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 Post subject: Re: 3D printing
PostPosted: Sun Apr 10, 2022 1:21 am 
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The early parabolic antenna radars on the Mk 37s were Mk 25 radars. The Mk 9 Mod 0 parabolic antenna dish was a highly perforated dish. These were later replaced with solid metal parabolic reflectors. I don't know the Mk/Mod of the solid dish.

****

Here is an anecdote about the Mk 25 radars. I was Director Officer in our Mk 37 and on one cruise off Vietnam the radar stopped working. The Navy immediately flew in a technician from Stateside to repair it. While he was working on our unit the guys in the director chatted with him and he told us a bit about the Mk 25.

Each radar transmitter had two large (about 12 inches tall) vacuum tubes, and these were the parts that failed most often. The technician carried a black case with two new tubes in it. He said they cost about $35,000 each (1970s dollars) and each director was allotted only two (installed) with no spares. He said the Navy had bought a stock of these tubes quite a few years earlier, and they were supposed to last the life of the Mk 25s fleet wide. But the war used them up pretty quickly. Consequently there were very few in stock so when a ship needed a new one a technician brought new tubes from the States.

Why didn't they have more tubes in stock? After the last order was filed the manufacturer destroyed the production line and used the space for something else. So if the Navy wanted more tubes it had to buy a new factory to make a relatively small number of parts. This raised the price of a few dollar vacuum tube to many tens of thousands of dollars each.

It turned out the part that failed was a simple TO-5 transistor that cost a few dollars. The humid salt atmosphere had corroded one of the three leads. It was gold plated over copper wire, and a tiny fault in the plating allowed humidity to get to the copper inside the plating and corrode it away. Only the thin tubular plating remained intact to make the circuit and support the part, and eventually vibrations broke it.

Phil

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 Post subject: Re: 3D printing
PostPosted: Sun Apr 10, 2022 7:53 am 
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Phil,
Interesting historical story on the Mk. 25. Very similar - when I served in STODDARD, my ship's office was 1/2 level below the main deck and 1/2 level above the mess decks (FLETCHER class DD) on the stbd side. A narrow passageway separated our space (hull side) from a storage locker facing it (inside). This was a metal lattice bulkhead with a metal frame door which was locked. It was a storage space for OC division as well as the SONAR gang. They stored spare parts. I recall seeing two of the wooden crates with a single vacuum tube in each one. They were roughly 8"x8"x24" tall. The tube was a bulb type with a round top end wider than the base end. My buddy in Boise, ID who was an SO3 called these Klystron tubes. I think a couple years back we were discussing the lower SONAR room in the bow of the ship (located above where the SONAR dome below the hull is located) and he mentioned that was the location of the elec. gear that these tubes were associated with. Of course, that space I never even had any knowledge about until I started working on the model.

This hobby can and does provide opportunities all the time to learn something that you never knew about - one of the reasons I enjoy it so much!!

Hank

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Builder's yard:
USS STODDARD (DD-566) 66-68 1:144, USS-LSM/R-194 1:144
Finished:
USS NEW JERSEY (BB-62) 67-69 1:200
USN Sloop/Ship PEACOCK (1813) 1:48
ROYAL CAROLINE (1748) 1:47
AVS (1768) 1:48


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 Post subject: Re: 3D printing
PostPosted: Sun Apr 10, 2022 11:50 am 
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Ah, Klystron Tubes, I remember the name but never saw one. Here is a link to a brief explanation of these devices;

https://www.electrical4u.com/klystron-t ... lications/

A development of the "cavity magnetron" which allowed the development of microwave radar. The Klystron tube is a microwave amplifier. I remember historical discussion of early British airborne Radar they dubbed the "Klystron Ray".

Back to printing... I was pleased with the airy aspect of the MK 4 units I printed for Alaska and replaced the existing ones. Missouri (both 1:192) has the MK 25 units so I have not replaced those. Last night I printed two of the 5" twin mounts in 1:120 but haven't fetched them as yet. 1:120 is a real resin hog compared to 1;192. On the larger platen I was bale to print two plus the separate barrel assemblies. I split the barrels off as separate files, this allowed me to angle the mounts at 15 deg and the barrels at 45 deg which should be more optimal.

