Considering how many thousands of BT-7s were built, it’s surprisingly difficult to find one in somewhat intact condition.
We’ve had to come as far as Minsk, a place called the Stalin Line, to find what they claim to be the last operational BT-7 in the world.
Now, there are going to be a couple of variances with history because, in order to keep it going, they’ve had to make a few modifications.
We’ll come to those later.
The BTs were the fast tanks.
The complimentary vehicles to the infantry support tanks such as the T-26.
The lineage of the BT goes back to an American designer by the name of J Walter Christie.
Christie was a bit of an eccentric, and he was obsessed by speed.
He basically didn’t make tanks, he made sports cars which had a gun, and tracks,
and even the tracks were optional, you could run the things usually on wheels.
But if you look at the T3 or T4 medium tanks that he sold the US Army, and then you compare those to the BT-2,
you can see the lineage from the T4 to the BT-2 to the BT-5 to the BT-7, it’s all a whole family evolution, of a similar pattern of tank.
As ever, we’re going to be taking a tour of the vehicle starting with the exterior and then moving inside.
So there’s no better place to start the exterior than at the front.
The first thing to notice about the hull, it’s all welded, which is an innovation for the BT series, but it’s also pointed.
So not only do you have slope on the vertical axis, you also have it on the horizontal.
Bearing in mind that this is an early 1930s design, there’s actually not very much complicated else about it.
The front slope is dominated by the two-piece driver’s hatch, which folds forward and up.
Outside of that, there are the two headlights, two tow hooks, and a horn on the left hand side.
That’s it.
Track tension, as you can imagine, is simple and old-school. It is adjusted in the normal manner by moving the idler wheel forwards and backwards.
In order to do this, you unlock a locking nut here, it disengages the teeth, you then get a large lever, insert it into the notch here,
you simply lever up or down, as it’s on an eccentric arm it moves forwards or backwards, when you’re in the right position,
tighten the locking nut, the teeth will mesh, and you’re fixed in position, off you go on your merry way.
And now the fun bit, the suspension, which is going to be pretty much unique of all the vehicles on “Inside the Hatch”.
Start off simply enough with the track, 46 links per side, a very simple construction, there is a guide tooth on every other link.
Held together by single pins, each pin is held in place by a small little cotter pin.
As you move back to the number 1 roadwheel, the first thing you’re going to see is the steering mechanism.
Now remember, Christie didn’t just make tanks, he made sports cars.
He wanted them to go fast, and if you didn’t need to use the tracks, you could take off the tracks in about 30 minutes,
and you could run the tank much faster, quieter and with much less wear and tear on the wheels alone.
Of course, to do this, you now had to steer, the varying speeds of drive isn’t going to do the job.
The suspension for wheels 2 and 3 are the same.
This is the center guide for a large coil spring.
Now if I were to lie down on the ground and look up, I would see that this is simply a protective covering
and there is a large spring which coils around the center guide.
As the roadwheel arm moves up and down, it compresses the spring,
that gives us the large range of motion that Christie suspension was famous for.
Auxilliary tanks.
Now these could be used for petrol or oil, usually petrol.
What we have here is one of the access ports for one of the side fuel tanks, there’s 150 litres per side,
if you did need to fill up, because there is no connecting piping between the external tank and the internal,
you would open the ports on both tanks and then either use a handpump, or siphon the fuel from the external to the internal.
Air and ventilation.
The side ports are for the air to cool down the engine,
whereas the round device in the middle is the air filter, to clean the air which is to be combusted.
This is an access port for oil, the jack, there’s one on the other side as well,
and lastly, this is the protective housing for the last of the suspension guide rods.
Power transfer all happens at the rear of the tank.
Unlike most tanks which have sprocket wheels with teeth which project out and intermesh with the track,
you’ll see that the BT has a solid drivewheel, there are no teeth sticking out.
Instead it uses a series of up to 8 rollers, only four are currently installed, which mesh with the center guides of the track,
and this pushes the track forward and around.
Now the advantage to this is that it’s almost frictionless.
The disadvantage though is that ultimately there’s only so much force that you can push through a single piece of metal to propel a tank forward.
So when tanks started getting heavier, you just couldn’t do it anymore.
Especially when there’s only one center guide every other track link.
Now, the other disadvantage with the track design, because the pitch of the track is so long,
there is a very large gap between the road wheel and the pivot point, the hinge.
What would sometimes happen is that the track link would bend making a very rough ride on the roadwheels, and also shortening the track a bit.
Eventually you would pull out the bent link and simply run a shorter track.
The other neat feature, or at least, neat if you were Christie, was that you could take the tracks off, as already mentioned,
and run on the wheels.
To do this, you had to have the power transferred to the last roadwheel.
On the earlier tanks, there was a chain.
When you took the tracks off, you added a chain to go from the drivewheel to the roadwheel.
By the time they got to the BT-7, however, they came up with a series of gears in a protective housing which was pretty much permanently closed,
and all you had to do was pull off the hub here, and instead simply plug this geared hub into the wheel,
you have no meshed with the drive train and your wheels are good to go.
Now we’ve come to the rear of the tank, not much to see. Your final drive housing here:
Open up this top bolt, and that’ll be your oil level.
Tow hooks, and finally the unditching beam.
A lot of people ask why there is always a log on the Soviet era tanks.
The answer is that if you get completely stuck, you’d take it off,
chain it to the tracks at the front or back of the tank depending on which way you wanted to go, and it would act as a massive snow chain,
for lack of a better term, or if you were high-centered you could use it. Just go the length of the track.
Take it off, mount it back off, and away you go.
The turret is a BT-5 turret.
Early versions of the BT-7 would have such a turret, later on it would change.
The radio antenna, as indicated by the white stripe, is the battalion commander’s tank.
Also on the top of the turret we have the panoramic sight, ventilator housing, and on the far right is a small little port for signal flags
to be displayed for all the other tanks which weren’t fortunate enough to have a radio.
Two piece main hatch.
Nothing exactly complicated about it, just lift up, lift forward, and you have a nice, roomy access port to a very cramped interior.
While I’m up here, another thing I’ll point out is that the rear of the turret actually swings open,
this is done to allow the gun to be removed or installed.
Moving further back we have an armoured ventilation housing which can be opened or closed,
and finally at the tail end for the main fuel tank. 400 litres, add that to the 150 on each side, and you get a total of 700 litres of fuel.