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Construction of a Continental Mark II model, scale 1:12


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Gerald Wingrove wrote in his book that the tiny imperfections are reproduced with fidelity by the silicone rubber; he wrote also that the best way to add the manufacturer name and dimension is done with paint. I did that with success on my 2 first models; the technique will not be modified.

First, I sprayed some filler on a portion of the tire; once dry, I "wrote" the name and dimension on the paint as you can see on the first picture. Then, with a sharp piece of brass, I just scratch the unnecessary paint to form the letters. A magnifying glass is needed for that, of course. The letters are far from perfect; I have as a reference a sticker I got once in a plastic kit. If I screw up, it's possible to correct with paint and, when viewed at a distance, these imperfections are unnoticed.

The second picture is showing the contour of some letters; I do the easy ones first!

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Edited by Roger Zimmermann (see edit history)
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The lettering is over. There is enough paint on the characters to be seen on the real tire. One correction is still to be done: the "Y" is not quite the way it should. Minor corrections can also be done on the polyester moulds. I'm not yet that far!

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Yesterday, March 21, I prepared the master tire to make negative molds. It is obvious that I have to do 2 half negative molds otherwise I could not take the brass part out. The half molds have to be done one after the other. If the first one gets bad, mostly with bubbles, I will only discover it when the second half mold is done.

To avoid that, the silicone is going everywhere, the brass tire is pub in a bed of plastilin. To have a nice and regular separation line, I did a donut with Plexiglas. Then I mixed some silicone with its catalyst and poured it into the mold. The mixing is creating a lot of bubbles; this is the enemy nr. 1 in such work, therefore the mold went into a desiccator. The vacuum is created with a hand pump (will get some strong hand muscles!). After half an hour of pumping, most of the bubbles are gone and the silicone gets slowly set.
The day after, I could remove the plastiline and the Plexiglas donut. I had to improve the separation line as some silicone could get between the Plexiglas and brass. Then I will have to pour silicone to form the second half mold. Will that be good? The answer in some days.
 

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Edited by Roger Zimmermann (see edit history)
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What did you use to act as a divider between halves that wouldn't stick to both halves?

The divider is just used to have a clean and straight surface. After the first half mold is done, the divider is taken away without problem. This silicone does not stick to any product except on itself. This is the next critical step.

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After cleaning, the the half mold is pushed back into its initial position. It is now time to pour another batch of silicone to get the second half mold. However, before this can happens, a critical little job must be done: to spray some release agent on the separation line, otherwise, the silicone will stick to itself like mad!

This morning, I took the whole mold out of the tin can. Will that be good? after gently working on the silicone to separate it from his companion and from the brass tire, it's YES! the result is good, no bubbles, nothing except that the material wend under the bands forming the tread, as they were just spot soldered. It's not a big problem, this flash material can be teared away, taken care that the whole tread is not coming with.

In fact, I could to right now tires with the molds. There are location tabs on the separation surface, it would be possible. However, it's not advisable. If the silicone for the tires sticks to the mold and damages it, the whole process is to be done again. Therefore these molds are just an intermediate step.

The next step will be to pour the same material into the half molds.

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Roger, you are fooling us. That obviously is a real Avanti. Now show us the model!

I am in awe of your work. Truly impressive. What fantastic work. Thanks for sharing the pics. And yes, pls. do post pics of your Toronado.

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Fantastic workmanship and talent! Have you thought about what your next project will be when you finish the Continental?

:) kaycee

Well Kaycee, let me start first! Then, if I do the math: in a couple of months I will be 65. 10 years (maybe less, who knows) for the Mark II, I will be 75! OK, my father was 92; if I'm getting that old, there are still 17 years to go...The big question is if I still can do then what I can do now...Fortunately, nobody knows!

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My father had a '68. He used to fool my sister all the time by waving his hand in front of the rear-view mirror and sounding the horn at the same time with his thumb on the pressure tube in the steering wheel rim.

My kid brother and I got a big kick out of her gullibility. :)

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Barry: those infame steering wheel are difficult to restore...Cadillacs had also a similar arrangement, plus fake wood on the rim!

Thank you for all who responded about the pictures. Unfortunately, pictures don't show everything. You can come home to see the models, no problem!

Meanwhile, the work continue with the tires. Yesterday, I cast the first half positive mold. I had doubts about its quality: some silicone would not cure. Fortunately, it was just the excess material. Why? I don't know.

The second half mold will be done this week-end; I have another "job" for the moment: I'm overhauling a 1959 Hydramatic transmission for a "customer". No, I'm not doing that on my desk, but in the place where my cars are stored.

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You know, looking at the pictues one would think that you would have take out a proper auto loan to purchase one of these great looking cars. And I’m sure that if you took the pictures with you to the finance people you could get one too. Time, paitence, comittment to detail and having the eye for the end product all coming together, beautiful work Roger… Scott

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Yesterday, March 28 was a rainy day. Ideal to do the second half positive mold! The catalyst is a difficult product to mix with the silicone; the repartitin is sometimes not so good. Yesterday, some of the product began tu cure before all the bubbles went away. I was almost sure that I had to do another one. Fortunately, I had the good surprise this morning to have a perfect piece.

