How do I build defroster vents?

[belfert]

I am just starting a new project.  I have about half of my old fiberglass dash removed.  I gave up demolition for now as I need to get a new bit for my Dremel tool.  I am building a complete new dash.  (I did partially sever one bundle of wires with my sawxall so I have some repairs to do.)

Any ideas for how I build the vents for the defroster?  The vents were built into the old dash that I am removing.  Basically I have four 4" outlets coming off the defroster and need to get them blowing on the glass again.

(Did I mention I hate fiberglass dust?)

[roadrunnertex]

Why build when you can buy them.
Find some one who is parting out a PD4104,PD4106 and use the defroster outlets from these GMC coaches.
Make sure you get the complete 2 part assembly including the mesh screen to keep the kid's from dropping gum and candy wrappers down the nozzles/outlets.
They are nice castings and can be powder coated.
lv

[paulcjhastings]

(Did I mention I hate fiberglass dust?)

I'm making the assumption that you meant to say ducts too.

I still say fiberglass is the way to go. Make the shape out of foam, cover with laminations, dissolve foam.

How else can you make rounded shapes with compound curves in fewer steps.

[JohnEd]

I have those flat circular vents that can be twisted around and directed and opened and closed.  Really a great idea.... on the surface of it.   The things  get locked up in short order ad that is without spilling anything on them.,  Has worked out poorly for me.

I shopped the new Monacos ad "unused" Country Coaches this weekend. ( there is a show across the street at the Fairgrounds).  They have a "new" vent that has no moving parts save the center ball.  You can shut it "off or on" but not modulate it.  The beauty is that you can direct it anywhere.  Those dash boards had 7 or 8 of the things across the dash and they could be directed to all blow on the windshield, some on the side windows, some on the copilot and some on the driver.  I like flexability.

The OEM placed and sized the vents so that they worked.  Chance the size or angle or placement and you may or may not get the air where you want it.  I like the KISS aspect of using the OEM vents or transplanted GM vents of cast metal.

Surely not a suggestion but rather things to consider,

John

[belfert]

(Did I mention I hate fiberglass dust?)

I'm making the assumption that you meant to say ducts too.

I really did mean to say fiberglass dust.  I've been cutting up my old dash to remove it and I really hate the fiberglass dust because it is hard to get out of my skin.  I wear a respirator so I don't get the dust in my lungs.

[belfert]

John, the OEM defrost vents are gone.  They had to be destroyed to get the dash apart.  The entire dash including the vents was one huge molded chunk of fiberglass.  I have no idea how they molded something so fancy.

I want to do something similiar, but not really sure how to make the vents themselves.  I need to convert from a 4" hose to a narrow slit.  I wish I was closer to Elkhart as they might have something.

[JohnEd]

Brian,

Re read Roadrunner's  post.  The GM vents did what you want.  My comments still stand though.

You don't need to go from 4 inch to a single vent. You can go from a 4 inch hose to 4 smaller vents spread across the bottom of the windshield.  More is better and if adjustable they are certainly better.

Good luck my friend...let us know what else

John

[Jeremy]

Defrost vents need not be particularly clever - there's no need for them to be directable or turn-offable like the vents that face the driver. A simple slot (or slots) across the base of the windscreen is all you need, and in fact far better than using discrete vents that will each only defrost a small area of the windscreen.

Making slots in the dashboard would be easy, but the issue (and, I suspect, the question you are really asking) is how to feed air from a hose to the slots. I don't know how you are constructing your new dashboard, but how about somehow bonding a length of plastic pipe (eg regular 2-3" diameter stuff from a plumber's merchant) to the inside face of the dashboard in the appropriate location (ie. across the base of the windscreen) - then machine the slots though the surface of the dashboard and directly into the pipe. Then you just need to attach your 'hot air hose' to the pipe and the job is done.

Jeremy

[belfert]

My defroster has four 4" outlets.  Right now each 4" outlet has a 4" tube going to two defroster vents.

I have attached a picture showing just two of the four outlets (They are covered with blue tape.).  The other outlets you can't see because they still have the flexible tubing attached.  I have also attached a photo of the four vents on the driver's side.  They are also covered with blue tape to keep debris out.

Yes, building the vents themselves and feeding the air to them is what I am really asking about.

[bevans6]

I confess that I have this sinking feeling that I wouldn't have done what you did, that what you end up with isn't going to be as good as what you took out, and that you've created an amazing amount of work for yourself.  But, to your point - if I was to start out to make defroster vents I would probably hammer-form them from sheet and tubular aluminium and TIG weld them together.  But knowing how hard that is, I would have moved heaven and earth to keep the stock system intact.  Making fiberglass molds and then making the parts is going to be very hard.    In fact, we used to fabricate parts out of steel and aluminium first, then make molds for the production pieces - but you aren't doing production work, you're just doing the one bus...

Brian

[belfert]

To be clear, I am not planning to make anything from fiberglass.  The original dash is all fiberglass.

And yes, this is probably going to be another project where I regret having done it because it will probably be more work than I imagine.

One huge advantage of doing this is I can build the new dash to try and seal out air from the outside.  Right now basically the entire inside of the dash is exposed to outside air which means all kinds of dirt gets inside the dash.

[buswarrior]

Take heart, the defrosters on those were CRAP anyway.

Would only clear the fog up about a foot from the bottom.

Try that in a snowstorm.

Older trucks had nice defroster nozzles, as well as older buses.

happy coaching!
buswarrior

[paulcjhastings]

Making fiberglass molds and then making the parts is going to be very hard.    In fact, we used to fabricate parts out of steel and aluminium first, then make molds for the production pieces - but you aren't doing production work, you're just doing the one bus...

Brian

One does not have to make molds to make fiberglass parts, the foam is the form. After the resin has cured the foam is removed and you have a part that can be used as is for this type of application. The part doesn't have to perfectly smooth like a fender or dash piece, it just has to direct air where it needs to be.

[belfert]

Take heart, the defrosters on those were CRAP anyway.

They seem to work for me.  Of course, the snowstorm I drove through last year the defroster wasn't working at all and we had to point an electric heater at the window.  (Wires had come loose from the switch.)

The main issue with the Dina defroster is the heat not making it to the defroster.  My bus has had the upgrades done that are supposed to help with that.  Those darn Mexican engineers never had to deal with real cold in Mexico and didn't engineer the heating system properly.

[Dreamscape]

Why don't you just take the two hoses and run them to their individual defroster vent, more air would be moved I would think. Have the dash vents moveable/directional.

I had a fiberglass one our Eagle and it were pretty beat up with lots of holes. I ripped it out and wilth the front heater I have there are four outlets for four defrosters on the dash.