ESM Hooker 8k Gallon Acid Tank — design thoughts

[bbussey]

Still grappling with some design issues on the acid tank.  Not so much the construction — but rather the amount of effort needed to decorate the model, which is starting to appear to be more challenging than building the thing.  The assembly of components wasn't that difficult to visualize.  The core parts and detail parts, as seen a couple of months back in a thread, will be rapid prototype.  The tank wrapper and dome wrapper will be etched brass, possibly three-step if PPD can become more consistent with the process.  The wrappers will be slightly longer than the core parts, so the end caps and dome top will fit snugly against the wrappers.  The wrappers will be cemented in place, but #00-90 screws also will hold the tank wrapper together while the dome wrapper will inset slightly into the top of the tank to help hold that securely.  The frame will screw to the tank through the bolster holes and through the spacer block in the middle.  The tank straps will be etched out of .002" stainless steel and be applied after the tank is secured to the frame.

The problem comes with applying the two-tone paint job.  The underside of the tank is black, as is the frame and the scale 6'5" wide band around the center.  The remainder of the tank including the entire end caps and the tank straps is Pilolite Mineral Red.  Not exactly an easy masking job, even without the ladders and handrails installed.

I'm leaning toward suggesting painting the wrappers and straps before installation, while still on the fret, and baking them after each color application to harden the paint.  That would allow the parts to be assembled without scratching the paint, as well as having crisp paint separations and making the model more durable to be handled after it is complete.  I already know how to insure the center band is masked to the exact scale width and perfectly centered.  The other parts also would be painted before final assembly.  Seems to be the best option.   Of course, anyone who will use this kit to model a single color prototype won't have to worry about this.
 Thoughts?

Also — MTL National B-1 trucks on this puppy with center (not offset) hole bolsters. 

[Sokramiketes]

The red gets painted first, then masked, then black right?  Are you picturing having to mask all the black area, because that would be hard. But masking the red areas is pretty straight forward.

[bbussey]

Yes, red first would be what I would do. But if the car is assembled, with the free-standing tank straps secured to the frame, it would be difficult to mask the red areas off to paint the black.

[Philip H]

What about a. If decal for each end color matched to a current model paint? Apply it. Seal it. Use the matched paint to do the details? That way the. Lack is all that gets painted.

[bbussey]

I don't know if I would trust Microscale or any decal manufacturer to produce a decal that matches the paint color, particularly when different brands of paint don't always match up. Plus, the convex nature of the ends with railing mounts adds to the difficulty of getting a decal film to lay flat without wrinkles. It would be Easter to paint the ends separately before assembly to the tank body, but in this scenario I don't know (yet) if it is possible to add the ends if the tank body is already secured to the tank frame.

[peteski]

The whole idea of using a blank core, etched brass skin, and separate ends seems like a lot of work to assemble. It seems as if each  modeler who bought the "kit" would be almost scratchbuilding it on their own.  Seems overcomplicated. Why can't you build a master using all those components and have the complete tank bodies cast in resin for the kits?

[bbussey]

It is a craftsman kit after all. 

I don't have a resin contractor available that can do what I want at the price point I want. And the painting/masking issue jumps to front and center. This will be easier to build than the KV Caboose, which I use as the barometer in designing these kits.

[Sokramiketes]

I guess I would just mask off the tank under the strap, spray away, and then come back to hit the strap with a brush. 

[chessie system fan]

That seems a little overly complicated to me too.  If it were me (and just going by your drawing), I would make the underside of the tank separate from the rest of the shell, kind of like how some other N scale tank cars are, so that there wouldn't be any masking on that part at all.  And masking the tank shell will be very easy.  Just paint it red and then mask off the center band.

I do a lot of resin casting and were I to make it there would be four pieces:  The under frame, the underside of the tank, the top 2/3 of the tank and the dome, and the little detail piece at the top of the dome.  I would probably use a single mold for the entire thing depending on the number of castings made.  Assembly would be with one or two screws.  This way is much less work to build (and paint!) and less casting work too.

I do some contract work for other people so I'm kind of curious what your price point is.  Send me a pm.

