News:

Due to a technical issue, some recently uploaded pictures have been lost. We are investigating why this happened but the issue has been resolved so that future uploads should be safe.  You can also Modify your post (MORE...) and re-upload the pictures in your post.

Main Menu

1932 Cadillac V16 scale model

Started by Roger Zimmermann, July 12, 2019, 01:40:19 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

Roger Zimmermann

The next step was to put the name and dimension on the white wall pattern. The "Firestone" script is not an easy one; my attempt to sketch the characters on the tire went bad. Fortunately, I found in the net a script which was the size I wanted. The print I did with that was not very sharp; anyway, I could cut the letters with a cutter. I glued them on the brass with paint; once dry, I scratched the excess paint.
The method for the dimension was different: I used thick paint and applied it on the brass with a thin brush. Once the paint dry, I scratched the excess paint to have a decent script. It's not perfect, but will be good enough on the rubber.
Now, I can do the negative mold for the white wall elements.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

Roger Zimmermann

Getting older does not mean getting wiser...
The facts: I decided to make a mold for the white wall. From the Avanti/Mark II projects, I still had some RTV material; I prepare a batch to pour on the pattern. Usually, after two hours, the product begins to be very viscous; after 12 hours, the RTV is set.
This time, after 2 hours there was no change at the viscosity. Same after 6 hours and again no difference after 12 hours. To me, it was obvious that the product was indeed too old. I heated a bit the whole; not too much because of the paint for the letters. There was a slight change at the viscosity so I let it in a corner because as the material is still sticking at the pattern, it could take away the scripts.
I began the preparation to pour the first half-mold from the tire. This time, I used a fresh product, mixing 9 grams harder to 180 grams RTV silicone. After creating some vacuum with my hand pump, the material was poured into the form. This operation creating again trapped air, the vacuum pump came again in action. The most vacuum I can generate with this pump is 14 to 15" HG. Enough for the purpose, but very tiring for the hands.
After one hour, I took the recipient out from the desiccator. After two hours, the viscosity did not change. I went to bed; the next morning, still no change. I was a bit upset and wanted to call the supplier. Just before that call, I had again a look at the syringe. The are two marks, 1 and 2 and 10 smaller lines in between. Suddenly, I saw my error: each mark is not 10 grams, but ONE gram! Therefore, the mix had just 1/10th of the necessary harder quantity! No wonder it cannot be set...
I have a similar problem with the tire pattern: there will be no paint on the surface, but the product in the uncured state is sticky. How can I remove the remaining material on the surface and, more important in the tread? I will put it on side for some weeks; maybe the small quantity of harder will be sufficient to set the RTV.
AS I'm blocked with my own stupidity, I ordered some material to do the springs. Of course, it's not available right now. Therefore, I will begin the shock absorbers...   
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

The Tassie Devil(le)

What a nuisance, and I can understand your problems.   Maybe it is time for new glasses? :o

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Lexi

#483
Roger back in the Forensic Lab and also with my molding and casting company, mineral spirits were used to clean up un-cured silicone, unless damaging to the item you intend to remove the RTV from. ISO alcohol may also work on some surfaces without corrupting them as I recall and save some plastics. Have plenty of paper towels handy. You may need a brush to physically abrade the RTV out of the tread along with the mineral spirits. BTW you are not the first to miscalculate the amount of catalyst and end up with a sticky gooey mess. Been there done that, which is how I know mineral spirits work for clean up! We had one of those hand pumps and a bell jar with an appropriate viscous lid seal for vacuum pulling but eventually used higher vacuum systems when working with larger projects & thixotropic or clear products.

Images are of a Rotary Piston High Vacuum pump which despite being from the mid 1950s still pulls down to a meagre but impressive for its age, 10 microns on a so-called McLeod electronic gauge. The other shot shows a magnified image of a thixotropic RTV with and without degassing done by this vintage unit. Same thing Roger was accomplishing in his chamber.

Just curious, but Roger do you use pressure pot work for some casting jobs? Such work can incorporate items that many of us already have especially if spray paint work is done, (pressure spray tanks & air compressors). Applying what Roger has done should make it apparent just how useful these processes are for re-manufacturing missing bits of Cadillac jewelry, as an example. That said I am blown away by his work and look forward to seeing his future progress in this model making project and his detailed photos and descriptions.

