TDC torpedo speed selector switches
 

I've searched seafarer's link for the Mark III TDC Manual and can't find any reference to the "simple selectors for the speed settings" for Mark 14 torpedoes. The only apparent possibility is the four dials on the poorly documented electrical section. There is one illustration and I can read enough to see that the right one is the power selector switch and the next one to the left is legible. That leaves two unidentified electrical knobs that may be the adjustment.

However, a schematic I've found shows a hand crank for Sz which is the torpedo speed. Hey, YOU try wading through all the calculation derivations to figure out what to look for! It's enough to make you plenty cranky if high level algebra and trig is not your native language.

http://i196.photobucket.com/albums/a...TDCinput-1.jpg

There's your input, Vern, right on this easy-breezy little diagram. Yer top crank there, labeled S sub Z (Sz phonetically rendered there), that's crank 5F-A, is adjustable torpedo speed between 25 and 60 knots.

So I'm STILL curious where this crank is on the actual unit. And now I'm really mystified as to the necessity to rebuild (presumably to the Mark IV unit) when a boat was in drydock being adapted for the electrical Mark 18 torpedoes.

I have an irrelevent aside, but I'll hold it as I don't want to hijack my own thread. Again, sorry CapnScurvy, for my irrelevent aside in your thread hijacking your masthead height and differing AoBs thread. Hope you can get it back on track.:huh:

Perhaps my poor choice of words, as I don't know actually how simple it is to input the data. I was also going by the schematic near the bottom here (this is for a Mk.IV - http://www.usscod.org/tdc-restore.html ). Sz is torpedor running speed. Another source I have somewhere mentioned that the TDC operator had to "input torpedo type and speed", but obviously if torp. speed is a discrete input parameter, then type would surely be unnecessary?

Sure seems like it but...
 

The cranks were not difficult to use and you only had to overcome the friction of the slip clutches. But using torpedo type as the input instead of torpedo speed would prevent lots of human error, I would think.

I still want to find a photo of the correct crank and its location on the TDC Mark III.

Indeed, setting the input values on either the Position Keeper, or the Angle Solver is a piece of cake. You just rotate the cranks untill the correct values appear. This can even be done while the TDC is running and therefore is calculating the angles.
The TDC rather quickly to any changes in the scenario, with some exceptions.
For example, if the submarine should pass beneath the target a number of the mechanical elements will have to travel clear to the other end of their range to get back onto the solutions. The follow-up heads will not match during the time it takes for the elements to drive all the way to the other extreme. The whole TDC makes some very interesting noises while that is happening. It's a great machine to work on (play with :D )

I'll have to look at some photographs I've got at home, to see where the Torpedo Speed crank is located. I think it's the one in the middle on the Angle Solver.:hmm:

The Cod has a Mark IV TDC which means it has a Receiver Unit in the middle between the PK and the AS. Therefore we have the advantage that values from periscope, radar and/or sonar can directly be fed into the PK.


By the way, each torpedo came with a piece of paper at what exact speeds it could run. Every torpedo was tested at it's possible speed settings. For a Mark 14 that would be two. For every torpedo fired, the TDC Officer had to dial in the correct speed setting, according to the papers sent with each torpedo. That's why, if you read a patrol report, you'll find for every torpedo fired, its serial number.

Let me see what I can find more on this topic.

groetjes,

I can hardly wait!
 

I feel like a kid in a candy store! In many ways, the production of a mechanical analog computer is more amazing than a digital one. Instead of invisible electrons moving from bin to bin, an invisible process, in the analog computer gears, shafts, clutches, readout dials where you might have to interpolate to find the answer, are all present. The machine has to be carefully adjusted to work properly, and as the manual says, haphazardly making adjustments may result in a web of anomolies so pervasive the machine cannot be set right again.

On one level, the thing is primitive. On another level, it is a work of art with inconceivably consumate craftsmanship. I can't wait to see those photos! Thanks Gino:up:

As far as I can tell, the best photo's available are those at http://www.maritime.org/tdc.htm but I cannot read any of the labels on the machine :damn:

The answer, I'm sure, would be in:

The Fleet Submarine Torpedo Data Computer
by Harvey G. Cragon (134 pages)
Cragon Books; First edition (November 23, 2007)
ISBN-10: 0974304530

But Amazon is out of stock. Anybody care to check their local library?

You may want to check: http://www.hnsa.org/doc/tdc/index.htm

There you'll find everything you don't want to know about the Mark 3 TDC...:D

It doesn't show you the labels at the machine, but it does tell you how it works :up:

I think the book you mentioned is also derived from that manual.

THE authority IMHO is Terry Lindell who is attached to USS Pampanito. He's also the one that brought Cod's TDC back to life.

Like I said in my previous reply, I'll check for photos at home...

groetjes,

Ok, so it is not the best of pictures, but here goes.

A glimpse of the Angle Solver on USS Cod

http://img253.imageshack.us/img253/5...0034hp6.th.jpg

Above the cranks. Label left: SPREAD AFT
Label middle: TORPEDO SPEED
Label right: SPREAD FWD

The rest should be legible from the manual...

Position Keeper drawing I have been working on:

http://img216.imageshack.us/img216/1...rwipib1.th.jpg

And the whole thing in one drawing. Mind that this is WIP, so some dials have not been put in there yet.

http://img216.imageshack.us/img216/4...drawxq5.th.jpg

Questions?

I have more photos, but the quality ain't that phenomenal :cry:

groetjes,

Awesome Gino, thanks. I could follow the schematics alright, but then trying to figure out just how that actually worked for input on the real thing was what I was missing. Just knowing which dial is which now makes it much easier to picture actually using the machine.

I take it that the FWD and AFT "spread" dials are actually represented by the offset dial that we see in the game?

Yep, you're right.

I found out that the Mark 3 has also a nice feature on their Torpedo speed crank. I don't know which revision level (or Mod) but it appears that later models had also the capability to set the Torpedo Depth with the same crank. On Cod the Torpedo depth is set at the torpedo tube. So, maybe this setting is related to later torpedo tubes.

groetjes,

And something else I hadn't noticed!
 

The bottom crank(?) is the radius of turn for the torpedo. This was one of the reasons given for the TDC overhaul in the book I read, that the electrical Mark 18s had a different speed and different turn radius. Now we know that the TDC could handle that anyway!

I have to locate the reference and determine who was so misinformed! Looks to me that they were just updating Mark III to Mark IV, most notably inserting the receiver module.

This just gets more and more interesting!:up:

I don't know if they did do upgrades from Mark 3 to Mark 4. Pampanito (SS-383) which was built later than Cod (SS-224) still has a Mark 3. Icefish (SS-367) and Hawkbill (SS-366), which both went to the Netherlands after the war (after being Guppied) had Mark 3's. One of which is on display in the Dutch Navy museum in Den Helder.
Also, inserting the receiver was a major operation, which would include opening the pressure hull on the conning tower, making extra room for the receiver etc.
Would have been very expensive...

So, yes it is getting more interesting...

groetjes,

I can't think of any museum boats sporting a Mk. IV TDC, but I do like the idea of being able to select where the input comes from. This is sort of modeled in the game with the "send bearing" switch on the sound stack.

The USS Cod (SS-224) that is in Cleveland, Ohio has a working Mark 4 Torpedo Data Computer...
I know, because I have operated it myself, and I hope to do that again this summer.

Also the drawings I put in an earlier reply, are from that TDC.

So Mark 4's were used during ww2, no doubt about that.

groetjes,