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tusharpc
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I recently completed the build of a 4-wheel /2-axle tank car denoted TP or TK,
and used extensively to carry petroleum and allied oil products on the Indian Railways.

These were once the workhorse of the majority of the liquid freight on the Indian Railways,
and have only recently been retired for scrap.

The model has primarily been built out of home etched brass,
and few detail parts that were 3D resin-printed.


tusharpc
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The prototype:





The completed model:





tusharpc
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The body is mostly 0.01” (0.254 mm) sheet brass from K&S Metals,
that was etched using a unique masking technique.

A few small high detail parts were produced using a resin 3D printer,
called Elegoo Mars Pro 2, that I’ve recently acquired.



I scoured through several online documents and maintenance manuals,
to define dimensions in HO scale (1:87)

I’m well aware of the HO track gauge and IR prototype broad gauge discrepancy.

But in the interest of compatibility I choose to ignore the track gauge discrepancy,
and focus on the model overall.



Once a few sketches were done, the plans were designed in 2D in Auto-CAD.
 
Most body shapes were flattened to their 2D forms, and then drafted.
eg. the tank rolls out to a flat rectangle.

Small detailed parts like, leaf springs, bearings for the axles and tanker caps,
were also designed and drafted in 3D in Auto-CAD.



Nice Guy Eddie
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Hi Tushar

Good to see you Posting here on Freerails.


Fantastic looking model building & design work.
Great to see your prototype & model photos side by side.

Our dedicated Freerails tankcar fans, are sure to love it !


The very long Page scroll, was caused by the Auto-CAD image in Post-3.
Once in a very rare blue moon, we get an image that appears Posted like that.

Your other 2 Posted JPG photos, as you can see, are both appearing just fine.
It may be how you did it, or the image itself, or maybe an odd connection ?

In any case, we are able to optimize such things, for best presentation.

What was the file format & size of the image, was it a PNG or large Bitmap ?
Have another go at Posting it, we can always move it or erase it if needed.


All the best

Eddie


tusharpc
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Thanks For your prompt reply Eddie.

Not sure what went wrong, but seems it's proper now ?

Looks like the Auto-CAD screenshot is gone,
if you have to, feel free to delete the whole post.

I've learned the hard way to save the text and images offline before posting!

The Auto-CAD image was a screenshot in JPG format (45.5 Kb) similar to the rest.
So I'm confused what caused the issue.

I will try once again. 
I will go ahead and add more pictures, and a write up of the build process.

Thanks, Tushar


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Hi Tushar

It's been rarely, that an image appears as text/characters like that.
So rarely in fact, that we can't say what caused it for certain.

It will probably turn out fine when re-Posted.


Generally speaking, it is good to make multiple Posts anyway,
rather than spending hours, typing it all down in 1 Post,
& then finding your Browser dumps it all !

If a single Post even contains as little as 1 photo & description,
then Pages are kept to a sensible size & load FAST as well.


Freerails is often complimented, on its SPEED in loading Pages,
by many Members, who are still on copper connection Internet.

Not having a zillion needless plugins, Facebook trash & YouTube boxes,
of course helps, seeing trains & not loads of ads. is also a relief !


Posts & new Pages are FREE on Freerails,
& don't even waste paper !


Probably a computer error ?
As they say !

;)

Eddie


tusharpc
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Ha good one!



tusharpc
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Auto-CAD design screenshot.
 




tusharpc
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Build process:

There is now a fork in the build process,
for the majority brass parts,
and the 3D printed parts.

Firstly...


Brass Etching:

Vinyl mask.

Once the 2D design was finalized,
it was exported to small desktop vinyl cutter Silhoutte portrait 2

(This has been extensively spoken about in the Thread: Paper cutting machines.)

The vinyl cutter essentially plots the design,
but instead of ink, uses a blade to slice through an adhesive backed vinyl sheet,
that will act as a kind of mask (similar to masking tape).





tusharpc
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Vinyl is ‘weeded’ to expose the brass that is to be ‘etched’ away’.

Once cut and weeded,
this is transferred to the prepped brass sheet using a ‘transfer paper’.

For prepping the brass sheet is cleaned,
with Isopropyl alcohol and a very high grit sand paper.





This is ‘one side etch’,
therefore the other side is simply covered by the same sheet of vinyl. 

The end goal is to etch away the parts that are not required,
the parts needed remain protected by the vinyl sheet during the etching process.





tusharpc
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Finally the brass sheet is immersed face down in a small bath of ferric chloride (etchant),
hot water is poured in another bath surrounding the etching bath to keep the solution warm,
this speeds up the etching process.

It took me about an hour and a half to etch through the 0.01” brass,
with occasional stirring and moving to ensure no etched away particles remain clinging to the brass.

Areas that require a half etch, for a relief feature or a bend line,
are exposed approx half way through the etch.





tusharpc
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When complete, the sheet is wiped down,
and rinsed in plain water, to stop the etching process.

The remaining vinyl covering the desired brass parts is carefully peeled off with a Xacto blade,
and the brass etch parts are ready for bending.

I’m very happy with the accuracy, sharpness and ease of the brass etch,
using mainly DIY and cheap spares available at home.





Brass parts are then bent based on fold lines (that were half etched).
And parts are soldered together.

