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#1580 by roma847 on 18 Oct, 2018 22:21
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Hello everyone,
the tea was good, and my friend Joe hardworking, who has already uploaded his Main Sprocket model.
Source: shapeways.com (Crackerjazz)
I was a bit scared when I looked at the 3D view and saw that the sprocket is hollow, which was completely new to me,
Source: shapeways.com (Crackerjazz)
especially since the sprockets of other crawler modelers in the Raumcon forum are full and not hollow, which I had in mind.
Source: raumfahrer.net (Sascha1990)
Source: raumfahrer.net (slimgo)
Therefore, I was very skeptical at first and have immediately searched for suitable photos to clarify this. But in my archives I did not find anything at first, because on the normal crawler pictures you can not really see the drive wheels under the chains.
In this photo, I found the first signs of cavities, if one looks closely.
Source: forum.nasaspaceflight.com (AnalogMan)
But here in NSF there is a special Crawler-Transporter thread about the modification of the CT-2 for the mighty launchers of the future Space Launch System (SLS) of NASA, in which I then have indeed found clear evidences.
Source: forum.nasaspaceflight.com (MechTech)
Here to see beautiful in the falling sunlight.
Source: forum.nasaspaceflight.com (sprtnsky)
And here's a Hi-Res look into a drive wheel or through it out, which would also eliminate the last doubts.
Source: forum.nasaspaceflight.com (MechTech)
And so I ordered two sprockets at Shapeways, both in FUD and in FXD in order to be able to test their interaction with the Track shoes.
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#1581 by roma847 on 19 Oct, 2018 07:24
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Good morning folks,
now I also got the corresponding screenshot with the Support Material showing the expected arrangement.
Source: shapeways.com (Crackerjazz)
The big lot of support wax would also explain the relatively high price of the Sprocket, half as much wax would certainly have been enough too, I guess ...
Therefore I also asked my friend Joe, also to upload a model with an upright print orientation of the sprocket. I think that this would require less support material, so the price might be slightly lower.
The side effect thereby is, that the top side should be smooth and the bottom rough, which in turn is important for cleaning.
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#1582 by Lar on 19 Oct, 2018 14:12
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What's the difference between FUD and FXD?
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#1583 by roma847 on 20 Oct, 2018 00:06
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Frosted Ultra Detail (FUD) and Frosted Extreme Detail (FXD) are both made of UV cured acrylic polymer.
While both offer high resolution, FXD uses a 16 micron layer height to produce incredibly fine features, making it a great choice for miniatures, model trains, and products with very fine embossed or engraved details.
Both materials are well suited for painting, and are relatively brittle, especially when features are thin. The material is heat resistant up to 80°C/176°F degrees.
Keep in mind, that Shapeways had changed the materials names:
Smooth Fine Detail Plastic instead of FUD, and Smoothest Fine Detail Plastic instead of FXD.
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#1584 by roma847 on 20 Oct, 2018 00:19
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Hello everyone,
after the first joy Shapeways came up with the next unwelcome surprise and has stated that they can not print the Main Sprocket.
Supposedly they have informed the designer about the problems with the part, but which is a smooth Fake News.
So slowly I start to doubt this club, I can't think of anything more ...
The strange thing is that the shape of the Sprocket is less complex than that of the Track shoes, and the wall thicknesses are all according to specs, as my friend Joe says.
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#1585 by roma847 on 20 Oct, 2018 06:43
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Hi friends,
the SW show goes on ...
After I was first informed on my astonished enquiry that my already well-known SW friend Mitchell Jetten from the Track shoe story would answer me, now came this joke message ... Awesome!!!
This reinforces my impression of SW, that's an case of the right hand not knowing what the left hand's doing ...
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#1586 by roma847 on 20 Oct, 2018 20:45
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Hello everybody,
after my friend Joe had uploaded the upright-standing Sprocket, to see how the Support wax is distributed at this printing orientation, I have ordered both variants (FUD and FXD).
Source: shapeways.com (Crackerjazz)
And this is the distribution of the Support Material which shows that the wheel is quite bizarre wrapped in wax,
Source: shapeways.com (Crackerjazz)
which is why I think that the flat printing orientation might even be more favourable.
Source: shapeways.com (Crackerjazz)
Since at least the top side does not come in contact with the wax, it would remain smooth, and the rougher underside of the wheels would hardly be visible between the truck chains from the outside anyway.
And then I tried the same trick from the Track shoe story again and ordered the sprocket once again in a flat printing orientation come hell or high water, in the hope that this time it might just as well come through the control like the criticized Track Shoe Set in those days, whereby this flat lying sprocket now, strangely enough, is only still offered in FXD.
Now I'm curious how the story ends this time, so keep your fingers crossed!
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#1587 by roma847 on 21 Oct, 2018 17:15
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Hello everyone,
I have at least achieved a partial success, because the upright standing Sprocket variant, which I ordered in FUD and FXD, went through and is meanwhile In Production.
Source: shapeways.com
The again ordered flat lying variant, however, is still under review (Processing), but still not rejected at least. 
No matter how, at least that would prove that the Sprocket is printable, so I have an argument in hand to demand the printing of the flat version as well.
So far there is also still no explanation why this variant could not be printed at the first attempt. So SW is somehow in a tight spot, let's see how it goes out ...
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#1588 by roma847 on 22 Oct, 2018 07:24
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Hello everybody,
this is the reason for SW's rejection what my friend Joe will check now.
Source: shapeways.com (Mitchell Jetten)
That's strange, because that is the same model as for the upright standing sprocket, which is in production. Why can this be produced and the flat lying sprocket not?
That is a contradiction, which SW should explain, whereupon I am curious.
