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 Author  Topic: Mk18 Torpedo Tube Details
Pat Matthews

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Pat Matthews  Posted on: Oct 1, 2023 - 8:59pm
It's done! Here's the text from my FB post about it:


Torpedo Tubes for ELCO PT BOATS

The Mk.18 torpedo tube, which launched the Mk.8 21” torpedo, was used on Elco PT boats beginning with the 77 footer and part way into the production of the 80 foot PT-103 class in its original form that I call Mod.0. Mods 1 through 5 followed, but you need a Mod.0 on your 77 footer or PT-109 80 footer. And it does differ in some visible ways from Mod.1, but it's not a well documented design.

I've been frustrated by the incomplete details needed to accurately model this very visible part of the early Elco PTs. A number of modeler's drawings exist, but they don't shed light on all the mysteries of this complicated assembly.
So I've assembled all the available Electric Boat drawings and the handful of historic photos that show any detail of the tubes, and built a complete CAD model of the tube in 1:1 scale. This project allowed me to fill in many of the blanks, interpolating between the existing knowns to flesh out possible solutions for the unknowns.

The 3D CAD model, my 2D drawings, and historic reference material is now all posted at GrabCAD:
https://grabcad.com/patrick.matthews-1/

GrabCAD is a trusted file sharing site run by the 3D printing technology giant Stratasys. Downloads are FREE but you do need to sign in there. Note that my model is NOT directly usable for 3D printing! But a CAD designer can work up printable parts from this information.

Once there, PLEASE read the NOTES document which provides much more additional detail on the torpedo tube and the available files.

CREDIT: All the source information comes from the PT boat community, in Groups like this, at the PT Boat Forum, and from books by more PT boat fans. Thanks to all who keep contributing to the knowledge base!


Screen cap from the GrabCAD site:

pL12t.png


My top level assembly drawing:
pLgYT.png


One of 20 detail drawings:
pLd53.png


Total Posts: 89 | Joined: Jan 7, 2012 - 5:41pm | IP Logged

  frankd

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of frankd  Posted on: Oct 2, 2023 - 11:02am
Pat, outstanding work as usual!


Total Posts: 12 | Joined: Apr 5, 2020 - 12:21pm | IP Logged

Pat Matthews

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Pat Matthews  Posted on: Oct 2, 2023 - 12:05pm
A detail I hadn't noticed before:

The earliest tubes have the portable front cover retained by three spring-loaded catch hooks. I can just imagine these popping loose when the boat pounds on a few waves.
This design was replaced with a tensioned cable set up to a small triangular bra that held the dome in place. A lower cable was strung through the bra and attached by shackles to either side of the tube stop. The upper cable had some sort of tension adjuster and hooked to the top of the tube.

But here's a first-series 77, still has the turret domes in place, and it has the newer cable set-up flopped onto the deck. So I have no idea when the change was made.



pLFOw.jpg


Total Posts: 89 | Joined: Jan 7, 2012 - 5:41pm | IP Logged

Dick

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Dick   Send Email To Dick Posted on: Oct 11, 2023 - 1:24pm
Pat - Just outstanding . . . .

I knnow just how hard it is to pin something down on PT boat matters! The discrepancies between drawings and photo are specially frustrating. Even when you're lucky and can find a clear/sharp drawing of an item you might be working on, there is always the diassapointment when you can't confirm it on photos.

Your CAD work is outstanding and your patience dealing with all the incomplete and at time confussing data, is absolutetly commendable. As you know, you, Jeff, Al and myself have been dealing with these issues for many-a-year.

Thanks for posting all your work here on the forum it is very much appreciated. The popularity of Facebook has drained many visitor from the forum over the last few years. Currently with only 30 or so visitors a day is a far difference from the 400 to 300 visits we use to get regularly. However, we can always count of the old Senior members, to visit atleast a couple times a week (thanks gang).

Keep up the excellent work! ! ! ! and please keep posting all your work here at the forum. To. see your great work always puts a smile on my face and I'm sure others also.

Dick . . .


Total Posts: 1416 | Joined: Aug 27, 2006 - 6:36pm | IP Logged

Dick

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Dick   Send Email To Dick Posted on: Oct 11, 2023 - 1:26pm
Pat - Just outstanding . . . .

I knnow just how hard it is to pin something down on PT boat matters! The discrepancies between drawings and photo are specially frustrating. Even when you're lucky and can find a clear/sharp drawing of an item you might be working on, there is always the diassapointment when you can't confirm it on photos.

Your CAD work is outstanding and your patience dealing with all the incomplete and at time confussing data, is absolutetly commendable. As you know, you, Jeff, Al and myself have been dealing with these issues for many-a-year.

Thanks for posting all your work here on the forum it is very much appreciated. The popularity of Facebook has drained many visitor from the forum over the last few years. Currently with only 30 or so visitors a day is a far difference from the 400 to 300 visits we use to get regularly. However, we can always count of the old Senior members, to visit atleast a couple times a week (thanks gang).

Keep up the excellent work! ! ! ! and please keep posting all your work here at the forum. To. see your great work always puts a smile on my face and I'm sure others also.

Dick . . .


Total Posts: 1416 | Joined: Aug 27, 2006 - 6:36pm | IP Logged

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