Re: Vacation Car - 56 Patrician
Posted by HH56 On 2020/5/6 14:01:52
Quote:
Believe me, I have been trying to reproduce them on and off for 30 years. The originals appear to have been pressure cast in multi part metal molds which is not a real option unless you have very deep pockets for a tool and die maker to make the molds. For a repro today it might be interesting to see what a scanner and 3D printer could do but I think it will mostly be limited to silicone molds of an original which have several drawbacks. If you have patience and the ability to think in 3D when making the mold then I would hope you are able to perfect both the mold and the vents. The vent availability is almost nil now so if those in the cars survive unbroken another generation it will be a miracle.
As you will note, the vents are somewhat complex with many thin sections and areas that when a mold is made are very prone to trapping the mold material making it very difficult if not impossible to remove the casting without destroying the mold. The mold needs to be in multiple sections and getting multiple mold sections of the original in silicone that cope with those removal restrictions and can also be held seamlessly matched together for the casting is one thing. A fairly slow gravity pouring or even using light pressure to force material into filling thin channels without deforming the silicone or trapping air is another. That air entrapment alone makes pouring a casting somewhat tedious and time consuming so needs a material with a thin viscosity.
The next problem is the pourable general purpose urethane casting material I have found has a variety of working time or pot life. Downside to those with a decent work time and low viscosity is they almost all have a low stable temp of 100-165 degrees. I am concerned a car sitting in hot sun would have a dash top that gets hot enough the plastic would weaken or completely deform. One urethane material I found with a decent stable temp of over 250 degrees has a very short working time of less than 3 minutes. That is not enough working time to mix, vacuum and gravity pour thru thin mold channels before it hardens.
A high temp epoxy I found has good working time but is also somewhat brittle in thin section. Not quite as strong as the original bakelite but maybe an alternative. It can be thinned to a usable viscosity (with drawbacks) and injected under light hand pressure. If I were ever to get interested in pursuing the vent project again that will be the material I try to perfect or maybe something you could look at.
What I made for my car is out of the low temp stuff and is very presentable but I will not offer them to others because of the deform possibility. I just try to avoid hot temps in my car and so far that hasn't been a problem since the car hardly ever leaves the garage.
Here are the pair I made and used plus photos of just a very few of many rejects and the last set of molds I made.
Attach file:
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PackardDon wrote:
Interesting to learn that the vents are plastic! I thought they were zinc castings as that's what mine feel like. Fortunately my dash is hanging upside down on the wall so they're safe. They should be easy reproduce, though, so I wonder if anyone has tried. If not, I might give it a go.
Believe me, I have been trying to reproduce them on and off for 30 years. The originals appear to have been pressure cast in multi part metal molds which is not a real option unless you have very deep pockets for a tool and die maker to make the molds. For a repro today it might be interesting to see what a scanner and 3D printer could do but I think it will mostly be limited to silicone molds of an original which have several drawbacks. If you have patience and the ability to think in 3D when making the mold then I would hope you are able to perfect both the mold and the vents. The vent availability is almost nil now so if those in the cars survive unbroken another generation it will be a miracle.
As you will note, the vents are somewhat complex with many thin sections and areas that when a mold is made are very prone to trapping the mold material making it very difficult if not impossible to remove the casting without destroying the mold. The mold needs to be in multiple sections and getting multiple mold sections of the original in silicone that cope with those removal restrictions and can also be held seamlessly matched together for the casting is one thing. A fairly slow gravity pouring or even using light pressure to force material into filling thin channels without deforming the silicone or trapping air is another. That air entrapment alone makes pouring a casting somewhat tedious and time consuming so needs a material with a thin viscosity.
The next problem is the pourable general purpose urethane casting material I have found has a variety of working time or pot life. Downside to those with a decent work time and low viscosity is they almost all have a low stable temp of 100-165 degrees. I am concerned a car sitting in hot sun would have a dash top that gets hot enough the plastic would weaken or completely deform. One urethane material I found with a decent stable temp of over 250 degrees has a very short working time of less than 3 minutes. That is not enough working time to mix, vacuum and gravity pour thru thin mold channels before it hardens.
A high temp epoxy I found has good working time but is also somewhat brittle in thin section. Not quite as strong as the original bakelite but maybe an alternative. It can be thinned to a usable viscosity (with drawbacks) and injected under light hand pressure. If I were ever to get interested in pursuing the vent project again that will be the material I try to perfect or maybe something you could look at.
What I made for my car is out of the low temp stuff and is very presentable but I will not offer them to others because of the deform possibility. I just try to avoid hot temps in my car and so far that hasn't been a problem since the car hardly ever leaves the garage.
Here are the pair I made and used plus photos of just a very few of many rejects and the last set of molds I made.
Attach file:
(89.09 KB)
(117.50 KB)
(98.28 KB)
(65.95 KB)
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