Machine Shop / Locomotive Drive Work

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Jay Criswell
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Re: Machine Shop / Locomotive Drive Work

Postby Jay Criswell » Sat Aug 01, 2020 11:07 am

Bob,

Maybe I shouldn't mentioned anything about them. From here I'll let Jim speak for himself.

Jay

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big bad jim
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Re: Machine Shop / Locomotive Drive Work

Postby big bad jim » Sat Aug 01, 2020 4:05 pm

No worries Jay, it's not like it's top secret or anything.

Bob, the flexicoils are a very slowly burning project in comcert with my sw1500 kitbash (another slow burn project, yes, it's a trend). In short, I needed flexicoil switcher trucks for my sw1500, and while Atlas offers a set of sideframes, they are sorely lacking. Being a bit obsessive about things, as you may recall from your Erie Built nose art, I decided I could do better. So I gathered up resources and created a 3d cad model that ultimately can be used to produce a physical model in 1:48.

The kitbash is based on trucks and drivetrain from the Atlas sw8/9/1200 models. They are known to run well, and everything would be a drop-in solution including p48 geared wheelsets, Howeever, the existing Atlas flexicoil sideframes suffer from the typical compromises to facilitate mass production, like lack of depth or lack of definition due to mold parting requirements. They also are kludged a bit from the prototype so that they can mount to the gearbox in the same manner and to the same attachment points as the AAR Type A sideframes. Lastly, while not specific to the Atlas trucks, there is a lot of missing detail in the area immediately behind the frame, including the bolster and also much of the brake linkages.

The goal was to fix any and all issues by creating a highly accurate model myself, and I will say that the final result is pretty much dead nuts to the prototype. The only things really missing are the traction motors and their mounting lugs on the frame. I didn't bother with those at the moment since the existing Atlas gearbox would take the place of them. If I ever wanted a model with individual gearboxes, like Jay uses, I would definitely consider working up a 3d model with the gearbox rendered as a traction motor housing. That's a bridge I've not gotten to yet, although such a gearbox would be viable for any EMD truck. The only other compromise is that the springs will all be castings rather than live springs, and the journals will be fixed, because A) I don't especially care about sprung trucks, and B) the journals aren't axle bearing anyway. The whole sideframe is just along for the ride in this case.

I've also added the pickup mounts to match the Atlas gearbox, they are intended to accept a strip of phosphor bronze similar to what Rod Miller offers, plus a terminal lug for the motor lead.

Some pictures should help to illustrate what I've done. The board limit has been reached, of course. Let me see if I can load them from Flickr.

Imageflex-assembly-001 by Big Train James, on Flickr

Imageflex-assembly-002 by Big Train James, on Flickr

Imageflex-assembly-003 by Big Train James, on Flickr

Imageflex-assembly-004 by Big Train James, on Flickr

Imageflex-assembly-005 by Big Train James, on Flickr

That was easier than I expected. The images are hosted from my Flickr account. The link to embed them here was a simple cut and paste exercise. You can click on the images to enlarge them, I chose the 800 pixel width, a larger version might read better. In the future I will test the larger format images to see if they fit here properly.

If you have any questions, ask away.
Jim

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ScaleCraft
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Re: Machine Shop / Locomotive Drive Work

Postby ScaleCraft » Sat Aug 01, 2020 4:10 pm

Bob- There's your flexicoils.
Dave....collector, restorer, and operator of the finest doorstops

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big bad jim
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Re: Machine Shop / Locomotive Drive Work

Postby big bad jim » Sat Aug 01, 2020 4:31 pm

The Atlas version....

Imagewt-atlas flex-002 by Big Train James, on Flickr

Imagewt-atlas flex-001 by Big Train James, on Flickr

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big bad jim
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Re: Machine Shop / Locomotive Drive Work

Postby big bad jim » Sat Aug 01, 2020 4:40 pm

And a 3d test print from Shapeways....

Imagewt-flex-001 by Big Train James, on Flickr

Imagewt-flex-013 by Big Train James, on Flickr

Imagewt-flex-014 by Big Train James, on Flickr

Imagewt-flex-010 by Big Train James, on Flickr

Imagewt-flex-005 by Big Train James, on Flickr

This is fun! I can post lots of photos without feeling guilty for hogging the board space.

