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Mobile Pillbox, "Fahrpanzer"

Picture 1:
Some time ago, Mr. Brad Browne sent us a number of digital images of two mobile turrets that he had
photographed at the Greek War Museum in Athens. In a quest for more information about these
turrets, I used one of Mr. Browne's photos for our Mystery Interior Quiz vehicle. The responses I
received provided more information about the machines, and included additional photographs by Mr.
Pietro Podavini.

Ever since I saw the original photos I have been curious about these machines, and with the assistance
we received from our readers we have finally been able to put together enough information to add a
new vehicle entry into AFV INTERIORS Web Magazine. You might argue that this contraption is
not officially an AFV, but it is close enough to warrant some exploration, and the history that has
gradually appeared is both strange and interesting.

These mobile pillboxes have been named "Fahrpanzers", or "driving tanks", by some. They
apparently were used as armored defensive weapon positions, typically placed in and near
fortifications. In some cases, they were rolled out only during combat, and then when they were not in

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action, were stored inside the fort. In other situations, the Fahrpanzers were placed in a defended
position and moved only if it was likely to be over-run by the enemy. One of the interesting things
about these Fahrpanzers is that they were designed to be lifted onto a horse-drawn carriage for
transport like you see here, and also were supplied with small railroad wheels to be rolled along on
rails, either for short distance placement or for longer transport.

Picture 2:
The transport carriage is made of steel beams and wooden wheels, and includes large wheels at the
rear supporting the weight of the armor and smaller wheels at the front under the driver's seat. I have
included a couple of exterior images of the Fahrpanzer to give you an idea of how the carriage was
designed.

Most of the carriage/wagon terminology is new to me, and if I have made errors in this area they are
my own. I would appreciate it if you would drop me a line to correct any missteps. In America, the
turning pivot at the front of the carriage or wagon is called the "fifth wheel", and you can clearly see
how this part was named from the appearance here of two wheels, one stacked on top of the other.
The pivot point allows the horses to turn and then have the carriage follow along. You have probably
seen the fifth wheel on a child's wagon that allows the handle, which is attached to the front wheels,
also to be steered in one direction.

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Picture 3:
The attached data plate over the double doors of the turret indicate that the machine was
manufactured by the Friederich Krupp AG, Grusonwerk, in Magdeburg-Buckau. This is Fahrpanzer
number 25, constructed in 1894. As you probably know, Fried. Krupp AG has been a long-time
manufacturer of steel products, at one time being the world's largest steel makers and arms
manufacturers, particularly well-known for their cast artillery in WWI, and the same, along with tank
and tank guns, in WWII. The company still exists, today called ThyssenKrupp AG. This line of
Fahrpanzer turret production was started by Grusonwerk before it was taken over by Krupp in 1893 to
become Krupp Grusonwerk AG in Magdeburg.

Picture 4:
A closer view of the
front of the transport
carriage for the
Fahrpanzer shows the
details of the fifth

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wheel and attachments
for the horse tack. The
handwheel under the
rickety seat applies the
brakes to both of the
larger wheels via a
metal girder under the
carriage. We will see
more detail about this in
a moment. Under the
footrest and metal
floorboard is the
attachment for the pull
bar that would extend
out forward and end in
a cross draw bar in front
of the horses. You can
see from the photo that
as the horses pulled the
draw bar to the side, the
fifth wheel would turn
with it along with the
attached front wheels.
Note the small step,
called a "short step",

attached to the axle nut
on this front wheel, allowing the driver a way to climb up into his seat with some dignity.

Pivoting on top of the lower portion of the fifth wheel is the connection for the big steel beams that
support the turret on the large wheels in the rear, as well as the driver's seat. The application of lots of
grease was the only way to keep the fifth wheel operating properly, and the same holds true for the
fifth wheels on tractor trailer trucks on the roads today.

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Picture 5:
A close look at the fifth wheel assembly and the front wheels shows the total lack of any springs for
the driver. Most of the material used in the manufacture of these parts appears to be steel, but the
wheels are still wooden, perhaps to help absorb some of the road shock. Note that the top of the pivot
pin that holds the two fifth wheel parts together is centered on the driver's foot board, which is
covered with a non-slip surface treatment. The original image was a bit dark, and when I brightened it
the colors shifted a bit.

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Picture 6:
This front view again shows the fifth wheel assembly and the socket for the tow bar that would run
forward between the horses. Again, notice the lack of springs for the front suspension. The wooden
spoked wheels are tired by a steel band. The cross axle does not turn. The hubs that are attached to the
ends of the axles allow the wheels to turn.

