1:12 1932 Cadillac V-16 frame and engine

[Roger Zimmermann]

I could do and install the various rods to the rear brakes. During the rear springs flexion, I expected a movement at the levers located to the rear axle, but there is none. Of course, my linkage may have some unwanted play, leading to the illusion. Anyway, the rear brakes are functioning when I'm pushing the brake pedal and I see that the hand brake lever will do the same when installed. As I have to put the frame on its back, I removed the hand brake lever because it's taller than the engine.
There is an inconvenient: the rods are not coming back to the release position because I skipped a spring located on the brake shield. I will have to add them.
As I don't have a die to cut the threads on the rods, which are 0.8 mm in diameter, I had to cut bolt's heads and silver solder the threaded part to the rods.
I calculated that the rods are able to withstand a force of up to 6.5 kg before they break. I will never go that far!

[MODEL A MODEL]

Roger, I am so glad you decided to continue to build models and post your work! -I bet the gentlemen on the other forums, the Cadillac and La Salle Forum? are in complete amazement!

[Roger Zimmermann]

They do, but there are more views on this forum. The AACA forum is the one with the most views, but there are so many people looking at this general cars forum!

[PeterDaicos]

Are you eventually going to paint the brass?

[Roger Zimmermann]

Yes. It may look good on pictures, but not in reality. Silver soldered joints are barely visible, but not the soft soldered ones.

[Roger Zimmermann]

The first tire is born. Unfortunately, I cannot use it because it's too wide! I had several issues when I did it and the RTV began to set when I put both halves together. I also noticed that there was material to remove at the half molds; not much, about 0.5 mm.
Today, I did another try. Some explanation are needed to understand the process. I know that it was already published, but it was more than 10 years...
The attached pictures are as follow:
First, I'm purring some transparent RTV into a cup, about 50 grams for one tire. Then, I'm mixing a tinting product as transparent tires are silly. The hardener is then mixed. I'm using a small cup for that, but at the first tire, while removing the trapped air, I saw that the volume increased so much that I had to stop the vacuum pump. I transferred the mix into a larger container so an overflow did not happen. After about 15 minutes, all air is removed so I could purred the mix into the half molds. This operation is again entrapping air so the half molds are back into the desiccator. Again, to avoid overflow, the half molds are not completely full.
After 10 minutes, both molds are taken out and more RTV is added as you can see on the next picture. Up to that, 3/4 hour elapsed. After one hour, the curing begin slowly. Then, I have to monitor when the mix will begin to set. Too early, the product will escape and create an air bubble; too late, the excess material cannot escape and the tire is too wide. After 1 hour and 15 minutes, I put both halves together and pressed them together to evacuate the excess material. This time, it could be that I was 3 minutes too late.
I added some weight on the assembly; I will open it tomorrow as 10 to 12 hours are needed for a complete setting.

[MODEL A MODEL]

Hi Roger, I don't see any venting? If you had two "Vents" you could close the mold halves run a tube down into your resin , draw a vacuum with the other vent, evacuating the mold, and under vacuum suck the resin into your mold. It's a way to guarantee a bubble free casting .

It really is a neat technique, and easy to do.

[Roger Zimmermann]

Don, frankly I don't understand this "method". My actual method is working well (second tire is OK), so I will not make other experiments especially if I'm not convinced.
By the way, the last picture has nothing to do with venting. It's just weight, but I will change my method.

[MODEL A MODEL]

It is better to show how it works, I'll try to put together a mold and demonstrate.

A tire with its tread, in a closed mold is pretty impossible to pour without capturing some air bubbles. Pouring two open face molds and then closing them as your doing is one way.

Closing the molds, running a tube from the mold down to a reservoir of resin , and another tube to a vacuum, will evacuate the mold and draw the resin in, to fill with no air bubbles.

Again, I'll have to demonstrate this.

[Roger Zimmermann]

Oh! I may understand a tad better. When I did the Toronado, I had a product from Dow Corning, still available but extremely expensive. I did differently: I put both half together and did a small hole at the top to fill up the inside. It went well, but I don't remember if I evacuated again the air when done.
For the Avanti, I bought a different product and did the same set-up: as the product is "thicker", it took too long to fill-up the tire. Therefore I imagined this method. I suppose to use your method, the parting line between both halves must be air tight, creating again another problem. Nice on paper, but hard to realized. Could be OK for 1000 tires, but not for 6 or 7!

[Roger Zimmermann]

One of the first things I did this morning was to open the molds! That story in pictures:



the weight is off, the molds are ready to be separated. The light gray surfaces are an indication that there is already a slight separation between the mold and the RTV rubber.



With a screwdriver, I'm forcing the separation. If I had slicks there would be no problem but the thread is offering some resistance. This is the crucial question: can the mold withstand the effort?



One half is away, no issue.



Now, by pushing and pulling, the tire is coming out of the mold.



Fortunately, this is a good tire. I cut the rubber which oozed between parting lines with a tool. The middle must also be cut away.



The tire is installed on a wheel. I noticed a difficulty with the white wall: there is a void between it and the tire. The reason is simple: all my white walls are too thick; when removing some material, the fit is excellent.
Now I can do the other tires, one each day (more or less...).

[MODEL A MODEL]

[Roger Zimmermann]

Now that I'm more or less confident with the tires "manufacturing", I would like to refresh the steps needed for that.
1. make a master tire with brass or something which can be machined
2. make half molds from the master tire; they are negative molds
3. make positive molds (or two half tires) from the negative molds
4. make negative molds with a resin which will be hard after curing
5. finally by using the negative resin molds, do the final tire (s)

I see an argument: why don't use the half molds described under the point two?
By using those RTV molds, it would be necessary to use separating wax for each tire. This is not a big deal, but if the wax is not going everywhere, the tire will get bonded with the mold, destructing it. The next argument with the way I'm doing the tires: by applying much pressure to the soft molds like shown with the attached picture, I doubt that the end result would be usable.

[PaulPK]

Well done Roger. I always look forward to the morning unveil when I am making molds. Coffee in hand and another successful demolded master to start the day. 👍

[Roger Zimmermann]

Due to the GE (an international Cadillac meet) and summer vacation, there was nothing to report. Now, I'm back and some progress was done: most tires are ready, I intend to do a last one in the next few days. With enough tires for the model, I had to do the knuckle arms to be able to install the front wheels. The shock absorbers are temporary installed too; I still have to do the actuating arms.
Now, I will do the tie rod ends and the tie rod because it's annoying when the front wheels are totally independent from each other...