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Scotsman
Posted (edited)
2 hours ago, greyman said:

Going by the manual, both the normal and powered mounts have the same firing gear -- which has both electrically powered firing and hand firing. I assume the latter is for back-up. 

 

I disagree about the rate of fire. I'll try and get the pertinent chapter available. The guns in the quadruple mounts always operated in the 'controlled' fashion -- this being integral to the firing mechanism, regardless of powered firing or hand firing.

 

The 'outboard' ends of the boxes are open to let the crew slide / clip in more ammunition.

GB6M1vp.jpg

 

Many thanks. I'm quite the dunce in the mathematics department ... am I reading this right to say:

2-pdr automatic fire --- 68% of rounds contained in a 4.4 milliradian circle (.252 degree circle)

 

http://www.navweaps.com/Weapons/WNBR_2pounder_m8.php

from the information below the quad was only produced in a controlled fire variant -but- as the octuple achieved its slightly higher rate of fire when free firing I know of no reason why the electric motor referenced would not be turning at the rate required for the slightly higher rate of fire. From my reading of the mechanics, there is nothing that prevents the motor from turning at the speed required for the higher rate of fire once fitted, as there was no change to the rest of the mechanism. 
 

I’ll have to research the motor connection specifically as that’s a retrofit...I’ve pinged the Australian navy among others. If as JWilly said the rpm on the crank is the only mechanism governing the firing sequence I’m not sure why you would limit yourself to the lower rate of fire in rpm. 
 

Controlled Firing - In any multiple automatic weapon mounting, if each gun is allowed to fire on its own then they are all going to cycle at a slightly different rate. This means that at some point they are all going to be firing simultaneously, causing obvious shock and vibration problems as well as creating a "gap" in the bullet stream. An alternative to letting the guns fire freely is to synchronize them in some manner such that they fire sequentially and in a pre-determined pattern. This was the path that the British chose for the multiple 2-pdr mountings, and the use of the cranked firing
gear for these mountings ensured that the guns were synchronized - which the British for some reason called "controlled." In other words, the cranked firing gear meant that all guns fired at the same rate and in a planned sequential order and effectively meant that these were semi-automatic, not automatic weapons. In the case of the quad mounting, the guns fired in pairs and the octuple mounting fired in quads. In 1939, the British apparently concluded that the concerns of allowing the guns to fire freely was less of a problem for the octuple mountings than it was for the quadruple mountings and so changed the octuple guns so as to eliminate the "controlled" firing gear.”

“As originally introduced, this was a recoil operated, "controlled" (essentially semi-automatic) weapon which used a manually turned crank to operate the firing gear in the quadruple and octuple mountings (see note below for a further explanation). In 1939 the octuple mountings design was changed to allow fully automatic firing but this was not extended to the quadruple mountings which were only produced in controlled versions throughout the war. However, the quadruple mountings did replace the crank-turning crewmember with an electric motor sometime during the war.”

 

 

Edited by Scotsman

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Scotsman

As for filling while firing...I’ve located the appropriate manuals but they aren't available online....hence the pings to the respective navies etc. the magazines are quite deep when fully loaded in any case. There is a 7 second  clip on YouTube that shows a loading number feeding the mount with a belt while the mount is firing 

 

hqdefault.jpg

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dre21

This might have been addressed but if not could we get like a clear indicator that we are in gear so to speak and the engine have engaged the props. 

It's rather slow going out of the gate and the 1st few times I thought my key mapper is broke or the Trawler is not working cause I didn't notice it going to sea. 

 

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BMBM

Rev it up some before you gear up. You’ll note a slight push and see the speedo pick up.

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Scotsman

Checking Norman Friedman and other sources the ROF listed is ‘approximate’ at 100 rpm for the mount prior to the addition of the motor...which is faster than controlled but less than free fire. That’s information specific to the quad itself. Checking other sources including Brown  and Burt for quad specific information. I’d be inclined to use controlled rof for any manual mount but it’s still unclear to me what the rof after the addition of power was. Hearing from the navies  themselves may take a bit. Checking to see if anyone still holds a quad mount in a museum somewhere.

