We thought it was about time for a change of scene, so we’ve come to College Station, TX, the Museum of the American GI,
and we’re going to go over their M24 light tank.
By March 1943, the Army had decided that its light tanks needed to have a little bit more firepower than the 37mm found then on the M3 and M5.
They decided to go with a 75.
They also decided that they were quite happy with the power train of the M5 and wanted to keep it,
although the tank had to be a little bit bigger and a little bit wider as well, not least, to mount the larger cannon.
What they ended up with was the M24 Light Tank, known as the “Chaffee” (Chay-fee) or “Chaffee” (Chaff-ee)
depending on how you want to pronounce it.
Adna is, of course, not around to tell us how –he- pronounced it, and I have met persons of the same spelling who pronounce it both ways.
M24 entered full scale production April 1944, 4,731 units were built in two facilities.
The description in the manual is simple enough.
It states, and I quote: “The light tank M24 is an armoured, full-track-laying combat vehicle mounting a75mm gun.
It consists of a crew of four men: The Commander, the gunner, the driver, and an assistant driver”, and no, I am not misquoting.
The hull is fully welded, and generally made of 1” plates.
Split into two compartments, a crew compartment in the front, and an engine compartment in the back, which is separated by a stepped bulkhead.
Hull sides, as you can see, are not vertical as in most tanks, they are angled inwards at 12 degrees.
An inspection of the hull front reveals no massive surprises: There is a bow.30 cal on the right hand side.
Front hull is, of course, dominated by the access panel for the differential.
Final drives are located in the traditional bulges on the insides of the sprocket wheels.
Front left of the vehicle, simple enough.
Service drive, blackout marker, siren, manufactured, it says, by the Federal Electric Company of Chicago, IL,
and for road marches, the driver has a windshield, collapsible forward, of course.
Lock down into position, and for road marches come up.
You can see it has a wiper and a heating filament for defrosting purposes.
One of the great mysteries of life that has been pointed out to me is that nobody seems to be entirely sure what these are for.
They weren’t, I’m told, on the original vehicles, later production vehicles had them added,
and there are also some at the back, so the idea of it being a bulldozer mounting doesn’t seem to be applicable.
Who knows, maybe by the time we have this video edited, I’ll have found out the answer.
As we move further back towards the rear of the vehicle, we’ve got a tow cable, first aid box, a pull hand.
This is the external handle for the engine compartment fire extinguisher.
It can also be set off from inside the tank.
You’ll see the sandshields have been removed, they tended not to last very long in combat anyway, they’re a bit of a nuisance,
so the museum has taken them off this particular vehicle.
Track blocks: The track blocks you see on the back here are in a different position to a lot of the M24s that you’ll see out and about today.
There was a post-war modification that the track links were moved to the front of the tank.
One of the more significant differences between the M5 and the M24 in terms of the running gear
is that the M5’s bogie system has been replaced by an individually sprung torsion bar system, five pairs of wheels per side.
Now, the thing about torsion bars is because you have to leave room for one bar to be in front of the other, the wheels are not actually even.
If you look straight sideways under a torsion bar vehicle, you’ll see that one set of wheels is further forward than the other.
Shock absorbers will be found on the first, second, last and second from last roadwheel arms, the center arm doesn’t have a shock absorber.
All the arms will, however, have a bump stop, this prevents the arm from going up too far and snapping a torsion bar.
Now, one of the downsides of a torsion bar system is that repairing it is not an easy task.
If a torsion bar breaks, what you have to do is pull off one of the roadwheels, disconnect the torsion bar anchor,
and pull out the part of the torsion bar which hasn’t actually broken.
Then what you have to do is reach inside,
and somewhere inside the tank is going to be the remnants of the other part of the torsion bar that snapped.
Fragments here and there.
If they’re inside a guide tube, that makes it worse, because if you can’t unbolt the guide tube,
then you have great difficulty reaching the fragments that you have to pull out.
It’s almost as if you wished you could turn the tank on its side and shake it and the pieces would fall out.
You have to get every last fragment out before you can put the new torsion bar in,
and it’s enough of a hassle that when we had an Abrams, one of my wing tanks, had a #7 left torsion bar snap,
we just drove around with it in that condition for two weeks before we bothered to change the torsion bar, it was just too much hassle to change.
Bogie system: unbolt the bogie, replace, bolt new bogie back in, easily done.
One of the problems if you have a broken torsion bar and you drive around with it for too long, however,
is that the weight of the vehicle is now concentrated on fewer torsion bars,
which means that the longer you wait, the more likely it is that you’d be standing in the motor pool, you’ll hear this almight ‘Clang’,
as another torsion bar breaks, and again it’s a cumulative effect:
You have two torsion bars broken,
if you don’t replace them pretty quickly you’re going to have three, and then four, and then five, and then you just have a mess.
So, difficult to change, but when you get a chance, you do need to change the torsion bars.
The running gear is going to be similar to the M37 Howitzer we saw before, which is logical enough since the M37 is basically based off the M24.
Two types of track were available, the steel, single pin T72, these particular track links are the T85 double-pin rubber.
Either way, there are going to be 75 track links per side.
End connectors will be found on either side of the double-pin track,
but the centre guides, unlike, for example, the Abrams tanks today, do not form part of the connector system.
