PRR K7a Stock Car build

[Lemosteam]

I finally finished one of my own full Shapeways kit offerings.  The kit utilizes the etched fret from the coming X23, and has full decals.

It is a complex kit to build, but only possible due to the Shapeways printing process.  I was never able to achieve clean board gaps (@peteski) using my printer, not sure if a DLP would work either.

Here it is after cleaning, building, painting, and decaling:

[bbussey]

A DLP definitely could print it.

[peteski]

A DLP definitely could print it.

But it might not be dimensionally accurate.   

But seriously John, that car looks quite good, especially with the photoetched bits. The board gaps on the ends also look quite good.  But is there some "fuzz" leftover under the paint on the end surfaces?

[Lemosteam]

@peteski Thanks, Yeah, I could have sanded it, but boards get rough over time. This was also printed in FXD before their latest material which supposedly (per SW) does not have this effect.

@bbussey , I'll send you the file  ?  Maybe that will convince me to buy one.  Where you gonna hide all of the support attachments?

[thomasjmdavis]

Quote from the N Scale New York Times, March 7, 1923:

Customers and shippers alike are relieved to see that the PRR has moved on from that strange notion they had of building solid sided stock cars with internal oxygen tanks for stock transport. Up until now, the vast majority of the cattle and hogs moving east of Chicago had to go in NYC Despatch cars- which are much more economical than the existing PRR cars, given the cost of the oxygen supply.  Insurance companies are also relieved, as the enclosed PRR cars also were more prone to fire or explosion due to the build up of methane in the enclosed cars. PRR stock rose 3.5% in early trading.

[thomasjmdavis]

Seriously, John, that car looks great, especially given that on my screen, the photos show it well over 3 times actual size. Great job!

[Lemosteam]

Quote from the N Scale New York Times, March 7, 1923:

Thanks Thomas.

Interesting. The quote doesn't mention a PRR class.  The K7/K7a was built in 1914 as a open sided car.  The K9 class was an X32 converted with holes in the sides after the PRR took 500 obsolete automobile carriers and converted them.

More here: https://www.trainorders.com/discussion/read.php?11,4254856

K7a


K9

[mark.hinds]

Nice job overall. 

Not being an expert on the prototype, was wondering why the kit doesn't use a stock truck assembly, such as Micro-Trains.  The truck side frames look kind of bulky, in the end views. 

MH

EDIT:  the website model160.com (which I can't find any more) used to have a page showing detailed images of all commercially available trucks. 

[mmagliaro]

Well, Shapeways "fuzz" notwithstanding, I think it looks great.  Yes, I immediately noticed the "fuzz" on the end shots, but heck, remember we are looking at this car magnified way beyond where human eyes would see that.  High marks for the nice clean open slatted look on the sides.  One thing I *did* notice, since you posted that photo of a real K7a, was that the board/slat pattern on your car is not the same as the prototype.  The wide boards where the "PENNSYLVANIA" appear are wider on the prototype, and you seem to have a wide board across the top that is not in that prototype photo.  Where there variations to these cars with different board widths in real life?

[thomasjmdavis]

Thanks Thomas.

Interesting. The quote doesn't mention a PRR class.  The K7/K7a was built in 1914 as a open sided car.  The K9 class was an X32 converted with holes in the sides after the PRR took 500 obsolete automobile carriers and converted them.

Well, when I made up the quote, I didn't have my magnifier adjusted to read the date on the N Scale NY Times.  And the prototype for the N Scale Despatch car is 1940s, IIRC (rebuilt from old boxcars). Just having a little fun at BLI's expense. 

The 'news article' should have included the other major feature of the K7 with slats- they are so much quieter than the solid sided cars.

[Lemosteam]

Nice job overall. 

Not being an expert on the prototype, was wondering why the kit doesn't use a stock truck assembly, such as Micro-Trains.  The truck side frames look kind of bulky, in the end views. 

MH

EDIT:  the website model160.com (which I can't find any more) used to have a page showing detailed images of all commercially available trucks.

