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HO Scale D&RGW GS Gondola Project with the Form 2

I just wanted to share what I’ve been working on: a series of HO scale drop bottom gondolas that were used by the Denver & Rio Grande Western Railroad from the 1920’s to the 1960’s. The bodies are one piece printed, with the truckframes printed separately, and the rest of the other parts sourced from traditional HO scale sources. There are three different variations so far, the standard 46ft car, a coke rack added to the 46ft cars in 1942, and the shorter, smaller cousin at 42ft. It’s been a great challenge so far, and so many new ideas learned. Hope you enjoy!

Some of the hurdles I crashed into along the way that might help others:

Coplanar Surfaces: I used Sketchup for the drafting, and I used the component feature for the grab-irons on the cars at first, but had these weird seam lines that would extend randomly from the grab irons to the edges of the cars. After reading a forum post about coplanar surfaces, and how that would confuse Preform, I exploded those parts, and made sure the manifold was closed, which solved that problem.

Drilling & Tapping Holes: I am using #2-56 thread screws to attach the truckframes and the couplers to the cars, but its taken a fair bit of experimenting to get it right. The best luck I have had is by drilling out the holes with the proper bit size, and tapping the car while its still “green”, before curing in the UV oven, using a bit of diluted IPA as a cutting fluid for the tap. Once the car is cured, the tap has a tendency to crack the resin around the holes. If I do have a crack, or the threads get messed up, I drill out the area with a 1/8th inch bit, and CA glue (IC-2000, or rubber-toughened) a length of 1/8th inch styrene tube into the hole, and thread it.


Nice. Are these printed in one piece?


Yeah, the main body has all of the details attached, including all of the brake parts, except for the brake wheel. My first iterations of the cars had the grab irons printed as minimum thickness wires, but they were much too brittle for any sort of handling, so I redesigned for the solid type grabs. The coke rack is printed separately, and glued on before painting. I can fit 3 of the car bodies on the build platform, or 4 of the coke racks. (2 pairs with a simple sprue)

In order to get enough weight for operation, the center sill channel was designed wider than the blueprints for the real car showed, and a stick of lead is added. It keeps the center of gravity low, and they track really well. If a person wanted more weight, 3/16" tungsten cubes will fit in the channel to double the weight, at about 6 times the cost…

I’ve been printing the truck frames in pairs (simple sprue), since they seem to do better with a bigger raft attached to the build platform.

Fantastic work… Super impressed you get the tap to work… I just ended up using Brass or Copper inserts and epoxy them post cure for items like that.

Really great job!
There are very few support points. Does the “unsupported” areas (upper left side of the preform screenshot) do have sharp edges and no warpening?

I think the angle I took the screenshot makes it look like its unsupported, but its really the down-side to the liquid, and is supported by the other side. I haven’t had much in the way of warping or soft edges, unless the tank is getting worn at about 2 liters used. I purposely put the brake details on the down-side as to not have removal of the attachment points mess up the details.

WOW! If Form2 was around for my childhood, my train set would have been so much cooler. Detail right down to bolt heads. Very nice!

If possible, could you post some pics of the full landscape? The rock face and bridge details have me drooling.

Alex, for some reason, my attempts at uploading some of the larger area photos is running into a size limitation (I didn’t think they were that high quality…), but I took all of the previous photos with scenery at my local model railroad club, the Golden Spike Train Club of Utah. Look them up on Facebook, or at I’ve done a few videos as well, and uploaded them to Youtube, just search the club or my name, they should come up.

I have to be selective with shots at the club though, a bunch of the layout is under construction. :smiley:

Great but I have O gauge trains.

@CoreyBonsall Is any hobby worth it’s salt ever “complete”? LOL. I’ll check out the videos, and amazing work by your gang. Kudos to all!

@alan1950 If Corey is OK with it, maybe we can do a quick CAD scale up to get their models to O. Perfect use of 3d printing IMHO. Detail level may be an issue… not sure. Willing to explore for sure. Won’t take 5min to check out the CAD model. Would need to address bolt pattern for running gear, etc but that’s the easy part.

HO is half O 1/8 to 1/4" to a foot. so twice as big scale factor is 2

however doesn’t always work because of the track gauge, ; where its rail to rail.

One of my model railroading accomplices that helped with some of my kit parts does O scale, and helped me to understand some of the complexities of O gauge. HO is 1:87 scale, and O is 1:48, but it gets fuzzy from there. The traditional O scale has rails that are closer to scale 5ft apart, whereas a break-away movement, known as Proto 48, has the rail at the correct 4ft 8.5in spacing. For poo’s and giggles, I scaled my original model, (since it was drawn in real dimensions) and scaled to 1:48, cut it in half to fit the build space, and removed some of the details:

It really needs a whole lot more refining. One of the scaling issues is that almost all of the car was drawn up with HO scale in mind, and that set the minimum thicknesses of the sides and details based on the printer capabilities. When I take that same model and scale it larger, the printer can handle those sizes, but it ends up looking “chunky”. If I were to offer an O scale car, I would want to go back and redraw the majority of the model to better reflect the scale. The same problem happens in reverse, with a request I had to take these to N scale (1:160), the model has to be “thickened” up, or the printer cannot print the smaller details reliably.

And herein lies my problem: I have spent a sizable sum of time, resources, and capital to get to this point, and being that I am focused on HO scale for my own hobbies, I chose to chase this project in that direction. (How to you make a small fortune in model railroading? Start with a large fortune! HA HA HA… Errr… Ouch…) I have started putting together kits in HO scale, with the decals and supplies all purchased for that particular scale, and casting my digital model into the wilds for the world doesn’t help me recoup my original project development costs, not yet anyway. I really do appreciate the interest in other scales, but I need to complete my original intent before moving on to other scales. I hope that doesn’t come across as being too crass.

Sorry, as you said the HO is Half O scale, and if HO is 1/87, so O scale is 1/43.5, you can use 1/43. There is a lot material at this scale, you can find in internet. Greetings, Gustavo

no crass interpreted.

No crass interpreted here as well. Sounds like the boat biz… wanna make a million, better start with two! Awesome work on the HO for sure.

Really amazing! Are you sharing this file anywhere or are you keeping it private?

CoreyBonsall I have this car in S Scaled brass - very nice.

I have some extensive experience in making train parts in Solidworks.

I have a Form1 that has not been used in 2 years, and am not sure if I want to try it again. I was wondering if you are interested in doing some printing for me with your Form2. I need some master patterns printed for brass casting

Please reply either way directly to to start the discusstion