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tater

Finding a vid of a quad pom pom firing to look at is surprisingly hard. That said, the crew of that gun is indeed 8 from what I can tell.

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tater

Actually, another issue. Positions 4 and 5 have entirely different gun models for some reason (all 3 trawlers).

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dre21
1 hour ago, BMBM said:

Rev it up some before you gear up. You’ll note a slight push and see the speedo pick up.

Ok, but I'm thinking along the line of the player that have not been with game forever .  That are not used to certain things in our game world,  it literally took me a while to figure it out cause I didn't notice a slight push , maybe got a bit impatient and downshifted again cause I saw no difference . 

Just trying to help and get a clear indicator . We loose enough new players cause they can't figure stuff out .

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tater
2 minutes ago, dre21 said:

Just trying to help and get a clear indicator . We loose enough new players cause they can't figure stuff out .

Go to free view and look down at the compass and speed.

Not super clear it's there, though.

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dre21
18 minutes ago, tater said:

Go to free view and look down at the compass and speed.

Not super clear it's there, though.

Not super clear, you said it yourself.  I did that later , again I'm thinking farther down the road not just here and now . 

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tater
10 minutes ago, dre21 said:

Not super clear, you said it yourself.  I did that later , again I'm thinking farther down the road not just here and now . 

What might be useful would be a secondary steering position for ships. The default view would be looking DOWN at a chart table (which shows the map we see when we pull the map up, but put on a table). Looking UP with free view and you're in the ship with an outside view, perhaps.

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jwilly
Posted (edited)
3 hours ago, Scotsman said:

As for filling while firing...I’ve located the appropriate manuals but they aren't available online....hence the pings to the respective navies etc. the magazines are quite deep when fully loaded in any case. There is a 7 second  clip on YouTube that shows a loading number feeding the mount with a belt while the mount is firing 

hqdefault.jpg

Here is that six second video. The latter three seconds are of two loaders. There is no visibility of the end of the already-loaded belt, and in the shown three seconds, no indication of the upper loader sliding the last shell out of the loaded belt so as to put the end center ring of the new belt in place and re-connect by re-inserting the removed shell.

See the previously posted still photo, above, for details of how the belt links are configured.

In any case, the sidewalls of the shell tray are just far enough apart to hold the shells and permit free lateral movement as the belt is drawn through the gun...so sliding the last shell out of the last link in order to connect another belt section would appear to be not physically possible except during the short time when the last layer of belt is exposed and nearly that full layer is still present so that layer can be lifted up in the air, last shell first, to gain slide-out access to the last shell.

Note importantly that the last shell in a fully loaded belt is at the gun end of the shell tray...not at the outboard end. That's because the tray holds 112 shells or eight layers, and obviously the topmost layer must have the first shell in the belt at the gun end in order that it can be loaded into the feed pawls. So, per the back-and-forth logic of the shell tray geometry, the first, third, fifth and seventh layers proceed outward in firing order, and the second, fourth, sixth and eighth layers proceed inward in firing order...resulting in the last shell in the belt being at the gun end of the tray. So, that last shell is unreachable until the seventh layers has been fired and the eighth layer is being drawn into the gun, beginning at its outboard end.

Here's a photo of a jolly loader carrying two belt sections. Note that he's carrying both sections with the last-to-be-fired shell downward and the first-to-be-fired shell upward:

mid_000000.jpg?action=e&cat=Photographs

Because the shell-removal-and-reinsertion process was easiest to do in an uncrowded work space, 112 shell belts usually were prepared in advance, then loaded all at once into an empty tray. Here is a prepared belt being taken to a gun, on destroyer HMS Ashanti in late 1941. There are eleven ratings in the workline, with at least eight of them and perhaps all eleven carrying the belt. A full belt weighed about 350 pounds...2.87 pounds for one complete shell, plus an ounce or two for the link...so there's plenty of weight for the men to carry.

mid_000000.jpg?action=e&cat=Photographs

And here's a gun crew preparing belts for their gun mount in advance of the next combat:

mid_000000.jpg?action=e&cat=Photographs

The above several photos are from:

British Naval Weapons of World War 2
Volume 1: Destroyer Weapons
John Lambert & Norman Friedman
Seaforth Publishing,
ISBN: 9781526747679

Edited by jwilly

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drkmouse

one  coment from  the ignroent :D I had a blast, once i figured out  how to  move the dmab thing :D>  the  guns worked as i thought they would, though th e quad  vis block was  took a sec to get used to.

great  job alaroudn rats and ty forf  assisting the navy gmae

 ( should be a limmeted # of those avail at aLL ports  on the coast) 

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Scotsman

This video is post war so I assume everything shown is powered at this point as its at the end of the gun's career. 2 scenes starting around 1:25 or so...both indicate a rate of fire exceeding 100 rpm and  either meeting or exceeding the spec of 115 rpm, but you guys can count for yourself. I think we will stay with the spec rate of fire currently used as its obvious from this that the rof is faster than 100 rpm  for a 4 barrel mount equipped with full power. 

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tater

So why are there 2 different 20mm mounts? One is lower res than the other, and the part of the barrel that recoils is different.

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Scotsman
12 minutes ago, jwilly said:

Here is that six second video. The latter three seconds are of two loaders. There is no visibility of the end of the already-loaded belt, and in the shown three seconds, no indication of the upper loader sliding the last shell out of the loaded belt so as to put the end center ring of the new belt in place and re-connect by re-inserting the removed shell.

See the previously posted still photo, above, for details of how the belt links are configured.

In any case, the sidewalls of the shell tray are just far enough apart to hold the shells and permit free lateral movement as the belt is drawn through the gun...so sliding the last shell out of the last link in order to connect another belt section would appear to be not physically possible except during the short time when the last layer of belt is exposed and nearly that full layer is still present so that layer can be lifted up in the air, last shell first, to gain slide-out access to the last shell.

Note importantly that the last shell in a fully loaded belt is at the gun end of the shell tray...not at the outboard end. That's because the tray holds 112 shells or eight layers, and obviously the topmost layer must have the first shell in the belt at the gun end in order that it can be loaded into the feed pawls. So, per the back-and-forth logic of the shell tray geometry, the first, third, fifth and seventh layers proceed outward in firing order, and the second, fourth, sixth and eighth layers proceed inward in firing order...resulting in the last shell in the belt being at the gun end of the tray. So, that last shell is unreachable until the seventh layers has been fired and the eighth layer is being drawn into the gun, beginning at its outboard end.

Here's a photo of a jolly loader carrying two belt sections. Note that he's carrying both sections with the last-to-be-fired shell downward and the first-to-be-fired shell upward:

mid_000000.jpg?action=e&cat=Photographs

Because the shell-removal-and-reinsertion process was easiest to do in an uncrowded work space, 112 shell belts usually were prepared in advance, then loaded all at once into an empty tray. Here is a prepared belt being taken to a gun, on destroyer HMS Ashanti in late 1941. There are eleven ratings in the workline, with at least eight of them and perhaps all eleven carrying the belt. A full belt weighed about 350 pounds...2.87 pounds for one complete shell, plus an ounce or two for the link...so there's plenty of weight for the men to carry.

mid_000000.jpg?action=e&cat=Photographs

And here's a gun crew preparing belts for their gun mount in advance of the next combat:

mid_000000.jpg?action=e&cat=Photographs

The above several photos are from:

British Naval Weapons of World War 2
Volume 1: Destroyer Weapons
John Lambert & Norman Friedman
Seaforth Publishing,
ISBN: 9781526747679

The question I've got doesn't concern linking of belts or loading of full belts per say. It's obvious that loading a full belt wasn't a trivial task. The question is how does the gun react to single belts added to the trays as the last of the full belt is fired off. Was the feed mechanism capable of grabbing the newly introduced belt even when it wasn't linked to the last round of the longer belt. I continue to deep dive but I dont have an answer. I found a picture of the linking mechanism for a single barrel and it involved a wheel/screw arrangement to seat the round joining belts...I don't believe I have seen any evidence of that on mount so belt linking was done below deck as best I can tell. The question remains though as to how the feed reacts to the introduction of a fresh belt as the last round of a long belt is fired. I don't have an obvious answer ATM. 

