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Armor/AFV: Allied - WWII
Armor and ground forces of the Allied forces during World War II.
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Sherman Skink
Pave-Hawk
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Posted: Saturday, September 08, 2012 - 01:32 AM UTC
I happen to like the unusual/ rare varieties of allied tank used during WW2. And a while ago when a conversion came out for the Skink AA version I was quite enamoured with it, but had neither money nor time.

Since I acquired money and time a ways back, the conversion seems to have vanished.

So recently I started work on a slightly different kind of model:



No plastic or glue involved yet . When it's complete I am contemplating getting it CNC machined, or 3D printed. May take me a while though.

PantherF
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Posted: Saturday, September 08, 2012 - 01:42 AM UTC

Quoted Text

I happen to like the unusual/ rare varieties of allied tank used during WW2.






I am the same way Iain as I don't fancy the usual Tiger this version, Tiger that version.

The Skink has always been one I thought was a great Sherman Prototype!

Keep going on it!






~ Jeff
Pave-Hawk
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Posted: Saturday, September 08, 2012 - 02:51 PM UTC
Will definitely keep going with it.

Currently up to what I suspect will be the hardest part, the gun area. Seems to be very curved in different directions, but it's not immediately obvious for the three view drawings, and there don't seem to be a great many photos of the skink turret in colour.
ericadeane
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Posted: Saturday, September 08, 2012 - 06:18 PM UTC

If you google "skink turret" for images, several come up. Also check out Panzerserra's scratchbuilt turret

Skink Turret 20mm AA Tank

Skink Turret 20mm AA Tank

http://panzerserra.blogspot.com/2011/09/skink-canadian-aa-tank-part-iv.html
Pave-Hawk
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Posted: Sunday, September 09, 2012 - 12:46 AM UTC
Getting closer to the final basic shape.



Will still need quite a bit of tweaking, the roof is much more curved than it should be at the moment.

Hopefully soonish I can start refining the details.
jon_a_its
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Posted: Monday, September 10, 2012 - 04:31 AM UTC
Superb work so far

I see you are using sketchup, something I'm "wrestling" with myself

How did you get the imported drawing to the correct size?

I'm trying to do something similar, I created a shape (aircraft canopy) based on 2 scans of the original, then traced 2 different shapes in Y and Y planes, but these were composed of dot-to dot trace & I can't get this as a solid so I can use this to cookie-cut the correct curves from my solid shape?
Hope that makes sense.

I have used Sketchup to output .Stl files & cnc milled them at Uni (I have some priveleges working here)
I could get this cut for you?
nb non-profit 1 copy each?
tankmodeler
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Posted: Monday, September 10, 2012 - 05:54 AM UTC
Iain,

It's a reasonable start, but I don't think you've quite captured the shape of the bustle at the back of the turretor how the rotor bulges blend (or don't) into the front part of the turret.

If you look at the photos Roy posted, you can see taht theh turret sides slope gently from bottom to top and that the radius if curvature wher ethe sides meet the roof is relatively consistent and relatively small (i.e.tight corners).

In plan (overhead) view, the front of the turret, forward of the transverse centreline, follows the outline of the turret ring, i.e. it round. It's only somewhat aft of that transverse CL that the turret elongates into the bustle.

I have a really good cross section of the turret that I'm going to use when I make a 3D model of the turret. But, for sure, trying to create the intricate and subtle shpaes of a large casting, like this turret, is not easy.

Also, beware of using George's drawing of the Skink turret. I don't think he's captured the bustle area well at all, making it far too broad (at least in the version of the drawing I have). He may have changed it after he & I conversed about this some years ago.

If you need more photos, I have a bunch of the three remaining turrets.

Marcos' model uses George's drawings and, as a consequence, nice as it is, the turret is too fat arsed. The walls are too vertical and therefore the space between the hatches and the side walls is too great. As you can see from the real turret photos, there is almost no flat space around the hatches whereas Marcos' hatches sit on a relatively large flat area.

