USS Monitor turret drive machinery

[starseeker]

I've uploaded higher resolution PDFs of the whole of Peterkin's book now, working from the original jpeg2000 images:

http://bzflag.bz/~starseeker/USS_Monitor/

As I write this the all-pages-in-one-pdf file peterkin_drawings_uss_monitor.pdf is still uploading - it's over 450 megabytes, so it will take a couple hours yet (assuming my internet connection holds up...)

These files have the disadvantage of not having "embedded text" to search with, but in all other respects should behave well. I adopted a "hybrid" approach - color is preserved in the few cases where there are genuine color images (in particular the foldout on page 67 displaying the magnificent drawing from the American-Swedish Historical Foundation Museum) and the remainder are greyscale images intended to display the black-and-white text and non-color drawings more clearly. The latter step, in addition to improving readibility, also reduces the size of the files (although I expect it doesn't appear so from the pdf sizes - that's due to the PDFs not using the jpeg2000 compression. These files should have good scrolling behavior, which trumps file size.)

Obviously a "proper" re-typing of this book using a word processor will produce smaller and even cleaner files (nice work bty DrPR with the GMM manual!) but in the meantime this was (relatively) fast and hopefully useful.

Cheers,
Cliff

[mcg]

Dean and Cliff, many thanks for your encouragement and help.

Rhino 5.0 beta has made it much easier to proceed. Everything loads, runs, and spins in 3D much faster. It also has a new feature called "artistic" mode which essentially turns your model back into a pencil sketch. I think it must be intended for making low resolution plans or presentations. It selectively drops out some detail and this seems to make the images easier to understand at a glance. I think it goes a little heavy on the shadows but I like the idea. Here is the turret drive as a "pencil" sketch.

. Here, on the other side of the bulkhead, is the spindle mount, butterfly flange, and turret lifting wedge.

Ericsson used vertical space to separate the valve gear motion from the gear train. The valve gear operates in horizontal planes above that of the first spur gear, and aft of the second pinion. It would make for a very busy animation.

[mcg]

Here is a divers' perspective, with the whole apparatus sitting upside down on the sea bed. The bulkhead is turned off (rusted away, let's say.) The gearbox layer is also turned off. In a way the machinery seems easier to take in, viewed in this inverted state.

It doesn't seem that this equipment would move or migrate much over time underwater, though as the deck beams rotted I suppose the pieces that were bolted to them would shift and sink a bit.

[mcg]

Next step is to change the USS Monadnock engine frames to conform to the design of the engine frames shown in drawings of the USS Monitor. In the Monitor, the frames were angled at the end to abut the central bulkhead. The square-ended Monadnock frames were simply extended in Rhino3D and trimmed by the plane of the bulkhead.

When these angle cut frames are re-introduced into the model, it looks like this:

Take Two: Well, that was a little too easy. I re-checked the drawings and the engine frames do not after all abut the bulkhead. They stop about 3 inches short of the bulkhead, at a line defined by the angle iron bracing the deck beam.

Long vertical bolts will secure the engine frames to the oak deck beam, which runs along the top of the bulkhead but is turned off in this view.

[Roscoe]

This is looking fantastic Michael!
And I really like that "artistic" mode, it gives it that old style, hand-drawn look, like an old book illustration, very cool.

Dean

[tea monster]

Ditto on the drawing mode, it does look really sweet!

I'm also impressed with the detective work on the model. That is sometimes more interesting than the model itself.

This is an impressive thread that keeps getting better.

Owen

[mcg]

Dean and Owen, many thanks for your support and interest.

Working on the linkage Ericsson designed to control the turret engine from inside the turret. There was a hand crank mounted overhead, suspended from the turret's ceiling. When the handcrank was at the middle of its travel, the turret was stopped. When it was cranked all the way in one direction or the other, the turret would rotate at full speed in the chosen direction. At lesser deflections in the chosen direction, the turret moved slower.

Belowdecks, the motion of the hand crank could be observed as a raising or lowering of the "swash plate" collar shown here. The collar rotated with and was free to slide up and down the (massive) spindle of the turret. The handcrank's motion was communicated down to the collar by two rods running in keyways.

The vertical positioning of the collar was "picked off" by a yoke with rollers, as shown. The yoke was mounted on a pillar bolted solidly to the bulkhead.

