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Sat Apr 23, 2011 1:47 pm

The cardboard under dash which covers the steering column on my 411 is quite damaged and I've been unable to find a replacement or any photos of what a new one should look like (other than what's in the owner's manual). So I sent it off to my brother who is a sculptor to have him repair it. The lower half of the piece is completely shredded, so I'm not sure of what the shape should look like; straight across or a smooth half circle? Anyone out there who has one or has seen what one should look like?

Below are the photos of the piece in question, as well as the diagram/question I received from my brother.

Sat Apr 23, 2011 2:53 pm

Here is a picture of one from a '74 412 2dr. sedan/4spd. I'm not sure how different it would be since I think they redesigned the column at some point for safety, but I can't remember what year.

Sat Apr 23, 2011 3:25 pm

They are all the same. Basically they fit around and covered up the sheet metal of the pedal cluster.

I would build a shipping crate for that for you...and would love to make a mold of it. I could cast them from urethane or zinc alloy an urethane. Same goes for anyone who has the cardboard for the back window of the two and four door. I would cast them for free for anyone save for material costs. Ray

Sat Apr 23, 2011 3:34 pm

Hmmm... that sounds like a good idea. Are you up for it uber? I have a back filler panel that's in pretty good condition. Perhaps we can have Ray make a mold of both and help us all out?

Sat Apr 23, 2011 3:52 pm

Let me think about it-I''m not even sure how many I have, which ones are the nicest, which are in cars, which ones I could part with, etc...

Sat Apr 23, 2011 4:12 pm

Here's a better photo of mine and you can see how much of the column cover is missing.

Sun Apr 24, 2011 6:13 am

sbritt,,you can go to see my pict. in the gallery, for my under dash carboard,, i have modified the merc.190 under dash carboard for to fitt in my 412,, very small modifications,,and it is plastic mold for the collum direction,,bb412

Sun Apr 24, 2011 9:59 am

I would certainly go for a rear window cardboard. Mine has almost turned to dust. Repairing the original is a job I have been dreading.

Sun Apr 24, 2011 10:27 am

There are two ways I can do this. Either way you get your original back. The first method has less risk to the original part but is harder to do andleaves more finishing work on the cast part.

(1) Spray the original with a very low tack adhesive (it will go away)...then carefully laminate it with a very thin polyethylene film (just like saran wrap). Then make a two part plaster vacuum cast. The issue with this is that you can only wrap it so closely. There will be wrinkles that shop up in the cast that I might or might not be able to sand and fill before casting the finished part. That means that you ahve more sanding and filling before painting. Also getting any of the original texture would be nil.....but I have other answers for that.

(2) Spray the original with a double coat of satin urethane to seal it. I like this method the best because actually its what I did to make my cardboard last years longer. Then spray it with a microscopic urethane mold release and cast directly to it. But it is adding something to the origina and you may not want me to do that.

As for texture....I prefer using the 2nd method. Then making one cast out of it...then sand and shape....then spray with adhesive and dust the outside with a pebble texture material (used for model railroad ballast...its actually clay). Then paint with several layers of plasticoat to fill in and cement the texture/ballast. It will not be the exact texture of factory but will look very even and normal.
Then make a new mold with this part.

I think these parts should be cast out of zinc alloy so they will be pretty permanent and not warp with ehat or moisture. Then cover the inside with a 1/16th" sheet of neoprene foam so nothing electrical can make contact. Ray

Sun Apr 24, 2011 9:27 pm

Hey Ray, how long do you think this process would take? If anyone has a better cardboard under dash/column cover than mine, then I think that'd make for a better mold. I took a look at a '73 4-door 412 this weekend that was in great condition and the column cover and back filler panel were both immaculate. I'm gonna head back tomorrow to see how much the owner wants for it (the car, not the parts). If I get it, then I'll have two perfect specimens for you to make molds from.

Mon Apr 25, 2011 6:08 am

If I can get the part in, doing the mold will take two weekends in a row. The first weekend will be prepping the part and letting it dry and prpepping the mold base. The 2nd weekend will be pouring the plaster and/or acrylic (probably some of both).
Then I can acrefully clean the original and ship it back to you. It will probably be another 2-3 days before i would first cast a high durometer urethane part to check the accuracy. I would send that to you so you can install it on your vehcile.
You can keep the urethane part if no corrections need to be done. Itwould be a viable part...but would have an effective life of only a couple of years because as it ages with heat it will most probably start to deform.