Not trying to dump on you, just pointing out things so you can capture the intricate shape.

Paul
Pave-Hawk
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Posted: Monday, September 10, 2012 - 03:25 PM UTC

Quoted Text

Superb work so far

I see you are using sketchup, something I'm "wrestling" with myself

How did you get the imported drawing to the correct size?



I am actaully using and old version of solidworks I managed to pickup. I tried sketchup, and found it too simplified to do the complex curves I needed.

The Drawings I am using have a scale indicator on them. So I selected two points on the side view, and measured them.

Then in the drawing I created a line and dimensioned it to the correct size, imported the drawing and then scaled the drawing to fit the line.


Quoted Text

I'm trying to do something similar, I created a shape (aircraft canopy) based on 2 scans of the original, then traced 2 different shapes in Y and Y planes, but these were composed of dot-to dot trace & I can't get this as a solid so I can use this to cookie-cut the correct curves from my solid shape?
Hope that makes sense.



I think I understand what you are saying, and I could probably figure it out after a couple of attempts in solidworks using surfaces, but can't really help with sketchup, sorry.


Quoted Text

I have used Sketchup to output .Stl files & cnc milled them at Uni (I have some priveleges working here)
I could get this cut for you?
nb non-profit 1 copy each?



If you could get it cut that would be awesome. But I really don't know how long it will take for me to finish the design, as I really only have a few hours on weekends where I can dedicate the time it needs.
Pave-Hawk
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Posted: Monday, September 10, 2012 - 03:35 PM UTC

Quoted Text

Iain,

It's a reasonable start, but I don't think you've quite captured the shape of the bustle at the back of the turretor how the rotor bulges blend (or don't) into the front part of the turret.

If you look at the photos Roy posted, you can see taht theh turret sides slope gently from bottom to top and that the radius if curvature wher ethe sides meet the roof is relatively consistent and relatively small (i.e.tight corners).



Yeah, I think I need to create more sections from which to generate the surface to reduce the bulging that the shape currently shows.


Quoted Text

In plan (overhead) view, the front of the turret, forward of the transverse centreline, follows the outline of the turret ring, i.e. it round. It's only somewhat aft of that transverse CL that the turret elongates into the bustle.



At the moment I am using the diagrams from the book "Skink In Candian Service", so My contours are fairly close to those but still need tweaking.


Quoted Text

If you need more photos, I have a bunch of the three remaining turrets.



Any photos you would be willing to provide would be greatly appreciated. While I don't expect I will produce something that is spot on, the closer I can get it to the real thing the happier I will be.


Quoted Text

Not trying to dump on you, just pointing out things so you can capture the intricate shape.
Paul



Constructive criticism is always welcome. Like I said earlier this is just getting the basic overall shape, I know there is a lot of work ahead tweaking all the details and getting the final shape just right.

It's also a challenge because I am only really starting to get my head around modelling complex 3D shapes, and it's my first ever time trying to use 3 view drawings as a basis.
Doesn't help when I really don't know the provenance or accuracy of said drawings, but when it's all you have to go by you do what you can and hope for suggestions and advice that will get you the rest of the way.
Pave-Hawk
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Posted: Friday, September 14, 2012 - 08:33 PM UTC
Additional reworking of the shape going on:



Think I may have bitten off more than I can chew, but determined to get it done.

panzerserra
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Posted: Friday, September 14, 2012 - 11:11 PM UTC
Wow...
Another Skink....

I love this model...

Following....
jon_a_its
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Posted: Sunday, September 16, 2012 - 08:37 PM UTC
looking good, keep going, best way to learn something is to solve real problems, like this!

