Landships II

MikeS0000 · Private

Hello and Question on Compasses

Rectalgia · Legend

Not aware of any photos but I take it you have looked at the several topics here dealing with tank compasses:

http://landships.activeboard.com/forum.spark?aBID=63528&p=3&topicID=11598921&page=1

http://www.activeboard.com/forum.spark?aBID=63528&p=3&topicID=12604338&page=1

There's also

http://1914-1918.invisionzone.com/forums/index.php?showtopic=161619 (Includes reference to both above.)

There's a Google book mention

Personal Perspectives: World War I (States magnetic compasses useless, hence the hazardous undertaking of laying out tapes at the starting point and beyond to mark the direction of objective.)

And it appears the tankers themselves weren't well versed in navigation and so on, at least not initially.

http://www.historylearningsite.co.uk/tanks_and_world_war_one.htm - States "The first tanks arrived in Europe on August 30th but the crews were faced with major problems. One tank commander wrote:

I and my crew did not have a tank of our own the whole time we were in England. Ours went wrong the day it arrived. We had no reconnaissance or map reading....no practices or lectures on the compass....we had no signaling....and no practice in considering orders. We had no knowledge of where to look for information that would be necessary for us as tank commanders, nor did we know what information we should be likely to require.

In forum commentary, comparison is often made with ship's (magnetic) compasses of the time. The difference is that ships typically operate relatively far from external ferrous/magnetic objects, well above any local perturbations of the magnetic field on/near the earth's surface and typically on longer time scales and with less criticality in terms of minute-by-minute location - the magnetic compass bearing of ships being just an indicator for steering between precise positional fixes by stellar navigation and land sightings/landmarks.

Local magnetic fields are complex things (almost fractal) and an accurate compass reading from within a moving tank might be possible but whether or not that can be relied upon, minute by minute and hour by hour, is another thing.

It seems to me, until the advent of the gyrocompass (and now satnav), tanks were more suited to the cavalry role (and landmark navigation/follow the leader) than might be implied by the "landships" characterisation.

-- Edited by Rectalgia on Thursday 24th of March 2011 07:42:47 AM

kieffer · Commander in Chief

Rectalgia wrote:

In forum commentary, comparison is often made with ship's (magnetic) compasses of the time. The difference is that ships typically operate relatively far from external ferrous/magnetic objects, well above any local perturbations of the magnetic field on/near the earth's surface and typically on longer time scales and with less criticality in terms of minute-by-minute location - the magnetic compass bearing of ships being just an indicator for steering between precise positional fixes by stellar navigation and land sightings/landmarks.

apart from the deviation caused by the magnetic North Pole (differs from the geographical NP, the magnetic changes daily a bit and turns around the geographical NP so to speak), ships compasses are calibrated before leaving port. The ship is moored on a buoy, turned in different directions by a tug and course is compared with the deviation. Influence of the ship itself is countered by two iron balls left and right near the compass, and iron underneath. For the direction there's a compass on the ships bridge, but for positioning there's another one usually on top, further away from the ships iron and lesser deviated, with all round visibility. With the sight on this compass one can determine the position, two landmarks have to be seen, plotted from the same position. But that's all old school now I think, in gps-time.

MikeS0000 · Private

Hello Folks -

Thanks to the gentlemen over on the Great War Forum, below is a photo of the Tank Compass in the IWM and another of one I ran across, where the owner thought it was a Tank Compass. And, it appears so.

Best regards!

- Mike.�

�

-- Edited by MikeS0000 on Thursday 24th of March 2011 03:02:23 PM

Rectalgia · Legend

Interesting, thanks. The first one appears to be a Pattern 200 which was an early aircraft type. Nothing to prevent it being used in tanks as well of course. Here is a picture https://i240.photobucket.com/albums/ff18/N704FS/77I1583b.jpg from http://www.theaerodrome.com/forum/replica-aircraft/33439-sopwith-baby-project-85.html. The compass is also mentioned in http://www.theaerodrome.com/forum/replica-aircraft/51123-british-compass-pattern-250-259-a.html - posted by member aircraftclocks: The following information is taken from what I believe is a RFC instrument repairman's course syllabus.

The patterns of liquid compasses now used are as follows:-

Pattern No. 200 (Very little used)
Pattern No. 250 (Very little used)
Pattern No. 251 (Very little used)
Pattern No. 252 (Used on large and slow machines)
Pattern No. 253 (Used on large and slow machines)
Pattern No. 255 (Obsolete)
Pattern No. 259 (Very little used)
Pattern R.A.F. Mark 2 (Generally used)
Pattern C.O. 5/17 (Widely used)
I think it is mentioned elsewhere there that the Patt 200 dates from 1911.

-- Edited by Rectalgia on Thursday 24th of March 2011 04:21:12 PM

Centurion · Legend

kieffer wrote:
Rectalgia wrote:

In forum commentary, comparison is often made with ship's (magnetic) compasses of the time. The difference is that ships typically operate relatively far from external ferrous/magnetic objects, well above any local perturbations of the magnetic field on/near the earth's surface and typically on longer time scales and with less criticality in terms of minute-by-minute location - the magnetic compass bearing of ships being just an indicator for steering between precise positional fixes by stellar navigation and land sightings/landmarks.

apart from the deviation caused by the magnetic North Pole (differs from the geographical NP, the magnetic changes daily a bit and turns around the geographical NP so to speak), ships compasses are calibrated before leaving port. The ship is moored on a buoy, turned in different directions by a tug and course is compared with the deviation. Influence of the ship itself is countered by two iron balls left and right near the compass, and iron underneath. For the direction there's a compass on the ships bridge, but for positioning there's another one usually on top, further away from the ships iron and lesser deviated, with all round visibility. With the sight on this compass one can determine the position, two landmarks have to be seen, plotted from the same position. But that's all old school now I think, in gps-time.

�As I reported on GWF a major problem sems to have been caused by other tanks sometimes being close. Not something one could adjust for using the above technique

