3D Printings Achilles Heels

It's also a good example of 'perfection is the enemy of good'. There are lots of mechanisms that are 'close', which means that you can either design a shell/boiler EXACTLY as it was, that fits nothing known, or 'tweak' the dimensions to fit a known mechanism. That was the decision I faced doing the CF7 project; the wheelbase is 'off', but the shell is exactly 6" too long behind the cab to fit the existing Atlas GP7 frame. That's just one example, the various Baldwin shells run into similar issues.

Decades ago John Coots of N Scale of Nevada made 'adapter frames' to fix the 'new' Atlas GP7 (the one with the RS3 chassis with GP7 trucks) that was horribly done on the wheelbase. John made them of solid cast lead, and all you had to do was disassemble the Atlas mechanism and drop the same parts in the new frame. There was one driveshaft extender necessary. Worked great, pulled more, and I had one for decades and decades. The genius of the concept was that you ONLY needed to get the frame, all other manufactured parts dropped in from another model. That's where I'm hoping RP goes for the metal part when the tolerances get there; make adapter frames only. I think its a lot closer than you think.

The trend of modelers to jump on manufacturers for everything from wrong hood latches to fan blades doesn't help, but RP offers alternatives. It's still a creative hobby; compromise is everywhere, and it's up to individuals to decide what they can accept and what they can't. It is frustrating when an RTR model has inexplicable glitches in it that could have just as been easily done right; it's quite another when the manufacturer didn't make phase/road/specific details for all known variations. That's what modeling is all about, and where RP can really, really shine here for all of us as the technology matures.

What would really, really help is developing some kind of online database of known mechanisms and dimensions so that you can choose what you want. You need axle spacing, wheel diameter, frame clearances, etc. of common available mechanisms. Very achievable, particularly to those that can already work comfortably in 3D. Because so many mechanisms really come from the same 'mother ship' in China, the dimensions of things like gears, trucks, bearings, etc. are relatively common, a lot more common than most people realize. They don't want to reinvent the wheel anymore than necessary and a lot of basic parts are very mature; no need to reinvent those. Just concentrate on the frames that fit the existing components.

 

Some 3D-printing patents are set to expire about now, and you better prepare for Wal-Mart to be selling 3D-printers soon. The technology is in its infancy, but some of the higher-end companies are demonstrating fine accuracy and some metal-printing techniques that will be game-changers for hobbyists like us. Also, it has been demonstrated that gearing mechanisms can be printed in-place and assembled by 3D printers, and after cleaning said gearing operates nominally. We may go back to lead weights, but some of those low-tech locos ran as good as a Kato.

If you're miffed that we don't have custom metal chassis yet? Just be a bit patient and appreciate this: Even if we've only got the upper half of some rare loco made so far, we've already got half of that rare loco made so far.

 

Whew for a minute there I thought I would have to hide this from the wife thinking it was about shoes. I for one welcome the available shells that are starting to appear. Finding the mechanisms to put under some can be a bit of a challenge but often can be found in other than American models. Over the years I have wrestled with both shells and mechanisms to come up with some of my stuff.

I watched a program on TV back a few weeks ago that showed the 3D printing of metal items that were done the same basic way the current shells are printed. I think at some point we will be close enough to be able to both print out the mechanism components plus the body shell of about anything that one can come up with the measurements for. One would simply be able to place their order for an NP A-3 or an Alco C-636 and have it hot off the presses in a couple of weeks. I look for the technology to do the chassis part of the equation to be fully on line in about five years.

 

Its always been difficult to find/modify/build mechanisms. Even back in the father nature resin cast days. I applaud the clever people that are making items that were un-thought of just two years ago. No commercial outfit would ever think of doing N scale interurban cars or obscure diesel or electric locomotives and freight cars. At least a nice body shell is a good place to start. After all isn't this model railroading and not model train buying? At least for a while until some new technology comes out ... we still gotta paint our models

Randy

 

love it!....Model railroading...or railroad modeling...as opposed to model train buying!

 

I would agree with the group that there are very many talented guys who can adapt what is available to what is 3d PRINTED. I would venture to say most of us in the hobby do not fall into that group. My eyes and dexterity prohibit me from doing that. Retrofitting existing mechanism is not as easy as other members suggest. If it was I would think they would have a cottage industry business supplying all of us vision challenged folks with all the mechanisms. I throw down my glove and challenge anyone to fill that niche.