The Shapeways prints are fine, but for a production print I would source better technology. They are however a good indication that fine elements like the lettering will render fairly successfully, and they also indicate that the 3d models fit the real Atlas gearbox as intended.

bob turner
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Re: Machine Shop / Locomotive Drive Work

Postby bob turner » Sat Aug 01, 2020 6:43 pm

I see what you mean about Atlas. Not knowing much about Shapeways, can these be done in something that could be "burned out" inside an investment? Wax, for instance, or a clean burning plastic?

Beautiful work, by the way.

bob turner
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Re: Machine Shop / Locomotive Drive Work

Postby bob turner » Sat Aug 01, 2020 6:48 pm

Oh - and I am an old-time user of Flickr. I should take the time to figure them out. I knew how th do Photobucket before they went all fancy on me, and joined Shutterfly, but just havent been motivated to follow all the helpful hints you guys have so generously provided.

Too busy flying and soldering, I guess.

Jay Criswell
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Re: Machine Shop / Locomotive Drive Work

Postby Jay Criswell » Sat Aug 01, 2020 9:52 pm

Bob,

Not to answer for Jim but, yes, we do it all the time. Just not with Shapeways.

Jim,

Going back to the model in question. I thought it was a 1500 but was told it was a 1200. I shrugged and said, whatever. Turns out, yep, 1500 it is.

Jay

bob turner
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Re: Machine Shop / Locomotive Drive Work

Postby bob turner » Sat Aug 01, 2020 10:25 pm

I wouldn't know an NW-2 from an SW1500, but I do know I want a pair of Flexicoils for a switcher. I just got the orange paint for my "Larry's Trucking" paint job, and will surely someday put Flexicoils under it.

One of my NW2s has cast bronze "Blunt" trucks. Quite happy with the appearance. Would not be at all happy with Atlas Flexicoils.

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big bad jim
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Re: Machine Shop / Locomotive Drive Work

Postby big bad jim » Sat Aug 01, 2020 10:44 pm

Patterns can be 3d printed, or they can be CNC machined, but Shapeways isn't the vendor for the task. I haven't used them in a short while, but unless something has changed, they don't print with a combination of technology (resin printer versus fused deposition) and resin that can be burned out cleanly. Their Fine Ultra Detail (FUD) and Fine Extreme Detail (FXD) resins that most modelers use for prints are definitely not suitable for burnout. They do print in ABS, which I believe can be burned out, but that's done with fused deposition modeling (commonly known as FDM), which doesn't offer the resolution level we need. Shapeways also offers "printing" in brass, but it's really just investment casting. They print a pattern in wax and burn it out, just like any casting vendor would do. They used to offer wax printing for retail, but went strictly in-house with that several years ago. Wax prints are pretty fragile, and I understand that the loss level on shipped wax prints was too high for it to be practical.

So clearly there are 3d printers which print in wax, custom jewelers have used them for years, although the process isn't limited only to jewelry. Solidscape is probably the most common printer manufacturer for this technology. Actually the Solidscape printer is a hybrid of sorts, it both lays down a bead of molten wax - the printing part - and then machines the newest surface with a mill cutter. This process thins each layer, which will increase resolution, but it also eliminates the tiny valley that is created by placing two round beads of wax next to each other. The surface is made flat and homogeneous before the next layer of wax is added. 3d wax prints made in this manner could be taken straight to the investment process without post processing, which can be critical for highly detailed parts where polishing or smoothing can soften or eliminate edges or details.

There is also a process where high rpm CNC mills are used in conjunction with miniature tooling to machine patterns out of solid blocks of wax. I've been told that this method actually yields better resolution compared to printing, and my experience is that this is true in some instances. However, the theoretical advantage of milling versus printing, which is the improvement in layer resolution and therefor surface finish (it's a solid block, there were never any layers to begin with), isn't significant enough in my opinion to be distinct. I did however feel that some of the features, like embossed lettering, was more crisply rendered by milling.