Tom


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 Post subject: Re: 3D printing
PostPosted: Sun Apr 10, 2022 3:17 pm 
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As part of an ongoing project, I printed the twin mount in 1:120. Strangely both barrel assemblies and one mount came out almost perfect. The second mount, sitting next to the other on the platen was just a blob stuck to the FEP.

Attachment:
Keyboard security.jpg
Keyboard security.jpg [ 266.04 KiB | Viewed 534 times ]


In these days of cyber security concerns one cannot overlook any form of keyboard security. In the raw and still having some of that irritating resin dust which comes from minor cleanup of the object. Exaggerated in a sub arctic climate, the indoor humidity currently at 2%.

Tom


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 Post subject: Re: 3D printing
PostPosted: Sun Apr 10, 2022 3:56 pm 
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can you show a picture of a blob beside it's perfect clone to see what is going on?


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 Post subject: Re: 3D printing
PostPosted: Sun Apr 10, 2022 4:15 pm 
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Fliger747 wrote:
The second mount, sitting next to the other on the platen was just a blob stuck to the FEP.

Tom


It happens sometimes, I have to check that the base of the supports is at zero on Chitubox. The bottom surface of the supports must be green. Sometimes Chitubox plays tricks on me, some bugs.

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 Post subject: Re: 3D printing
PostPosted: Sun Apr 10, 2022 4:32 pm 
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I think I found my sweet-spot in 3D printing and I've been trying to get everything I need printed before it fades away.
So far I'm finding a lot of "light" supports are working for me better than fewer larger supports, especially on edges and corners. I think they release from the FEP easier with each lift.


Attachments:
File comment: Articulated, studded, anchor chain
con20220406c.jpg
con20220406c.jpg [ 291.21 KiB | Viewed 524 times ]
File comment: Chain and shackle printed all-in-one attached to anchor printed a while back
con20220408g.jpg
con20220408g.jpg [ 362.04 KiB | Viewed 524 times ]
File comment: New, more detailed panels for the skylight. They'll be hinged to access the models power on/off switch underneath
con20220407b.jpg
con20220407b.jpg [ 201.97 KiB | Viewed 524 times ]
File comment: A few more figures printed "as acquired" but with many light supports instead of medium supports - all printed perfectly where-as several from the first batch failed out-right or partially.
Even Stella the cat's "thumbs" printed on her paws.

con20220408a.jpg
con20220408a.jpg [ 225.69 KiB | Viewed 524 times ]

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 Post subject: Re: 3D printing
PostPosted: Sun Apr 10, 2022 4:59 pm 
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Surprised with all that black powder about that ships didn't disappear with a loud boom and a pall of black smoke with more frequency. Nice thing about the small supports on the chain is it often zips right off the supports!


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 Post subject: Re: 3D printing
PostPosted: Sun Apr 10, 2022 9:48 pm 
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They did, on occasion, except the smoke was white ;)

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 Post subject: Re: 3D printing
PostPosted: Sun Apr 10, 2022 10:21 pm 
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Right! I have a Sharps rifle that I shoot Black Powder, it s sort of a gray, darn opaque! Allegedly the Arizona was done in by the bomb setting off the black powder magazine used for signaling and catapulting. I would guess a lot of volly's from the age of sail were launched with no sight of the target, sound shots as it were. As ship of that scale you should be able to reproduce absolute scale!

Thanks for sharing! One question, do you have any idea when a transition was made to anchor chain?

Regards: Tom


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 Post subject: Re: 3D printing
PostPosted: Mon Apr 11, 2022 10:40 pm 
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Tom,

According to the font of all wisdom:

"In 1808 Samuel Brown, a Naval Leutenant, fitted out a Navy vessel, the 'Penelope' with chain anchor cables and rigging and sailed her to the West Indies to prove the superiority of iron chain. In 1818 he and his cousin Samuel Lenox established a chainworks at Pontypridd."

James Lees "Masting and Rigging of English Ships of War" also says that anchor chains were introduced in the early 19th century.

Rope anchor cables continued to be used well into the 19th century, especially on smaller vessels and merchant ships. They are still used on small boats.

Phil

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 Post subject: Re: 3D printing
PostPosted: Tue Apr 12, 2022 1:52 am 
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Phil:

Good info, nothing like a reference library, let's see, where is that volume, opening the pages and quickly thumbing to the right spot.

