THE GG1 STARTS TO TAKE SHAPE

[Trainman4602]

Hi All
About a month ago I discovered a 1 Inch scale GG1 site on Face Book. I was looking thru the pictures and discovered that the builder of this 1 inch model was using the wrong driver print. This is a common mistake. The print being used was that of the R1 62 inch 7 spoke wheel.

The R1 was a prototype locomotive that only one was ever made. It was in competition with the GG1 design and lost because of it being too ridged and prone to derailments.

I mentioned this to the builder and he promptly came back to me with the statement. " check your drawing sources" Well This \sort of upset me when I was willing to share my extensive collection of GG1 prints with him.

Well I decided to draw up one and make a pattern and get some cast in iron.

My casting friend DavidF on this forum offered to make up a 3D print of it .

This is it pictured below I will use it as a master to make repro's and mount two on a match plate.

[ALCOSTEAM]

Dave are you building those parts to 1" or 1.5" scale

[Trainman4602]

1 1/2

[FKreider]

Its cool to see 3D printers being used more for pattern making at a hobby level. I just printed out a cylinder pattern (for a model IC enigne) yesterday on my 3D printer.

[Trainman4602]

Yes it is cool but has it's draw backs. I have to coat the pattern with something to fill in the print lines so the pattern will draw from the sand cleanly.
DavidF he is the person who printed for me said to use a special coating that auto bady guys use to fill in things on automobiles. I could use a thin coat of bondo but whatever I use would require lots of sanding.

[Mike Walsh]

I have not tried filling 3d printed materials yet, but I can see some difficulty that could arise from lack of adhesion to the filament used... Wonder what folks out there have used thus far.

[steamingdon]

There is a process now to smooth out the pattern/model. I saw a demo @ Eastec last year, very good idea.

[Tharper]

Very Nice!

The layering in a 3D print can be an issue. I do in fact use a skim coat of bondo since the PLA filament I typically use doesn't sand well. There is also a specific paint you can use. Its fairly quick to sand down the bondo and follow-up with a couple of sanded coats of primer. If your using ABS you can use Acetone fumes which actually softens and smooths the plastic but the one time I used that method it distorted the pattern.

Recently I have been milling a number of patterns on the CNC mill. Granted its not for every application but where it does apply it's wonderful!

[FKreider]

I just spent about an hour sanding down a couple of 3D printed patterns this evening...and I still have a bit more work to do. However I would have probably spent at least two full days making the patterns out of wood if I had not printed them out so I don't mind a few hours of sanding and finishing work.

[Fender]

It may be possible to polish the patterns in a tumbler to smooth out the ridges. Shapeways offers this service for their “strong flexible” plastic, if the part is below a certain size.

[DavidF]

Hey Tharper, long time no see...

Evercoat 4:1 primer (sprayable bondo) Is about the best I have found for priming 3d printed patterns. Unfortunately it has to be mixed and sprayed.
I would like to find something similar in a rattle can. Ever since they made rattle can primer VOC compliant, It just does not dry properly and clogs the paper when sanding.

[DavidF]

Maybe???
https://youtu.be/Y6bLPBlaQgM