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» Forum Category: PT Boats of WWII
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» Forum Name: PT Boats - General
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» Topic: Roll-Off Racks
http://www.ptboatforum.com/cgi-bin/MB2/netboardr.cgi?cid=101&fid=102&tid=1712



As a mechanical engineer and amateur PT historian, I am interested in the design and operation of the roll-off racks for the MK XIII torpedo's on late vintage PT's. Has anything been published on the forum concerning these supposedly simple machines?

SteveS156

Posted By: SteveS156 | Posted on: Mar 14, 2010 - 3:50pm
Total Posts: | Joined: Unregistered



About15 years ago, I developed these plans from ELCO drawings, tech specs, and photos.
[IMaGe]http://i73.photobucket.com/albums/i204/alross2/rack_0001.jpg[/IMaGe]

The photos are from ACF V2.

[IMaGe]http://i73.photobucket.com/albums/i204/alross2/rack_0002-1.jpg[/IMaGe]
[IMaGe]http://i73.photobucket.com/albums/i204/alross2/rack_0003-1.jpg[/IMaGe]
The extensions outboard were removed once the torpedo was secured.

I also have the manual for the torpedo alignment tool that was used to align the MK13 in the rack.

Al



Posted By: alross2 | Posted on: Mar 14, 2010 - 5:26pm
Total Posts: 993 | Joined: Oct 30, 2006 - 8:19pm



About15 years ago, I developed these plans from ELCO drawings, tech specs, and photos.
[IMaGe]http://i73.photobucket.com/albums/i204/alross2/rack_0001.jpg[/IMaGe]

The photos are from ACF V2.

[IMaGe]http://i73.photobucket.com/albums/i204/alross2/rack_0002-1.jpg[/IMaGe]
[IMaGe]http://i73.photobucket.com/albums/i204/alross2/rack_0003-1.jpg[/IMaGe]
The extensions outboard were removed once the torpedo was secured.

I also have the manual for the torpedo alignment tool that was used to align the MK13 in the rack.

Al



Posted By: alross2 | Posted on: Mar 14, 2010 - 5:27pm
Total Posts: 993 | Joined: Oct 30, 2006 - 8:19pm



Thank you Al! This is just what I was looking for. Once again the Forum comes through.

SteveS156

Posted By: SteveS156 | Posted on: Mar 15, 2010 - 5:20am
Total Posts: | Joined: Unregistered



Steve,

As a fellow ME type I was also interested in these racks, very simple concept. The second photograph shows two outboard rail extensions that were used as a cradle for loading only. The torpedo was held in place by two keys in slots on the bottom of the two rails. These keys were actuated by the level to the stern of the rail mechanism. The linkage is very clear in hte bottom of the rack. The cables were a safety hold back for rough weather of excessive motion of the boat. For the most part a statci system witht he exception of the linkage to lower the leys.



Bill Smallshaw

Posted By: smallwi | Posted on: Mar 15, 2010 - 7:27am
Total Posts: 130 | Joined: Jun 21, 2007 - 3:02pm



This simple design looks a lot better than the BuOrd tube that used gun powder to blast the torpedo out of the tube.
Wasn't this designed by a couple Lieutenants in a bar, sketched out on cocktail napkins? Cheers!



Posted By: RUSSELL WHIPPLE | Posted on: Mar 15, 2010 - 9:39am
Total Posts: 13 | Joined: Dec 16, 2007 - 9:38am



Hey, Al, dumb question. Were the release levers aft of the rack on both port and starboard?

SteveS156

Posted By: SteveS156 | Posted on: Mar 16, 2010 - 4:58am
Total Posts: | Joined: Unregistered



The racks were "handed". That is, the lever was on the aft facing side. The drawing shows a rack for the port side.

Al



Posted By: alross2 | Posted on: Mar 16, 2010 - 6:37am
Total Posts: 993 | Joined: Oct 30, 2006 - 8:19pm