Cheers: Tom


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 Post subject: Re: 3D printing
PostPosted: Tue Apr 12, 2022 3:15 am 
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Fliger747 wrote:
Thanks for sharing! One question, do you have any idea when a transition was made to anchor chain?


In the US Navy through the 1840's, the Brits maybe a little sooner, or about the same time. I'd have to research that more to be definate. By the 1850's there were far more iron fittings being used in Naval vessels, including chain. Her tops'l halyards were also chain to a gin-block and then blocks and rope purchases. I'm basing my model on a painting of the ship done in 1856 (she was launched in 1854) which clearly shows chain.


Attachments:
File comment: Constellation at Naples 1856
constellation1856a.jpg
constellation1856a.jpg [ 65.34 KiB | Viewed 462 times ]

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 Post subject: Re: 3D printing
PostPosted: Mon Apr 18, 2022 11:21 am 
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Just sharing minor discovery.... Printing props, the myriad of supports under the blades leave a stubble that mars the finish. I discovered by accident when I failed to add supports at all that the underside of the blades still print perfectly. So as it turns out, just supports under the hub still provides for a perfectly printed blade with both sides very smooth!

Cheers: Tom


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 Post subject: Re: 3D printing
PostPosted: Thu Aug 18, 2022 3:08 pm 
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Under the Wah hail clause of any kind of scratch building, I have an issue with items waiting to assume a banana shape when drying and curing, with the curve radius normal to the platen side of the print. With a boom or mast i can insert a steel rod, with a hull more problematic. Trying printing one vertically, 28 hours vis 3...


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 Post subject: Re: 3D printing
PostPosted: Thu Aug 18, 2022 11:18 pm 
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Hi Tom,

If I understand your comment correctly, you are talking about objects that are printed in a plane parallel to the platen. After printing they are becoming banana or "U" shaped. Are they sagging toward the platen in the middle between supports?

Is the curving happening while the print is still attached to the platen, or after removing it from the platen?

I know you have been using a water washable resin, and you have implied in the past that you allow the parts to air dry for a while before they are UV cured. Is this correct? Is the curving happening during drying , during curing or after curing? At one time I think you said some of the curved parts would straighten out as they dried, before curing.

I guess we have all seen thin pieces distorted or bent between supports - things like hand rails. Or flat surfaces becoming "lumpy" between supports. But this distortion occurs during printing due to separation forces between the print and the platen. Is this what you are talking about?

You mentioned a hull, and that would be much more substantial than a thin railing or pipe.

****

I haven't studied the solidification of resins, but the material does seem to form a crystalline structure when it cures. Some materials develop stress when they crystallize, resulting in curved crystals. If you have ever seen hoarfrost you know what I mean. Water freezes into very long thin curved crystals.

I wonder if printing resins have internal stresses when they cure? I can imagine that the resin layers might cure unequally if the layer is too thick or the exposure time is too short. The UV light intensity will decrease as it passes through the printed layer. The side of the layer on the film at the bottom of the tank (more UV exposure) might cure differently from the side of the layer more distant from the film (less UV exposure). Maybe this is causing stresses that make long pieces curve?

If this is a problem perhaps thinner layers and longer exposure times will produce more even curing and reduce stresses.

Phil

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 Post subject: Re: 3D printing
PostPosted: Fri Aug 19, 2022 12:44 am 
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I'll make a WAG , perhaps the first layers continue to cure as the later layers pile on top and don't have time for shrinkage from drying and curing whereas the upper layers are still shrinkable? In the case of a hull printed vertically there should not be a bending moment along the length. Currently printing a vertical version of the DE hull, which takes over a day as opposed to a few hours. We shall see!


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 Post subject: Re: 3D printing
PostPosted: Fri Aug 19, 2022 1:40 pm 
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So far the vertically printed hull is going well, doing it this way I could add the bilge keels which would not work out with the hull horizontal. A few more hours to go, it does seem the hull sprinting a little faster than the originally prognosticated time. If I do this again I'll try a .05 rather than a .035 mm layer thickness as there is really no detail. My primitive program certainly does not allow the capability of Pascal like weld lines and rivets on the hull surface.

Cheers: Tom


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