Modeling of the Italian FS-691 steam locomotive wheel. Step-by-step tutorial.

[domad]

Greetings to the Community!

At the suggestion of mario52, I am pleased to share with the vast FreeCad community the tutorial, posted on the Italian forum, for modeling an Italian model FS-691 steam locomotive wheel, as it can very well be applied for other similar modeling.

Below is the translation from Italian (I hope it is clear and understandable).

As anticipated in the previous intervention (https://forum.freecadweb.org/viewtopic. ... 4&start=20), here is (unfortunately with a considerable delay) the work flow that allowed me with FC to model, entirely, the wheel of the FS-691 steam locomotive.

First consideration / reaffirmation: FreeCad is a parametric with excellent functionality, great power and "manageability". He was not at all "intimidated" by the complexity of the modeling and managed to have excellent performance in particular where other sw, with a very high probability, would have failed or otherwise highlighted limits.

To my great surprise I did not have to invent any "alchemy" to obtain a result fairly related to the two available drawings (as far as it was possible to obtain from them) and of undoubted real-visual impact.

There were no particular difficulties in the "forging" of the model, despite the approximately 200 Mb of the construction file. However, it should be pointed out that the modeling of the spoked wheel presupposes a precise chronological order of the various phases of "processing" (planning) in order not to incur in the "refusal / s" of FC in performing certain functions / processes or in having to correct a some phases re-proposing, unfortunately, the topological renaming / redefinition error (which hopefully will be resolved very soon).

The fillet are numerous and of good complexity, resolved by FC, I repeat, with disarming simplicity, showing the great power of the graphic engine it is equipped with (the images speak for themselves).

I would like to point out, addressing FC newbies, that the workflow unequivocally clarifies the difference between a "Part" container / object (marked by the prismatic "L" icon in yellow), which in this case represents the entire wheel of the FS-691 locomotive, and a container / object "Body" (marked by the prismatic "L" icon in blue) intended as a single / monolithic object:

a) the spoked wheel; (single monolithic object)
b) the rim; (single monolithic object)
c) the locking ring and / or shoulder (single monolithic object).

As already mentioned above, given the "heaviness" of the original construction file, I preferred to lighten it by converting the 3D into "* .step" format, re-importing it and inserting all the sketches (grouped) as "sources" of the entire modeling, with which you can , possibly, try your hand at reworking it from scratch (certainly improving it or perhaps adapting it to other similarities).

Find the link at the end of the post.

The object was modeled, obviously for convenience, on a 1: 1 scale.

Appropriately resized, it could be used: for 3D printing, or for serial reproduction for model assembly boxes through the creation of molds for die casting and / or plastic, as well as for the real realization / construction in full size, be it also for forming sand molds.

The steps followed for modeling the spoked wheel are the following:

"PartDesign" workbench

- create a new "Body" object - extrusion (Pad) of the hub shape with eccentric connecting rod;
- additive extrusion (AdditivePipe Sweep) along a path with different profiles of the shape of the peripheral hub rib (the profiling provides one for the hub area in axis and a less accentuated one for the one insistent on the eccentric);
- spacer-shim extrusion (Pad) placed on the rear face of the hub;
- subtractive extrusion (Pocket) central hole of the hub;
- subtractive extrusion (Pocket) eccentric hole of the hub;
- double additive extrusion (AdditiveLoft) along ordered profiles for the generation of the "standard" spoke (the first for the transversal connection of the hub-spoke base connection, the second for the extension towards the external ring-belt);
- double additive extrusion (AdditiveLoft) along different profiles for the generation of the first spoke that begins to insist on the eccentric of the hub;
- double additive extrusion (AdditiveLoft) along different profiles for the generation of the third spoke which insists on the eccentric of the hub;
- double additive extrusion (AdditiveLoft) along different profiles for the generation of the second and more complex spoke that insists between the hub and the eccentric;

i specify that i had to resort to double extrusion as the uniqueness gave completely wrong results.

Once the modeling phase of the non-standard rays is completed, you can move on to the functions of:
- creation of polar pattern (PolarPattern) for standard rays: 120 ° angle and 8 occurrences, angle
120 ° and n. 8 occurrences; (I recommend running the functions separately)
- mirroring function (Mirrored) for non-standard rays, that is, those that start from the eccentric (I recommend performing the functions one at a time);

Completed this phase we will have the complete hub of all 21 spokes.

