1932 Cadillac V16 scale model

[Roger Zimmermann]

SUCCESS! This morning, I separated the positive molds from the negative ones. At first, it was difficult to get the edges being separated; once I got that, the rest was easy. No bubble, all the material is well cured.
The next step: doing the definitive negative molds with a product like polyester. The product I used to do the negative molds was no more available at the store I'm going; a different product is no offered. Will it be so good as the previous one? There is a fundamental difference: the old product got cured with the addition of 3% hardener. This product is used by mixing tow parts from one element to one part of another one. Certainly easier to mix with the right proportion, but how are the characteristics of the cured product? I will have to make a test with a very small quantity.

[Roger Zimmermann]

I can see the axle has been scraping the road surface by the missing paint.

But, seriously, you can leave all the spring leaves in the pack, but to allow the required flex, I would advise modifying the middle leaves to be more flexible by removing the centre of the leaves, leaving 1/8" on each side....

PS.   Maybe I am overthinking this fix.   I remember seeing the grooves in the rear leaf springs on my '55 and '57 Chevs.   Maybe the Factory did this to give the cars a softer ride, as they did ride nice.

Indeed, Bruce, I missed to answer correctly to your post.
About the scraped paint: yes, roads in Switzerland appear to be the worse in the world!
The idea to remove material from the middle of the leaves came also from somebody located in England! However, if I'm leaving 1/8" at each side, the leaves will be wider than before: they are now 4.7mm wide! (0.18")
I also saw leaves with the grooves; never thought about the purpose, but you may be right as the leaves must have some width to get some transverse stability.

[Roger Zimmermann]

After having a too stiff front suspension, it was logical that the rear one would follow. This time, I did only 3 leaves per side and, indeed, the suspension is rather soft. However, the rear springs are much longer than the front ones! According to the specifications, there were 9 leaves at the rear; I will add some later.
As you can maybe see, the rear suspension is very unstable with shackles at the front and at the rear: the drive tube is the element which locate the rear axle longitudinally. As you can understand, some more work is needed to have a working suspension...
I will soon do a test with the new resin: I just read that it's dry to the touch after two days and completely cured after five days!

[Roger Zimmermann]

Yesterday, I did a test with the new product by mixing two parts from the base with one part of the harder. Not too much: 6 grams! Just to see if this product will have the expected properties for the half molds. This morning, the mix is almost tack-free. One of the big advantages compared to the polyester resin: no smell!

[Roger Zimmermann]

As I wanted to have a functioning rear suspension, I did the torque tube. Its length is critical because the wheelbase is managed by that tube. That element is not yet ready: I have to add the bracket for the strut rods. Without those struts, the rear axle is unstable and, in real life, the differential carrier could be bent by driving on a rough road.
I will also have to modify the "shoes" for the rear axle; I did its top surface parallel to the pinion; it must be at an angle to match the transmission's end without binding.

[carguyblack]

Roger,
When you look at this most recent photo of the frame assembly you posted, do you even amaze yourself??!!
So cool.

[Roger Zimmermann]

Well, Chuck, it's a nasty question! Put it my answer that way: most of the time, I like what I'm seeing!

[carguyblack]

I know. Patting yourself on the back is not the best look but my point is that when you look back on all your hard work, it has to be somewhat satisfying to see this outstanding result. I'm always eagerly looking for your next post!
Chuck

[Roger Zimmermann]

With the addition of the struts, the torque tube is now complete. If you are looking at the picture, you'll see that the thread near the tube is much longer than the one towards the wheels. There is a reason for that. Which one?

[The Tassie Devil(le)]

So that you can install the rods without destroying the joint of the Torque Tube to the Diff.

You can slip the nuts right back, insert the other ends of the shafts into the housing, and then bring the nuts up to tighten?

Plus, in real life, assist in tuning the rear driveline for alignment.

Bruce.

[Roger Zimmermann]

Good answer, Bruce! At first, I wanted to make the thread as short as possible, but I saw that I could not install the rods as the nuts must be screwed in before the installation.

[Roger Zimmermann]

Before I go to the rear brakes (as the rear suspension is a necessity to do that), I wanted to continue with the tires. The next step is to create the negative molds with a suitable material. I began with the side walls, allowing enough space between the RTV molds and the exterior diameter. Then, as I did long ago, I attached the walls to a brass plate with masking tape.
Then I did a mix with resin and hardener and evacuated the trapped air. After the majority of the bubbles was gone, I poured the liquid into the molds; then the trouble began: as the mix is also as thin as water, the resin began to soften the glue from the tape and oozed out. I tried to do a dam with the plasticine; it was good for a few minutes, no more. To reduce the gap between the plate and the walls, I put some weight on the walls. This reduced somewhat the "flow", but not stopped it.
During almost the whole afternoon, I catch as much resin as possible and put it back where it belongs. When the resin began to get thicker, I could do something else.
The next morning, the resin was almost set and I began to remove as well as I could the masking tape and the oozed resin. One thing is sure: that product stick well on brass!
In one or two days, I will take the RTV molds away. For the moment, the product is still flexible. Remember: on the notice, the material is set after 15 days!

[Roger Zimmermann]

Half success...This morning, I separated the molds from the brass plate. I noticed that the RTV went under the positive molds; this is the first time that it happened. I will have to remove some material from the negative mold's flange, otherwise the tires will be too wide and the width irregular.
There are some tiny bubbles which did not went away; I don't think this will be an issue with the tires.
I had to cut the center of the positive molds to remove them from the hardened resin; if I would do new half molds with the resin, I would have to do new positive molds because I need the center to locate the half molds during the tires "production".

[Roger Zimmermann]

Parallel to the tire saga, I'm continuing with the torque tube/rear brakes. There is a relay between the main actuating lever and the rear axle which is attached to the torque tube. Honestly, I don't know its purpose; there must be one...
Anyway, I finished both pieces just to discover that either the brackets screwed to the torque tube are too short or the levers are too long: if I had the rods going to the rear axle, they would touch the rods which is not good. By looking at my pictures, it seems that the levers are too long. However, I will redo the brackets, there is less work involved.

[Johan Boltendal #158]

As far as I know the reason for these is the difference in height between the rear axle brake take up and the operating system on the chassis, just after the trans.
Besides that the height of the rear axle differs under load,  this relay takes this difference easier then straight rods,  length wise Johan

[Roger Zimmermann]

Johan, thanks for your explanation. I'm not convinced from it, but what I think is not important. Anyway, you have more experience in those cars than I have!

[Roger Zimmermann]

Well, it seems that the explanation from Johan is the right one. 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!

[The Tassie Devil(le)]

......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!   

Roger,

If you do break them, then you are driving the car simply too hard.

Bruce.

[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.
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.

[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 wall are too thick; when removing some material, the fit is excellent.
Now I can do the other tires, one each day (more or less...).