Picture 7:
This photo is taken stooping down between the two wheel sets, looking down and back under the
turret support. The main axle can't be seen from here, but the pipe traversing above the I beam that
holds the two brake pads is part of the braking mechanism that applies the brakes to both rear wheels
when the handwheel is turned. I suspect this brake is more like a parking brake, as it would take a
number of turns to apply them and it isn't something you would want to do with the machine in
motion while driving the horses.

Note how the Fahrpanzer is mounted on a smaller carriage with railroad type flanged wheels, the
whole thing now sitting on the side rails of the carriage beams. The railroad wheels ment that the
Fahrpanzer could be transported on the small 60cm narrow gauge railway tracks. Apparently, the

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whole sled platform slides up onto this carriage for horse transport, and is then held in place by the
brackets you see on either side.

Picture 8:
Notice that the hand brake wheel has Russian or Greek instruction on which direction to apply the
brakes, and which way to release them. These turrets may have been sold to the Bulgarians and were
used during WWI. Apparently, the Greeks captured them from the Bulgarians, and then Fahrpanzers
somehow ended up in this Athens Museum. Let's take a look into the Krupp turret now and see how it
is constructed.

Note the door hardware and the brackets for stowing unknown items. Inside is a pedestal mounted on
a wide cast floor, and two seats are visible here, probably for a gunner and a loader/commander. Let's
take a closer look.

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Picture 9:
Most of the pedestal and turntable floor appears to be one large casting, with both seats and a large
handwheel for rotating the pedestal attached to it. The handwheel was most likely operated by the
person in this closest seat, the seat support is attached at the base of the pedestal with a wingnut that
would allow the seat to swing over closer to the handwheel if needed.

Note the short metal strip that is welded around the pedestal, circling the entire floor. I suspect the
area near the wall was stacked with ammo, and the metal strip kept anything from interfering with the
pedestal and possibly jamming it.

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Picture 10:
This view looking down at the base of the pedestal provides some idea of how the turret worked. The
handwheel rotated the pedestal on the turret floor via a gear system hidden from view by the pedestal
base. The top of the pedestal is attached to the hemispherical turret roof over our head, which rotated
on the turret walls on bearings/wheels. So as you sat in these seats and worked the traverse
handwheel, the walls of the casement would stay still, but the pedestal and the turret up above would
rotate, taking the gun along with it.

The large bolt at the base of the turret might have been provided to allow you keep the turret from
rotating using a braking system. By turning the bolt, you open or close the ends of the metal strip that
surrounds the pedestal base. By slowly closing the gap between the ends, you essentially put braking
pressure on the pedestal base, keeping it from rotating in relation to the floor. You could then turn the
bolt the other direction and open the ends, releasing the pedestal base and allowing it to rotate again.
That is our first theory as to what this bolt thing does.

The alternate theory is that the threaded bolt is a way of precisely aligning the over-head turret with
the pedestal. In this case, by screwing the bolt in one direction you bring the turret around slightly in
relation to the pedestal, and by reversing your direction on the bolt you bring the turret around
slightly the other way. Mr. Browne and I like the first explanation best, but you can pick whichever
you like. On the other hand, if you actually know what this mechanism does, let us know!

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Picture 11:
Here is the other side of the turret floor. Not much to see here but the absence of any really interesting
equipment. I wonder what the foot pedal looking thing is rising up from the floor at our left. If it
pivots at the base, and it looks like it might, it is possible that it could then lay back over the pedestal
base. If there is a hole in the top of the "pedal", it might align with the holes in the base and allow you
then to put a pin or bolt through the two holes. That would also lock the pedestal in place, keeping it
and the attached turret from rotating, acting like a travel lock.

On the other hand, Roy A. Lingle wrote to suggest that the holes could be used for staking out
traverse limits. By placing stakes in the holes and flipping the "pedal" down, the turret could only be
traversed in either direction until the pedal hit a stake, therefore setting a left and right limit of fire.

From the one drawing I have seen of the interior of the Fahrpanzer (see our references at the end of
the web page), ammo was placed inside in vertical racks around the perimeter of the armor. That
would just about fill the space you see between the armor wall and the strip of metal welded to the
floor around the pedestal base. Unfortunately, nothing remains of the ammo racks today.