Parts shown above the gap in the rods are inside the turret. The central control rod went straight up the centerline of the turret. The collar on the turret spindle was split to enable its installation. It was held together by six square headed bolts. Here it is mounted on the turret spindle:

Note that I flipped the yoke so that the output lever points up. The system anticipates in some ways the swash plate used to feed control deflections into the rotor heads of helicopters. Additional linkage was used to convey the deflections of the yoke to the reversing lever of the turret engine.

Below the main spur gear, the linkage connects arms on shafts that rotate on two different axes -- one horizontal, the other vertical. This called for a pair of double-jointed end connectors, one at each end of the interconnecting rod.

Here is a detail. A modern linkage might use ball and socket joints (tie rod ends) but Ericsson used these.

The vertical shaft carried the motion around the big spur gear. From the arm rotating in a plane just above the spur, it is a straight shot back to the V-twin steam engine's reversing lever.

There was a second control for the turret, a setting for steam pressure delivered to the turret engine. This control valve was located in the engine room. When the turret was active, the steam pressure was about 25 psi. Maximum allowable pressure from the boilers was 40 psi. Michael

[mcg]

Here is an overview of the turret control linkage. The reversing lever on the engine controls which way the turret engine turns and how fast. The purpose of the linkage is to connect the engine's reversing lever with a hand crank mounted to an overhead beam inside the turret. The crank was suspended so that a man standing to one side of a Dahlgren could use it to direct the turret. At Hampton Roads this might have been Green, who commanded the turret, or perhaps Stimmers, who completely understood the machinery.

The linkage follows a roundabout path described in the preceding post. Here the components below decks are shown highlighted. The main spur has been turned off for visibility.

Here is the same shot with the big spur restored. A vertical shaft is used to bypass the big spur and elevate the final link rod, as shown. The parallel rods and spreader bar, shown at the center of the turret beam, carry the motion up into the turret chamber.

Finally, here is another one of those places where the USS Monitor meets the USS Monadnock. Everything in front of the bulkhead is from drawings of the USS Monitor. The long rod between the bulkhead and the reversing lever is known to exist but we have no overhead view of it. The reversing lever itself is from the drawings of the USS Monadnock.

The vertical plane of the USS Monadnock's reversing lever is essentially the same as that for the rotating arm (above the spur) from the USS Monitor's linkage.

This is the second time we have seen good agreement, or fit, between the USS Monitor and the Monadnock's V-twin turret engine. The first good fit was noted during the engine's installation, as recounted here:

viewtopic.php?f=27&t=66949&start=60#p472520

It seems reasonable to me that after Hampton Roads, when there was a rush to put monitors into production, the Navy specified the same basic off-the-shelf V-twin turret engine in several ships, including the Passaic class and in the Monadnock. It appears this 2nd generation Monitor turret engine was not changed, or changed only in detail, from that of the original USS Monitor. Michael

[Roscoe]

Michael,
Very impressive! This is one fine looking project!

Dean

[mcg]

Thank you Dean. We run fairly complicated linkages in RC aircraft, for the ailerons for example. Or in the rigging for RC sailboats. But I have never seen a linkage quite so extensive as this one. I guess that in the 1850s, when Ericsson hit his stride, this is how they controlled machinery. No hydraulics, no servo motors, no electricity. Just links and cranks and pivots.

It is beautifully thought out, but there would have to be some slack in it. It was entirely sheltered under the turret, so I guess it was not vulnerable, but you have to wonder about its long term reliability.

I think there was a turnbuckle on the horizontal link between the swash plate and the vertical shaft -- down where a sailor would be able to adjust it. But I can only half guess at it's design from the drawings, so I left it out for the time being. Michael

[mcg]

The turret bearing surface was a brass ring. It consisted of 12 brass segments, each covering 30 degrees of arc.

Below is a closer view, showing how the segments were bolted together.

The brass had two broad tiers. The upper tier was the bearing surface. The wall of the turret was laminated from 8 one-inch layers of armor, but only one of these (1-inch thick) protruded down to contact the brass bearing surface.

