Question about RPC firing while turning the ship

Guns, torpedoes, mines, bombs, missiles, ammunition, fire control, radars, and electronic warfare.
alecsandros
Senior Member
Posts: 4349
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania

Re: Question about RPC firing while turning the ship

Post by alecsandros »

Thorsten Wahl wrote:
As I have said several times the germans had a technical solution of that problem, wich was quite similar to an true RPC-for train-solution
I know you have, Thorsten, that;s why I wrote "in 1941".

But when was this implemented and realy functional ? Prinz Eugen made firing trials with 360* turns in 1943...

Bismarck almost certainly did not have this operational...
ede144
Member
Posts: 157
Joined: Mon Oct 10, 2011 5:09 pm

Re: Question about RPC firing while turning the ship

Post by ede144 »

I believe it"s more than just RPc and FC computer. The computer were analog working and producing constant solutions, however when the ship turns, the deviationbetween tqo solutions does increase. Second also the data input in range and bearing changes drastically. If I'm remember correct, than range was done at Km ships by stereoscopic range finders. Every time the range taker got a single clear picture than he pushed a button and the range data was transmitted to theFC. Similar was done. By bearing. If the change in range changes more rapidly,it takes more time to find the new distance.In this time your solution gets worse with every second. Even Radar doesn't help, because there operator hAs to keephis target in the middle of his small screen. I wonder if this is an easy task. When you are up in a coning tower which is turning and swinging.
Regards
Ede
steffen19k
Member
Posts: 77
Joined: Fri Jun 08, 2012 5:31 pm

Re: Question about RPC firing while turning the ship

Post by steffen19k »

Ede is pretty much hitting on the head what I was I was trying (and apparently failed) to get at with my 3 part breakdown of the fire control solution.

For an example: On the m1 tank, with 2 axis stabilization, Laser Range Finder (LRF) digital ballistic computer, GPS, ring laser Gyrocompass, and shooting at a normal battle sight range of 1200 meters, with a mach 3 projectile, if the tank turned sharp enough, the gunner would have to "dump the lead" and re lase the target.

And that's with a modern digital computer, so I can't imagine what a 10 (let alone 40) degree turn would do to the accurate plotting of a battleship round that's in flight for 15 or 20 seconds.
Here is everything I know about war: Someone wins, Someone loses, and nothing is ever the same again. Here is everything I know about life: The only certainties are death and taxes.
The enemy of freedom are those who proclaim only they can uphold it.
alecsandros
Senior Member
Posts: 4349
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania

Re: Question about RPC firing while turning the ship

Post by alecsandros »

ede144 wrote: Every time the range taker got a single clear picture than he pushed a button and the range data was transmitted to theFC. Similar was done. By bearing. If the change in range changes more rapidly,it takes more time to find the new distance.In this time your solution gets worse with every second.
Hi Ede,
THis applies to earlier systems, but from 1943 or so USN and KGM had pretty good radars, and the range was automaticaly determined and transmited to the FC computer...
lwd
Senior Member
Posts: 3822
Joined: Sat Jun 17, 2006 2:15 am
Location: Southfield, USA

Re: Question about RPC firing while turning the ship

Post by lwd »

On the otherhand with battleships you can have some pretty significant time of flight issues which means even if your opponent isn't trying to mess up your solution it's easy for it to be off a bit.
alecsandros
Senior Member
Posts: 4349
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania

Re: Question about RPC firing while turning the ship

Post by alecsandros »

lwd wrote:On the otherhand with battleships you can have some pretty significant time of flight issues which means even if your opponent isn't trying to mess up your solution it's easy for it to be off a bit.
This was compensated by the fire control computers.
lwd
Senior Member
Posts: 3822
Joined: Sat Jun 17, 2006 2:15 am
Location: Southfield, USA

Re: Question about RPC firing while turning the ship

Post by lwd »

alecsandros wrote:
lwd wrote:On the otherhand with battleships you can have some pretty significant time of flight issues which means even if your opponent isn't trying to mess up your solution it's easy for it to be off a bit.
This was compensated by the fire control computers.
Not really. Perhaps I was not as clear as I should have been. The fire control system compensates for time of flight based on estimates of the course and speed of the opposing ship. However there will be errors in the estimation of both course and speed. Since these are unknonws there is no way for the fire control system to compensate for them. The further you are from your opponent the greater the errors are likely to be and the greater the time for said errors to multiply positonal errors.
alecsandros
Senior Member
Posts: 4349
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania

Re: Question about RPC firing while turning the ship

Post by alecsandros »

lwd wrote: The further you are from your opponent the greater the errors are likely to be and the greater the time for said errors to multiply positonal errors.
Aha, yes, agreed.
Siegfried
Member
Posts: 20
Joined: Sun Nov 20, 2011 9:40 am

Re: Question about RPC firing while turning the ship

Post by Siegfried »

The distinction between gyro stabilising a gun mount and RPC (Remote Power Control) must be made, they are distinct.