Clay/Lexi

Roger Zimmermann

1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

Roger Zimmermann

Quote from: Lexi on March 18, 2022, 07:55:46 PM

Just curious, but Roger do you use pressure pot work for some casting jobs?
Clay, I'm not using pressure pot for my castings. I did a quick search for electric vacuum pumps; I may get something soon (maybe).
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

Roger Zimmermann

The tires are waiting for better days...and I began the shock absorbers. To give you an idea how they look like, I'm attaching two pictures from the real ones.
At first glance, the shape is easy; a good look at the shape is revealing some interesting details. It would be one thing to replicate the shape as well as I can, but I want also that they are absorbing the suspension's movements. I will be use the same sticky fluid/paste as I did on my telescopic shock absorbers. Here, I still don't know exactly how I will do that. Certainly not like the original design as compression and rebound had probably different rates. The medium I will use is usually slowly leaking at joints without gasket; I will have to find a method to keep the medium inside the bodies.
On one picture, you can see the end caps which will be soft soldered on the body. Can you imagine the shape of the wrench used to torque them on the body? I replicated the hexagon shape by punching the caps and soldering the inner side.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

The Tassie Devil(le)

Are the originals adjustable on the move?   And are you going to include the adjusting rods?

Thanks,

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Roger Zimmermann

Quote from: The Tassie Devil(le) on March 22, 2022, 08:31:47 PM
Are the originals adjustable on the move?   And are you going to include the adjusting rods?

Yes, Bruce: the shock absorbers were adjustable from the driver's seat. 3 or 4 settings I don't remember exactly. I will add the adjusting rods and levers, but without function.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

Alex D.

"the shock absorbers were adjustable from the driver's seat. 3 or 4 settings I don't remember exactly"

The shock absorbers have a variable adjustment from the driver's seat via a lever to the left of the steering column. That lever is linked to a gauge that reads, 1to 5, free to firm.   

1932 370B  V12

Roger Zimmermann

Alex, thanks for the better explanation!
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

Roger Zimmermann

There are some good and bad news. First the bad: despite 2 weeks without disturbing my bad mix, both preparations did not cure. Today, after one hour at 100°C, same result. I will have to bite the bullet and remove manually the sticky and almost liquid products.
The good news: while in France in our vacation house, I ordered an electric vacuum pump. The on-line shop is French, the pump came from Germany after 3 days and the pump is made in...China. Bad luck as I try not to support this country...The same search done in Switzerland gave no result...with the exception of that French store!
A quick test was done this afternoon: I can pull 25"Hg and the vacuum is slowly decreasing, like it was with the manual pump with which I could only get 15" Hg. It will be really a pleasant job to "cast" the various parts, but first I have to clean and maybe redo the marking on the white wall mold.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

Lexi

Roger sorry to learn that your RTV did not cure. Good that you tried heat as I recall that can assist in cure times. You could try leaving a heat lamp on it, but probably won't help in this case. Maybe a heat gun would work without destroying the master piece underneath? Cured RTV can be quite heat resistant. Not sure if in this case it will force a cure though. Perhaps worth a shot as you pick away at removing the RTV.

Fantastic news on your  new vacuum pump. Make sure your glass "Bell Jar" is designed to withstand the pressure exerted your pump will draw. Remember that glass becomes quite sensitive to stress failure while under vacuum. Small imperfections, earlier damage and age, increase the chance of an implosion. This risk increases with rising vacuum levels. I remember that when up around the 29 inch mark I was always cautioned not to even bump the jar. I don't remember the specs on the various glass vacuum jars but at 25 inches I believe you are still well under the safe limits so you should be OK.

Attached is an image of an inexpensive head set magnifier with LEDs. Like the ones Dental Hygienists use but a lot cheaper. They have changeable lenses. I have a set and it works great. You could wear this and illuminate you RTV in the tire mold as you use a heat gun while you pick away at cleaning it out. It may help. They are available on Amazon as well as other retailers. Clay/Lexi

Roger Zimmermann

Interesting tool...It could be a future addition!
The glass desiccator was manipulated with great care since 40 years...Mostly not in use as it comes in play only for the tires. It's a professional tool made in Germany. No idea what was the cost then; most probably not cheap. Anyway, I don't have to go to the maximum vacuum from the pump, I can stop the pump at any vacuum.
I began to remove the material from the white wall mold. The good news is that the scripts are still intact. I hope to get the uncured material without problem.
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

Lexi

#494
More good news that clean up is going well. Those glasses locally cost me about $25 USD or less as I recall. They would be fantastic for you to use on your projects Roger.

On your new pump, you noted that 25 inches on a mechanical gauge is the output. When using my vacuum system to degas RTVs there comes a point where suddenly the mixed product will froth to about 5 times its height. This is standard operating practice that I have noticed when working with RTVs. The thixotropic nature of the RTV (centipoise) would impact this also.

Not sure if you have already used your new pump to "pull down" any moulding or casting chemistry, but you may or may not notice this frothing. I can't remember at what vacuum reading that it takes place. I seem to recall that it was at 25 inches or a little more. So your pump may be operating at that threshold. If it is, and you walk away from your chamber during pull down, you may wind up with a mess on your hands. As the mixture froths, or as they say "boils off", (not by heat but by vacuum), the RTV may very well rise to a level above the mould or mixing container that it is contained within. It is quite dramatic.