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Picture 12:
There is some evidence from old drawings found in the Military Historical Museum in Dresden,
Germany, that the ammunition racks in the Fahrpanzers were based on a design very similar to these.
There were individual racks that stored the munitions vertically, each rack removable independently.
A hinged metal plate cover protected the rounds in the racks, and provided a convenient flat surface
for the crew inside the turret. If these are indeed the racks, there were thirteen 53mm rounds
(although some period sources state they were 50mm) stowed in each rack, with space around the
casement for approximately eight racks.

Picture 13:
The view looking up more into the
rotating turret shows how this
whole design works. The photo
was provided by Mr. Pietro
Podavini from Italy, a past
contributor to AFV INTERIORS
and also a visitor to the same
military museum in May of 1992.
The interior is not freshly painted
and it is possible that Mr. Podavini
visited the museum at an earlier
date than Mr. Browne. The seats
have been moved from what we
saw previously, but the turret
traverse handwheel is still
dominating the front of the
casement.

Above the handwheel, you can see
that the pedestal branches out into
three posts, two going up to either
side of the turret ceiling, and the
third rising to attach to the armor
under the gun. Each of the tubes
flattens out slightly as it leaves the
top of the pedestal. The Krupp gun

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is also visible in this photo, at least
the breech and elevation
mechanism are visible. Notice that
the breech block is raised and in
the closed position in this shot,
and the breech handle is forward

and therefore mostly out of view.

Picture 14:
We are back in the freshly painted Fahrpanzer again. This is one of the best images we have in this
series. If one picture can tell a thousand words, this is the one. The ends of the pedestal tube branches
can be traced out the sides of the image to end in a flattened section that bolts directly to the domed
turret. The 53mm Krupp gun sits above a shelf, the gun trunions attached to the same shelf. But
notice that the gun breech is now in the lowered and open position, and that the breech handle at the
right is angled back toward us. The breech is apparently still workable.

To the left of the gun breech ring is the elevation mechanism, consisting of the screw rod with a small
handwheel at the bottom, and a riding, cylindrical housing that bolts to the same shelf. As the
elevation handwheel is turned, the screw rod rises or lowers in the housing, making the gun breech

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ring also rise or lower because the end of the screw rod is attached directly to it. A very simple and
yet elegant mechanism, but one that would take a lot of wheel turns to elevate or depress the gun. I
guess the designers were not thinking of the crew having to elevate or depress the gun much in action.

Notice that the breech block seems to be intact, and is of the simple falling type. The breech is open
here and the block can be seen sliding out the bottom of the breech ring. You can also see the 53mm
weapon's breech activating lever on the right side of the ring; it has a very interesting shape. When it
was manufactured, the weapon was regarded as a rapid-firing cannon, not because the breech was
semi-automatic, it was not, but because the ammo was one-piece and could therefore be loaded faster.
One of the turret bearing wheels is partially seen under the turret lip, directly under the gun. There are
probably three of these evenly located around the perimeter of the turret ring.

Picture 15:
A closer view of the breech of the weapon shows some writing stamped into the back of the breech
ring under layers of paint. The writing says, "FRIED KRUPP" on the top line and "ESSEN" on the
bottom. Notice the clean design of the interior armor plate and the use of both screws and rivets to
hold everything together. I don't know why the breech lever is curved like that; you'd think it would
get caught on things, but it seems to be original. Notice that the handles on either side of the lever are
missing-- these were probably made from wood and attached by screws or rivets through the holes

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you see in the handle.

You can also see a small slotted hole on the front of the turret, above the breech, just to the right of
the gun. I suspect this is the peephole for sighting the gun, although, unfortunately, none of our
interior pictures show this area to determine if there is a sight bracket there.

Picture 16:
From a side angle we
can better visualize the
elevation gearing
bracket and its
attachment to the shelf
under the gun. I get the
feeling that things are
missing from the
elevation mechanism,
but I don't know what.
There is a hole on this
side of the bracket
where a set bolt can be
inserted to keep the
screw from moving in
the bracket, but why
was the bracket
designed with the
cylindrical shape
ending in the
concentric cap and bolt
at the left? Perhaps it is
just to deep the gears
inside tightened.

From this angle you
can also see the gun

pivot bearing, or trunion, on this side of the breech ring. There does not seem to be any recoil
mechanism, and this thing surely must have resounded with a shock and a roar when the gun was
fired! Ammunition supply in the turret is said to have been around 130 shells per gun, with a canister
round attaining a range of 400m, a shrapnel shell of 3000m range, and a high explosive with a range
of around 3000m.