If corrections need to be done we can swap photos on line and then send the urethane part back with gerase pencil markings and I can correct the mold.

It will probably be near the end of june or early july before I can have a casting weekend if everything works.

The metal I will be using is 94.5% Tin / 3% Zinc / 2.5% Antimony and has a melt point of 446 F.

While they parts might crack if dropped hard....these will certainly be much more durable than the original cardboard. I would use 1/16" neoprene sheet and weatherstrip adhesive to coat the inside to make sure the metal cover does not become a ground point for anything.

The rear cover behind the seats is not just a pretty fascia. Its an active part of your defroster system. It connects the two outside corner louver vents with an air guide (the cardboard fascia) to draw air across the rear window to pull moisture away...and pull heated air from up front. The airflow in these cars is carefully d esigned. When you crack the front windows...that ground "swoop" in the glass allows draft free air to be pulled along the ceiling to the back glass to enter the slots in the cardboard and be pulled out the louvers. It is instrumental in keeping the moisture level in the car down. Ray

Mon Apr 25, 2011 9:43 am

Wouldn't a simple fiber glass be easier to produce? Then you would only need a one sided mold where you can easily laminate as many layers of fiber glass as needed. I've been thinking about making replacement panels too but i was definetely going to use fiber glass. I was just not sure how to protect the fragile original knee pad.

Mon Apr 25, 2011 10:00 am

Lahti411 wrote: Wouldn't a simple fiber glass be easier to produce? Then you would only need a one sided mold where you can easily laminate as many layers of fiber glass as needed. I've been thinking about making replacement panels too but i was definetely going to use fiber glass. I was just not sure how to protect the fragile original knee pad.

Long ago I thought about doing fiberglass. Personally...I hate fiberglass. It would be fine in Europe, but thin fiberglass like that with underdash temperatures well over 150F like we find here in hot weather would very quickly warp and almost always smell in hot weather. Also...in order to get a smooth outside without seeing fiber....it would require more than a few coats of gelcoat with sanding.

Its really not that hard to make by the methods I listed above. I am staying away from virtually all plastic polymers that can be cast for the same issues I list with fiberglass.....very dimensionally unstable with heat.

All the structurally sound types of plastics will still have some sort of life span issue eventually...but could at least be vacuum formed. A vacuum form mold would actuallu be virtually identical to a casting mold except for the vacuum ports. Ray

Mon Apr 25, 2011 10:59 am

Good point Ray! Wasn't thinking about the extreme hot weather -we certainly don't have such issues here in Finland...
There was actually another reason why i was thinking about using fiber glass: I thought it might give some protection for drivers knees in case of frontal collision. I'm silghtly worried about those master cylinders pointing directly to drivers knees... I thought some 3mm of fiber glass could work as a protective padding and wouldn't crack into sharp pieces that would cause even more damage.
And ofcourse an it's important aspect, that making fiber glass parts is something anybody could do in their garage.

Mon Apr 25, 2011 12:38 pm

Ray, would it not be better to use a silicone rubber to make the mold from, backed with a plaster shell. The silicone will copy the texture exactly and you can then lay any material in the mold to make the copy. Also the silicone would not harm the original in any way, unless the card has any exposed fibers which might soak up a small bit of the rubber causing it to tear a little when removed.
You could make a male and female mold then layer wet card mixed with PVA glue into the female half squish the male part into the wet card then strap the two together using mold straps and leave to dry.

Mon Apr 25, 2011 2:42 pm

3nero wrote: Ray, would it not be better to use a silicone rubber to make the mold from, backed with a plaster shell. The silicone will copy the texture exactly and you can then lay any material in the mold to make the copy. Also the silicone would not harm the original in any way, unless the card has any exposed fibers which might soak up a small bit of the rubber causing it to tear a little when removed.
You could make a male and female mold then layer wet card mixed with PVA glue into the female half squish the male part into the wet card then strap the two together using mold straps and leave to dry.

Stop that!....you are giving away all of the secrets! :D

Yes, I might very well use an inner silicone layer. Its typically how I have made vacuum forming molds in the past. It will really depend on several factors.

(1) Most pourable silicones...which is what will be required for an object this large...are quite expensive if you want them to have the high temperature range needed for using casting alloys. Thats not saying the price is out of the question at all....but one of the better ones I use is this one http://www.freemansupply.com/datasheets/Rhodia/V-240.pdf ....but the issue is that my casting temperature will be about 50F over the contant maximum temp of this pourable material. I see that as a potential problem for multiple casts in the same mold.

