Z Scale SW1200

shortpainter Jun 8, 2018

  1. shortpainter

    shortpainter TrainBoard Member

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    Hi,

    I am starting this thread so people can post progress photos and discuss building the SW1200. The first half of the assembly instructions is complete.

    If your interested in acquiring an SW1200, see this post for links to all the needed parts.

    [​IMG]
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  2. ZFRANK

    ZFRANK TrainBoard Member

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    Hi,

    Great looking shell, did you also drill the headlights open to be able to install an optic fiber?
     
  3. shortpainter

    shortpainter TrainBoard Member

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    I have doubts I can drill straight enough by hand without damaging the front of the shell. If I had a drill press, I would try it for sure.
     
  4. Kurt Moose

    Kurt Moose TrainBoard Member

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    I'll be keeping an eye on this thread, that switcher is awesome!! Just what we need in Z!!

    Love how the cab is all open!(y)
     
    Kez likes this.
  5. southernnscale

    southernnscale TrainBoard Supporter

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    On the lights when I do my 3D printing design I place a hole were the light goes as a pilot hole. so the hand drilling is easier! I do this with the bolster pins on the plastic models! I have the two SW I bought and there outstanding! I'm glad you started this post! thanks for posting! I was wondering if you were thinking of doing a B unit SW ? would be cool to have a set of A & B units SW's.
     
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  6. mdvholland

    mdvholland TrainBoard Member

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    Got my handrails in the mail, yesterday. Looking good! Shortys came in last week, time to order from Shapeways. Hope you'll share your proceedings with the switchers...

    Matt
     
  7. shortpainter

    shortpainter TrainBoard Member

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    The good news is that the lights are printed as a dimple shape so they should serve as decent pilot holes. Concerning B units, I'm still trying to figure out how to fit the shorty mechanism into the B unit's body shape. If I can't make a powered version, I'll make a dummy unit in cheap plastic. The shorty really needs help pulling cars so a powered B unit is my preference.
     
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  8. Kez

    Kez TrainBoard Member

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    Any progress on Part 2?

    No pressure.... (y)

    ;)
     
  9. rvn2001

    rvn2001 TrainBoard Member

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    Here's a photo of the parts you'll need to buy to complete the SW1200. You'll also want the couplers of your choice and paint and decals.
     

    Attached Files:

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  10. minzemaennchen

    minzemaennchen TrainBoard Member

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    B-units or better called "calf" have the same hoods as the main switcher ("cow"), but....SW1200 Cow/Calf were never built, offered as TR12, but nobody bought them. All similar looking cow/calf combinations are based on earlier SW7 to SW9. But to be honest, there are hardly any visual differences between SW9 and SW1200, therefore in a model they can go as both...
     
    Last edited: Jun 12, 2018
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  11. shortpainter

    shortpainter TrainBoard Member

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    Some progress, yep. Photos were not cutting it so I decided to go with illustrations instead. I'll be done with the instructions this week. (y)
     
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  12. Loren

    Loren TrainBoard Supporter

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    An understatement Kurt......a switcher has long been needed in Z scale. A shame some 'big' company didn't go ahead and spend the money to do it right in the first place, long ago. I think it would have sold a lot of units.
     
  13. bostonjim

    bostonjim TrainBoard Member

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    Amen, to that. Perhaps Mr. Big will see how much the average z-scaler will spend just to try and build a working switcher. I would like 4-5 for my urban, switching layout. A tip of the hat to all that Shortpainter has done to bring this to us. Cheers, Jim
     
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  14. woodworker19

    woodworker19 TrainBoard Member

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    walkway.jpg shell.jpg frame.jpg I received my shell Monday and it does look good. Spending a little time with it, I have seen a few things that I hope help others. I don’t see any of them being a major concern. I read on the Shapeways website that the brass parts are actually made in a lost wax casting process. The 3D printer is used to make the wax master. Who knew ? Anyways, I’m assuming my findings are related to production tolerances, material shrinkage and warping.

    My first item was on my shell, the front stack was bent slightly. A pair of smooth jaw pliers straightened right up. Next, the front truck attachment was bent slightly. The bend shows in the frame picture. Pliers again to the rescue. Lastly, the walkways on my shell were warped or bowed inboard ~0.030” per side when held against a straight edge. The starting inside dimension of my cab was about 0.425”. I was able to straighten the walkways by clamping the shell to some barstock with a 0.025” cardboard spacer at each end. I then used a pair of small machinists clamps right at the front of the cab to pull the wall outboard. The first picture gives the you idea. It worked well with not damage to the brass surface.

    The second picture gives the inside dimensions of my straightened shell. Now, the third picture is the outside dimensions of the frame. You can see there is about a 0.020” interference between the too. Here’s where I’d like a little advice Rudy. Would you mind sharing the shell and frame dimensions in the two areas? It’ll help me judge my next move. I think the easiest adjustment is to take a file to the frame sides. A couple of strokes per side should take off enough material so that’s the way I’m leaning. It’s possible that I need to spread the sides a bit more too. Clearance for the motor doesn’t seem to be an issue. That’s only 0.275” in diameter.

    Thanks again for all your work. These are going to make great little switchers when finished.
     
