We are back at Tankland, and redlegs rejoice,
we’re in front of a 155 mm gun motor carriage M53.
The story for this starts just after WW II.
The War Department equipment board identified a requirement for an advanced,
self-propelled 155 mm gun.
They sent it to Detroit, Detroit took a look at it
and they developed a concept which they thought would work.
That was in 1946.
In 1948, Pacific Car & Foundry were given the contract to build a wooden mockup—
presumably funds were short—
based off of the Detroit Arsenal design.
This became the T97.
It wasn’t until 1950 that an actual prototype was ordered,
once the wooden mockup had passed muster.
Ten months later in February ’51 the contract was modified.
PCF would also build the 8 inch howitzer T108,
which would develop into the M55.
In order to do this they had to develop a whole new system of components.
There was a new short recoil system, a new equilibrator,
an ammunition handling and loading system.
However, with all these things sorted out,
orders very soon followed because there was a war on.
What’s interesting about the timeline,
is the first production order for a hundred T97s was placed in August 1950,
before the delivery of the prototype in February ’52.
Indeed, even more bizarrely, the contract was modified to 87 T97s,
and 70 T108s in January 1951, a month before the contract to design
and build the prototype of the T108 was even placed.
So obviously they were very confident as well as in a hurry.
Later contracts upped the orders to 294 T97, and 124 T108.
Now you may notice that these dates do not match with the figures
that you’ll get from Hunnicutt.
I don’t know why.
I saw the documents in the archives myself for one set of dates.
Hunnicutt’s sources, I don’t know what they were.
However in my experience
it is not unusual for official archive documents to say two entirely different things,
even though they are both produced by the same department.
Make of that what you will, what I’m saying is what I’ve seen.
The solution they came up with was actually pretty simple.
Firstly, to simplify production,
they had to use as many of the components of the medium tank
in production as they could.
This meant that as the medium tank changed production,
the actual configuration of M53 and M55 changed as well to match the parts.
Also in order to have room for the turret,
servicing the turret and keeping the balance,
it was decided that the best way of doing this was to put the armament
at the rear of the vehicle,
and the engine and transmission at the front.
So as you come around at the front of the vehicle we’re gonna start,
of course, with the head-lights on the corner.
Service and infra-red, there’s also blackout and markers.
Coming a little bit further in,
remember the front of the vehicle is the back of the vehicle,
if you’re a regular tank.
So we have the final drives, we have the transmission access ports,
which has to be said are not very accessible, and some towing eyelets.
The travel-lock of course has pride of place at the front top-center.
Then if you come around to the side
you start seeing some of the more signature features of an artillery piece vs. a tank.
Now certainly the front half of the running gear
looks pretty similar to the back half of a tank.
You have the same sprocket, you have the same road-wheels on torsion bars.
The difference starts to occur when you get towards the back of the vehicle.
In order to reduce the effect of recoil,
what they’ve done is they’ve taken the idler wheel and they have moved it.
No longer is it up here,
but they’ve simply moved it down onto the ground,
making seven road wheels in contact with the ground.
It is a trailing idler. This does two things.
Firstly it increases the length of the track contact area,
so when the cannon fires and the recoil comes back,
you have more track at the back to support the cannon.
Also they had this neat feature
that you can now lock the rear suspension in place,
and that would help with the recoil absorption.
And then of course you add the spade to that.
Other than that though,
the actual suspension and running gear is very similar to the M47.
So to help absorb the recoil we have the locking system here, for the trailing idler.
And this is of course mechanically done from inside.
We also get a good view here of one of the volute spring bump stops,
and every road wheel arm will have one of these.
It just prevents the road wheel arm from swinging up so high
that it breaks the torsion bar.
Moving up and forward to the driver’s door, you can see that it,
like the gunner’s door on the other side, is split into two parts.
If you just want to, have your arm I guess sticking out the side,
get a little bit of fresh air, open up the top half.
If you want to get in and out, open up the bottom half.
This allows you access to the drivers compartment.
We’ll come back to that in a few minutes.
So if you were looking at the 3D model and wondering
why there are four periscopes around the front left side,
where you would ordinarily expect one of the loaders or maybe the gunner to sit,
it’s because this is the driver’s position,
and he’s got to be able to see as he’s driving.
