At this state, even if the RTV should cure after some time with the help of heat, I will discard it.
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At this state, even if the RTV should cure after some time with the help of heat, I will discard it.
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.
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That would be a very large hex key!
And the slotted head bolts to either side, would also require a CADILLAC sized screwdriver!
Headless socket head screws should be available in a size suitable for end plugs. they come very small, inch and metric. A loose fitting piston, moved rack and pinion fashion by the lever and immersed in your viscoelastic fluid should provide damping. Making it adjustable - that little rod and clevis - would be trickier.
Actually, taking the time to read your post, I see that you punched out the hex and soldered that to a backing plate to close those out and give the part the right thickness.
Clever.
@ Buck: this lever is indeed for the adjusting shock absorbers on the real cars, something new on Cadillac cars for 1932. The damping on my parts will be done with a blade soldered to the shaft.
@ Don: Glad you noticed how I did the plugs!
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.
Attachment 36694
I'm glad you had a vacation. (Now back to work!)
What is your altitude? I believe that affects the vacuum that you can achieve. Where I live and where I work, we are only a few feet above sea-level, and I can get 29" Hg. I think I could get more if I were to work in Death Valley! (The lowest point in the U.S.)
Make sure to wear gloves when cleaning the RTV, and if you do get some on your hands, clean super thoroughly, and do not touch your eyes for a while. It really stings, and doesn't take much residue to get the point! (I know from what I'm saying!)
Our altitude is about 400 meters above see. With that pump, I can get about 27.5" Hg. Enough for the job! It's maybe dumb, but I never wear gloves. I hate them! The sole time I'm wearing one is when I'm spraying some paint with a rattle can. The hand holding the part is protected by a transparent glove, used for cooking I believe.
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!
Attachment 36700
The third tentative for the white wall's mold seems to be the good one. The first picture is showing the little quantity of material was mixed with the catalyst and black paste (the used product is transparent). When some vacuum was applied to the mix, the volume expanded and expanded. I had to stop the pump to avoid an overflow. After some pump's cycling, I could let it run for a longer time. After almost one hour, I opened the vacuum chamber and purred the RTV into the mold; I used simple cardboard to create the wall. Then, back into the vacuum chamber. There was still air trapped, you can see on the third picture the elevation of the mix. After 1 1/2 hour, I saw almost no bubbles and I let the mold out of the desiccator. After 2 hours, the mix began to set.
This morning, I took the cardboard away; some plasticine was used to close the interstices between cardboard and brass mold. The crowning of the day: the black rubber is removed from the brass part. Now I have a perfect mold for the white walls, one at the time.
Attachment 36701Attachment 36702Attachment 36703Attachment 36704Attachment 36705
The first white wall is born. It's good looking but the tire's dimension is somewhat weak, depending to the lightning. Still 5 to do!
Attachment 36808
Mazel tov!
Is a translation available?Quote:
Originally Posted by MODEL A MODEL
The white wall fabrication is going well, about one each day. A fourth is to be separated from the mold soon.
On the post #808, I was pouring white silicone into the mold. As you remember, it created a mess as I used not enough catalyst. I did this job again and, today, I removed the plasticine from the back. To avoid that the plasticine in going into the tire's grove, I used some masking tape to avoid it. I noticed that the tape was not sticking to the brass but did not thought more about that. The result: the silicone went between the tape and brass and filled up the groves! After painfully removed the undesired material and using wax, I poured the silicone into the other side. To tell the truth, I'm not at all confident that I will succeed. I will see that this week-end when the new material is completely cured.
Attachment 36819
Congaratulations!
On the "birth" of your first white wall!
Thanks, but in which language?