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Updated on my Kendall Tower project


Marshall, Ralph
 

Before getting into the project I want to respond to Bruce's call for a new topic. I agree with the idea of spending the next interval catching up; that's probably because I'm working on one of the really old projects (wooden towers), but in any case, it seems like a good thing to do now.

As a quick recap, I've started working on an O-scale version of Kendall Tower that I'm going to produce with my 3D printer. There are some design images in the Wooden Towers photo collection but I found I had to go back and redo much of it as I've learned more about how the CAD software works. I've finally gotten to the point of trying some test prints to figure out how small of a detail I can expect to produce, and also to try out some design variations.

The attached picture doesn't look much like a wooden PRR tower, but hopefully it shows progress towards the goal. I'm trying out several things here:
  • Does it work better if I print the walls vertically as one solid unit or horizontally as flats that are glued up?
  • Do I make the window trim part of the wall print and then mask it off for painting or do I make separate trim pieces?
  • How wide and deep should the lines be that represent gaps between the boards?
  • What's a suitable wall thickness?
I'm interested in opinions (the photo isn't great, but was the best I could do), but I think I've concluded that it looks better with walls printed flat and separate trim pieces. I'm not sure what to think about the line sizes - the ones on both sides of the window are 0.1, 0.2, and 0.3mm wide, and either 0.1 or 0.2mm deep. I think I'm going to go with 0.2mm wide x 0.2mm deep (the middle left one on the horizontal part). My printer will produce layers that are 0.1mm thick and individual rows of plastic are about 0.4mm wide, but you can space individual elements closer than the 0.4 distance.

In O scale that size is pretty big for a gap between boards (0.2mm is about 4/10ths inch full scale), but anything smaller just gets lost in the printed wall. The wall thickness works out better - what you see there is a 2mm thick wall with 1mm thick trim, which I calculate as about 2" and 1" respectively.


Bruce Smith
 

Ralph,

To be honest, I like the finer line size on the horizontal part. The bottom line (so to speak) is that gaps between boards should not really be visible. I like what some folks have done with scratch building and that is to vary the board thickness by a very small amount, and not necessarily over the whole board. That way, instead of a gap, you have a thickness offset that gives you a very subtle shadow line.

With respect to trim, it it's a different color, I would print it separately and paint it before gluing it on. But that's my HO scale mindset to get great color separation.

Regards
Bruce
Bruce Smith
Auburn, AL


From: PRRPro@groups.io <PRRPro@groups.io> on behalf of Marshall, Ralph <Ralph.Marshall@...>
Sent: Monday, June 29, 2020 7:35 AM
To: PRRPro@groups.io <PRRPro@groups.io>
Subject: [PRRPro] Updated on my Kendall Tower project
 
Before getting into the project I want to respond to Bruce's call for a new topic. I agree with the idea of spending the next interval catching up; that's probably because I'm working on one of the really old projects (wooden towers), but in any case, it seems like a good thing to do now.

As a quick recap, I've started working on an O-scale version of Kendall Tower that I'm going to produce with my 3D printer. There are some design images in the Wooden Towers photo collection but I found I had to go back and redo much of it as I've learned more about how the CAD software works. I've finally gotten to the point of trying some test prints to figure out how small of a detail I can expect to produce, and also to try out some design variations.

The attached picture doesn't look much like a wooden PRR tower, but hopefully it shows progress towards the goal. I'm trying out several things here:
  • Does it work better if I print the walls vertically as one solid unit or horizontally as flats that are glued up?
  • Do I make the window trim part of the wall print and then mask it off for painting or do I make separate trim pieces?
  • How wide and deep should the lines be that represent gaps between the boards?
  • What's a suitable wall thickness?
I'm interested in opinions (the photo isn't great, but was the best I could do), but I think I've concluded that it looks better with walls printed flat and separate trim pieces. I'm not sure what to think about the line sizes - the ones on both sides of the window are 0.1, 0.2, and 0.3mm wide, and either 0.1 or 0.2mm deep. I think I'm going to go with 0.2mm wide x 0.2mm deep (the middle left one on the horizontal part). My printer will produce layers that are 0.1mm thick and individual rows of plastic are about 0.4mm wide, but you can space individual elements closer than the 0.4 distance.

In O scale that size is pretty big for a gap between boards (0.2mm is about 4/10ths inch full scale), but anything smaller just gets lost in the printed wall. The wall thickness works out better - what you see there is a 2mm thick wall with 1mm thick trim, which I calculate as about 2" and 1" respectively.


Marshall, Ralph
 

Bruce,

Thanks for the quick reply. The notion of slight changes in board thickness sounds like a good one but I don't think I can make that work with this printer. I'll take another look at the finer line and see how it looks. I'm wondering if it will be less prominent once I paint it since I imagine some of the gap will fill with pigment, but we'll see. I do agree with you on the trim, as masking/painting all that seems like much more of a hassle than just gluing on trim after it's painted.

I'm beginning to reconsider the horizontal orientation. By doing it that way you get the diagonal pattern across the face which doesn't look very realistic. I could try using filler and sanding, but upon further reflection, the slight grain from the layers of plastic in the vertical one might look better without any additional work. At some point I guess I have to print a version of the building shell and just see how it looks.