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-   -   Saturn 1b 1:156 Scale 3d Printed (http://www.oldrocketforum.com/showthread.php?t=17915)

timorley 05-20-2019 07:21 PM

Saturn 1b 1:156 Scale 3d Printed
 
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Besides the Pershing 1A, I have another 3D printed rocket project underway, a Saturn 1B. The main body is constructed around a BT-60 sized body tube. The scale will be about 1:156. The 3D files were created by scottdee (who frequents YORF as scott_mills) and I downloaded them from https://www.thingiverse.com/thing:2958861. I upscaled the fin unit to 103% so the inside diameter matched the inside diameter of a BT-60. By chance, 8 BT-4 Semroc tubes from eRockets seem to fit perfectly inside the BT-60 and the fin can now that I slightly upscaled it. Unfortunately a BT-20 for the engine mount is a tiny bit too big to fit inside the BT-4s without deforming them, but no worries, I'll trim a tiny bit out of the BT-4s the length of the engine mount. Unfortunately the vendor shipped the wrong length of BT-4s, they made it right with no hassle, as soon as the replacement tubes arrive I can start assembly this coming weekend, along with starting to assemble the Pershing too!

timorley 05-20-2019 07:27 PM

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And while the BT-4s I got were too short, they were long enough for me to verify BT-4s will work just fine for the 8 tanks.

Earl 05-21-2019 02:27 PM

That's an interesting scale size for a 1b. That would be good for demos in small fields.

If you can, post photos of the Pershing and this 1b as you go along on your build.


Earl

scott_mills 05-22-2019 11:29 PM

Nice can't wait to see it finished

timorley 06-03-2019 07:43 PM

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The replacement BT-4 body tubes arrived today. Dang Post Office, I fear the worst......

timorley 06-03-2019 07:48 PM

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Miracles of miracles, nothing was crushed. The top of the box was crushed, but the tubes were in the bottom, safe and sound.

Earl 06-03-2019 08:07 PM

Whew! That was a close one!

Yeah, that's a sinking feeling when one gets a rocketry related package in the mail looking like that. I've gotten lucky a few times and not had any damage, like this one.

Once however I received a flattened package in the mail. It was really squashed. Sad thing was the package contained a mint (really truly mint) Centuri Saturn 1b kit, the version in the nice color box. EVERY tube was crushed. Some plastic parts, wrappers and chutes were salvagable, but the rest was pretty much toast.

Post some photos once you get it assembled and/or painted.

Earl

timorley 06-03-2019 08:26 PM

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To Engine Mount or Not to Engine Mount? That is the question.

I have a dilemma. An 18mm BT-20 engine mount will not fit in the space left from the BT-4 tank tubes. The math doesn't work and I tried anyway, it is so frustratingly close. I was planning on cutting out a small strip down the length of each BT-4 to accommodate the engine mount. However, the diameter remaining within the BT-4s happens to be almost exactly, the interior diameter of the BT-20, this means an 18mm rocket motor fits snug as a bug nestled within the BT-4s. So, I could use the BT-4s as the engine mount. I can still glue an engine block in, it would only have 8 touch pints for glue, versus the entire circumference, I could even put in a longer engine block for more glue surface. I plan on using epoxy to fill triangular gaps to prevent ejection gases from flowing backwards anyway, so that will further strengthen the engine block attachment. I am capping off the BT-4 ends with a BT-60 to BT-20 centering ring for the same reason. I can also still have an engine retaining hook, by placing it inside one of the BT-4s , it would still be pushed through a slit in the BT-4 at the engine block. It would further be secured with a piece of BT-4 pushed up inside the BT-4 tube and glued to keep the retaining hook in place. All the BT-4s would be glued together as well. I am sure this will work, it just feels odd to not have a traditional engine mount. I'm including a picture where I mocked it up with the previous too short BT-4s. Obviously the easy way out, but I still may go the hard way.

Anybody have any options one way or another?

Earl 06-03-2019 08:33 PM

Actually, that looks like a pretty good solution.

If you get good surface contact on the BT-4s with the engine block and have some good 'blobs' of glue on the 'north' side of the engine block, I think it would be quite secure without any real worry of letting loose under thrust.

Earl

timorley 06-16-2019 06:38 PM

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Here is a dry fit of the BT-4s with proper length. I also had the idea to use one of the Estes engine spacer tubes as the core tube for the ejection gases to blow up through inside the upper portion of the 1B tanks. The picture with the space tube, engine block and engine stacked should give an idea of what it will look like internally.


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