Again, I cannot remember at what vacuum level this occurs with typical RTVs, but it is something to consider. Your RTV will be seen to bubble and churn quite violently during this process, with increased vacuum causing an increased reaction. If you have poured your RTV as a casting medium into a mould to obtain positive cast for your tires, for example, and if the RTV rises in height due to the boiling off effect, your cast will be potentially ruined. You will also have to clean up the mess as it will over flow where you have poured it.

The answer to avoid this it to continually vent your chamber just prior to the material beginning to froth. The weight of the atmosphere will keep  "pushing it down", so to speak. This would have to be done several times, after which there is enough chemistry (such as air), removed from the mix to no longer cause the expansion to occur. This is a pain to do. The other option is to mix the RTV in a large enough vessel to contain all of the material when it froths, then after pull down & removal pour it into your mould being careful not to entrap ambient air. The "hand splash up" technique is used and works quite well.

Again, not sure if your pump will pull enough vacuum to cause this frothing with the materials you are using, but be mindful of this phenomenon when you first use it. You may experience it. I would hate read that you had another mess to clean up!  :)  Clay/Lexi

Edit 1: Forgot to mention that following product expansion, the frothing will stop when enough of the chemistry boils off. The product will then return to its original level. It is at that point that you know that de-gassing is complete and to turn off your system and vent to atmosphere.

Edit 2: Found this photo I took years ago of a small amount of clear resin in a 1 ounce plastic medicine cup, before and during out gassing. Notice the extreme height the froth obtained in the bottom picture, even though the mixing container is wider at the top. The mix will revert to its original level once the more volatile chemistry has been removed. If left in too long other chemistry that the mixture is dependent on to cure may also be expelled and cause improper cure.

Roger Zimmermann

Thanks for your explanation. I'm aware of this situation; when doing the Mark II tires with my hand pump, I could increase the volume of the mixed RTV to a safe level, but I went not further than 15" Hg. With 25", I can imagine that the volume increase will be dramatic! This will be aggravated by the rapid vacuum increase, when I had maybe 5 minutes to manually get the 15" vacuum. This is an aspect I was not thinking about; therefore, thanks for the warning!
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

Lexi

Its good to know. Even at 15 you may see a lot of bubbling as the more volatile chemistry is expelled. I think it is only around 25 or a little higher that it can become quite violent with a lot of rising. In the edited post above I added two pictures of this. I can't recall what vacuum level it was at, probably 29.999 but think it starts before then. The amount of creep will depend on the volatility of the chemistry and its thixotropic nature and measurement in centipoise. Sounds like your system is in good hands. Keep us posted. Clay/Lexi

Roger Zimmermann

It's impressive! I'm adding one picture from my own Mark II experiment; the increase is less dramatic than on your picture!
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101

Lexi

Nice shot Roger. The higher the vacuum the more height and action is seen. My pump pulls down to near zero air so the boiling off is extreme. It looks like that victim in the horror movie the Blob, where you see all sorts of appendages and things trying to poke out of the solution, like a trapped animate object inside trying to get out. Water is the worst as I believe it is what the centipoise scale starts off at as a base, with a level of either 0 or 1. Did a mix of plaster once which is thicker but still it has lots of water. It splashed inside everywhere and made a thorough mess! Learned that lesson that day. Yes, I forgot to mention working time. A lot of the RTVs have a short set up time so as you indicated you will save a lot of time with your new pump. When we used a hand pump in the lab some RTVs would start setting up prior to the necessary pull down. So lots of air left inside and trapped once set. Great work as always and keep us posted. Clay/Lexi

Roger Zimmermann

Finally, I could clean the mess I inadvertently created. The use of soap and nitro thinner removed the uncured material.
This time I did the mix right and used the electric pump to removed the trapped air. It's impressive to see how the volume is increasing when enough vacuum is applied! I did also an interesting observation: when I had 25" vacuum, I stopped the pump. Of course, the vacuum diminished slowly; I restarted the pump to get at about 25", and so on. I was surprised to see the small bubbles on the upper surface, but almost none burst. Finally, I let the motor run and there was much more action! It seems that the removal of air is more efficient when the pump is running for a long time. in the situation, the vacuum is about 27.5" Hg.
Anyway, the black rubber part is perfect, but not usable. I need to modify the brass part to have a dam at the outside diameter. With the actual mold, I could only do a partial white wall as the exterior wall is lower than the inner hub. I had a long time to figure what was wrong and how I have to modify the brass part. This is the next task!
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham (sold)
1972 Coupe de Ville
2011 DTS
CLCMRC benefactor #101