Just now, tater said:

So why are there 2 different 20mm mounts? One is lower res than the other, and the part of the barrel that recoils is different.

bmbm question 

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jwilly
Posted (edited)

A previous post in this thread says that the quad guns fired in diagonal pairs, and I thought I had seen that same information elsewhere, but at 1:26 in the video above it's very clear that the guns are firing left two then right two.

Maybe different marks of the mounts...which included the mechanism to fire the individual guns...had different orders?

Edited by jwilly

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BMBM
16 minutes ago, tater said:

So why are there 2 different 20mm mounts? One is lower res than the other, and the part of the barrel that recoils is different.

Probably because Hatch and I worked different versions of the file just prior to release. Expect a cleanup and correction in upcoming patches. Hardly a showstopper in my book. The main thing is: does it work; does it fulfil a useful role, and more importantly are you having fun with it?

We ran some experiments to add wave action but were unsuccessful in the first attempt. Having another go at it.

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Scotsman
18 minutes ago, jwilly said:

A previous post in this thread says that the quad guns fired in diagonal pairs, and I thought I had seen that same information elsewhere, but at 1:26 in the video above it's very clear that the guns are firing left two then right two.

Maybe different marks of the mounts...which included the mechanism to fire the individual guns...had different orders?

No idea...but I consider video of firing like that as conclusive with regards to the manual vs power mounts. Again that is at the end of the line for the gun mount more or less so it should be in its final form I should think. From what I see in the video the rate of fire met or even exceeded spec for the octuple mount so rate of fire will stay where its at for now 

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tater
7 minutes ago, BMBM said:

Probably because Hatch and I worked different versions of the file just prior to release. Expect a cleanup and correction in upcoming patches. Hardly a showstopper in my book. The main thing is: does it work; does it fulfil a useful role, and more importantly are you having fun with it?

We ran some experiments to add wave action but were unsuccessful in the first attempt. Having another go at it.

Cool. Just throwing it out there in case you missed it. Guns seem to work as expected, just look different.

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Scotsman

Thanks for all the updates guys - useful for us. I consider the ROF thing put to bed for now so I am off to work other 'stuff' having to do with the naval and the harbor

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greyman
2 hours ago, jwilly said:

A previous post in this thread says that the quad guns fired in diagonal pairs, and I thought I had seen that same information elsewhere, but at 1:26 in the video above it's very clear that the guns are firing left two then right two.

Maybe different marks of the mounts...which included the mechanism to fire the individual guns...had different orders?

It must be something that showed up later. Here is a wartime clip showing the guns firing as described in the manual:

https://i.imgur.com/nBwsl7Y.mp4

For what its worth, I took the clip Scotsman posted and the wartime one here into video editing software in an attempt to make sure of the rates of fire. In the 1950 one the guns are firing at 102 rounds/min and the wartime clip above is 96 rounds/min. 

Rate of fire notwithstanding, it would be great to have the diagonal pairs firing -- it would add immensely to the pom pom 'feel'.

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jwilly

Regarding measurement of elapsed time based on image sequences in historical film:

A lot of WWII movie footage...certainly 8mm, but a lot of 16mm and 35mm too...was shot with cameras that were driven by wind-up spring motors with mechanical governors.

Battery motors of that era had imperfect speed control too, but in any case were less often used by mobile users because the batteries were lead-acid-type and therefore were much heavier.

Such spring motors had generally good governors, but they weren't perfect. It was common for them to be +/- 5% or even +/- 10% on frame rate. In cold weather, they could be much slower than -10%.

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Scotsman

I think we have done due diligence here...the post war footage is 1950 or so and I have no idea what that was shot with. I've looked at several clips and the rate of fire from timing is somewhat variable. We aren't talking a great deal of difference from say 96-98 rpm to 115 rpm...footage confirms rates of fire in-between these two as well. In the interests of KISS and until we get confirmation from a commonwealth navy source I'm going to leave things where they are. It may be a tad fast...but I think the variability is of interest too as it appears to have something to do with how the gear is being driven and motor selection/condition. I don't think there is any doubt some of these weapons were exceeding the controlled fire specification....and we know from the octuple that the guns can be allowed to free fire without harm/damage. 