Of course there are the same limitations to machining a wax pattern as with machining anything, meaning undercuts and cavities, or sharp inside comers. A hollow part like the Flexicoil casting could be successfully printed as a closed section, but could never be milled that way. So I think choice of methodology would depend on the type and complexity of a part and which of its features are most critical. Or it may just depend on required lead time, and one machine is available right now while the other is already booked for the next week. An old rule of thumb for machining, always do it this way, unless you can't, then do it some other way.

So that's the process with wax as the medium. There are also resins which can be 3d printed and burned out cleanly in the same way that wax is. They are frequently being used with the consumerist (that's people like us) level printers that are improving continuously to the point where many are quite competitive with the Solidscape printers with regard to resolution. One caveat when using resins rather than wax, is that the times and temperatures for full burnout are often longer than required for wax. So the procedure is different from the norm that casters have used for ages, some of those casters ignore or balk at utilizing the proper procedures for a specific material, and consequently the parts fail. But if the process is followed as specified, resin patterns can be burned out with the same success as traditional wax patterns.

The bottom line is that if you have the 3d cad model, then you can produce the patterns in wax or a clean burning resin. The advantage is in accuracy, complexity, and repeatability. Plus there's a safety factor of sorts. If the pattern is somehow damaged in the burnout process, print a new one. If the mold wears out after a while or gets damaged, print a new pattern and make a new mold. The other big advantage which can not be oversold, is making adjustments to a pattern to dial in the shrink percentage. It's a lot simpler with a 3d cad model.
Last edited by big bad jim on Sat Aug 01, 2020 11:05 pm, edited 1 time in total.

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big bad jim
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Re: Machine Shop / Locomotive Drive Work

Postby big bad jim » Sat Aug 01, 2020 11:01 pm

Yeah, I could have said it was a 1500, but I didn't want to be argumentative. The fuel tank gives it away. Pretty sure this model was also "presented" to me at the Chicago show, GN Big Sky Blue paint if I recall. Anyhoo, the sw1200's have an odd tank, where the bottom of it wraps under the shorter fatter air reservoirs, with a bunch of piping running around. The sw1000 and sw1500 , and the mp15 variants, all have the EMD 2nd generation fuel tank profile and the 13' long air tanks that are standard up to the sd90's. Caveats are that the late sw's could be ordered with 600 gallon tanks, which were rectangular and similar to the early switchers although I've never seen one like that, and I believe starting with the 60 series locos, the modern fuel tank profile changed slightly to have a flatter top and taller side.

Bob, one alternative to consider is the ex-Keil-Line, currently Scale City Designs Flexicoil truck kit.

http://scalecitydesigns.com/48-099-flex ... keil-line/

I think they are a white metal kit, they're not bad but could use some clean up like opening out the holes in the frame. I think they are intended to be sprung trucks, with axle bearing. I think Jay had a set pass through his hands, he may be able to comment on them.

They will be quite a bit cheaper than anything I ever get made, even if I have molds made to produce extras.

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big bad jim
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Re: Machine Shop / Locomotive Drive Work

Postby big bad jim » Sat Aug 01, 2020 11:10 pm

Can't help but take note and be amused. Jay - short and to the point. Me - never shuts up.

Jay Criswell
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Re: Machine Shop / Locomotive Drive Work

Postby Jay Criswell » Sun Aug 02, 2020 10:51 am

Jim,

Totally opposite when we're talking in person. Strange.

Anyway, I posted a little blurb on the SW.

https://www.facebook.com/Right-O-Way-235082016964918/

Jay

E7
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Re: Machine Shop / Locomotive Drive Work

Postby E7 » Sun Aug 02, 2020 8:45 pm

big bad jim wrote:Can't help but take note and be amused. Jay - short and to the point. Me - never shuts up.


Jim, It is ALL very interesting! Thank you! I wish I had your expertise.

Rich
"We have met the enemy and he is us!" Pogo Possum

Chris Webster
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Re: Machine Shop / Locomotive Drive Work

Postby Chris Webster » Sun Aug 02, 2020 9:49 pm

Jay Criswell wrote:Anyway, I posted a little blurb on the SW.

https://www.facebook.com/Right-O-Way-235082016964918/
Jay, I'm curious why you used Weaver-style chains instead of belts -- are belts not available in the size you needed?


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