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Tuesday, May 15, 2012

What Are Those Red and White Poles For?

Editor's Note: This is a guest article by Rob Kelly- I found it incredibly informative, I hope you do too!  Thanks Rob!

I’m sure that everyone has seen those red and white poles either mounted on the trails of a gun or howitzer or on the side of an armoured vehicle.  I served 18 years in the Royal Canadian Artillery, so I feel qualified to answer that question.

The short answer is that they are “aiming posts”.  The longer answer is that they are cleaning staves painted up to look like aiming posts. So, what exactly are aiming posts and what are they used for?  First of all aiming posts are only used for indirect fire weapons such as artillery guns and howitzers or mortars. When guns are deployed by an artillery battery a survey device known as an aiming circle or director is set up to the left front of the battery.

When guns are deployed by an artillery battery a survey device known as an aiming circle or director is set up to the left front of the battery.
It has a compass in it to allow it to aim the guns in the desired direction towards the enemy.  Once the director knows which way its pointing, it takes a series of angles to the guns’ sights.  The gun sights then set that angle and moves the gun left or right until the director is centred in the sight.  As long as the director is visible in the centre of the sight, the gun will be pointing in the desired compass bearing.

Now the gun will record itself so that it is not always reliant on the director.  It does this in two ways, by using a distant aiming point like a tower far off in the distance or by the use of aiming posts spaced 25 or 50 apart away from the gun.  So, the gun will send out the first aiming post 25 or 50 metres to the left front of the gun and plant it.  The second post will go an equal distance and be planted so that both posts are lined up with the sight.  The posts go out left front so that the sight won’t be obstructed by the guns barrel.  The aiming posts can also be set up right rear for the same reason.  The gun then records the angle to the posts. 

When a fire mission is received it will contain the bearing or azimuth to the target.  That bearing is applied on the sight (which will turn) and the traverse wheel is turned until the sight is lined up with the aiming posts.  Once that occurs the gun knows that it is on the correct bearing. Keep in mind that the gun sight has two scales, one for the bearing of fire and one for angles to the director and aiming posts. Everything in the artillery is based on the right angle triangle. 

So, if those red and white poles are only used for indirect fire weapons, what are those poles on direct fire weapons like anti tank guns and tank destroyers? They are just unexciting cleaning staves or rods.  They come in two or three parts depending on the length of the gun barrel and come with a variety of attachments, such as a bore brush for cleaning (though in a pinch, with 105mm guns a roll of toilet paper would fit just fine). There is also an attachment commonly known as the “suicide cone”.  If there is a misfire on the gun the detachment will wait a short period of time hoping that the propellant will eventually explode firing the round out of the barrel.  If not, the suicide cone is attached to the cleaning stave, the barrel is lowered and the shell is pushed back down the barrel through the breech.  It is shaped like a cone, so that it does not hit the fuse. It can also be used if the wrong ammunition is loaded or if the gun must be unloaded and there is not safe area to fire it into.

In practice we usually stored our aiming posts in canvas bags and put them in the back of the truck.  They could fit on the trails of the gun, but there was always the chance they could fall off on bumpy roads.  Same with the cleaning staves.  Now if you want to be historically accurate, if your gun is deployed the aiming posts should be out and assembled, not on your trails.

Hopefully those with red and white poles on the sides of their tanks or anti tank guns will now be getting out their green and brown paint and start covering over those red and white poles. 

Rob Kelly

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