The lower tier of the brass was presumably used to bolt the ring to the deck. The planking under the ring consisted of 7" x 14" pine. The brass was 4" deep, and is shown here floating 3" above the oak deck beams. I assume the brass ring was mortised into the pine decking so that at its top, it was flush. Two 1/2 inch layers of armor plate overlaid the pine and the edge of the brass. Here is a pencil mode view of the ring. It emphasizes the junctures between the segments.

Finally, here is a view of the framed structure from below.

Notice the two stanchions flanking the crankcase. These two rods also served as the rear "legs" of the galley stove. As noted in an earlier post, the holes in the floor timbers were for ventilation. Note that the floor timbers were 15 inches high forward of the bulkhead, but 12 inches high aft of the bulkhead.

[starseeker]

Michael,

Impressive! It's coming together nicely.

I don't know if you already have copies of these, but it looks like volumes one and two of the original Project CHEESEBOX report from the Naval Academy are online:

Project Cheesebox: a Journey into History. Volume 1
http://handle.dtic.mil/100.2/ADA033069

Project Cheesebox: a Journey into History. Volume 2
http://handle.dtic.mil/100.2/ADA033070

Peterkin will have covered all the drawings in those volumes, but perhaps some of the documents themselves might have useful information... anyway, thought I'd mention it in case they are of interest.

[Roscoe]

Great stuff Michael!
I like the little functionality snippets of the various parts, it really adds to the whole project. So is there a cutaway turret on the horizon to top off this baby?

starseeker,
Another great find, thanks for the links.


Dean

[mcg]

Good idea Dean. Never done a cutaway. I wonder if there isn't a plug-in that does the jagged edges. Cliff, thanks for finding and posting the Cheesebox. I had not read these. It is interesting to remark Capt. Peterkin's early contribution to that project.

Every now and then you have to go back and tidy up. A problem with the current model is the gear train. The gears were drawn from a table of values reproduced in Peterkin's book. The Rhino3d sketches are numerically faithful to his table, but the spokes and details were just dummied up using TLAR. I guessed there were 8 spokes, and drew them as bars. Much later I found the Library of Congress image of the Comanche's gear set, reproduced here:

USS Camanche gear set. The spur used six T-form spokes.

I am going to use the Camanche gears as a reasonable prototype for the USS Monitor gears. The spur has 6 spokes, not 8, and the spokes are T-formed. There is a crown gear in this picture as well, and two pinions. The crown gear also appears to use T-form spokes, but they are inverted relative to those of the big spur gear. I found on the net another gear of this same general type:

Early 1900s

To follow this style in Rhino, I first made a blank spur gear, and then made a set of Boolean cookie cutters.

Blank for spur gear

Boolean molds, cookie cutters

The cookie cutters are pushed through the blank gear, and then, using Boolean commands, subtracted out of it. This was done in order to draw fillets around the spokes, the rim and the hub. Here is how the operation looks in progress:

Boolean molding, cutting in progress

The net result is a new and and, I hope, more realistic impression of an 1860s spur gear to replace the modern-looking, Rotary Club gear I have been using. I will use the same technique to re-make and replace the bigger spur on the turret shaft.

[dafi]

Fascinating and very interesting

Thanx for showing, Daniel

[starseeker]

Michael, did you ever substitute in that 1860's style spur gear in the turret shaft?

Fran, just curious - how did the March 10 presentation at the Mariner's Museum go?

CY

[mcg]

Hello Cliff -- have not yet finished the main spur gear. Sleepin' in the sun.... Michael

Update. Both spur gears are now re-done using the Camanche's gear set as a model. Each spur has 6 spokes, and each spoke follows a T-form. The gears look light but strong. The bigger spur reads from above, the smaller from below. Not sure why they should be inverted relative to each other, but this is the pattern established in the Camanche photos.

[Roscoe]

Sleepin' in the sun....

Well, wake up. You really need to get this great project going again, and if there's anything that I can do to help inspire you, just let me know.

-Dean

[mcg]

Thank you for your encouragement and enthusiasm for the project. Actually I am renovating a house, not sleepin' in the sun. Hope to get back to Monitor and other CAD projects soon. Michael

[DrPR]

Michael,

We understand that life sometimes interferes with modeling, despite our best efforts. But I will be glad to see you back on this "digital archaeology" project. The depth of your research and attention to detail is exemplary! I have learned a great deal, and you have stimulated much discussion about early ironclad steam navy ships.

Phil