(2) The molding silicone is very accurate....possibly more accurate...surface texture wise than we really want. If the original part is not exactly pristine...any warps,cracks, chips and blemishes will be imparted into the silicone. AS part of that I worry about what you noted that it might even be an issue getting it to release on pressed cardboard.

The use of a low temp, low strength metal allows me to use regular plaster instead of a gypsum based refractory plaster like you would use for higher temp metals.

In fact...originally....I was thinking of making these partsout of ceramic....but i did not want that around my knees. It woudl be excellent for the rear window fascia. I could actually pour the mold out of ceramic "slip" and have it fired for a small fee.....making a rather permanent mold with some very small distortions.

Ray

Mon Apr 25, 2011 4:18 pm

you could use a faster setting catalyst and paint the silicone on instead of pouring it on, uses much less rubber. also if you coat the original with a thin layer of Vaseline it would act as a release agent and also help to smooth over any small imperfections, bigger imperfections can be filled using childs remoldable clay (oil-free kind) I think you guys call it silly-putty. When the vaseline is removed it will leave the part looking brand new (also works great to polish the dash)

There is a silicone on the market that can be used for making lead soldiers but not sure what it's called and no idea of the temp differences between lead and what you want to use.

with the silicone you would probably get around 50 pulls before the mold starts to degrade.

We recently got a new casting material to try out in the workshop, i cant remember what it's called right now (will check tomorrow) but it's basically a water based resin with a cotton like reinforcing material not unlike fiber glass, but a lot less itchy. we've only done a few tests with the stuff but so far it seems very strong and light, sets quickly and much easier to clean up any spills. Also it smells a little like ice cream when mixed so no plastic-gluey fumes like normal resin. No idea how it would hold up under hot conditions though.

Mon Apr 25, 2011 4:27 pm

hey,,3nero,, first if you have the 411-or the 412,, the dash light is différent,,you can go to se my pict..in the 412 gallery ,,on the samba,,the pict,11,, for my 412-73,, what year your car,,

Mon Apr 25, 2011 4:34 pm

ops,,my error for the seat belt,,bb412

Mon Apr 25, 2011 8:19 pm

3nero wrote: you could use a faster setting catalyst and paint the silicone on instead of pouring it on, uses much less rubber. also if you coat the original with a thin layer of Vaseline it would act as a release agent and also help to smooth over any small imperfections, bigger imperfections can be filled using childs remoldable clay (oil-free kind) I think you guys call it silly-putty. When the vaseline is removed it will leave the part looking brand new (also works great to polish the dash)

There is a silicone on the market that can be used for making lead soldiers but not sure what it's called and no idea of the temp differences between lead and what you want to use.

with the silicone you would probably get around 50 pulls before the mold starts to degrade.

We recently got a new casting material to try out in the workshop, i cant remember what it's called right now (will check tomorrow) but it's basically a water based resin with a cotton like reinforcing material not unlike fiber glass, but a lot less itchy. we've only done a few tests with the stuff but so far it seems very strong and light, sets quickly and much easier to clean up any spills. Also it smells a little like ice cream when mixed so no plastic-gluey fumes like normal resin. No idea how it would hold up under hot conditions though.

The lead based metals are a bit lower in casting temp. Its why I'm not keen on using silicone with the tin based compounds. I can get higher temp silicones, but as you note they must be painted on because they are far higher in viscosity than 120,000-130,000 cp...and that leaves voids. In order to get rid of voids while the silicone is still uncured I have to use vacuum. That a big jig for vacuum on this part.
I agree on possibly using a faster catylyst but that also makes thesilicone weaker.

I would rather make a slightly less complicated mold....of more dimensionably reliable materials...and occasionally recast it. I will probably use a portion of refractory gypsum in the plastor and then vacuum it to get bubbles and voids out.

Once its dry....I heat the mold to about 200F while casting 450F metal into it then let it cool slowly.

There are some much better high temp mold releases out there (mostly used in injection molding). I have micro powder silicone and urethanes that are good to 600F and leave no residue. If I can get an original and make a single buck from it I would rather use plaster even if I have to remake the mold more often. Great thoughts though! Glad to see someone else playing in the "dark arts" :D Ray