[Missaberoad]

Likely I'll be painting mine to represent a close enough SHPX 7000 gal car, the hooker scheme is a little flamboyant and I already have a couple Atlas examples...

http://resincarworks.com/images/kit1-01_SHPX7006.jpg

Bryan, will you be making the variation with the platform or without? I'm assuming both from the artwork?

[bbussey]

Likely I'll be painting mine to represent a close enough SHPX 7000 gal car, the hooker scheme is a little flamboyant and I already have a couple Atlas examples...

http://resincarworks.com/images/kit1-01_SHPX7006.jpg

Bryan, will you be making the variation with the platform or without? I'm assuming both from the artwork?

Both variations in the same kit.  It will be possible to represent each of the four Hooker tankcar prototypes.  Of course, other acid tanks also can be represented accurately including the Shippers car, but the decals won't be included.  The trucks will be wrong as well, as only the Hooker tanks ran on National B-1 trucks.  You would have to procure the MTL truck frame of choice on the medium-extended bolster (same truck bolster as used on the B end of the drop-end gondola), as that design is the only one with a centered bolster hole.  Using another manufacturer's trucks could possibly affect the ride height (and coupler height) of the model.

If painting one-color cars, this becomes academic.  This is a problem specific to the Hooker scheme

[bbussey]

That seems a little overly complicated to me too.  If it were me (and just going by your drawing), I would make the underside of the tank separate from the rest of the shell, kind of like how some other N scale tank cars are, so that there wouldn't be any masking on that part at all.  And masking the tank shell will be very easy.  Just paint it red and then mask off the center band.

I do a lot of resin casting and were I to make it there would be four pieces:  The under frame, the underside of the tank, the top 2/3 of the tank and the dome, and the little detail piece at the top of the dome.  I would probably use a single mold for the entire thing depending on the number of castings made.  Assembly would be with one or two screws.  This way is much less work to build (and paint!) and less casting work too.

I do some contract work for other people so I'm kind of curious what your price point is.  Send me a pm.

I'd have to think hard about the design aspect of having a two-part body and having all the parts in alignment.  Very easy to do with the body wrapper on a one-part body, or if cutting tooling for a two-part injection-molded model from a digital solid model.  For a hand-crafted model, not so much.  The shell thickness at the edges also becomes a factor with the resin castings, as opposed to the brass wrapper.  Currently, I compensate for any tolerance fluctuation in the rendering of the rapid prototype parts.  The etched parts are constant, so component assembly is keyed off of them.

The current tank body design isn't difficult to assemble at all.  Everything keys together, with the dome inset into the body to hold the dome wrapper securely and the tank supports over the bolsters screwing into the body to hold the body wrapper securely.  While this isn't going to be the simple press-fit construction that injection-molded tankcars are, the tank body construction will not be time-consuming.  The frame will take more effort.  The painting is the tedious task.  Most likely I will build a pair with one pre-painted and one post-painted to see the pros and cons of each.

[sirenwerks]

Bryan,


OOC, did the car get used at the Tacoma facility too and, if so, will the decals have the Tacoma option, rather than Niagara Falls?

[daniel_leavitt2000]

Most resins are pretty stable, and I have not has any major issues with contraction, especially if the parts are on the same resin sprue in the same batch. Draft angles would help both with demolding and thin walls where the black tank base meets the orange upper tank assembly.

[OldEastRR]

That seems a little overly complicated to me too.  If it were me (and just going by your drawing), I would make the underside of the tank separate from the rest of the shell, kind of like how some other N scale tank cars are, so that there wouldn't be any masking on that part at all.  And masking the tank shell will be very easy.  Just paint it red and then mask off the center band.

I do a lot of resin casting and were I to make it there would be four pieces:  The under frame, the underside of the tank, the top 2/3 of the tank and the dome, and the little detail piece at the top of the dome.  I would probably use a single mold for the entire thing depending on the number of castings made.  Assembly would be with one or two screws.  This way is much less work to build (and paint!) and less casting work too.

Yeah, I agree about the two-part split tank. The AG1 tankers sold in N in the '60s and beyond had the split tank construction. It would make assembly of the kit easier too. Bottom half with frame, tank supports and underrigging, top half with domes, valves, and handrail, then put the pieces together and add the ladders, brake wheel, etc. So you won't be knocking pieces off the top while putting pieces on the bottom during assembly. Or vice versa. And weight easily inserted.