Before proceeding with the transverse-peripheral jointing: hub -> base of the spoke, it is necessary to cut those spokes that fit on the eccentric balancing mass placed peripherally to the wheel:

- subtractive extrusion (Pocket) of the vaguely sickle shape with which the upper part of the intersecting rays will be cut;

now it is time to model the outer ring (on which the rim will be mounted) and which will intersect the non-sheared spokes of the previous phase;

- solid creation of additive revolution (AdditiveRevolution) with 360 ° angle and axis coinciding with absolute "Y";

we should find the hub complete with: rim holder ring, whole and sheared spokes.

Now you can generate the transverse-peripheral fillet: hub -> base of the spokes

- “Apply a dress-up feauture” (Fillet) function with fillet radius equal to 15 mm;

i recommend to proceed by single beam:

a) since the particular shape of the hub (eccentric) generates differences in the development of the grooves between the spokes, making with a joint that is the same for all it will generate overlaps that will give rise to errors, therefore, operating by single jointing, should it not succeed, it is possible to proceed by trial and error by adjusting the radius value by a few tenths until the desired result is obtained;

b) it avoids overloading the processors and therefore the possible blocks and / or long recalculation times;

before modeling the peripheral eccentric mass (balancing sickle) it is necessary to connect the spokes that intersect the rim holder ring and the same, since for one of them, once the balancing mass has been added, it would then be impossible to operate such function;

- “Apply a dress-up feauture” (Fillet) function with a fillet radius of 38 mm;

now you can model the eccentric balancing mass and proceed with the fillet’s of the relative spokes that intersect it, thus creating the 3 reinforcement ribs (two curves and one straight) between the hub-eccentric and the relative spokes:

- extrusion (Pad) of the sickle shape for 135 mm;

- “Apply a dress-up feauture” (Fillet) function with different fillet radii (35, 37, 38 mm) depending on the radius to be joined;

- solid creation of additive revolution (AdditiveRevolution) with an angle of about 17 ° and axis coinciding with absolute “Y”, for the right reinforcement rib;

- mirroring function (Mirrored) for the creation of the left reinforcement rib;

- extrusion (Pad) of the shape for the creation of the central straight reinforcement rib;

to conclude, the edges of the holes in the hub and the eccentric can be rounded off with the "Chamfer" function with values of 2.5 - 3 mm (or other).

After modeling the wheel, you can move on to that for creating the rim and the locking ring and / or shoulder, taking care to create a new "Body" object for each of them.

It should be noted that to obtain the various shapes / sketches a pre-work-study of construction / proportioning / positioning was carried out using mainly the "Draft" workbench and experimenting the solid result through the "Part" bench, before validation and insert the sketch inside the "Body" structure.

I think I was exhaustive, apologizing for some "obvious" clarifications that for the most (experts) could have been avoided, but not for that "neophyte".

Link “RUOTA_LOCOMOTIVA_FS-691-sketch_costruttivi.FCStd”

http://www.filedropper.com/ruotalocomot ... ostruttivi

Have a nice weekend (covid permitting) and good luck!

[bitacovir]

[freedman]

Very cool.

[domad]

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Thanks for your appreciation!
I hope someone will benefit from it to be able to model with ease!

[LHC]

This is amazing. I've been trying to learn Freecad for months and am making headway but it's slow going. I have downloaded your model in hopes of being able to learn something by looking at how you structured it and the sequence of steps used to create it.

Thanks very much for posting this.

[thschrader]

Wow!
Good work, man.
It is good to see tough people here.
Regards Thomas

[domad]

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Thanks very much for posting this.

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It is good to see tough people here.
Regards Thomas

Good morning to the Community!

Thank you for appreciation! We must always be altruistic this is what makes FreeCad grow and make it great by giving developers a lot of push to make it better and better!

[montyl]

Absolutely beautiful!

And I thought I'd accomplished something building the Hudson http://modelengineeringwebsite.com/Huds ... EET-17.PDF in FreeCAD...

Monty