Monday, March 19, 2018

Comparing 3d Printed Models Against Kits of the Past

When I talk about those Hart gondolas I made a while back, I like to highlight how the models represent freight cars that haven’t been done accurately in the past. There’s no resin kits or brass kits for Hart gondolas, let alone for SP's own version. However, combing through old Walthers catalogs will show two Hart gondola kits: the craftsman kits from Silver Streak in the 1960’s, and Train Miniature’s plastic shake-the-box kit from the 1970’s. Both are good for their time, but we can do a lot better in the 2010’s. How much better? I picked up examples of both the Silver Streak and Train Miniature cars at a train show a couple weeks back. Let's compare them against the 3d printed model and see how forty years of technology has helped model building. (Click on any of the photos for a higher resolution version.)

Let’s first look at the Silver Streak kit. For the time, this is a neat kit. It has the underframe trusses from the real car, brake cylinder mounted on the side of the car, and matches the SP cars with 8 spaces between posts on either side. Just like the modernized SP cars, the Silver Streak Car has grab irons on each end supported by a short vertical piece of wood.

However, the kit lacks the car sill and floor you'd see on the real cars. Instead, it has the car side boards going all the way down to the bottom edge of the car. It’s also missing all the door hardware; the real cars had castings at the bottom of each post, but that’s a pretty tiny detail to include. The modeler who built this kit didn’t quite get the bulkheads at the correct location - they should line up with the outer post.

The model’s a little coarse with 6x6 strip wood serving for the top rail and for the posts, but it’s a fair tradeoff for intermediate modelers building their first car. It’s nice to see the board detail on the inside faces of each side. Overall, the car is a bit oversize, with the sides measuring almost five feet high compared to three on the real car.

Here’s the Train Miniature car. Again, it looks like it got inspired by the Southern Pacific cars that would have been seen in the 1930’s and 1940’s… or they just copied the Silver Streak car. The car has the correct eight spaces between posts. The grab irons arrangement doesn't match any of the real cars, though. More importantly, the trusses are pushed out to be even with the sides - definitely not how the real car was built, and a detail that hides one of the neat details of the Hart design. Like the Silver Streak car, Train-Miniature left out the car floor visible on the sides. Again, the car sides are taller than they should be - partially out of scale, and partially fallout from removing the side sill.

And finally, here’s one of my models. I pulled out one of my “original” cars just to highlight the detail. 3d printing gives us a lot of advantages, including the ability to throw in all that detail for the door hinges , the door latch mechanisms on the posts, and the various bolts all over the model. The truss is lighter than the Silver Streak car, we can see the car side frame and floor sticking out beyond the car sides.

Here’s all three from the top: Silver Streak on the left, the Train Miniature, then the 3d printed model. The Silver Streak car did correctly model the sloping hopper. It’s not perfect; this kit shows the hopper as incorrectly extending up along the bulkheads on each end. But I’m pleased to see they included the supports that ran through the hopper, even if they’re not quite at the right location. There’s no detail on the hopper doors, but then that’s a pretty tiny detail.

The Train Miniature kit’s hopper is hidden by the load, but that brake cylinder and brake gear in each end is completely wrong for the car, and misses the fact that those partitions were meant to be removable so the car could be used as a typical gondola.

And finally, for the 3d printed version. We see the braces running through the hopper (with the notch to hold the 4x10 that supports the doors when closed. We see the end bulkheads definitely look removable. On the far end of the car, you also might see the hinged apron that allowed running a plow through all the cars - a detail that wouldn’t be needed on either of the other modernized cars, but does highlight how 3d printing lets us throw all that sort of detail on the car.

Finally, here’s the underside of each car - Silver Streak on the left, mine in the middle, Train-Miniature on the right. This photo highlights how the other two cars are a bit oversized compared with the actual cars. Both Silver Streak and Train Miniature made some parts oversized (like the trusses) and also placed the trusses differently to make the car easier to manufacture. Both also had to lose some of the interesting detail: braces for the trusses, side sills, etc. in order to make an economical and easy to build kit.

All in all, the Silver Streak and Train Miniature kits are fine for both their time and for what they’re intended for. They had to design parts to be manufacturable. Train-Miniature moved the trusses out to the car edges so they could be injection molded in one piece. Silver Streak made the trusses thicker to survive manufacturing and clumsy fingers, and left off detail on the hopper so the fiddly shape could be made in cardstock. Both kits needed oversized parts for easier assembly, dropped details to keep part counts low or permit injection molding, and did the best they could from the photos and plans they could find.

The 3d printed model gets to benefit from being 30 years in the future. I had access to the SP blueprints which the earlier manufacturers may not have had. 3d printing meant I could make parts closer to scale, and could easily add details and embossing that would have fouled up molds and part ejection. 3d printing also allowed me to refine the models, and quickly make variants: doors up vs. doors down, or the modernized cars without the side dump doors. If I found some railroad back east had a similar car but with a minor tweak, I could make that too. That's a luxury that anyone doing injection molding doesn't have. Cutting a new mold is an expensive, start-from-square-one sort of action. Anyone trying to run a business would want to cut those molds once, and getting a detail wrong isn't enough of a reason. Doing a different model requires a different set of molds; again it isn't worth doing unless you're going to sell a ton of the new design.

All three models also show how model building's changed. Silver Streak's kit dates from the craftsman kit era, and a time when you could run a reasonable model railroad manufacturer out of your garage. As long as you could cast white metal and cut strip wood, you could sell a model railroad kit. Because of the lack of good models, if you had an even partially realistic model, you'd have a hit. Train Miniature dates from the heyday of small-scale plastic kit manufacturers. You need a lot more skill and equipment to make injection molded parts, and even more to print the car sides. Worse, the effort needed to cut those molds meant you had to sell thousands of cars - great for a forty foot boxcar, but not so good for an odd misfit maintenance-of-way car.

3d printing gets us back to those garage days. My Hart gondolas were, after all, made in a garage. (Or at least I wash the extra resin off the printed models in the garage; the printer stays inside to stay away from dust and cold.) And yet the models still have some pretty impressive detail - approaching resin kits, but certainly better than the kits we saw in the 60's and 70's. We'll see more 3d printed models like these in the coming years, and it'll be great to see the prototypes that folks find interesting enough to manufacture in their garages.

In case you'd like a Hart gondola for your Southern Pacific, Union Pacific, or Pacific Electric layout, I've still got 3d printed kits available. Check out photos, prices, and ordering details over at Dry Creek Models site.