I've previously looked at the development of the shell fuze from the earliest days through WWII. But all of those were intended for use against surface targets, and during WWI, a new threat emerged, that of the airplane.

A powder time fuze's internals

This led to a reemergence of the time fuze, as the sky was very big and planes were small, and setting off the shell when it should be near the target was a lot more effective than hoping for a direct hit from heavy guns. This was surprisingly easy, as time fuze development had continued for use with shrapnel shells.¹ The mechanism was surprisingly similar to some of the early time fuzes, but far easier to use. Essentially, the nose fuze had two horseshoes of delay composition which could rotate relative to each other, with a vent between them to allow the combustion to spread from one to another. To set, the operator (who was quickly replaced by a mechanical setting machine) merely rotated the nose section to the correct position, then loaded the shell into the gun, where the setback force would start the powder burning in the upper ring. Once it reaches the vent, it spreads to the lower ring, where it burns back towards the detonator. Minimum fuze time was generally limited for the safety of the crew (1.8 seconds was the US standard), but the use of setback to start the fuze train (even if a centrifugal safety mechanism would keep it from going off) meant that dropped time fuzes were particularly dangerous and generally needed to be thrown overboard immediately. Some early time fuzes also had a secondary impact detonator, although this seems to have become less common as dedicated AA time fuzes were developed.² Read more...

With the development of the delay impact fuze, the basic form of fuzing for AP shells was set, and a number of nations appear to have simply gotten fuzes they liked in the early to mid 20s and then stopped developing them. The major exception was the US, always paranoid about things that might go boom. Pretty much all US fuzes³ had at least two if not three independent mechanisms for making sure that nothing went boom before it was supposed to.

A standard USN base fuze

The standard US base fuze (which came in several Mk variants depending on the caliber of the shell, the main difference being the length of the fuze delay) was a complicated device, carefully designed to not arm until the right moment and as a result baffling in its complexity. There were the usual safety pins pulled out by centrifugal force, some of which were held in place while the shell was still in the barrel because setback pushed the sensitive firing pin onto them. The impact force pushed the fuze plunger forward, aligning the holes through which the detonator's flash would pass into the booster and bringing the sensitive primer onto the sensitive firing pin and setting it off. Instead of directly setting off the delay element, the gas from the sensitive primer locked the plunger in the forward position (thus ensuring that the holes would remain aligned even while the delay was burning) and freed the secondary firing pin to impact the secondary primer, which in turn set off the delay element. When that had burned (which took between .01 seconds for 6" shells and .035 sec for battleship shells) it set off the detonator. Some of this complexity was probably to improve fuze reliability during oblique impacts, which could otherwise fail to set off a shell because things get pushed out of alignment.⁴ This fuze worked quite well in general, although it was soon discovered that fumes from the explosive filler of the shells tended to corrode the fuze internals after 6 months or so, a problem ultimately solved by providing a Bakelite coating. Read more...

It's time once again for our regular Open Thread. Apologies this one is late, I got distracted with other things. As usual, talk about whatever you want, so long as it isn't culture war.

One of the things I got distracted with was the book, which I've been making more progress on revising. Hopefully I can keep the momentum up and get it finished in the next few months.

Second, remember that the 2024 Meetup is coming up in New England. We still have some slots available, so sign up if you want to come see ships with me.

Overhauls are Bringing Back the Battleships, Carrier Doom parts two and three, The Ticonderoga Class, The Virginia Class, and for 2023, Miramar 2022 and Hornet Part 1.

Any explosive shell requires some mechanism to set it off, preferably on impact. Early shells had been forced to use time fuzes thanks to the difficulty of designing a safe impact fuze for a round shell that might strike in any orientation, but after the introduction of the rifled gun, it was possible to make a fuze that was generally safe until it was fired and set off the shell immediately upon impact. But they generally relied on a pin or wire that sheared on firing to keep the striker from setting off the detonator, and it was entirely possible that if the fuze was struck or dropped, the strike would break loose. Orders were given to disarm and discard any fuze which was struck or dropped, but the possibility of accident was never too far away.