Hi Mark, no one sells this truck directly but me and it is THE standard for almost all PRR designs using this chassis. PRR classes K7 & K8 (livestock), R7 (refrigerated product), X23 (goods boxcar) etc., used this specific PRR class 2D-F12 truck.

The proto trucks have long bearings; you’re just used to squashed sideframes which are low relief for clearance and axle length.  I designed these to the PRR drawings (with N Scale compromise, of course).

Here is an end view of the car. Note the length of the journal, and the proximity of the grease door relative to the side plane of the car. 3D printed trucks allow for that look, where multi-slide injection molds may not.

That said, the journal boxes have to be a little bulky to allow for the generous 60 degree tapered pockets on the inside of the frame that allow for axle point insertion and running clearance. This is the lot of N Scale design. Almost all dimensions must be compromised in some way to allow the car to function, be manufactured, etc.

True N Scale fidelity (read reliability, or durability) is impossible, I’m afraid. But it can come pretty close.

[Lemosteam]

Well, Shapeways "fuzz" notwithstanding, I think it looks great.  Yes, I immediately noticed the "fuzz" on the end shots, but heck, remember we are looking at this car magnified way beyond where human eyes would see that.  High marks for the nice clean open slatted look on the sides.  One thing I *did* notice, since you posted that photo of a real K7a, was that the board/slat pattern on your car is not the same as the prototype.  The wide boards where the "PENNSYLVANIA" appear are wider on the prototype, and you seem to have a wide board across the top that is not in that prototype photo.  Where there variations to these cars with different board widths in real life?

Max, just to print the the gap, which is about minimum to print, is 0.25mm so adding up the gaps you end up losing one 4” board to maintain the closest roof height from the rails, and having to get a reasonable proportion it is what it is. There is a board at the top, but the groove is minuscule at 0.1mm and so disappears under paint. There is also a groove at the floor height outside.

See my response to Mark as well.

[Lemosteam]

Well, when I made up the quote, I didn't have my magnifier adjusted to read the date on the N Scale NY Times.  And the prototype for the N Scale Despatch car is 1940s, IIRC (rebuilt from old boxcars). Just having a little fun at BLI's expense. 

The 'news article' should have included the other major feature of the K7 with slats- they are so much quieter than the solid sided cars.

Ha! That went fight over my head and parted my hair!

[bbussey]

@peteski Thanks, Yeah, I could have sanded it, but boards get rough over time. This was also printed in FXD before their latest material which supposedly (per SW) does not have this effect.

@bbussey , I'll send you the file  ?  Maybe that will convince me to buy one.  Where you gonna hide all of the support attachments?

1) Yes, you should buy one and stop using SW;
2) I'd have to see the STL, and then I can tell you.  It appears in the photos that the roof is separate from the body.  So my first inclination is that I would support the body upside down at a 44 degree angle.  The roof would be either upright or on its side, also at a 44 degree angle.  I use .20mm diameter supports at point of contact so they basically are non-existent and require little clean-up after removing.  No FXD post fuzz either.

The latest SW tan material has its pros and cons just like the ProJet stuff.  Just a different set of issues to circumvent, as opposed to being a better option than ProJet FXD.

[Lemosteam]

1) Yes, you should buy one and stop using SW;
2) I'd have to see the STL, and then I can tell you.  It appears in the photos that the roof is separate from the body.  So my first inclination is that I would support the body upside down at a 44 degree angle.  The roof would be either upright or on its side, also at a 44 degree angle.  I use .20mm diameter supports at point of contact so they basically are non-existent and require little clean-up after removing.  No FXD post fuzz either.

The latest SW tan material has its pros and cons just like the ProJet stuff.  Just a different set of issues to circumvent, as opposed to being a better option than ProJet FXD.

Hi Bryan, love your confidence! I'll send some stl files to you.  I'll reimburse you for your print, if you are willing.

I don't care for the SW tan, the clear is much better now than that and the old FXD. The two materials are just new Projet material iterations.

Have you done any accuracy studies to verify against CAD?

The print volume is not there yet for me and the things I want to print and I want to be convinced of its accuracy, and I still don't like the resin mess.