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  15. tjdreams

    tjdreams TrainBoard Supporter

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    Woodworker you are spot on with your findings i also received mine last weekend and have come to the same conclusion The chassy is bigger than the opening in the shell + the front truck mount is not straight. It took quite a bit of hand sanding with fine and ultra fine files and sanding sticks to get the rear 1/2 to fit under the cab` but the front truck mount is crooked to the side a little.


    20180610_190258 (Medium).jpg 2018_0610_190626_002 (Medium).jpeg 2018_0610_190643_003 (Medium).jpeg


    The openings for the rear truck mount pin are also too small. They will need to be sanded / filed open. you will need to be very careful doing this as the slots must be perfectly aligned. If they are not straight smooth and square to each other the pin and/or the truck will not pivot freely.
    I will post more pictures later this week

    David
     
  16. southernnscale

    southernnscale TrainBoard Supporter

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    Shapeways says, Your model may shrink about 0.25 mm plus 2.5% after casting and finishing.

    For rings the inner diameter is accurate within +/- 0.1 to 0.15mm. On average, the model shrinks about 2.5% after casting and finishing. We do our best to polish the internal diameter to match your model file.


    Brass
    Copper Alloy (80% Cu, 15% Zn, 5% Tn)

    To create brass products, a plaster mold is poured around a wax print of your product, and then brass is cast into the plaster mold. For products with hollow areas, escape holes are essential for two parts of this process. First, the liquid plaster must be able to enter the hole to fill in the hollow area. Then, once the metal is cast, the escape hole must be large enough to allow removal of the hardened plaster from the hollow area. If escape holes are too small, the hollow area may be completely filled in with metal or plaster.
    A single escape hole at the end of a cavity will not allow material in the corners near the escape hole to fully escape. So we recommend multiple escape holes at both ends of the cavity.

    I found my to measure 0.480 and 0.330 on the inside as places in woodworker19
     
    Last edited: Jun 14, 2018 at 5:05 AM
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  17. Loren

    Loren TrainBoard Supporter

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    Kudos to all you guys working on making this project a success. From all the work being done, it is very evident that to get the best end product, injection casting of plastic as done by AZL and MTL is the best and most accurate way to get precision and detail. Good things take not only time, but great expense.

    We're all looking forward to seeing the end results. Keep up the good work and sharing of info.
     
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  18. shortpainter

    shortpainter TrainBoard Member

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    Hello all,

    I'll address all the above concerns as I have experienced most of these issues. Some of this is covered in the instructions that I am working on (almost done, promise!). First off, the model has been scaled up to account for shrinkage for proper fit with the Shorty parts. Second, the shell can simply be pried open a bit to fit the frame into it. I have ordered four of these models and two of the shells needed to be pried open. No sanding is needed to fit these parts together. The frame may need to be bent back into shape with a pair of pliers, as some of you have mentioned above. Below is an illustration that shows how the frame fits into the shell. Notice that the bottom of the frame is not flush with the bottom of the shell. When pushing the frame into the shell, the shell should come to a stop at the four tabs on the frame. The tabs cab be seen just behind the pilot/steps of the shell in the image. Just keep in mind, if the frame does not fit, pry open the shell until it does. The main walls of the shell(the long hood) are likely bent inward when the parts are put into the tumbler to smooth the surface. Same goes for the frame. I am concerned by the amount of deviation you guys are getting. I'll have to adjust the design to make a stronger frame.


    [​IMG]

    As for the shell being out of shape, I have not experienced crooked walkways or bent coupler mounts. If these problems cannot be fixed with a pliers, it may be necessary to contact Shapeways help desk for a reprint. They need photos for proof so if the print error is big enough to come out in a photo, you should have no problems getting a reprint. Contact help here

    Thank you all for your efforts to support each other. Early adopters are the best!
     
  19. minzemaennchen

    minzemaennchen TrainBoard Member

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    Rudy, who knows how good and repeatable the casting process is at Shapeways. You can have the perfect design and raw model and an ordinary cast is stuffing it up. I wouldn't be too concerned, it's a craftman's kit and not Lego. Thanks for all your work and effort!
     
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  20. woodworker19

    woodworker19 TrainBoard Member

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    I went back to my shell and measured the ID at the very front and rear figuring the radiator and back wall of the cab are going to determine the maximum width that I could achieve without distorting the shell (0.475" at the rear and 0.335" at the front). I fine tuned the width along the inside length and was able to get the gap pretty consistent which dropped my worst interference down to 0.005”. A file easily took care of that at the front and rear. The tapered area just in front of the cab took more finesse than anywhere else. I spent about 45 minutes tweaking the fit. Now the frame slides in easy and I'm not concerned with bending anything when I pull them apart. Might need to revisit that statement once I start getting some paint on pieces. I saw the tabs and their purpose so I was careful not to damage them during my work. Still no major problems on my end. Building is 3/4's of the fun for me.
    If you're considering design adjustments, adding some design clearance in the taper may make future assembly a little easier. That’s a spot that will be sensitive to the unavoidable manufacturing variation. I noticed pads on each end of the frame to locate it along the length inside the shell. For length, my frame fit the shell well. Then there is the taper and flat wall at the front of the cab. The fit there is also trying to locate the frame in the shell. That's too many constraints in my opinion. Food for thought. It would be a bigger problem if this was mass production. At a one off, each one a custom built prototype like this, not such a big deal.
     

    Attached Files:

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