For instance the 10.5cm FLAK gun mounts on German capital ships were tri-axially stabilised and articulated. The gun mount could not only traverse and elevate but the guns could yaw in their cradle so that the always elevated in a vertical plane.

Imagine a US BB with the famous 5 inch mount pointed 45 degrees of the beam. If the ship pitched or rolled (eg say a 12 degree roll from a high speed turn or waves) then not only would the gun need to elevate to compensate it would need to traverse. In the German tri axial mount the gun would need to only yaw and elevate without traversing. This needs to be born in mind when the slow traverse of the German heavy flak is criticised, they needed little traverse control reserve. The fact that the DOP mounts were open and the gun crew walked around them probably made this necessary but the next generation enclosed turreted versions intended for the H class battleships maintained the tri axial stabilisation.

Essentially the German guns were power stabilised in all three axis against ship motions and turning, accepted direct remote control commands from the director for elevation but required follow the pointer power assisted manual traverse.
Thorsten Wahl
Senior Member
Posts: 919
Joined: Mon Apr 27, 2009 4:17 pm

Re: Question about RPC firing while turning the ship

Post by Thorsten Wahl »

the 3rd axis (Kantwinkel) was remotely controlled too
Attachments
Kantwinkelantrieb.jpg
Kantwinkelantrieb.jpg (10.88 KiB) Viewed 5498 times
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!
Siegfried
Member
Posts: 20
Joined: Sun Nov 20, 2011 9:40 am

Re: Question about RPC firing while turning the ship

Post by Siegfried »

Yes indeed, the gyroscopes via pickoffs passed their signal to magnetic amplifiers which operated electro hydraulic valves to operate the gun elevation via hydraulics (and presumably yaw as well) and controlled variable speed electric drives to operate the traverse. The gun mount was fully power controlled for stabilisation and the gunners need do nothing to compensate for ships pitch, roll or turn. However only one axis was remote power control from the FLAK predictor, the other was tracked via "follow the dial". There was apparently a good reason for this relating to the way aim was corrected rather than pure economy. The heavy FLAK predictors on German capital ships were advanced for their day not only being fully tachometric but stabilised on all 3 axis; Bismarck was to have 4 of these however 2 had to be supplied to the Soviet Union under cooperation agreements and so Bismarck sailed with only two of these capable devices with the rear two being more basic.
dunmunro
Senior Member
Posts: 4394
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: Question about RPC firing while turning the ship

Post by dunmunro »

Siegfried wrote:Yes indeed, the gyroscopes via pickoffs passed their signal to magnetic amplifiers which operated electro hydraulic valves to operate the gun elevation via hydraulics (and presumably yaw as well) and controlled variable speed electric drives to operate the traverse. The gun mount was fully power controlled for stabilisation and the gunners need do nothing to compensate for ships pitch, roll or turn. However only one axis was remote power control from the FLAK predictor, the other was tracked via "follow the dial". There was apparently a good reason for this relating to the way aim was corrected rather than pure economy. The heavy FLAK predictors on German capital ships were advanced for their day not only being fully tachometric but stabilised on all 3 axis; Bismarck was to have 4 of these however 2 had to be supplied to the Soviet Union under cooperation agreements and so Bismarck sailed with only two of these capable devices with the rear two being more basic.
Campbell states that the KM AA computer was not tachymetric. Can you supply more detail?
dunmunro
Senior Member
Posts: 4394
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: Question about RPC firing while turning the ship

Post by dunmunro »

alecsandros wrote:

The USN may have had better luck with them, but I don't know of certain examples. At Casablanca and Second Guadalcanal for instance, main battery fire was done with RPC for elevation only...

Cheers,
Main battery control in both the above battles, was entirely done by follow the pointer control.
alecsandros
Senior Member
Posts: 4349
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania

Re: Question about RPC firing while turning the ship

Post by alecsandros »

dunmunro wrote:
alecsandros wrote:

The USN may have had better luck with them, but I don't know of certain examples. At Casablanca and Second Guadalcanal for instance, main battery fire was done with RPC for elevation only...

Cheers,
Main battery control in both the above battles, was entirely done by follow the pointer control.
That would be odd, as both ships had RPC systems on board.
dunmunro
Senior Member
Posts: 4394
Joined: Sat Oct 22, 2005 1:25 am
Location: Langley BC Canada

Re: Question about RPC firing while turning the ship

Post by dunmunro »

alecsandros wrote:
dunmunro wrote:
alecsandros wrote:

The USN may have had better luck with them, but I don't know of certain examples. At Casablanca and Second Guadalcanal for instance, main battery fire was done with RPC for elevation only...

Cheers,
Main battery control in both the above battles, was entirely done by follow the pointer control.
That would be odd, as both ships had RPC systems on board.
The 5"/38 Mk 37 GFCS was fully equipped with RPC, but not the 16" guns.
Post Reply