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Discussion Starter · #1 ·
A few weeks ago I bought 3D TurboCad and after a few hours playing about have become reasonably proficient , this has lead to me designing stuff that I could n't possibly make. The logical step was to look at rapid prototyping and after a lot of emailing and to and fro-ing I have a couple of contacts who can do SLS and SLA RP at reasonable prices . I have been through an exercise of redesigning much of the LBSC's Dot that I am building and have just put the frames back together. I have changed the axle boxes, they now have curved inner faces to allow the axles to float without binding.
The springs have been moved above the boxes, The wheels have been machined to G1MRA standard spec which is thinner than the drawings and enables the cylinder centres to be moved considerably inboard. giving a front profile very much nearer a black5.

The motion brackets have been redesigned and are now much more rigid and easier to set up true.
The axle boxes were machined in the lathe on this simple jig.

I am impressed with TurboCad , this is idea for the boiler .
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and the dies for the chimney casting.
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Using a combination of 3D software and RP should cut down development time by months , I hope
:)
 

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Discussion Starter · #3 ·
Hi KFRANK13 , and thanks for the compliment , my own view is that the finished part is the most important factor , and any method that can improve the quality , price and production time is good. I find the wonderful thing about model engineering is the huge range of methods people have used to produce their particular requirements , nothing is right or wrong , and the solution to any problem will depend on the ability and access of the solver. If you enjoy hacking from the solid then good for you , likewise to the guys who machine everything whether its winding the handles or writing the database , at the end of the day hacksaw and file , CNC or Myford , 3D CAD and rapid prototyping , they are all simply tools to be learned and used.
Can't wait for the invention of the replicator LOL!
 

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I agree completly. I actually love using cad work for laying out designs, which a good thing cause I have to use auto cad for school anyways. Any thoughts about when it's all said and done about posting your designs?
 

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Nice virtual modeling! Not to rain on your parade but.....

I use a solid modeling program (Rhino)for design along with a CAM program (I use visual Mill) and cnc machines to bring design to reality. Various cnc and rapid prototyping methods are possible but are costly and aren't always the best route to take unless you have ready access to all the machine type toys.

A part like your chimney would be a fairly quick job ( maybe an hour tops) to mill and turn manually with only the lower edges on the sides of the skirt to be finished with a diegrinder and files.

In the case of multiple parts requirement cad/cam makes sense because of the need to make duplicate parts. Some very complex surfaces/shapes might also benefit from cad cam.

The models you posted look great as does your "DOT". I am familiar with the loco having started it many years ago but never finished it.

What type of boiler do you plan? Any modifications to the general design?

Regards,

Jack
 

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Discussion Starter · #7 ·
Hi Jack , my thing is casting , so naturally wherever a part can be cast then it is , the chimney profiles on most loco's don't lend themselves to straight forward milling and turning by hand and are often the subject of forum posts , some of the curves have to be blended using - like you say- files and die-grinders , my casting is almost finished from the mould. All of my castings have a repeat accuracy of 2-3 thou and often can be used without any machining , cylinders require reaming down the bores and facing but steam passageways are cast in saving much time when building.
I have an idea for the boiler which I am trying at the moment , it is not greatly different from the drawing but does have some modifications . I will post further when I have steamed and tested it and have some figures.
I do of course have machining facilities , most of which goes into the making of the wax injection dies from which the patterns are produced , but as I said at the start of this thread it looks like RP from now on.
 

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Abby

I know a little about casting/RP. I own a small casting business. I spincast in Britannia metal, Zinc-aluminum, resin, and wax (for investment casting).

What materials do you cast??? Where are you located? Sometimes I need investment castings made.

In making multiples, casting is worthwhile. IMHO "one off" parts for something like a G1 loco are faster and cheaper to make by machining if the part isn't too complex. A chimney is pretty standard fair in model engineering practice. Also remember that the skirt of a Brit chimney isn't a constant radius so is an interestng shape to model either virtually or in brass.

Parts like the tender axleguards, on the other hand, would be worth casting since the shape is complex and they really need to look identical.

There are many ways to "skin a cat" and you can certainly make a nice chimney as a casting.

Narrowing the cylinders is a good improvement. I like your method of turning the bearing boxes. Strengthening the motion brackets is also wise since many I have seen are a bit flimsy.

Jack
 
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