Interestingly, the steel tracks are 16” wide, but the rubber tracks 16 ½” wide.
The entire track system itself will span an 8’ trench, climb a 3’ wall, or ford 3’4” of water.
At the front end, the sprocket is simple enough.
It is reversible, you just undo the bolts here, pull off the sprocket, flip it around, put it back on,
and you will then get the same amount of wear on the tooth as you did the first side.
Checking track tension is simplicity itself, at least according to the manual.
All you have to do is bring the vehicle to a stop, lift up the sandshield if you happen to still have one after all your running around,
and then between the 2nd and 3rd return rollers you take a 4’ pry bar, AKA a tanker bar.
I just happen to have one here.
Insert it above the track right in the middle between the two return rollers, and exert downwards 200lbs of pressure according to the manual.
Now, how you know you have 200lbs of pressure I’m not entirely sure, the manual doesn’t bother to tell you how you figure this out.
Once you have your 200lbs of downwards pressure, you then measure with the use of a straight edge,
the manual suggests a block of wood resting on top of the track,
how much of a sag you have got between the two return rollers.
In the case of steel track, you wanted somewhere over 2”, in the case of this rubber track you want it to be 3 ¼”
Adjusting track tension, you’ve seen before on the M37.
Identical.
Undo the locking bolt, slide up the bolt stop, you then take a wrench, 41, W1315, that’s what it says in the manual,
and adjust the track tension by screwing forwards or backwards, it will move the idler wheel forwards or backwards.
When you’re done, slide the bolt stop back down, tighten the locking nut, and away you go.
Also, common to vehicles of the era including the M37 of course,
you’ll see that there is an arm connecting the idler wheel to the last roadwheel arm,
so that as the roadwheel goes up and down the idler wheel will move forwards or backwards, maintaining track tension.
While I’m here, I’ll also point out the other plate at the back of the vehicle here similar to the ones at the front,
which nobody could tell me what it was for.
As we move up from the comp(ensating) idler, having a look at the right rear of the vehicle.
Tail lights.
You’ll notice that the tail lights are different on each side.
The one on the right rear has the blackout marker, and the blackout stop light.
Above it, we have a vent for the fuel tank, and the exhaust pipe is located right here.
Finally as we go to the left rear stoplight, this has the blackout stop and a service stoplight and tail light.
Now, if you have to replace a roadwheel, there are two ways of doing it.
The easiest is to use a lifting ramp.
It’s a simple wedge shaped piece of triangular metal, you place it between the roadwheels,
and drive forwards or backwards so that the roadwheel you want to change is now lifted up,
you hook the roadwheel arm into place by use of a spring arm retaining hook,
and then you drive forwards or backwards, the ramp will lower a little bit, and you can change out your roadwheel.
Your next bet is a hydraulic jack.
Easy enough, you get a piece of wood to brace it, you put the top end of the jack against the arm itself, and pump up.
It takes 9,000lbs of force to lift a roadwheel arm,
so you want to be very sure it’s secure and not about to slide forwards or backwards or you’re going to have a very bad day.
M24’s maximum allowable speed was 34mph, with a maximum cruising speed listed in the manual of 25.
Fuel consumption was listed as 0.875 miles to the gallon, giving us a cruising range of 100 miles.
So I’m going to climb up, open her up, and let’s have a look and see what makes it go.
So opening up the engine compartment, we can now see what makes the M24 move.
There are two Cadillac V8s, model 44T24, each of which is 346 cubic inches and cranks out 110hp at 2,400 rpm.
Now, a bit of an oddity, and this also happens with the M37, is that the front of the engine is the designated part which has the generator.
The generator is right at the very back of the tank, which means that this is the front of the engine, and that’s the back of the engine.
The left and right sides of the engine refered to where it is compared to the front,
so the left side of the left engine is to the right side of the right engine, if that makes any sense to you.
When you’ve seen one engine, you’ve seen them both.
The engines are absolutely identical.
Carburetor, engine oil.
It’s both the filler and the dipstick, or gauge, if you want to call it that.
Look for the mark… there you go.
So you can see it’s a hell of a lot of stick and not a lot of engine.
Capacity, 8 quarts.
Fuel lines: Again, they’ll connect both tanks to both engines, so you can run one or both engines off one or both fuel tanks.
Oil filter is way down at the front here, next to the generators,
and down behind the engine, or in front of them depending on your perspective,
you can also make out two very large cooling fans: Force air induction.
Will draw air from the outside, over the engines, and then out the vents at the back.
Forward of the fuel tanks, and above them, in fact mounted on basically a cut-out of the fuel tank,
directly onto it with no separation or partition whatsoever, you’re going to find the batteries.
Two batteries each side, each of which is 6 volts, gives us, in series, a 24 volt electrical system.
The batteries are mounted under the access plates which are bolted down, so they’re not an easy job, or convenient job at any rate,
to access for checking the fluids or whatever else you may happen to do with the batteries.
You can’t see the transmissions because they’re way down low.
Cooling systems, there are two absolutely identical and independent cooling systems,
the fan for which you’ve already seen.
Each cooling system will take 40 quarts.
They are filled through the ports in the top here.
And thus ends our tour of the suspension, power train and hull.
Next time we’re going to go inside.
See you then.