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james10
Posted (edited)
8 hours ago, jwilly said:

Regarding measurement of elapsed time based on image sequences in historical film:

A lot of WWII movie footage...certainly 8mm, but a lot of 16mm and 35mm too...was shot with cameras that were driven by wind-up spring motors with mechanical governors.

Battery motors of that era had imperfect speed control too, but in any case were less often used by mobile users because the batteries were lead-acid-type and therefore were much heavier.

Such spring motors had generally good governors, but they weren't perfect. It was common for them to be +/- 5% or even +/- 10% on frame rate. In cold weather, they could be much slower than -10%.

Predominately true.

I believe the standard "home movie" during the 30's to 50's used 16mm. Film emulsion was not all that sensitive and color was out of the question in 8mm. 16mm was also predominately monochrome as well. 35mm was usually destined for the Newsreel cinemas.

The biggest issue is frame rate. The standard frame rate for cinema release was 18 fps for mute (No sound) and 24 fps for sound. Notwithstanding that synchronized sound for film only really commenced in 1927 with the release of "The Jazz Singer". Most film shot during the war was mute. The cameras may have been ungainly and heavy but the sound recording kit was significantly more so. Actual "magnetic tape recorders" in the "more modern sense" didn't really see the light of day until post war. Sound would be recorded directly to acetate or wax disk.

So the framerate of a film can have variances simply due to the method used to drive the cameras action, clockwork being pretty common for the more portable cameras. Depending on the display destination the films framerate could be either 18fps (mute cinema) or 24fps (sound cinema) with the attendant speed variances. Newsreel films which are the most numerous available from WWII would end up for display at 24fps. 18fps was selected because it was the lowest framerate where the viewer perceived the least flicker in the image onscreen vs running time for the reel. The increase in fps to 24fps was dictated by the requirement of the sound system and to set a long overdue standard in cinema presentation so a film would be presented as the producers intended regardless where in the world the film was shown. Alas the story is not yet finished.

Here is where it gets a whole lot more complicated. Transferring film to video. Historically speaking the standard framerate for video, specifically and originally television would depend on the country you were in at the time. The US framerate for broadcast television (NTSC) was 30fps. The other common framerate was 25fps (PAL, SECAM). Film to video transfer was called telecine, Basically a film projector and a video camera combination. They were either early on optical (quite literally a projector and a camera) or later a scanning electron beam in nature. The later ones were predominantly scanning electron beam, or also called flying spot scanners. Guess what happens to a film that was supposed to be presented at 24fps but is presented at 30fps. Yep it runs faster. So much so in the US they had to develop methods to pitch shift the audio down so the soundtrack didn’t resemble the “chipmonks”. The shift from 24 to 25fps wasn’t so audible. Just also imagine if you will the results of a film shot at 18fps played back at 30fps. An almost double framerate. All of this is way before the advent of digital video files. Modern digital video files can be played back at pretty well any framerate it is the intervening conversions that are important. Film regardless of anything will have to be transferred to video via some form of telecine. What was the original films framerate vs the framerate the telecine process was performed at? Original film 18fps to video at 30fps? Even 18 to 25fps is a significant speed shift. This will have a SERIOUS impact in the perceived rate of fire of any automatic guns recorded.

The video presented by scotsman being made in the 50’s is likely to originate at 24fps, also Pathe was a cinema Newsreel company. Being a British film, the telecine transfer is very likely to be PAL at 25fps. Also, during the 50s television was still in its infancy and not yet a dominating force but the writing was being written “on the wall”.

The upshot of this is relying on a “film”, especially historical films on video as the basis for determining the rate of fire of an automatic weapon recorded on that film is spectacularly problematic, especially if the province of the film is unclear. You can make “guesses” based on the displayed motion especially people walking. If they look to be walking “smartly” as can be seen in a lot of silent films, the film is probably exhibiting the results of framerate increase in the telecine process. Fortunately, people’s movements are pretty constant. If the movement seems fast it probably is.

Cheers.

Edited by james10

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