So I’m just gonna hop down right quick,
and I can still speak to you through the open door, hooray.
Now, point to note, driver’s position in a turret.
Bear in mind we have the transmission and the engine in the hull at the front.
Where does the driver go? Well the answer was there wasn’t any room for him.
So they put him in the turret,
and as far as I can recall off the top of my head this is the only production vehicle,
together with the very similar M52 105 mm,
that has the driver in a rotating turret.
There were others, the Object 416, the MBT-70 for example,
but they were slightly different in that it was expected
that the turret would traverse and the driver would be driving at the same time.
Well this is an artillery piece,
you’re shooting or you’re driving, you’re not doing both at the same time,
so it wasn’t so much of an issue.
The linkages didn’t have to be so complicated,
and you certainly didn’t have to keep the guy facing forward at all times.
Now this is the wobble stick.
It’s officially called the manual control, but everybody knows it as the wobble stick.
It came out in the M47, so as you can tell this is an earlier M53.
Later M53s were produced at the same time as the M48 tank,
and so they would have the M48’s steering wheel control, the M48’s engine, and so on.
There is another giveaway that this is an early M53,
in fact the builder’s plate up in front of me says T97, serial number 31,
so this was a very early vehicle.
Pedals to his front, he’s got a brake, he’s got an accelerator,
he has the headlight dimmer switch under his left foot.
Transmission, your gear is selected by the wobble stick,
and so is your steering left or right.
The dash has been removed.
Apparently this vehicle was going to be used as a bombing range target,
and the Navy didn’t want all those radioactive,
glow-in-the-dark, tritium or whatever was in them,
elements polluting the world so they took out the dash, unfortunately...
and then they saved the artillery piece.
He has his four periscopes to look out of.
Of course the seat will raise and lower in theory, although it’s well frozen in place here.
Other parts to note,
you can just see to my right the large equilibrator system
for the vertical elevation designed specifically for the vehicle,
and one of the four recoil compensators.
Nothing else of note in here, so we’re gonna move back.
There are two fuel tanks on the vehicle.
They are filled in front of the turret, at the rear of the front hull.
You can also see the two bump-stops, again volute spring.
They will mesh with the wedges welded to the front of the turret,
and they are hard stops to stop the turret from traversing too much.
You get 30 degrees of traverse to each side.
Also on the front you’re gonna find the spare track blocks and the track fixers.
Well, that’s what they are officially called;
in actuality everybody just calls them track jacks.
Now what they do is they hold the track together
while you put on the end connectors.
So as you move forward onto the engine deck
the sleeping accommodations are marred by a number of bumps and protrusions.
The muffler-housing might maybe work as a pillow, but mm…
not so much.
Underneath each side you’re gonna have on the outermost areas
the storage compartments, and then you can open up the louvers.
On the right-hand side of the vehicle you’re gonna see the battery system.
There are four 12V batteries, giving you a 24V system,
so as you can imagine they are wired in series, in parallel.
Under the left-hand side is where you’re gonna find your air cleaners.
Underneath, in the center where you can’t get at it without a crane,
you’re gonna find the Continental AV-1790 engine.
It’s a 29.4 liter V12, cranks out about 810 hp.
Again, depending on which version of M53 you have,
what the appropriate tank was that was being built at the same time,
you have a different version of the engine.
So the earlier ones had the 5, later ones had the 5B.
Moving further forward from the engine compartment,
the transmission, cross-drive 859-4, or in the later versions the 4B.
Filled up through here.
The whole shebang will get you going at about 31 mph.
380 gallons of gas, that’ll get you about 150 miles.
Exterior features on the turret:
pintle-mount for the commander’s 50 cal. machine gun.
There are two ports here for gunner’s periscopes,
a vision block, and an actual panoramic scope used for primary indirect fire.
Down on the front in the mantlet here is the direct vision telescope used for direct fire.
Obviously at the rear of the vehicle you’re gonna find your recoil spade.
It is lifted up and down by a hoist.
The control for the hoist is located here, next to the rammer.
As for the rest of the rear doors,
well the original rear doors were your typical barn-door style,
but that was only on the very, very original vehicles.
