the bottom of the gauge housing needed a little trim to fit in the way that i wanted it to, but overall it went straight in, and fits snug.


I ran this for a little while, but the colour on the 3D print started to fade with exposure from the sun. Also the texture was bothering me a bit, it didn't really match the dash at all.

So i thought about trying to cast it in black resin, using the print as a buck. I had to make a new print (the buck has to be oversized slightly because of resin shrinkage), and this one i sanded back so that the surface finish was nicer and closer to what you would see out of an injection molded part. Kinda difficult to see in the pics, but you tell the surface finish is smoother than the black print before it:

Then i went and visited a local casting and arts supplies shop where they recommended a couple of different products to try. The silicone mold is a super flexible material that allows you to have undercuts in your part (which i do, the clip features) and you can flex the mold away from the part to still be able to get the part out.

Also i went with a black 2 part casting resin which is easy to mix (1:1) ratio and is machinable and super solid. The brand of the resin is Alumilite, check them out if you get a chance... Some really good 'how-to' videos.

I started making my bounding box that keeps the silicone in place while it sets, also the plastesine (sp?) helps to seal around the part and define each side of the mold. Also added a locating feature so the two halves would lock into each other when rested together. So then it was time to mix up the silicone and do my first pour!

Well, nearly... Firstly i made up a makeshift vacuum chamber out of a cheap deep saucepan, some acrylic and some closed-cell foam:

As you can see, once the cavity is put under negative pressure, the foam seals the acrylic against the pan and the bubbles are pulled out of the silicone and to the surface where they burst. It's important to remove the bubbles out, or your mold might be ruined by a bubble against the part.

Poured in!

Even with the vacuum chamber there was still some bubbles in there that took some pouring technique and an air gun to remove.

I accidently positioned the part a little low in the box, so i had to reposition it once the first half set:

Lowered down:

So because this was going to be the back face, i didn't pay much attention to the surface finish. Also i decided this back of where the gauge sits will be my fill point. You can see i'm constructing a fill point out of the plasticine:

The other little doo-dads are to prevent air pockets from forming in the high points of the part and lets them vent.

So to prevent air bubbles trapping near the part, i gave it a real thin layer of silicone first, and blew it all over to cover the whole part. Atleast this way there'll definitely be silicone touching up against the part, and no air pockets.


I filled up the rest of the mold, enough to cover the part and give it a little more so the mold would be sturdy enough.

More bubbles... Hard to get rid of really. Here's some air-gun work to pop them and bring more to the surface:

But looked pretty good when it was done for a bit:

Then I left it to set overnight and came back to see how it turned out...

I pulled the bounding box off:

And prised the two halves apart. I'd used vasoline on the mating surfaces so the two silicone halves didn't bond together:

Keeewl! Came out ok. I pulled out the fill point and risers:

This is where i'll be pouring the resin into.

I gave it a few goes to start with, and holy learning curve.. lol... Pretty much did everything wrong the first few times, made a huge mess. The two part resin is easy enough to measure, but it sets within 30-40 seconds so you have to work real fast. Also there's a lot of things to consider for example, how tight to clamp the mold and even with my risers i was still getting a lot of bubbles on the visible surface.

Here's a couple of the firsts:

You can see the one on the left, the mold was clamped too tight and the two halves were touching each other. So i modified my technique a bit, made some boards to clamp the mold with, and angled the mold to prevent air building up as it had been in one of the corners:

And overall they're coming out pretty good! The back surface has the odd small bubble, but it's not noticeable once the part is installed. Also the surface finish is fairly consistent and looks good when installed.

This is how they're turning out with a bit more technique:

Gave it a test fit:

They're designed to be installed with the top clips engaged first:

Then pushed down and into position until the bottom clips snap into place:

And this is how it looks:

Pretty happy with how it's turned out:

Here's some proper product shots:

I've made a few for now, but can still make more later. So far i've got 4 that i'm going to sell.

At the moment they suit 90-91 RHD sedans only. I might start prototyping prefacelift sedan or hatch next in LHD... I'll keep everyone updated Smile

Another one installed, thanks for sending the pics through Hayden:

EF Sedan Enthusiast

So awesome!!!

So cool.  Deff need 1 for my crx dash lol

Nice.. I'll go RHD for this.. hahaha! Laughing Forum Index -> Interior/Exterior/Electrical
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