Wouldn't worry about timescales, you need to learn a totaly different headspace for 3D.
Personally speaking, anything less than a year is a 'speed-build' for me anyway...
Pave-Hawk
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Posted: Sunday, September 16, 2012 - 10:59 PM UTC
Got a little bit of work done on it over the weekend.
Managed to get rid of a lot of the surface wrinkling, and thre some surface thickness on it to get an idea of how it might come out as a hollow 3D printed model.

Side view.



Also did a quick mirror to get an idea of the overall look of the turret rathr than just the one side I was working on.



The final shaping will definitely be done on a physical model. There are bits where I simply cannot for the life of me figure out how to get looking right.
tankmodeler
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Posted: Monday, September 17, 2012 - 02:55 PM UTC

Quoted Text

Think I may have bitten off more than I can chew, but determined to get it done.




Check out the Skink images I uploaded to the same album as the image below:



The shape of the face of the turret where the rotor bulges are is still not quite there. The rotor bulge seems to sit on a flat face. The edges of the bulge don't go out to intersect with the turret wall, but end with a hemispherical shape just short of the walls.

A suggestion I might make from many years of 3D modelling (I'm a mechanical design engineer by trade and have been doing 3D CAD modelling for 12 years) is to get the basic shape of the turret correct first, omitting any radii where any two surfaces meet, like where the walls meet the roof or where the rotor bulges meet the turret face. Put those in only _after_ you get the basic shapes correct. Otherwise you're messing with those details and allowing them to change how you view the model before you get the actual basic shapes correct.

Paul
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Posted: Monday, September 17, 2012 - 03:34 PM UTC

Quoted Text

A suggestion I might make from many years of 3D modelling (I'm a mechanical design engineer by trade and have been doing 3D CAD modelling for 12 years) is to get the basic shape of the turret correct first, omitting any radii where any two surfaces meet, like where the walls meet the roof or where the rotor bulges meet the turret face. Put those in only _after_ you get the basic shapes correct. Otherwise you're messing with those details and allowing them to change how you view the model before you get the actual basic shapes correct.




That seems like really good advice, and I had been contemplating doing something like that, I just really hate having to go back and completely rework things. But it's a learning experience so I shall forge ahead.

I should probably add that it is the gun rotor area that is giving me the most trouble as far as how I should go about modelling it in 3D.
rpas764
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Posted: Monday, September 17, 2012 - 05:06 PM UTC
Does anyone have pics of the inside of the turret for the skink? I know its a long shot, just wondering because I have access to an original skink turret but can't seem to find any interior pics.
tankmodeler
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Posted: Tuesday, September 18, 2012 - 07:46 AM UTC
No real interior photos. But I do have a cross section drawing from Waterloo Manufacturing showing all the interior bits inside the turret. This is not a "Stowage Drawing" but a proper scale layout of everything on the left side of the turret including the gun rotors, sighting hatch, etc.

Unfortunately what I have is four photocopies of a drawing too large to put in the photocopier at Bovington, where the original blueprint lies in their Skink reference document box...

The photocopies overlap, but do contain all the information from the original, it's just a b!tch to stitch it all together properly for measurements, and the like.

I also have the official interior stowage drawing for the Skink, similarly segmented by photocopying.

Bovington has a pretty good package of info on the Skink, including, I seem to remember, an original vehicle operators handbook plus test reports from the testing performed in England before the test vehicle went into combat.

If that's any use to you, I can send you off some scans.

Paul
Pave-Hawk
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Posted: Tuesday, September 18, 2012 - 12:10 PM UTC
Sounds like a fairly comprehensive document.
Now I wish that I had had time to make it to the tank museum while I was in the UK earlier in the year


Quoted Text

The photocopies overlap, but do contain all the information from the original, it's just a b!tch to stitch it all together properly for measurements, and the like.



