Dome Patterns

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k36no4862002
Posts: 151
Joined: Sun Feb 08, 2009 4:27 pm
Location: Surrey, UK

Dome Patterns

Post by k36no4862002 »

Hello,
I'm building an over-scale 7 1/4 Challenger locomotive, problem with over-scale is that the standard parts offered don't fit!!
So I want to have a go at making some dome patterns and casting them myself.
I'm not too bad at making a pattern but I'm a little confused about how I cast this. Normally if it's complicated you would split the pattern so you have an initial flat surface to work from but whatever i do I seem to have issues with the flare around the boiler bit at the base of the dome (eg where the bolts fix the done to the boiler).
Does anyone have any examples of how they have managed to cast domes?
I think it's the same process for all of the Challenger dome's once I get the idea!

Thanks
Paul
Paul Edmonds,
Surrey, United Kingdom.
2.5" Scale D&RGW K36, 1/6" Scale Challenger 4-6-6-4 (nearly done!!)
hoppercar
Posts: 616
Joined: Sun Jul 22, 2018 4:09 pm

Re: Dome Patterns

Post by hoppercar »

The easiest solution is to use a follower board, to match the contour of the flange
jkimberln
Posts: 133
Joined: Sat Dec 05, 2009 10:32 am
Location: Richmond, California

Re: Dome Patterns

Post by jkimberln »

Even easier is to use lost foam casting. There are lots of instructions on how to do this on the internet.
jscarmozza
Posts: 599
Joined: Mon Mar 03, 2014 5:09 pm

Re: Dome Patterns

Post by jscarmozza »

Paul, a few years ago I made aluminum dome castings for my 1" scale Atlantic, they're very different in configuration from those on a challenger, but I think you could use the same technique to cast what you want. I made solid wood patterns for the sand and steam domes and sand cores to hollow them and form the saddle fit on the boiler. I attached a photo of the the patterns and core boxes. If you use this technique, just take care to properly align the cores in the mold.
John
Attachments
image.jpeg
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Dick_Morris
Posts: 2842
Joined: Sat Jan 04, 2003 2:09 pm
Location: Anchorage, AK

Re: Dome Patterns

Post by Dick_Morris »

I'm a fan of 3D printing for small patterns. There was a learning curve involved, but for the last 18 months my patterns and "waxes" for investment cast parts have all been printed. Once the learning curve of the drawing software was overcome the printed items take less work and result in a better pattern. Need parts for the right and left side? Just select "mirror" and print another one. Other advantages are that a printed plastic part can be printed to check the fit without committing to metal and if you make an error the file can be edited and reprinted. This morning I've been drawing the pattern to sand cast one of the side rods for my 2-8-0. If I focus my time on it I should be able to draw and cast the part within about a two day period from start to finish. (Make that three days, the actual printing will take about 12 hours.)
hoppercar
Posts: 616
Joined: Sun Jul 22, 2018 4:09 pm

Re: Dome Patterns

Post by hoppercar »

3d printing has become the new norm....its almost put the traditional patternmaker in the poor house..
FKreider
Posts: 338
Joined: Fri Feb 02, 2018 8:44 pm
Location: Massachusetts

Re: Dome Patterns

Post by FKreider »

hoppercar wrote: Thu Sep 24, 2020 4:54 pm 3d printing has become the new norm....its almost put the traditional patternmaker in the poor house..
I guess they should have paid attention to changing/disruptive technology and adapted/embraced it!

Like Dick Morris I have used 3D printing extensively for sand patterns and master patterns for investment casting molds.

Someone made the steam dome too big on my 3/4" Yankee Shop Atlantic's boiler so the original decorative dome casting will not work, here is a picture of my "overscale" 3D printed pattern that I will use to make a new casting. I'm planning on using the follower block method as mentioned above and I will likely just make the follower block out of some hobby store clay.
92758628_10218869646785642_880471216257761280_n.jpg
Last year I cast a 1.5" scale brass safety valve dome/cover for a British engine and made a thread about it in the casting and foundry section of this forum:

viewtopic.php?f=14&t=108708
-Frank K.
hoppercar
Posts: 616
Joined: Sun Jul 22, 2018 4:09 pm

Re: Dome Patterns

Post by hoppercar »

Wow, thats nice...maybe someday ill get into 3d printing too...lol....but for now I just do.it the old way...outta wood, or just carve the whole thing outta steel...lol
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gwrdriver
Posts: 3439
Joined: Mon Jan 06, 2003 10:31 am
Location: Nashville Tennessee

Re: Dome Patterns

Post by gwrdriver »

I have a dome to cast also (brass), but I haven't begun pattern making yet. Since 3D technology seems to be advancing faster that I can get a "round tuit", maybe I won't need to. Still, there's a part of me that says "You've made everything else, might as well make the pattern too."
Attachments
Dome.jpg
GWRdriver
Nashville TN
k36no4862002
Posts: 151
Joined: Sun Feb 08, 2009 4:27 pm
Location: Surrey, UK

Re: Dome Patterns

Post by k36no4862002 »

Gents,
Thanks for your input, I'm going to have a go and I'll let you know how I get on.

Thanks
Paul
Paul Edmonds,
Surrey, United Kingdom.
2.5" Scale D&RGW K36, 1/6" Scale Challenger 4-6-6-4 (nearly done!!)
k36no4862002
Posts: 151
Joined: Sun Feb 08, 2009 4:27 pm
Location: Surrey, UK

Re: Dome Patterns

Post by k36no4862002 »

OK so I have had a go at the big dome for the Challenger, wooden pattern made from MDF and filler, didnt come out too bad. At 15" long this was a big pattern and after pitting it into a bucket of water it displaced 3 litres. My crucible for melting the aluminium only holds 1 litre of material . . . . so I cut it into 3 and cast the pattern in 3 pieces, the idea being that I weld itback together again or use some durafix to stick the casting back together when complete ( not tried durafix but it seems to be a wonder solder so it's worth a go me thinks!!) So the castings I did at my local club and are as rough as hell, but apart from a small hole and some roughness I hope a good file and application of durafix to fill various defects I should be ok, I hope.
Paul Edmonds,
Surrey, United Kingdom.
2.5" Scale D&RGW K36, 1/6" Scale Challenger 4-6-6-4 (nearly done!!)
k36no4862002
Posts: 151
Joined: Sun Feb 08, 2009 4:27 pm
Location: Surrey, UK

Re: Dome Patterns

Post by k36no4862002 »

A few pics
Attachments
casting 1.jpg
casting 3.jpg
castings 2.jpg
Copy of casting 1.jpg
dome pattern 2.jpg
dome pattern 3.jpg
Paul Edmonds,
Surrey, United Kingdom.
2.5" Scale D&RGW K36, 1/6" Scale Challenger 4-6-6-4 (nearly done!!)
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