1/20th home made accessories :)

don_jarr · 03-09-2007

Hi all

Due to the lack of well detailed parts for a 1/20th scale boats, I set about making some myself. I have done things like window frames, and portholes so moved onto the deck stuff, in this case the oil drums.

I think boats of this scale need to be really well detailed, as when people look at the boat when it is out the water, being much bigger floors in the detail show up more.

The oil drum was turned on my lathe from a rod of tooling resin. This is really nice to work with, as not only does it turn down very cleanly, it finishes off very smooth as well, making it good for making a mould from, resulting in a good clean cast.

The main body was turned down using a picture of a real barrel, but the cap was a cast of a model motor bike oil cap as it had nice detail to it.

As I want some to lie down and some to stand up, a full mould was made, (no pouring spout) and it was rotary cast so it’s hollow and light weight, but without external holes in it.

They came out quite well, and just need a bit if weathering and rust adding for effect. I have included pictures from all angles, and the master next to the casts.

Don

**Bunkerbarge** · 04-09-2007

Very nice they are as well. Using the same casting technique I'm sure you can look at packing cases, gas bottles, fire extinguishers etc... etc...

A nice paint job, some oil company logo's and a bit of weathering and they will look superb.

**Bluewavestudios** · 05-09-2007

Welcome Don,

A very nice job too on the accessories, these are what really finishes a model off if fitted with the right bits.

Those Oil Drums look great and would not look out of place on most models that we have seen on here, especially for the Military vehicles and Tanks and we have plenty of them on here.

Regards.....Mark

jankers · 05-09-2007

A very nice job there Don.

I have not come across "rotary casting", can you explain the technique?

J.

don_jarr · 05-09-2007

Hi m8

It’s basically a gyroscope type thing like the pilots train in, adapted with a mould holder in the middle. You can make one out of one of those old globes that’s supported on a gyroscope type base.

The mould is in two halves, with the join preferable on an edge so it won't notice, and most important of all no resin pouring in spout. The resin (under half the moulds capacity,) is poured into one half of the mould, and then the mould closed and inserted into the mould holder, and then spun in all directions. It’s a bit like centrifugally casting, but being spun on both axis not just one, you don’t get the hollows at each end centrifugally casting tends to get. Fast set resin is preferable or you are turning forever. For small moulds you can turn by hand, but as its slower, air bubbles don’t tend to be forced into the middle the same, so the finish is not as good.

I don’t know if that’s the right name I called it by, but this elderly gentlemen who used to live across from my grandad and made boats years ago, had one in his workshop for making stuff and called it that. He used to use lead though back then, and everything was much hotter. He actually got me into making boats when he gave my grandad two boats to give me, both which I still have. I figured the same set up could be used for resin.

The best bit is well detailed hollow castings with crisp detail, and no holes.

crash93 · 06-09-2007

any chance of a few pictures , it seem like the way to Go in modeling Thanks Peter

jankers · 06-09-2007

Thanks Don, it's certainly something to consider making as my current attempts are incurring a lot of scrap.

J.

don_jarr · 06-09-2007

Hi all

Crash93, I am currently adding a bit to my web site on it, so will give a shout when it’s done.

Jankers, I meet a lot of people that attempts at moulding are not coming out as clean as they want. The produce a really good prototype piece, but the casts from there mould are not coming out well. I don’t mean this in a spiteful or nasty way, but most of the time the mould is at fault due to the person doing it not understanding moulding properly. Post a couple of close up pictures of the prototype piece, and the mould, and a cast and I will try and point out what is wrong.

In the meantime a few pointers for a good clean cast.

Avoid very sharp edges. Just by sanding the edge to a slight round, will help stop air bubbles getting trapped.

Avoid sharp corners. Again just take the point off, and this helps stop air getting trapped.

Prior to making a mould try to make it in such a way, the resin can flow in, and the air out without any undercuts or air traps. Many people make something, and just mould it without thinking about the casting process.

Sometimes a multi piece mould will take longer to make, but give much better results, however try and make any joins on an edge or part it won’t show.

Choose your resin carefully with enough of a time gap to it gel’ing to make sure its all poured in and shook about.

As I said post a few pictures and I might be able to help.

Don

jankers · 09-09-2007

Don,

Thanks for the info.

I don't have a camera but have examined the mould and know where i have gone wrong;- i used large air evacuation tunnels in the two part mould. These where much lager than i have previously used and so the resin did not rise to the surface as i expected, added to which i was experimenting with colouring the resin using Humbrol paint.

The method you use would be of limited benefit to me as the parts i generally cast are 1/128 or 1/192 scale, so hollow casting could prove problematic. If i move to a larger scale then i shall certainly give it a try.

I have now managed to rescue one of the parts so shall just do another mould, it's not really a problem as i use the hot-melt rubber so can just re-use the old stuff. the problem arises due to the very small quantities i normally cast, about 5cc, thus making the mixing a little difficult, the addition of a drop of paint helps considerably in judging if the stuff has been thoroughly mixed as the hardener is only about 3 drops for that quantity of resin. I normally use a syringe to 'fill' the mould, then swing it on the end of a string to mimic the centrifugal machines, it's not perfect but the scrap rate is decreasing.

J.

don_jarr · 10-09-2007

Hi m8

I have and do sometimes use hot melt rubber, but due to using polyurethane resins mainly which generate heat while curing, it tends to sticks to the hot melt rubber.

You should have a look at this web site, www.tiranti.co.uk as they sell all moulding stuff. If you only do smallish things, it might be worth buying some proper addition cure silicon, and 5 minute polyurethane resin, and do them that way. Poly resin is much better for small amounts as most are 1:1 which means you can buy those children’s medicine syringes and mix that way. I do a lot of small stuff that way. I bought some 100ml plastic bottles which I put resin and hardener into and the syringe bottle neck bits fits in the top perfectly, that way I can fill the syringe accurately to half a millilitre of each.

I also find on smaller things, to make the mould in two halves, but fit a fill tube into the mould when casting, so the resin is injected in via syringe from the bottom of the item being cast, not the top. You can fill it slowly so the air is pushed out the top as the resin goes in the bottom.

All said and done, however the best way to do smaller intricate things is to pressure cast, but this is a whole new ball game requiring far more equipment. The plus side is very detailed wafer thin castings perfect every time, air bubble free.

If you have any pictures of bits, it would be good to see what you are doing.

Don