Charlie...that second picture is exactly what I am building! except with different tires.
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The Limber
a Limber is actually not an "ammunitions carrier".
A "Caisson" is an ammunitions carrier (originally towed behind a Horse Hitch or Wagon).
Limbers were originally the "hitching" point between the Horse Hitch and the towed trailer.
A Limber could tow one or more Caissons which carried the ammunition,
while another team towed the Field Gun using a Horse hitch and Limber.
With the advent of mechanized warfare, Limbers were modified to do double duty, and carry ammunition and supplies.
Although, the connection to older Artillery equipment, as Charlie points out, is obvious.
I'm sure any Limber with space carried supplies long before anyone decided to clarify their uses.
Interestingly, adding a Limber to a towing vehicle has the effect of correcting inline stability of a heavy Trailer...
basically helps to correct uncontrolled steering and fishtailing.
The Limber also reduces the vertical movement of the hitch and tongue at the trailer, keeping it more level during transport.
It can also help absorb and reduce the shock at the hitch from push and pull.
A great example of a Limber's effect can be seen in a Horse drawn Funeral Cart.
In this case the Limber replaces any type of driving cart, to be the hitching point between the Horse team and the Casket trailer.
This "limber" might also be a Caisson, which are often used in funeral processions.
The Limber helps keep the casket Cart more in line with the Horse Hitch, and more importantly, stabilizes the casket to a more level and stable ride.
If the Cart were connected directly to the Horse Hitch, the cart would bounce and jerk and be very unstable.
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The Field Artillery Tractor towed an 18pounder British Artillery Gun as shown in the photo above
...later, a 25pounder Gun (roughly 3.5" calibre)...with an Ammunitions Limber installed.
Although my Ford FAT is an earlier version, and may have originally towed an 18pdr gun,
most vehicles would have been updated during the War when better equipment became available.
I am fitting my model with a more common 25pdr Howitzer and therefore, a later design of Limber.
The Limber can carry 32 rounds of Ammunition in 16 separate trays in two compartments on either side of the Limber.
I seriously considered whether or not to build a Limber with working doors, interior compartments, and ammunition trays.
But this would seriously complicate the design and make this a more involved component than the Tractor itself!
And then there is still the Field Gun to think about.
Even simplified, the Gun will have a lot more parts and be a lot more complicated to assembly.
I am anticipating a lot of time to get that designed.
So, I decided to go with a simpler approach...the box former interior, and closed rear doors.
But there are plenty of other details to focus on.
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as was pointed out...those holes will receive dowels.
The central dowel is the long central shaft/tube that passes right through the Limber
and has the hitching points at either end.
I have created a full paper part, with a lead-in section, if you want to roll a paper tube.
Unfortunately it will still require more tubes, or a dowel inside for strength.
So, my suggestion is: cut off the lead-in section...and using a 7.5mm dowel (a standard craft dowel size)
wrap it with the paper part...to create an 8mm tube.
After the paper wrap is secure, burnish the seam to smooth it out.
Then cut off the excess dowel and smooth the ends if necessary.
Caps will be coming later for the ends, so theres no need to colour.
Then you need to make sure the hole in the Former assembly is big enough to receive the part.
I have a number of dowels (different sizes) wrapped with sand paper, to sand and clean up holes like this.
