Whatever you want to say about the state of British tank design,
the Royal Artillery did not muck about.
They produced some of the finest field pieces of the war.
In terms of anti-tank guns,
a year before the 6-pounder had entered production at full rate,
they had started working on the successor.
By the middle of 1941 they had concluded
that a 3-inch round was best,
and by May 1942 what was known
as the 17-pounder entered production,
finally seeing service
at the late end of nineteen forty-two.
It was only a matter of time before somebody had a thought:
“hmm, let's see if we can put this into a tank.”
Well, the solution
from the Department of Tank Design
was the A.30.
However, a number of folks
looking at this design were not massively enthralled
by it and thought,
“well, can we do better?”
Enter two folks by the names of Brighty
and Witheridge,
initially working independently
but then they ended up working together.
Their initial attempts to fit the 17-pounder
into the Sherman turret were less
than successful in the middle of 1943.
Eventually, however, they were ordered
to stop by the Department of Tank Design
and quit mucking around trying to upgrade
the perfectly good gun on the Sherman.
Now, David Fletcher intimates
that was probably actually just a little bit of protectionism,
the DTD were worried
about their own A.30 design.
Being good officers, however,
they did indeed heed the direct order
and they stopped working on it.
Then they immediately
started working on getting the order changed.
It happened that Witheridge knew
from service in North Africa
the new director of Royal Armoured Corps,
a chap name of Briggs.
He said “Mr Briggs.. or General Briggs,
would you mind awfully getting this decision reversed?”
Briggs very happily did do so.
He went off to the Ministry of Supply,
“can you get this order changed?”
“Yes we can” said the Ministry, “just for you”
and the 17-pounder Sherman
became an official program of the British military
This however meant that you no longer
could have the amateurs trying to do this.
Enter now Mr Chertsey of Vickers.
Mr Chertsey is now the guy who's really responsible
for figuring out how to get a really
big gun into a really small turret.
Now, what he did exactly we'll get into a little bit later,
but the bottom line was it worked.
Orders for about 2,100 of these things were placed,
and it would enter service
with the nomenclature “C” at the end of it.
Most of us however will know it
as the Firefly probably
the most famous of the various Sherman variants.
We're still at Arsenalen in Sweden,
and we're taking the opportunity to take a quick break
from the Swedish tanks to check out the Firefly
they have because it’s proven
surprisingly difficult
to get access to one
that we can clamber around inside.
Sweden, of course, never did use the Firefly,
they simply got a couple for testing purposes
and they were nice enough
to leave one lying around for us.
Now we're probably
gonna cut a couple of corners
because already done a small hatch Sherman,
but this time we've gone
through a welded front slope
so it’s the constant two inches thick up
all the way to the top.
You can see the bulges
for the driver and bow gunners’ positions.
That is necessary basically to leave room for there
actually be a hatch for them.
In order to reduce the vulnerability of these bulges
you would sometimes see welded armor
plate in front of them
and this tank was originally equipped with it.
However it seems that
when they were converting
it from a trials vehicle back to a museum vehicle,
the people doing the conversion
thought it was something
that the Swedes had added
so they chopped it off.
The obvious point that you are dealing
with a Firefly and not another Sherman,
assuming you can’t see the gun,
is the blanked off bow gunner’s position.
Because the ammunition was so big,
in order to carry a reasonable
amount of ammunition
they had to drop a guy.
The seat was removed,
he was replaced by a rack of ammo
although curiously in this particular tank
they took the rack out
and put the seat back in again.
The mantlet has to be the big type.
If you use the earlier m34 mantlet
you couldn't fit the 17-pounder into it correctly.
There is actually a small slew of requirements
that made eligibility
for a tank whether or not you could
convert it to a 17-pounder or not.
The housing is the original three-piece type,
Chrysler built their tanks
with three-piece housings pretty much
all the way through.
Not much else to be said,
your standard array of headlights.
The British always
did like the steel-type track.
As you come around to the side
you can see the two armored
panels for the protection of the ammunition
and an additional applique armor panel up
on the turret,
and the reason they
did this was because in order to leave
room for the traverse mechanism
they had to grind out
part of the inside of the turret wall.
This led to a weak point
which they had to fix.
The short-term fix was the appliqué armour,
the long-term fix was they simply cast thicker turrets
with a bulge on the outside.
As you move down,
you can see another distinguishing feature.
There is a large gap
between the road wheels with the bogeys.
This is done because the A57 multibank engine
was so long that they
had to elongate the entire hull,
and they had to spread out
the suspension accordingly.
And so we get to Chrysler’s A.57 multi-bank engine.
This marvel of mechanical complexity is basically
five conventional L-head inline-six engines
all mounted around a common shaft.
Each engine has its own crankshaft,
gears are then used to match up
with a single power output shaft.
This has the flywheel and the clutch on it.
All in all, the 1253 cubic inch engine puts out about 445 horsepower.
Now, the catch is that all this together
comes in the somewhere
North of two-and-a-half tons.
By way of comparison,
the Ford V8 GAA is about a half a ton
and also adds an extra 60 horsepower to the total.
Now if you add the extra weight of the engine
to the extra weight of the metal
that you are using to stretch the tank to fit the engine
into in the first place,
you start to see a significant reduction in the power-to-weight ratio.
Indeed the vehicle becomes
so heavy that this is why the heavy-duty VVSS bogey
was created to work for the M3A4 medium tank
which was the chrysler multi-bank
powered version of the m3.
The US Army was never a huge fan of the A57 multi-bank,
they considered it overly complex
and “full of bugs.”
They thought that carbs were inaccessible,
the clutch was too weak, so on and so forth.
Now the British had a slightly different point of view of things,
because they were going to be allocated
pretty much the full production run of the 4300 or so
of the m4A4s that was scheduled to be produced,
and they didn't like
the idea of having an unreliable tank engine.
Similarly Chrysler were not incredibly pleased either:
Not only do they consider it their duty to give their fighting men
the best possible equipment,
but they also saw this reputation
as a smirch upon the company name.
As a result the British and Chrysler joined forces
and set about fixing the problem,
and some of the most obvious fixes are easily available:
For example the carbs are now quite visible
and accessible at the top of the engine bay.
By the time they were done the A57
was proving to be the most reliable of the petrol engines.
Indeed I ran across a document in the British archives
dated late 1943, it was one of the American-based liaison officers
notifying home that the m4a4 was about to go out of production
and that they were going to lament the loss of their old friend.
Because the engine is so big it's
taking up room in the engine bay
which would otherwise be used by the vertical fuel tanks.
On the other hand you have now extended the length of the hull
which means that the sponson tanks can now be bigger,
they each holds 80 gallons.
Total of a hundred and sixty is only 8 gallons less
than a regular M4 anyway,
so the difference is pretty negligible.
The 30 cylinders sipped relatively little of the 80-octane fuel
and you were expected to go a good hundred miles on a single tank.
Another advantage to having the elongated hull
was that your trench crossing
ability has now gone up from seven
and a half to eight feet.
This was not however the fastest of the M4 variants,
the maximum sustained
speed was only 20 miles an hour,
and maximum burst, twenty five.
All the Fireflies were converted from low bustle 75 turrets,
but the other visual distinguisher that you're
looking at the Firefly if you can’t see anything else
is the addition of the radio box on the back side.
This was done for two reasons.
Firstly it left a bit more room to manipulate
the radio without interference from the 17-pounder.
The other reason was that it acted as a counter-weight
for the rather large heavy gun
which has just been added to the front of the vehicle.
This brings us to an end of the tour the exterior and part 1.
Guess what we're doing in part two?
Yes, inside. See you then