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Discussion Starter · #1 ·
I bought a resin casting of the Karmann Ghia on the bay. Not sure where it originated but I knew from previous comments on the forum that it was likely to be oversize. I thought I might try some surgery. It arrived with a wheelbase of 84mm so a scale of about 1:28 roughly. For 1:32nd scale it should be 75mm.

By chance I came across a web video of how to shrink silicone rubber moulds by adding odourless mineral spirit to the silicone rubber before pouring into the mould. So I thought I'd give it a go. I didn't measure the quantity of spirit just added a dollop and mixed it in thoroughly. Thinning the rubber did make it more prone to leak from the moulding box.

I waited about a week before trying a casting. The wheelbase was down to 78mm and the mould didn't seem to be shrinking anymore. So I repeated the process using the new casting as the master and with the second mould I am down to 75mm. I am going to try storing the mould in an airtight box while I take a few castings.


Tire Wheel Car Vehicle Automotive parking light



Not sure if anyone else has tried this. Just thought I'd share it.

Thanks for looking.
 

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More wonderful work, Michael. Thank you for posting the picture. I also spy with my (useless) eyes an Airfix Beetle, and wonder.

Would love a Karmann shell if possible, please...
 

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Well done. For me casting is still one of those aspects in slotcar that is more like magic for me (the other being making brass chassis).
 

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Discussion Starter · #6 ·
Laurence

Thanks. Are the first two pictures of the Vanden Plas version? I also like it better without chrome.

The beetle in the my post was there as a sort of visual scale check. I'd read that the Karmann was based on a widened beetle chassis.

Grunz

Thanks. The casting process is still magic to me. I do find it can become addictive.

As for brass chassis building that is a complete mystery.
 

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By chance I came across a web video of how to shrink silicone rubber moulds
Había oído hablar de que se podía encoger o agrandar carrocerías y neumáticos, pero no sabía que se podían encoger los moldes de silicona.

I had heard that you could shrink or enlarge car bodies and tires, but did not know that silicone molds could shrink.

Frederic
 

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dvd

A good point. I'm tempted to imagine where this marvellous technology might be in future years. Mind-boggling, eh?

How long before there are the good folk of the Forum showing pictures of 1:32-scale printed tracks of, for example, Spa, Nurburgring, Monza and Monaco - all complete with accurate buildings and scenery?

I imagine it's inevitable.
 

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Having attempted to expand a Karmann Ghia, I am impressed by your shrinking method, excellent work (y)
 

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Laurence

Thanks. Are the first two pictures of the Vanden Plas version? I also like it better without chrome.

The beetle in the my post was there as a sort of visual scale check. I'd read that the Karmann was based on a widened beetle chassis.

Grunz

Thanks. The casting process is still magic to me. I do find it can become addictive.

As for brass chassis building that is a complete mystery.
AFAIK the K-G was built on a completely standard Beetle "kipper". Any difference in width would have been a result of the Beetle's body sides rising more or less vertically from its outer edges, whereas the K-G had enough tumblehome to extend far enough out to incorporate the wings.
 

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This a concept that has taken some of my mental processing time in the last few years. I make molds and cast for my model railroad and have thought about trying to throw a mold of a shell and wondered if I could shrink a model. It'd certainly open up a wider range of shells , particularly from 1/24th.
What do you use for your molds and resins? I'm using PinkySIl (50/50 silicon) and fast cure 50/50 urathane at the moment.
 

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Discussion Starter · #17 ·
Thanks for all the positive comments and likes.

I have seen commercial shrinking silicone rubbers on web videos which are capable of doing bigger reductions but I was just using what I had readily available. Using this method I had to repeat the process to get to the scale I needed. Obviously the more times you do it the detail of the original can be lost.

I'm currently having problems with supply of silicone rubber so having to experiment with different suppliers. It's just RTV silicone rubber slow cure with a shore hardness of 25 or 28. The resin I use is Axson F160 Urethane resin.

Thanks again for your interest.
 

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Using this method I had to repeat the process to get to the scale I needed. Obviously the more times you do it the detail of the original can be lost.
Aunque se pierdan los detalles, ya no sería empezar un coche desde cero. Solo tendrías que reparar los daños y las perdidas. Es decir, que te ahorras mucho trabajo.
A menudo me he planteado utilizar silicona para mis moldes en la construcción de un coche (en los pasos intermedios). Pero normalmente solo hago una única carrocería para mí y no compensa económicamente.


Even if the details are lost, it would no longer be starting a car from scratch. You would only have to repair the damages and losses. That is, you save a lot of work.
I have often considered using silicone for my molds when building a car (in the middle steps). But I usually only do a single body for myself and it doesn't pay off financially.

Frederic
 

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Discussion Starter · #19 ·
Frederic

Acordado. Es más fácil comenzar con algo sobre la escala correcta que comenzar desde cero.

Agreed. It is easier starting with something about the right scale than starting from scratch.
 
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