I found using solder paste and a hot air solder gun ($45 on Amazon),
work wonders for control and precision.

The gummy/tackiness of the paste, hold small parts slightly,
allowing for a quick hot air solder.










Almostretired
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Thanks, Tushar, for posting this process.

I am familiar with etching circuit boards,
but I never thought to use the process like you did, to "cut" pieces from brass sheet.
Very clever.

I am intrigued by the hot air soldering instrument you used.
So I just spent a few minutes looking at the amazing retailer's website and was confused.
Are these also sold as "hot air reworking stations"?

Would you care to specify the one you are using?


tusharpc
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Almostretired wrote:  
Thanks, Tushar, for posting this process.

I am familiar with etching circuit boards,
but I never thought to use the process like you did, to "cut" pieces from brass sheet.
Very clever.

I am intrigued by the hot air soldering instrument you used.
So I just spent a few minutes looking at the amazing retailer's website and was confused.
Are these also sold as "hot air reworking stations"?

Would you care to specify the one you are using?

 
Thanks @Almostretired

I felt the conventional way of photo resist etching has too many steps,
and involved too many chemicals with several areas that could lead to inaccuracies,
the vinyl mask method leaves most of the precision stuff to the machines,
and just involves the one ferric-chloride chemical.

Besides, the vinyl cuter has multiple other uses as well,
including cutting thin styrene and decals.


Hot air soldering station:

This is what I have: link  This one is $45 as of Feb 15th 2021.
(yes it may be termed as a "reworking station" that works just as well)

It's important to ensure it can reach at least 400F or a bit more; power of 7-900 watts,
and reviews say they have good grounding (for safety).

The kits are good if you don't have any other instruments for soldering,
but just the device is good enough if you have other stuff.

Note

Don't confuse this with a standard hot air gun, available to seal stuff or shrink tubes,
they are cheaper but don't heat up enough for solder.


tusharpc
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3D printed resin parts:

Just like their 2D counterparts, 3D designs were created in Auto-CAD as well,
and exported as .stl files, to a resin 3D printer.

I won’t go into much detail on these here,
as many YouTube videos and online articles cover this well.

It's impressive what this little printer can produce in terms of size and detail,
at pennies worth of material.

Sure it takes a while (3-4 hrs for a print),
but if you compare it with scratchbuilding it yourself, and in large repetitions,
the resin 3D printer wins hands down.





tusharpc
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Final assembly:

Once all the brass parts are soldered,
I use Zap- A-Gap medium CA glue, to attach the resin parts.

Quick coat of primer and we’re done!


I used intermountain 38" semi scale wheels
which are held in place by resin 3D printed bearings (this ensures electric isolation).
 
And Kadee whisker couplers that are held in place by 3D printed draft gearboxes,
and a #2-56 screw (as is tradition)

:old dude:

Next on the agenda is weathering and decaling, but I’m going to leave that for another day.
(I don’t have the decals yet and maybe I will invest in an airbrush for weathering)

Before I splurge on an airbrush, I’ve set a goal,
to have at least 5 different stock cars or locos built in this process,
so I have enough subjects and justification for the sprayer.


Some more build and finished pictures below, enjoy,
and would love your comments and suggestions,
or any ideas that may spark to do this better?

- Tushar


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Almostretired
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Wow, I am truly impressed!
Thank you for sharing.

I see some public libraries are offering 3D printing as a service,
my daughter's library is one of them.

Hoping my library gets on board with it some day, too.


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Hi Tushar  :wave:


Great to see you Posting here on Freerails !  :thumb:


I am the Worlds BIGGEST railway modelling DIY fan.  :P

But when it comes to 'repetition', methods can prevent MADNESS.  :Crazy:


Your DIY home etched-brass, is an awesome way to avoid printed-masks.


It would be really good to see a 'mini-Thread' on the sticky-vinyl material ...

... in the Freerails 'Paper Cutting Machines' Forum.  L:


I have etched electrical PCBs, of copper on glass-fibre backing before ...

... but without using any complex silkscreen-printing or suchlike.


Your results, along with the resin 3D-printing look ACE !  :bow:

I count myself as a 'tankcar fan' as well !!  :java: :cool:


:moose: :moose: :moose: :moose: :moose:


Si.


Kitbash0n30
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Scratchbuilding while taking advantage of non-stereotypical tools and techniques,

cool stuff!




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Related material perhaps of interest.
Just saw this on Flickr.

Cover image is a 4 wheel oil tank wagon.
With an interesting cabinet on the end, which has a pipe to the top of the tank.

https://www.flickr.com/photos/124446949@N06/50983294617/in/feed-124401627-1614367670-1-72157718448359867



India Railways - Railway Gazette India Special - November 1929

The front cover of the Railway Gazette India Special (11 November 1929).
Selected pages from this publication are available as a digital file upon request.

tusharpc
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Hi Si.

Thanks for the kind words.

I will love to start a mini thread on the paper cutting machines,
so others may adopt or benefit.

Now, just to find the time and patience to type it all out.


tusharpc
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Interesting find.

I've seen some variations of these tank cars,
even used for water service.


Kitbash0n30 wrote:  
Related material perhaps of interest.
Just saw this on Flickr.

Cover image is a 4 wheel oil tank wagon.
With an interesting cabinet on the end, which has a pipe to the top of the tank.



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