Landships II

Paratus23 · Sergeant

Compass and clock mounting

TinCanTadpole · Legend

There should be some photos showing the inside of the cab, though it may be easier to find modern pics of surviving vehicles - which may have had items removed. I'll post a link if I come across something, but in the meantime, have you looked at this compass-related thread?

Gwyn Evans · Legend

Good question, and one I've tried and failed to answer so I'm looking forward to future posts in this thread. There's a reference in Frank Mitchell's book "Tank Warfare" to the clocks fitted to Mark IVs being discontinued because too many went missing. Mitchell implies this was because they looked more at home on a mantlepiece than in a dirty tank.

Gwyn

Rectalgia · Legend

I've looked around and had no luck either. The types proposed, the old marine Type 200 or similar, gimbal-mounted or not, require horizontal mounting. I suppose (Mk IV) Hans de Regt's photo might show some possibilities in the driver's and commander's positions. More views of that area in this Fray Bentos blog, specifically
http://4.bp.blogspot.com/-YEy4KxM1_n0/TbiTiwrmJRI/AAAAAAAADSc/MGoSY2tUKHg/s1600/t2.jpg if the site allows the viewing, also
http://1.bp.blogspot.com/-RIY_bh1nmoE/TbiTbOb-hSI/AAAAAAAADSU/a23YpBIhl3c/s1600/t1.jpg which doesn't seem to offer any such accommodation but adds to the depiction of the general area.

Maybe the compass (also the clock) were on removable brackets that simply slotted into an anchor on the bulkhead somewhere close to the commander.� The answer is out there somewhere.

-- Edited by Rectalgia on Saturday 8th of December 2012 06:26:23 AM

Gwyn Evans · Legend

I agree they would have been removable. I've read accounts of tanks being abandoned and the compass and clock removed and taken with the crew. Evidently Frank Mitchell thought the clock was too removable.

Gwyn

TinCanTadpole · Legend

Logically the compass must have been fitted near the commander's station; I'm wondering if they were fitted on the seat-mounting beam, between driver and commander. I've seen a few photos of this area, just a few days ago. It's probably in an old thread, rather than on flickr - will see what I can find.

MK1 Nut · Hero

As far as I can tell, the Compass and 'maybe' clock, were on a drop down shelf type thingy that the gimble compass mounted.

When starting my plans I purchased some photos from Bovington.Unfortunately I was only interested in outside views. Although that soon added up to �70 plus. Didn't mind as it goes to running the records side of Bovington.

They kindly sent me a series of photo copies that I could look through and send back with my selection. I did, I must confess..... scan them... I'm bad, I know.�

What it does mean though that anyone wanting a definitive answser, they can send off for these two photos and get the answer....�

Helen x

MK1 Nut · Hero

Oh, and although not a MK1, this plan shows something similar to what is shown in the photos.

�

Paratus23 · Sergeant

Thanks all for your replies. I'll take Helen's useful advice and get in touch with Bovington to see what shelf thingy photos they have. Let you know how I go

Cheers

Dave

Rob · Legend

From David Fletcher's 'British Mark I Tank 1916' by Osprey Publishing, page 17;

"Shortly before the tanks went to France the War Office asked the Admiralty Compass Department to advise on the matter of compasses in tanks. They decided upon a boat compass, the sort of thing that is carried in ship's boats. The compass had to be carefully adjusted to counter the deviating effect of a dense mass of metal. Even so, according to some sources, the compass deviated every time the driver moved the gear lever and one wonders how it stood up to the continual vibration"

-- Edited by Rob on Tuesday 11th of December 2012 07:24:48 PM

MK1 Nut · Hero

Paratus23 wrote:
Thanks all for your replies. I'll take Helen's useful advice and get in touch with Bovington to see what shelf thingy photos they have. Let you know how I go

Cheers

Dave

Hi Dave, Just realised I didn't meantion something... The numbers at the top of the photo descriptions are Bovington reference numbers. 35-H-1 and 33-H-6. Just quote them with the description and this should speed things up a little. Of course ask them for any other information while you're at it.

Hope this helps

Helen x

�

Paratus23 · Sergeant

Ok, thanks Helen

Rectalgia · Legend

Interesting - the gear lever was not all that massive, the compass must have been within some few feet of it, although for prismatic (marching-sighting) compasses I seem to recall stern warnings about no use within 10 feet of any ferrous materials for precision sighting (yeah, right, leave your rifle and bayonet behind and go stand on yon hilltop). Still, the (presumed) moveable compass compensation masses in the nautical type would reduce the sensitivity of the instrument, I think.

Coping with vibration - don't know about boat compasses but those service prismatics use(d) osmium-iridium to ruby bearing surfaces for the cards which gave many, many (and a lot more many) years of reliable, low-friction service under "rugged" conditions, undoubtedly "over-engineered" by today's standards. They're still going strong. And so's the radium in the "luminous" elements (should be down to half intensity in another 1,500 years or so).

Bagnold of the desert motor group never came to terms with compensated magnetic compasses, which is why he developed his sun compass. And other designs of sun compass became standard for such service after WW1. Long-range navigation across relatively feature-deficient terrain is surely a different circumstance to that mostly experienced in battle tanks but speaks to the difficulties of getting anything like reliable magnetic bearing courses (even when having the luxury to pause in uncontested ground to take them) anywhere near a mass of iron and steel - let alone inside one.