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#1589 by roma847 on 22 Oct, 2018 13:06
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Hello friends,
here is the answer of "my" SW-Service Team employee Mitchell Jetten:
It looks like these 2 orders are checked by 2 different people.
One of them didn't mind the 0,21 mm thickness while the other engineer did catch it and rejected the model for this reason:
Source: shapeways.com (Mitchell Jetten)
So right now the order 2672981 is being produced! These are the two standing variants (FUD & FXD).
As all models are subject by manual checking, if a part does't meet the minimum required the 0,3 mm thickness, there are chances it gets rejected
Would you be able to ask the designer to increase the thickness to 0,3 mm to make sure these are not being rejected again?
There you look!!! This is the same nonsense as at the Track shoes dispute.
I just wanted to answer him that this change would mean quite an effort for the designer, and that it would be easier if SW internally would enforce that this flat variant is to be printed since it is based on the same 3D model as the current upright standing variant which is just in production.
Only well, that for the umpteenth time I've checked the processing status of the newly ordered (previously rejected) flat version, because lo and behold, suddenly this sprocket is now also In Production ...
Source: shapeways.com
What does that tell us? One has to go only long enough on the SW-species' nerves to the motto Steady drops hollow the stone, then it works already ...
Now I can sit back and wait until both variants are there to inspect the wax residuals ...
And then we can decide from which variant my friend Joe should upload a Set of 16.
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#1590 by roma847 on 23 Oct, 2018 16:42
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Hello everybody,
today came the happy message from Shapeways that both ordered Sprocket variants are shipped.
Now I'm curious how they will look!
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#1591 by roma847 on 25 Oct, 2018 23:42
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Hello everybody
today, the Main Sprockets have arrived, which should not be printable at first and were rejected by Shapeways because of too small wall thicknesses (< 0,3 mm) were.
When looking at the photos, one has to take into account that FUD/FXD prints do not provide much contrast when unpainted, which makes it difficult to see details.
In the following pictures I have to differentiate between the upright and the flat print orientation, which I wanted to test with regard to the supporting wax problem.
Here one can see the sprockets in FUD (left) and FXD (right), printed in upright standing orientation, whereby one can see the clearer details of the FXD Sprocket.
And now still the FXD Sprocket (left) in flat print orientation comes in addition, in the middle the FUD Sprocket (upright print orientation).
In this picture below the two FXD Sprockets lay side by side, on the left the flat and on the right the upright print orientation. But I have to say, I can not see any differences in the surface roughness between the two variants, which could have been due to the different support wax arrangement.
And here once again the FXD Sprocket (upright orientation) in mounting position,
as well as on four Track shoes that go well together, which I had hoped for.
As matters stand I will probably decide for a Set of 16 (FXD) with flat print orientation, which my friend Joe could have to model now.
From close up, it looks pretty big and clear on those macro shots. But with a little more distance (about 30 cm), the chain is clearly shrinking already,
so that I could probably live well with FUD Sprockets.
Therefore, we first wait for the Set of 16 model and then continue. Maybe in the end SW will throw again their arms in the air ...
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#1592 by EG on 27 Oct, 2018 05:10
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Looks good so far my friend.
But,
I would make the suggestion to link together ten or twelve track shoes together and then try them around the sprocket. The tracks have to go around the sprocket about 110 degrees. with 4 links you only have about 35-40 degrees around the sprocket.
I know it is tiny and probably won't make a whole lot of difference if they don't line up exactly but the problem comes when you have to link a whole track together. The top part of the track can have a little slack to it, but the bottom on the ground can't.
The track has to be at the correct pitch so the track lays flat....
With the work your putting in for accuracy's sake, I would make the one last check on track fit.
If a linked section of track can mesh correctly with the sprocket for 180 degrees, I would say it's good to go....
It probably will but then there is making sure... -
#1593 by roma847 on 28 Oct, 2018 00:14
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Thanks EG for your critical comment.
With your objection, you are certainly right initially.
At first, my only concern was to check that the Sprocket wreath (1,75 mm) would fit into the Pin Lug gap (W1 > W2).
Here's an original photo, where one can see that the Pin Lugs of six Track shoes are in direct both-sided contact with the Sprocket, which corresponds to an angle of about 150°.
Source: NASA
I checked it out and connected eight shoes and put them around the drive wheel.
And as one can see, these eight shoes are in direct contact with the sprocket, which normally does not happen, as the first photo shows.
Therefore, this criterion of the accuracy of fit of the chain is also fulfilled.
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#1594 by EG on 28 Oct, 2018 04:44
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Good Deal!
Looks like a perfect fit.
Let me know if you want the drawings for the side sponsons and center hull....
I have those in Nasa originals also.... -
#1595 by roma847 on 28 Oct, 2018 09:25
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Thanks EG,
but I unfortunately don't know what you mean with these parts, have you an image for me, or send me the drawings, please.
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#1596 by EG on 28 Oct, 2018 13:22
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They will be in the same place you got the sprocket drawing....
As soon as I upload them you will get the notice.. -
#1597 by EG on 28 Oct, 2018 14:30
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Thanks EG,
but I unfortunately don't know what you mean with these parts, have you an image for me, or send me the drawings, please.
Ok, the sponson is the part the sprocket mounts to and the track rotates around, carries the ground rollers and return rollers.... It's in your image above where you point out the track engagement, there are two for each truck, one on each side.
The hull is the piece that joins the two sponsons together to make a complete truck. It carries the mount tube, Jel Tubes, drive motors, steering arms, etc etc... (I have the print for the steering arms also)
Oh yeah, original weldment drawings. -
#1598 by roma847 on 28 Oct, 2018 17:00
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Thanks EG,
I think, I know what you mean, which one can see in this photo, right?
Source: NASA
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#1599 by Fequalsma on 28 Oct, 2018 19:00
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EG can you share more of your CT drawings?
F=ma