The solution was to look at the various forces imposed on a shell when it was fired. The shock of firing, known as setback, had been used from the start, but it could be duplicated by accidents. Harder to duplicate was the centrifugal force produced by the shell's spin,⁵ because it pushed on different parts of the shell differently. The solution was to restrain the striker with two or more spring-loaded safety pins,⁶ so that even if a shock was to temporarily dislodge one pin, the other(s) would remain in place. The fuze pictured above has a secondary centrifugal safety feature in the form of a separate firing pin, which is normally concealed within the striker and held in place by the safety pins. When fired, the setback holds it concealed within the striker, and after it leaves the muzzle, the centrifugal force swings it into the unlocked position, a device to make the fuze "boresafe". Also worth noting in this fuze is the creep spring, which is designed to counter the force produced by air resistance on the shell and keep the striker at a distance from the primer until the shell actually hits something.⁷ Read more...

One aspect of battleship ammunition that I have not discussed very much (with one notable exception) is fuzing, the process of making shells go off at the appropriate time. But this is a critical part of gunnery, as a shell that doesn't go off is of very little use, while a shell that goes off early is potentially disastrous. Designers have to meet both of these challenges while also keeping the fuze compact and setting it up for best effect against the target.

An early tubular time fuze

The earliest shells used time fuzes, which at their core were tubes of packed gunpowder calibrated to burn for a specific length of time after being ignited by the powder gasses on firing, in the hope that they would go off after the shell was lodged in the target. This posed a number of problems. First, shells that bounced off or broke up on impact would do no damage, and there was even the possibility that a very brave man could douse a shell's fuze or throw it overboard. Second, the packed gunpowder was easily damaged by the force of firing, particularly on the early wooden-cased fuzes, which would tend to expose more surface area and cause the fuze to detonate early. Third, the burning fuze could be snuffed out on impact, a particular problem if it ricocheted off the water before reaching the target. And fourth, while the burning time could be adjusted by cutting the fuze tube, and most fuzes, whether metal or wood-cased, were marked to accommodate this, it was a rather involved process in the heat of battle, particularly because the fuze then had to be inserted into the shell before the gun could be loaded. Cutting fuzes could be eliminated by supplying each shell with a number of different fuzes cut and formulated to burn to different times, but that didn't solve the problems of needing to fit them to the shell in action. And of course the exposed fuzes were vulnerable to mechanical damage or water. Read more...

It's time once again for our regular Open Thread. Talk about whatever you want, so long as it isn't Culture War.

Also, a reminder that signups for the 2024 Meetup in New England are still open, and you should come.

Overhauls are Carrier Doom Part 1, NWAS Cruise Missiles Part 1, Naval Video Games, and for 2022-23, the Fatherly One's review of the Musée de l’air et de l’espace and ESSM.

It's been a very long time since I dug into my collection of photos from the Iowa and shared some of them with you. This time, we're going to look at Iowa's ground tackle, the technical term for anchors, chains, and the like.

To keep her from drifting when the engines are off and she isn't tied up at a pier, Iowa is equipped with two stockless bower anchors of 30,000 lb each. The anchor is designed to dig in when pulled horizontally and free itself when pulled vertically.

Read more...

After the success of last year's meetup in LA, I am doing another one in New England, from May 2nd to May 5th. We'll be staying in Providence, Rhode Island, where I have an AirBnB reserved, although it's currently full, so anyone who hasn't signed up will need to get a hotel room.

Why should you come?

Read more...

It's time for our regular Open Thread. Talk about whatever you want, so long as it isn't Culture War.

Watching recommendation: Netflix has They Shall Not Grow Old through the end of the year. This is a selection of colorized film from WWI, with audio from interviews with veterans overlaid. Well worth a watch.

Overhauls are Electronic Warfare Part 1, Phalanx, The Two-Power Standard Today, and for 2022 Norway Parts eleven and twelve and More Missiles!.

As is well known to readers of this site, I am a connoisseur of military museums of various types. And in my visiting of every museum I pass by that Lord Nelson doesn't drag me away from, I've noticed a problem. Most air museums aren't very good, because planes are big.

The basic problem is simple. It's very rare to find an artifact (broadly defined) which can hold a typical visitor's interest for more than 30 seconds, maybe a minute at the outside. Which is fine if your museum is full of small things (Roman weapons, paintings, 16th-century dresses, Pokemon plush) so you can put dozens into each room. But this poses an obvious problem for air museums, whose artifacts are each the size of a room. A few museums (Dayton, Pima and Udvar-Hazy spring to mind) are able to bury this problem under the sheer number of planes they have, but most museums can't do that. A typical small air museum has at most a dozen planes, and even if they try to stretch their artifact count with an engine here and a flight suit there (as most of them do) that's still maybe a half-hour visitor experience. Read more...