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1:64 coal hopper wagon - thoughts on kit design

Started by Lawrence@NZFinescale, February 25, 2023, 03:08:18 PM

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Bernhard

Very interesting, Lawrence. I will follow closely the construction and explanations.

Bernhard

Peter_T1958

  ;)

Thanks again for your thoughts! And yes, as I have to send my own model to a printing service I have no influence with regard to resin, printer resolution and so on. But I already had to split a lot of parts into subcomponents (as you proposed), this also might be the solution here, I will try to omit the finer details to add them later.

Cheers,Peter
"Simplicity is the ultimate sophistication" -Leonardo Da Vinci-

https://industrial-heritage-in-scale.blogspot.ch/

Lawrence@NZFinescale

In today's installment - Suspension.

Why bother?  Rigid 4 wheeled wagons can be a trick to get perfectly flat and even when that is achieved the track on which they run may not be.  Suspension greatly improves track holding, particularly when running scale flanges.  More than this though, the moving wagon looks better as it appears to have mass and flows around the track rather than bouncing over any imperfections. Suspended wagons also run quite a bit quieter, so it's all benefit for little cost.

The original prototype for the suspension was the first etch I drew myself back in the late '90s.  It wasn't an original idea then, although this implementation is all mine and has evolved a bit over the years.

In principle, the wheel bearing is mounted in a hidden slider that is free to move behind the axleguard.  The slider has an attached leaf spring made from music wire (guitar string).  The spring rate can be adjusted by altering the gauge of the string.  I typically use 0.008" string in 1:64.

The first pic shows the etched slider.  On the left is the etching cut from the fret.  The long tag is looped around and fed through the slots to form the spring retainer (centre).  This looks tricky, but is really easy and very reliable.  I feed the tag through with tweezers and then pull tight with flat jaw pliers.  On the right the wire, and pinpoint bearing have been soldered in and the excess tag trimmed back.  I deliberately make the spacing a little loose so that the fit of the axles can be adjusted using etched spacer washers behind the bearing.

The second image shows the slider assembly in place in the chassis subframe. The turned bearing sits between the horns which are a relaxed sliding fit.

This is possibly the simplest implementation of the suspension method that I've done.  The bearing sits in a void within the cosmetic printed axlebox which is rigid (more on that later).  Different brake/axlebox/spring arrangements have demanded slightly different solutions.  Typically I use a cast axlebox that is soldered to the outside of the slider and moves with the bearing.  I also attach brakes to the sliders so that the brakes move with the wheel and can be close fitted without the need for a large gap.  This wagon has a spring arrangement that doesn't suit my usual approach and isn't fitted with air brakes, hence the simple solution.
Cheers,

Lawrence in NZ
nzfinescale.com

Ray Dunakin

Visit my website to see pics of the rugged and rocky In-ko-pah Railroad!

Ray Dunakin's World

Lawton Maner

You have too much spare time on your hands. 

Peter_T1958

I came across a smilar system in an English forum, when some fear came up, my Narrow gauge tramway loco (somewhere pinned down in this forum  ::)  ) could derail at every slight bump due to its scale flanges. Naturally, I do not have complete peace of mind now, when I read your lines... :D

Seriously: A very clever way of sprung mounted axles indeed, but I should have included that before... Now it's too late to improve and all what remains, is a prayer !!!

Anyway, I will safe this article on my harddisk under «modelling hints»!
"Simplicity is the ultimate sophistication" -Leonardo Da Vinci-

https://industrial-heritage-in-scale.blogspot.ch/

finescalerr

Clever design and masterful execution.

Maybe I should limit myself to simple static models ....

Russ

Lawrence@NZFinescale

Thanks Russ.  But if it is clever and masterful it's by iteration over time.  MkI was not as elegant of as effective.
Cheers,

Lawrence in NZ
nzfinescale.com

finescalerr

Nobody cares how long Michelangelo spent creating the ceiling of the Sistine Chapel; they only care about result. -- Russ

Lawrence@NZFinescale

Quote from: Peter_T1958 on March 01, 2023, 11:29:45 AMAnyway, I will safe this article on my harddisk under «modelling hints»!


I hope it helps!
Cheers,

Lawrence in NZ
nzfinescale.com

Lawrence@NZFinescale

The underframe of this wagon was of timber and a 3D print was a good way to represent this.  As the pic shows, the functional etched parts are largely hidden away within the 1 piece printed part except those areas where the etch conveniently represents the metal of the prototype.

The brass and printed parts can be glued together with CA glue to give a structure with no visible joins to be tidied up.

The handbrake pivot would have been quite vulnerable if only 3D printed, but it is backed up by an etched pivot point. This will allow the operating shaft to be securely soldered in later on and provide a robust assembly.
Cheers,

Lawrence in NZ
nzfinescale.com

Ray Dunakin

Visit my website to see pics of the rugged and rocky In-ko-pah Railroad!

Ray Dunakin's World

Lawrence@NZFinescale

Moving on...

I chose to cast the decks primarily to add weight, but it also allowed the brake hanger and shoe to be included as well as providing a robust mount for the couplings.  I did toy with the idea of pewter, but at the time I didn't have a viable supplier.  The brass is more expensive for production but is a little more convenient to assemble.  Later in life these wagons had plate decks so I could easily do that version if the inclination took me.

I carefully drill and tap M1 to mount the couplers - more on that in a future installment.

Handgrab tails are part of the casting, which is relieved from behind so drilling out is painless.  The handgrabs can then be soldered into place from below using a little spacer jig to ensure consistent height.

Once cleaned up the casings just clip into the etch/print assembly (as shown).  Once I'm happy with the fit, I attach with CA glue and then reinforce with some epoxy.

Cheers,

Lawrence in NZ
nzfinescale.com