Picture 17:
This is just another of the wheel
bearings the turret sits and rolls

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on. The right branch of the
pedestal can be seen rising to
attach to the turret over-head.

The gun in the turret had an
elevation of +10 to -5 degrees and
the rotating dome armor was
approximately 40mm thick. This
was sufficient for protection
against most small arms bullets
and shrapnel that were around at
the turn of the century. The turret
had a very fast rotating speed of a
full 360 degrees in around 15

seconds.

Picture 18:

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This view provides some interesting detail of the turret opening for the gun. You can see the edge of
the vertical sight opening on the turret on this side of the gun barrel. The object mounted to the base
of the barrel appears to be an aiming point that is adjustable up and down. This may mean that there
was no optical sight inside the turret, but just a second aiming point that could be aligned with this
exterior one to get a general bead on the target. There is also a small rain guard over the turret
opening.

Also, up on the top of the turret you can see part of a small hatch opening that was undoubtedly used
to exhaust the stale air from inside the turret. It is very small, and I suspect was insufficient when
repeatedly firing the gun.

Picture 19:
Look what Mr. Browne found along the inside edge of the turret. These appear to be mil markings,
there being a total of 6400 mils in 360 degrees, at least as far as the US military is concerned. But if
you look carefully, you will see that there are not 6400 mils in this 360 degrees. Therein lies a story.

The term "mil" is short for milli-radian, a radian being a unit of angle measurement commonly used
in mathematics. Since there are 1000 milli-radians in one radian, there are about 6283 milli-radians in
a complete circle. The US military found the idea of using milli-radian very useful with maps,
artillery spotting, and a number of other such things requiring degrees or bearings. But the US
military made things easier on themselves by standardizing on 6400 mils in a circle, instead of 6283.
Then other countries did something similar, I'm thinking now of the Russians and the British, but they
decided there should be 6000 mils in a complete circle. As far as the math is concerned, the
differences are not that great. But if you learn in one place that there are 6400 mils in a 360 degree
circle, and use some other country's equipment that thinks there are 6000, something isn't going to

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work out quite right. Artillery guys in particular are fun to get talking about this; each thinks they are
right and the other group is wrong.

As this is a static placement weapon, it makes sense that there are mil markings around the inside of
the turret, as this would assist the gunner in finding targets observed by other spotters and then
relayed into the Fahrpanzer to him. What is really amazing to me is that someone in the foundry
where this thing was made was very good with his tools and was able to make (one way or another)
6283 tiny marks on a strip of metal, and then fasten it onto the inside edge of the turret so there were
no gaps.

Picture 20:
There are also a few peep slots in
the dome, covered with the
traditional pivoting steel cover,
here in the opened position. Notice
the small pin to the right that
keeps the cover from rotating
around. I also noticed in this photo
the excellent finish of the cast
turret dome. Krupp was world
famous for their casting
technology, and the quality of
their work surely shows in this
photo. The end of one of the
pedestal branches attaching to the
dome is visible at the upper right.

Mr. Vermeulen says that the Fahrpanzer had at least two successors. The first was the German MG-
Panzernest, which was a mobile MG turret armed with a single MG34. It was possible to turn this unit
over (to lower its center of gravity) and then attach wheels for transporting. The French developed a
different idea. Their mobile turret consisted of several rings, so that the parts could be transported
independently and therefore more easily.

There are a few other Fahrpanzers in museums around the world; for instance, one is in the collection
of the Belgian Royal Museum of the Army and Military History in Brussels. Our contributor, Mr.
Vermeulen, has studied fortification weapons for some time, and he recommends a few web pages if
you are interested in additional information about Fahrpanzers, or fortification weapons in general.
For pictures of a Swiss Fahrpanzer that will look very familiar to you now, visit this

photo site

. Mr.

Vermeulen took those photos near Airolo, where some of the Fahrpanzers still remain. For some
photos of a Fahrpanzer under restoration, you might want to take a look at

La tourelle mobile

"Gruson"

. And finally, for images of the French version of the mobile turret you may wish to go to

this

photo web site

.

My thanks to our photographers, Mr. Brad Browne and Mr. Pietro Podavini. And of course, I
sincerely thank Mr. Caspar Vermeulen for coming to our rescue and providing some excellent

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information about Fahrpanzers in general. It is an interesting and unique piece of armor. I wonder if
one of these things every fired at targets while traveling via horsepower? That would then make it an
"official" AFV, wouldn't it?

BACK TO AFV INTERIORS HOME PAGE

(c) 2003, AFV INTERIORS Web Magazine

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