On the first picture, there is a plate on the material poured into the mold; why? the reason is easy to understand: the next step will be to make half negative molds in polyester. The half positive molds will be placed on a flat surface and the polyester poured on them; therefore the "under" surface of the positive half molds must be flat.

Confused? me too, sometimes!

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  • 2 weeks later...
It's been two weeks. What's the hold-up????

As we say, no news = good news! Well, not exactly: we were for 10 days in vacation in our house in France, we came back Sunday. Even if I have a lap top with me during my vacation, I still have a lot to do when I'm back. I hope to pour the polyester on the half forms at the end of the week.

Anyway, thank you for asking!

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In fact, I had to change my mind and the polyester molds was a good oportunity.

I put some carboard on a brass plate, sprayed some releasing agent, put the half tires into the molds and finally poured the polyester.

I'm not sure if the result will be good: for about one hour, I chased the air bubbles traped into the tread. Maybe all are gone, maybe not. The answer when the polyester is hard.

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This morning, April 14, the polyester was still not completely cured. I waited till the afternoon to put the whole plate in the oven (please don't tell it to Christine) for half an hour. The whole flat was stinking and I was still unsure of the result! After making draughts, the smell went away. I could not resist seeing if the parts are good. Surprise! They are nice and usable!

The first picture is showing the molds upside down, the soft silicone is ready to be peeled out. The other pictures are self-explaining.

Some may wonder why there is a metal part embedded in the polyester. As the silicone is very light, I thought that maybe the half positive tires would swim; therefore I added a brass piece on each half tire as weight.

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Today, April 16, I poured some silicone in the polyester molds. After 6 hours, I was able to remove the molds; it is a success! The tire is nice, without major problem (the perfection is not available) and usable as is. Now, I can do the mold for the white wall. Some more pictures to follow!

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You sure do some GREAT work!! I have always loved scale models of any sort of vehicle, but to see your detail and precision is a very sweet treat. Thanks for all of the photos and explanations of how you went about all of this. John

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Thanks for all of the photos and explanations of how you went about all of this.

Thank you John for your comments! As you probably noted, my pictures are not coming on a regular basis. This is not my sole occupation and, to publish pictures, I have to do parts first!

When the mold for the white wall will be ready, I will publish step by step how such a simple part like a tire is done.

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Today, April 20, I did a new tire. As promised, I did pictures of the steps to show what is involved.

First, I'm pouring the material into a plastic recipient, a little bit more than the real weight of the tire to have enough excess material: 45g (the scale shows 51 g, this is with the cup); as you see, the material is translucide.

As I don't like translucide tires, a black paste is added to the silicone; very few is needed: less than 1 g. It's important that the mix is well done. Then the catalyst is coming: 10% of the wheight. A syringe is ideal for that.

Once the product is well mixed, it is poured into the forms, however they are not completely full.

Both forms with the cup are placed into a desiccator to remove the air trapped during the mixing. The silicone is kept under vacuum for about one hour; at the beginning, the volume is raising, this is the reason why the forms are not full. After one hour, the molds are back to normal pressure and more silicone is poured into them.

Now, it's waiting time...I have to wait until the silicone is no more flowing; it happens usually 2 hours after the catalyst is added. Today, it was a little bit less; maybe because the temperature is higher in the room.

At the right moment, both molds are put together and pressed to expel the excess silicone. Some weight is added on top of the forms to have as little silicone as possible between the parting lines of the molds.

The result is for tomorrow, the silicone must cure for 8 hours.

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Edited by Roger Zimmermann (see edit history)
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All the pictures could not be sent together...

The second picture from this serie is showing the raising volume of the silicone under vacuum; unfortunately, the camera is taking the lid as focus and not the molds; sorry for the bad quality.

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Late in the evening, I decided that the rubber was cured; I attempted to release the tire from the mold.

When it was out, I noticed that some bits of the mold came with the tire. After inspection, the damage may not be noticeable; I will do another tire to verify. If the result is not good enough, I will have to do another polyester mold.

I did also a white wall. The form is brass and it was designed that I can put a plate in the back to have a perfect piece. Unfortunately, my plan did not work as intended. Probably during curing, there is a recess of the material. If one part is exposed to the air, there is no problem. If the mold is completely closed, the recess is creating a bubble inside the mold.

Each day is an opportunity to learn something!

I installed the white wall into the tire; on the picture the problem cannot be seen; however, the white wall is scrap.

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  • 2 weeks later...

Yesterday, I noticed that the white wall of the tires are now loose! It seems that the white silicone rubber is retracting with the time. I will have to think about a system (maybe an O ring embeded in the white part) to prevent the problem. The white walls of the Avanti are also now loose into the tires; it's less of a problem here, I can do the wall wider, but not on the tires for the Mark II.