If you have decent scans of the copies you could try a program like Hugin(?), or Microsoft ICE (free, can't remember off hand what the ICE stands for, Image something), which will do all the compositing together fairly quickly. I have used both for doing photographic panoramas and so long as there is some distinguishable overlap, line drawings shouldn't be too much of a hassle to align.
recceboy
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Posted: Tuesday, September 18, 2012 - 01:17 PM UTC
Iain

Here is a link to my photos of the Skink turret:

http://s87.photobucket.com/albums/k130/ldshrecceboy/?action=view¤t=DSCN1198.jpg&newest=1

If you need more, just ask.

Anthony
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Posted: Tuesday, September 18, 2012 - 04:46 PM UTC
Thanks, I will give it a look over when I get home.

[darn work not letting me access photobucket )
Pave-Hawk
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Posted: Wednesday, September 19, 2012 - 01:17 AM UTC
Here's the design so far. Please ignore the "nose" piece, threw that on there just for an idea of how the model was progressing overall, I know it is far from right :





The Gun rotor area is still not looking like the photos. I have been keeping the 3D model close to the outlines on the drawings I have, and the only way I can see to get that front area even close to correct is to ignore the drawing shape and make the front end much more square in plan view than it currently is.
tankmodeler
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Posted: Wednesday, September 19, 2012 - 07:44 AM UTC
Iain,

One of the problems is that the two rotor bulges don't actually go all the way to the edge of the turret. The top one, especially, stops short and is terminated with a 1/4 sphere shape, kinda like cutting a scuba tank in half lengthwise. That has a radius down to the an angled surface that then runs out into the edge of the turret.

Also, I'm, not sure what you are using to define the side of the turret up near the bulges, but something wonky has definitely happened there to throw off the shape at the outer end of the lower bulge.

Are you doing this all as surfaces? It would probably work better doing it as a solid and then, when everything is finished, shell it out to a rational thickness.

Paul
Pave-Hawk
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Posted: Wednesday, September 19, 2012 - 12:40 PM UTC

Quoted Text



Also, I'm, not sure what you are using to define the side of the turret up near the bulges, but something wonky has definitely happened there to throw off the shape at the outer end of the lower bulge.
Paul



The reason I did that was an experiment. The photos seem to show the lower bulge coming right out to the outer edge of the upper gun gun slot before curving down. So that's what I did, aligning it with the drawing I have. But as you point out it looks wonky, so either the front end needs to be more square, which I think it does looking at the photos, or additionally the upper gun slot needs to be more inboard in relation to where it is shown on the drawing.


Quoted Text

Are you doing this all as surfaces? It would probably work better doing it as a solid and then, when everything is finished, shell it out to a rational thickness.



My first two drawing attempts were actually using solids, but it looked like it was going to be a hell of a lot of work to refine the curvature of the turret.
I have been finding it much easier to tweak and refine the shape using sketch profiles and surfaces.
Pave-Hawk
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Posted: Wednesday, September 19, 2012 - 05:25 PM UTC
I borrowed one of the photos to draw on to try and better highlight where think the differences between my model and the real thing are creeping in.

In blue, is the point where I see the lower gun bulge coming out to before curving down(red arrow) to meet the turret sidewall.


My bringing the lower gun bulge out to that in the model is why it looks rather odd at that point now.
In brown, I have indicated what i believe to be the cause of this, the highlighted area appearing much more square with the upper bulge, before angling in at the lower bulge, than is shown on the drawings I am using.

At this point to get the front area correct, I believe what I will need to do is deviate quite significantly from the drawings and use the TLAR method. (That Looks About Right)
Pave-Hawk
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Posted: Thursday, September 20, 2012 - 07:19 PM UTC
Ok, learning curve getting slightly less steep.
Figured out that I should be modelling the gun bulges as one entity and the hemishpere shape/sidewall blending as another. That way I can tweak the shape to fit without affecting any bits where I am already happy with the general shape.

Spent a few minutes throwing some hatch openings in so I can at least feel that I am making some progress
Slightly alleviated the feeling of 'One step forward, two steps back, giant leap sideways".
 _GOTOTOP