Shrinking model parts

[ubermodel]

How do you shrink model parts that are too big?

In building the AMT '62 Bel-Air, I noticed that the dog dish hubcaps are too large in diameter, perhaps 2-3 scale inches. I needed a way to shrink them, and this worked pretty well....provided I had the patience of a saint. All you'll need is some Elmers Glue and resin mold-making compound. Due to its nature this method only works for small parts.

First, make a resin mold of your part, in my case it was the Bel-Air hubcap. When that cures, brush a thin layer of Elmers Glue onto the surface layer of the mold, making sure to coat all areas, and to eliminate all bubbles. Place it somewhere warm to speed drying time. Once dry, fill the mold approximately 1/4 full with Elmers Glue, and let that dry fully, then repeat that step until the mold is full. You can't fill it all in one step because too much glue at once will just fill your mold with mush that won't dry.

Let it sit for a day or so, then carefully remove from the mold. You should have a duplicate of your part, made completely of dried Elmers Glue. Take your new part, place it in a small container where dust won't get on it, and let it sit somewhere warm and dry for a week. As Elmers Glue "cures" it actually shrinks, so your part is getting smaller while you wait.

Now, the part that requires patience: after a week of drying time, your part will be smaller, but to get noticable results, you'll have to repeat the whole process two or three times, using each successive shrunken part as a master to create a new resin mold from. Once the part is the size you require, make a final mold and you're ready to create as many resin copies as you need.

Yes, this process is a pain in the ass but it worked. In the photo below, I was able to shrink the original hubcap a little over 1/16", which worked out to almost 2 scale inches, and the final assembly showed a lot more of the steel wheel's detail.

Edited October 6, 2007 by ubermodel

[Phil Patterson]

Wow, that's pretty cool! Tedious, but still cool!

I can see where that method could come in handy in several instances, but one thing for sure, take good care of that mold and master once you get to the correct size!

[ubermodel]

Wasn't really that tedious, just a lot of waiting. The final glue "master" is actually a couple of years old now, so could be it's shrunk a bit more and is even closer to the right size. If I ever drag my Bel-Air out of mothballs to finish it (it turned into one of those ultra-detailed but never-finished works-in-progress) I'll have to repop a few new resin pieces.

[James W]

I like this tip. It is the kind of thing that makes my projects take so long. Some times whatever-it-takes is the only method out there.

Maybe you should offer some of those hub caps to other builders for a small fee, hint hint, nudge nudge.

By the way, include your real name in your posts so the site cops won't arrest you.

[Jairus]

This is the perfect way to make parts from a 1/24th fit a 1/25th scale model!

Excellent tip, I might have to "borrow" it for the "Ask Gregg & Jairus" collumn in Model Cars Magazine. 'course you get the credit!

ubermodel, the site police have been notified of your failure to abide by forum rules. Please put your name in the "signature box" found in your My Controls section. Thanks!

(Otherwise, how can I give you credit for this fine tip? Hmmmmm?)

[MonoPed]

That has to be the most interesting tip I've read so far... neat stuff!!

[ubermodel]

Sorry Jairus, signature has been added.

James W., if I ever start resin casting again I'll definitely make them available. 'Til then, click on the link in my signature for a couple of other neat things I've been working on.

Edited October 9, 2007 by ubermodel

[mr moto]

That's brilliant! I don't know how in the world you ever thought of that!

[ubermodel]

Lots of experimentation. Now that I think of it, at the time I was also experimenting with enlarging small parts. I found a method that worked pretty well, but please use caution and common sense if you try this as it involves heat. As everyone learned in elementary school, heating something generally makes it expand. I tried taking an existing resin mold of a steel wheel, one that had seen better days, and before pouring the resin I heated the mold in my oven for several minutes. A microwave oven won't work, as there's no water content to heat in a rubber resin mold, and I don't remember the particulars regarding what temperature or how long, this is going back several years. The result was a resin wheel that was slightly larger than one made in an unheated mold. As with the shrinking procedure, to get appreciable results you'd have to perform this several times over.