When Is True Scale Too Small For HO or N Scale

[regme]

Hi

 

I'm currently modelling a re-fuelling building followed closely by an ore wagon, using structural steel components, which I'll modelling is true scale and scale it down to HO. 

 

When does the scale become too small to either print or be structurally sound.  I must add I do not have a printer yet, this would influence the type of printer I should go for from a resolution point of view.

 

So for example I need to use a 150UB member the flange thickness are 9.5 and 6mm, so at HO scale that's 0.11mm and 0.069mm.  Say the thickness of the wagon side is 20mm thick plate, that makes it 0.23mm for HO.

 

This seems a bit flimsy, or would you beef it up to say 1mm thick to give it some strength?

 

Cheers

[Mark Saunders]

If it looks right that that will do!

 

If unsure put it back on the workbench and go make a cup of tea and have another look!

 

 

[MGR Hooper!]

5 hours ago, regme said:

Hi

 

I'm currently modelling a re-fuelling building followed closely by an ore wagon, using structural steel components, which I'll modelling is true scale and scale it down to HO. 

 

When does the scale become too small to either print or be structurally sound.  I must add I do not have a printer yet, this would influence the type of printer I should go for from a resolution point of view.

 

So for example I need to use a 150UB member the flange thickness are 9.5 and 6mm, so at HO scale that's 0.11mm and 0.069mm.  Say the thickness of the wagon side is 20mm thick plate, that makes it 0.23mm for HO.

 

This seems a bit flimsy, or would you beef it up to say 1mm thick to give it some strength?

 

Cheers

If you want any models, be it static or working, I'd say any wall thickness should be a minimum of 0.8mm to 1.0mm thick. An then you build up all the raise detial on that like bracing, rivets, latches etc.

[regme]

Thanks, that puts it into perspective.

[andrewnummelin]

If you intend to use 3D printing then the minimum part thickness will be determined by the characteristics of the printer and the material used in it.

 

If you scale down a metal object, and make it in the same material as the prototype, a scaled down thickness will have more than enough mechanical strength for prototype use. One may have to increase the thickness to allow for the well out of scale forces imposed by squeezing between your fingers to pick it up.

Your suggestion of 20mm thick plates for a wagon side sounds excessive to me - I believe GWR steel sided wagons were from 3/16" sheet (~5mm or 0.06mm in 4mm scale).

When modelling locos in 4mm scale I'd tend to use 8thou metal (0.2mm so a scale 0.6"), but for a wagon I'd use 5thou.

[Siberian Snooper]

A lot of ships sides are only 10mm on a good day,  I have seen them worn / corroded to 2mm or less, when they have been cut out to allow a shipping route for machinery replacement or renewal. Wagon sides should have a structural stiffening to probably be only 6mm thick unless subject to mechanical wear.

 

I use 10 thou plasticard for coach bodies laminated below the window line to allow for handling, additional stiffening coming from compartment bulkheads.

 

Have a look at Ron Heggs thread Manchester Central,  sorry no link,  but he does some amazing structural engineering in plastic strip mostly 10 thou thick.

 

 

[regme]

I only mentioned 20mm because I measured a HO ore wagon side and scaled it up, maybe the wagons you buy are not strictly prototype.  As Andrew said scaling down in the same material should have roughly the same strength but changing the material type may have a bearing on this.  I've since found out that the wagon sides are only 5mm thick (just looks small for a 40tonne car).

 

May its be a matter of printing at the scaled thickness and seeing how it goes and change it where some added strength is required.

 

I checked out that Manchester Central thread, very impressive.  Went to my layout looked at my shed that I built, think I'll take it out the back and torch it

 

I have much to learn

Edited July 15, 2019 by regme

[JimFin]

On 14/07/2019 at 00:26, regme said:

I'm currently modelling a re-fuelling building followed closely by an ore wagon, using structural steel components, which I'll modelling is true scale and scale it down to HO. 

 

When does the scale become too small to either print or be structurally sound.  I must add I do not have a printer yet, this would influence the type of printer I should go for from a resolution point of view.

 

 

In deciding to model steel based structures, you probable need to choose an SLA printer as the FDM type will leave you with more clearly visible layer lines which need post production sanding to remove. On something like an HO steel hopper, the sheet between the frames would be a nightmare, if not impractical to get a reasonable finish.

 

I would also raise the question though, why would you want to print this? Is it actually the best process and material for your subject? As has been noted, you can do wonders in plasticard with the right approach - on the other hand the thread on Anycubic Photon printing shows what can be done (underframes on P1) and once set up, you can knock out enough for a complete rake. There are pros and cons but do not fall into the trap of thinking 3D printing is the modellers silver bullet.

 

The other factor to consider beyond the printer, is what material you are going to print with as this is an area of increasing choice and complexity which impacts your question re wall thickness e.g. PLA has many variants including engineering grade which will produce different structural outcomes.

 

3D printing is one area where research before jumping in is recommended, including using/developing your 3D modelling skills as well! Wish you all the best and am sure you will find lots of advice and help on this forum.

 

 

 

 

 

 

[regme]

JimFin you bring up some interesting points, I'll be the first to admit that my skills in modelling have a long way to go and anything that will make it easier as well as producing a realistic model is worth considering.

 

From what I've read and seen on this forum there are many different ways and techniques that can be used to build models.  I think in this instance 3D printing may be more applicable due the small detail and shapes I would like to achieve, that my limited modelling experience may not be able to with other techniques.  That said, using styrene beams maybe easier and less expensive than a 3D printer for metal structures.  However it doesn't mean you couldn't use both styrene and 3D printing to model a steel structure or wagon for that matter.

 

From the previous posts, I will be looking at my modelling from different points of view.

 

Regarding the wall thickness, if I put it into perspective a 5mm thick steel plate would equate to only 0.06mm thick in HO, now that's the same thickness as 80gsm paper, food for thought, maybe in a derailment the carnage would look authentic but then you would to build more wagons.

 

 

[regme]

Well the wagon has gotten to the stage that I can print it.  Would it be better to print it in parts or as a completed model.  If I print it complete (resin printer) is it better to orientate  the model so the supports are attached from the underside of the wagon or from within the body of the wagon.

 

The only other issue the height of the coupler, since I haven't designed the bogie, maybe I just buy one and see how it goes first?

 

Cheers

[Marbelup]

Don't expect to be able to print items in scale thickness, e.g. if representing metal prototype parts. The minimum printable thickness very much depends on the type of printer being used. For example, I work on 0.5 mm minimum thickness for small details and 0.8-1.5 mm for main body parts, as these suit I.Materialise SLA print capabilities. (Some small resin printers can print considerably finer, I know.) Strictly speaking, I.Materialise specify 1 mm wall thickness as absolute minimum and I have to take risk/responsibility for anything less. 

For something like a hopper or open wagon, I design the body to true scale dimensions outside then remove the inside to achieve the desired wall thickness. Thus the visible top of the sides is thicker than scale, but the same goes for commercial plastic models. 

Sometimes, I disguise thicker-than-scale parts, e.g. brake gear levers, by bevelling the rear edges so the visible edges appear thinner while the part is still reasonable robust. 

[regme]

I have basically done that also, designed it true scale, scaled it down then thicken the inside to 1mm to retain the detail on the outside.   I've been using the Backmann ore car as a guide for the HO version. 

 

I have to admit there is a lot that goes into this and the worst part is, I know that first print is going to be out on so many levels.