Later on they decided that, “well, if we’re gonna tailgate, let’s tailgate properly,”
and so we actually have a dropping tailgate,
and an overhead protective roof to keep the sun off
while you have your barbecue and bar.
And if you think they didn’t do that in the field, think again, they would have.
Now this is still an early-model vehicle.
Later production vehicles,
on the roof of this would have had an additional rail similar to the one
on the inside roof of the vehicle, and that rail was used for an ammunition hoist.
You would run it out onto the upper door,
and you could then lower down the hoist, pick up the six-inch round—
155 mm is about 6 inches, or with the M55 the even bigger 8-inch round—
and hoist that up onto the platform and then into the vehicle.
Now you can see the size of just the projectile there to my left.
That’s the 155, imagine how big an eight incher is.
Twenty rounds could be stored in the M53,
10 rounds of 8-inch in the M55.
Now at this point it’s probably worth pointing out
that converting an M53 to an M55 was really easy.
All you had to do was change out the gun,
change out the ammunition racks,
modify the pressure in the equilibrator,
and you’re done.
Hey presto, re-designated.
Well the rear of the vehicle seems nice and spacious—
I’m actually standing at pretty much full height—
until you realize that there’s actually six people in this turret,
so things start getting a little bit more cramped and probably annoying.
To my front we’re gonna see the ramming mechanism.
As you can see there is a ramming tray which would fold up out of the way,
and an actual rammer system, controlled to one side.
As you look down
you can also get a pretty good view of the sub-turret floor and the turret ring.
The item in the middle,
which transfers any electrical power from the generators in the hull to the turret,
is called the slip ring.
The ammunition racks,
they actually fold up out of the way for convenience.
It’s actually handy.
So you start with the top one,
fold it up out of the way, and then work your way down.
They lock in place, there’s a rather ingenious little locking system here.
It’s an open eye, you pull it down
and you simply thread it onto the pin of the rack beneath,
and you keep doing this all the way down,
and that’s how you load up your ammo.
The commander’s in a fairly lofty position at the top right.
The seat is locked in the upper position right now,
I haven’t figured out how to get it down,
but I will note that the turret hatch itself is actually very narrow
and not something that I find very comfortable.
Outside of that he doesn’t have any other real controls—
he’s got the radio I guess, but his main job is as much the safe
and efficient running of the crew.
With so many people running around it’s a few more pieces to keep track of
and generally speaking the CO probably wants to keep an eye on what’s happening.
The gunner’s position,
I don’t know if I’d want to be living in it very long, but I’ve certainly sat in worse.
Obviously he will have the elevation and traverse controls.
There is a power system as well.
Azimuth indicators located to his rear and left.
He’s gonna have two primary telescopes,
a T149 and a T159, that will allow him to aim.
The gun itself will elevate to a maximum of 65 degrees.
He’s got a small, little guide here to his left.
So it’s currently in the “lock-horizontal” position.
It looks like maybe 10 degrees;
15 degrees is the loading elevation position,
so the ramp is actually a little bit off kilter.
There is also a negative 5 mark,
so this cannon would actually depress 5 degrees.
Maximum range is about 23 km, 23.5 km for the 155.
The “eight incher” with the bigger round will only go about 14 km.
Outside of the other controls that he has in here,
what I have to say that is probably the most fun:
there is a housing which says in big letters “FIRING SWITCH.”
It’s a foot-trigger, you just depress down with your left foot,
gun go boom, technical terminology.
That’s it in here because I don’t have the operator’s manual.
So we’ll move outside.
And that’s it for the M53.
The US Army had converted its M53s to M55 standard by 1960,
but the Marines kept some of the 155s around.
It saw very limited export success, the only other users were Turkey and Belgium,
and the vehicle did see combat in Vietnam.
There was one additional variant produced:
the T162, which is basically the same vehicle but with a 175 mm cannon.
That never entered service.
What ended up happening was the Army decided
that air-portability was more important than NBC capability,
and the M53, M55, and T162 were replaced on the line by the M107
and the M110 self-propelled pieces.
Ironically they themselves were later replaced
by the NBC-capable M109 and MLRS.
That’s it for the M53.
See you on the next one.