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Yesterday, I did a discovery by accident: as I saved a white insert which was not good for the model, I inserted it into the brass tire of the Avanti. I removed it and saw that its dimensions did not changed!

I assume that there is a reaction between the black and the white material, letting the later shrink.

I placed an O-ring into a new white wall for the Mark II; unfortunately, the O-ring went down into the mold and is slightly visible. Not a good idea.

In between, I began a futile part: the wiper motor. This part is looking so simple: "it will be quickly done" was my first reaction. With a nearer look, the part is not that simple; some days I was even discouraged (need a lot to me). Anyway, it's almost finished; some small details and surface finish are still needed: an afternoon of work...

In retrospect, the same amount of time will do a good part of the frame!

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  • 2 weeks later...

After the windshield wiper, I'm doing another futile part at this stage: the power brake assembly.

It's less complicated than the wiper motor because it's larger! The picture is showing the part which is not yet finished.

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1.Awesome detail and interesting techniques on this model.

2. Like many of you, Roger has a very cool list of other cars. When I see this I usually go to the members profile hoping to see more on these other fine autos, in the section provided "albums". I sent a request to Roger and he obliged. What a treat, check them out, and I encourage others to post theirs if you haven't yet. This is a great site and although I am more of a spectator, thanks to all who participate.

John

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  • 2 weeks later...

Last week I could take some measures on a Mark II located in Switzerland. In fact, it was disappointing as the man has many cars (too much for one life) in various stages of repairs. I doubt that only one could be driven.

Anyway, the 2 afternoons spent with a pencil, camera and paper will let me occupied for the next few months.

The first part I wanted to measure was a wheel center. Finally, he found one which was not installed on a car...

Doing the wheel center on a lathe is not that complicated, it makes just a lot of brass chips!

There are some details which cannot be done on the lathe: the stamped reinforcements near the studs' holes. How to reproduce that?

Well, I prepared 5 small pieces of flat brass for each wheel (first image), bored each small part (second image), temporary glued them in place on the wheel center, bored the wheel center (third picture) to be able to put a small pin of 0.5 mm. After removing/cleaning the contact glue, I could soft solder the small parts on the wheel center. The pins have the only task to keep the small parts in place during the soldering.

Then I cleaned the excess solder (fourth picture). The centers are not yet completed, the reinforcements need some more work to be acceptable.

The last picture is showing 3 centers; only two more to do!

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Finally, all 5 wheels are ready; the centers are soft soldered to the rims. They are still unpainted as it would be premature to paint them now.

I'm still busy with the white wall: on the pictures only one is OK, the other 2 white inserts are retracting and a gap is visible between the black and white parts.

I let cure the good one for 3 weeks and installed it; after 2 or 3 weeks I then will see if a longer curing time prevents the white silicone to shrink when in contact with the black silicone. If not, I will have to choose another product.

What next? Well, the wheelcovers are waiting! I still don't know how I will do the 40 ribs or vanes per wheelcover; a solution will certainly come in time. Anyway, it will be time consuming.

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  • 4 weeks later...

During my vacation, I studied how I could do the vanes or fins for the wheelcovers. As I had a lot to do after my return, I could not try my plan immediately. I dit it this morning and created the prototype of the vanes. It took about 1 hour to get it; once the set-up is done, it will be quicker, at least I hope so: there are 40 vanes per wheelcover.

As the result is the way I expected, I ordered 10 feet of 1.5 mm thick brass!

I ordered also round brass diameter 40 mm to do the dies for the "dishes". I still don't know if I will do the wheelcovers in one piece or if I will be forced to do the center as one piece and the outside diameter as another part, soft soldered together. With steel dies and a strong press there would be no problem; however, I can only work with brass and if ripples are formed during the process, they will damage the dies if too much pressure is applied, without eliminating the ripples as I learned when doing the wheelcovers for the Avanti.

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The brass needed for the wheelcover will be available next week. In between, I finished the wiper motor; the mounting plate was still missing. Thanks to the various dimensions I took from a real car, I could complete the motor.

On the picture, it's amazing to see the dirt on the part; it will surely be cleaned before painting!

Total length is about 1".

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Hello Roger,

As I follow your intriging skills and amazing patience, I am recalling similar construction problems. In 1962 employed by HMS Co as a modelmaker we created original car models for the Aurora Co. To reduce air bubbles when pouring silicone or epoxy mix, use a paper drink cup (dixiecup), combine the two components, then put cup and mix into the vacuum chamber. Once the air stops breaking the the surface, remove cup and instead of pouring out over the lip, penetrate the cup wall close to the bottom using a pointed scriber to open as large a hole as needed. This produces the least bubbles in the mix.

Thank you for the thorough description as you create your art. Phil

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Phil, it's an interesting method! Fortunately for me, the tires problems are solved. I had also the luck to have a product which was not too thick with a 2 hours curing time, letting enough time to avoid problem with air bubbles.

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