 

Exactly, apart from failing eyesight most of us just don't have the knack. If I do more than look at a steam locomotive mechanism it never runs smoothly again, I would contemplate taking up brain surgery before building a steam mechanism from scratch or performing extreme kitbashing of existing ones.

 

As Gifford Pinchot said(do your history research) "where conflicting interests must be reconciled, the question shall always be decided from the standpoint of the greatest good of the greatest number in the long run"

 

It seems to my fairly ignorant (in respects to the topic at hand) self that the real mechanism issue with diesels is the truck. Some folks who know more can correct me, but aren't there really a fairly limited number of trucks used under diesels out there in the real world? How many of those haven't appeared recently on a model? So, if you've got the trucks, you've got the tower, you've got the geartrain, you've got the motor. So the only thing for most diesels will be to craft a new frame and driveshafts. The frame can likely be prototyped from the donor in the first place. Once it's prototyped, limited production/CAD/molds can proceed. Shell is 3D printed, along with driveshaft. Donor drivetrain is identified. Chassis is molded/3dprinted, whatever.

Even if the trucks aren't available, as long as they have the same axle spacing as an available truck, then 3D print the sideframes on the rest of the truck/tower mech is donor. It's only when you get into something wacky that the whole tower need be 3D printed.

Steam is more challenging, of course, but those who are dedicated can design and 3D produce almost everything needed. Sure, and N scale steam kit would also take some dedication to build, but it's certainly doable. I for one look forward to what comes along.

(btw, molding/3D printing frames opens up the door to using much heavier materials for the frames, which can mean better drawbar pull. This is a good thing)

There is, theoretically at least, a business opportunity in designing and producing reliable steam components. How much of an opportunity? Imagine, if you will, model railroading taking off in China and/or India....

 

Take one of my interurban shells, take a tomytec / tomix chassis out of the box, cut the coupler boxes off, slide it under the shell, put it on the track, run it. How can I make it easier than that.

That said it does not apply to all of my interurbans, a few take slightly more work to get correct truck centres.

Take one of my Horizon coach under frames, bolt a kato truck to each end, fit under frame into Horizon coach shell, put on track, haul it.

As a designer the model is no good to the vast majority unless there is an easy solution to completing the model, and to achieve that sometimes compromise has to be made, all my Interurbans are 0.9mm to wide, if I made them an exact scale width then every modeller would need to build a custom chassis, ooops the project has now fallen flat and very few will build them.

 

It appears that the majority of the nay-sayers take issue with custom steam chassis and I can't say that I have a solution for them. As for diesels, Atlas makes a vast number of parts available for repair or custom builds. Atlas has made locomotives which utilize almost all common diesel trucks and most are still available as spare parts, or broken donors on auction sites. Kato too has some parts available in one form or another. Members on this board have created kits available on Shapeways which offer replacement side frames for certain trucks. Frankly, unless it is something completely off the wall like a critter or something huge, the drive train isn't the hard part of building a custom chassis. There may not be an easy solution for those who, for whatever reason, can't do the chopping, etc., needed to build a custom frame but the majority of us could, with a little work and patience, put something together to make a custom diesel chassis to match a 3D printed shell.

I kind of feel like the people who are being hard on this advance in our hobby are looking a gift horse in the mouth. People are working hard and sinking a lot of time into designing these shells and many are making them available to purchase. No one says you have to participate in this new portion of the hobby, if you can't make a current mechanism work or build a new one yourself, don't buy the shell and hope a major manufacturer provides what you want someday... Or maybe I am just being grumpy.

 

The problem is, what happens when that isn't an option? As someone working on Alco locomotives, particularly Canadian MLW models, I'm well aware that there is such a thing as unique axle spacing.

On that note, through the Briggs Models DOFASCO truck kit, we can see that there is definitely demand for "corrective" products that use mass produced donor parts.

 

I've sniffed around a lot of N mechanisms for TT scale application, hunting for wheelbases that suit TT but this principally involves locos that can be regauged to 12mm. Serendipity does occasionally strike, for example, the N C628/630 chassis, with a centre wheel removed and larger NWSL wheels installed, is correct for a TT scale RS1, RS11 and a few other things.

I was looking around for other mechs that the C628/C630 truck could be transplanted into, as this truck scales to 9'4" in TT and that is a common wheelbase, used by most Alco and GE units. However I couldn't find many other candidates.

If such a database were created, it would be handy for me, and I would contribute what I know of N chassis to it.

Ben

 

The future is coming, whether you are ready or not.