Restoration of an AH-IV-S tankette in the Czech Republic

The tankette had been standing outside for at least 20 years, and the external finish left something to be desired, but it was surprisingly complete, and most of the really sensitive internal parts had been kept indoors and were well preserved.
The Czech team received the tankette with an enthusiasm that we had never been able to imagine, and it was not left standing for long before the restoration began.

So far we have assisted by photo-documenting and describing the restoration object and the tankett that the association restored (Swedish no 146). This vehicle was also brought to Prague for Tank Day 2006 and was thoroughly documented by the Czech museum staff.

Each step of the process is thoroughly documented. You never know which piece of information which might later be critical, and it is important to be methodic.

This is a small tankette, but it is technically advanced and contains an astonishing amount of parts.

The picture on the left shows the tankette from above, with its front downwards. The drivers place is to the left in the picture, approximately to the side of the gearbox. Furthest to the rear in the hull is the engine (with the valve cover removed) and forward of the engine is the gearbox. From the gearbox the drive shaft in the centre of the hull goes to the steering gearbox, on each side of which the steering brake drums are mounted, and from them a drive shaft each side transmits the power to the drive sprockets.
To the right of the engine is the radiator, and to the left in the picture, rearmost in the hull you can see the main fuel tank.

The engine and gearbox are removed from the hull. The engine is a 6-cylinder over-head valve engine with a dry sump lubrication system, designed and manufactured by Volvo. The gearbox is a so called pre-select gearbox of Praga-Wilson type (similar to the one used in the Daimler Dingo). In modern language these are often described as "semi- automatic". You (pre)select a gear using a mechanical control mounted on the gearbox, but the actual shift only takes place when you depress and release the gear shift pedal. If you plan how you drive and select your next gear in advance the actual gear shift will be very smooth and quick. There is no clutch in the classic sense, the smooth engaging of the next gear takes place in the gearbox itself.

Consider the fact that this is a design from the 30's - technically miles ahead of unsynchronized crash-boxes, demanding hours and hours of training to become a reasonably skilled driver. This one is even easier to shift gears on than a modern car with a manual gearbox.

To the right is the tankette after engine removal. The radiator is still in place to the right in the picture. To the left in the picture you can see the entire main fuel tank. The reserve tank is placed behind the radiator.

The cooling is an intricate story, which requires that all plates are installed and that the joints are reasonably well sealed for the cooling to work well. The cooling airflow is such that air is drawn from the crew compartment, which ventilates noxious fumes but also makes it pretty cold during the winter.

To the left is the removed turret with the hatch open. The mantles for the two machine guns (which were the only armament of this little tankette) show to the left in the picture. The purpose of the small round hatches open one on each side of the turrets were to defend the tankette against close-up enemies - one would then use a pistol from the hatch.

In the cupola on the turret hatch there is supposed to be a leather polstering (removed in the picture), because this is where the commander (cum loader, cum radio operator) would have his head(!). The cupola can rotate, independent of turret motion. The cupola though, is about as heavy as it looks, so with modern ergonomics in mind, today this would hardly be an acceptable solution.

Concurrent with the "heavy" work on the hull itself, there are of course many hours of labour inspecting and restoring all the little details of the tankette:

The left picture above shows the pistol hatches removed and disassembled, and the right picture shows some of the parts for the turret front and the machine gun installation.

Now the tracks are removed, and still in the hull you can see the steering gear and the radiator. Note the circular hole in the rear armour where the fan is normally installed. The antenna base is also still installed (a cylinder with conical lower end, to the right in the picture)

What is not shown in these pictures are all the boxes, shelves and stands with removed and disassembled parts which it is important to keep perfect track of and which are also thoroughly documented.

It was really inspiring to receive a new set of pictures from Prague. It has been a while, like us all they suffer from lack of what we all wish most for - time and money.
Please enjoy their beautiful pictures which mostly speak for themselves!

The shaft for the drive sprocket nearest, and behind it the road wheel mounts. The antenna mount is still in place (the cylinder with a conical lower part and a metallic top). In the background can be seen some copies of drawings which we provided, together with pictures from our restoration.
Inside the chassi the four engine mounts are clearly visible. In front of those two smaller gearbox supports (cylindrical) are in view.

Simultaneously with the work on the chassi there is no end to the amount of work that needs to be done on the disassembled parts to restore them to mint condition.

From these images it is clear that the "turning point" - i.e. when removal and disassembly are replaced by assembly and installation - with a good margin has been passed during the time span of these pictures. Shot blasting of the hull and subsequent painting is the basis for assembly of major components.

As in most veteran restoration projects the dependency on old scrap objects for parts is total. These parts cannot exactly be bought "over the counter"

Many components are a challenge in themselves, not least the steering transmission, a critical part of the transmission.

There are always loads of "little jobs" which need to be done before anything can be installed. Below can e.g. be seen how the temperature gauge is tested for accuracy, and on the right is a closer look at the carburettor (not quite the original, but something to use for running the tankette) where it is obvious how many manhours have been invested in it...

The electrical system is of course just to rebuild from scratch. Starting with the basics and drawing up a schematic... New wiring is routed through the refurbished conduits.

The "roll-out" is estimated to take place this summer (2010). Unfortunately the gear selector mechanism is missing, and since it has so far been impossible to source one, a copy from one of the Swedish tankettes will be made.

Keep visiting this page! We will update it as soon as we hear further from the museum in Lesany!