Inside the Chieftain's Hatch: M4A1 Sherman part 1

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Inside the Chieftain's Hatch: M4A1 Sherman part 1

Even before the ink was dry on the design for the m3 medium, in August of 1940, Ordnance told the designers to get started on the replacement vehicle, but this happened in February of 41 simply because they were too busy putting the finishing touches on to the m3 The resulting product was manufactured in September 41, it was the a medium tank t6 The remit the designers were given was pretty simple Put the 75 millimeter into a rotating turret, and make the tank smaller than the m3 The t6 showed up in Aberdeen for testing, it was a strange combination of the archaic and the modern Certainly the stabilized gun and the synchromesh transmission showed promise On the other hand it still has something that had fixed forward firing machine guns and had all four hatches for the five crewmen, two of those hatches were in the whole sides The first of the production m4a1s was built in the Lima locomotive works in February 1942 this was sent to Aberdeen Proving Grounds to work out some of the bugs They were built to a British contract, the second tank was sent to the United Kingdom for testing, it was named Michael, and possibly after Michael Dewar, the head of the British tank mission in the US that tank can still be seen today at the tank museum Bovington, still in a shiny gloss green with the fixed forward firing machine guns As such it is the oldest surviving Sherman tank We’re going to move forward a little bit to august of 43, and the reason we’re going to do this is that’s when the Montreal locomotive works ceased production of the Ram and started production of the Grizzly The Grizzly is basically an m4a1 built with a couple of local tweaks in Canada Most of the hundred eighty-eight Grizzlies that were manufactured did not see combat and as a result they generally survived the war Thus, most of the M4A1s you see in private hands in museum today are actually Grizzlies which have been backdated to look like an American M4 This vehicle behind me here at the military vehicle technology foundation in Portola Valley California is indeed one of these Grizzlies and will be the subject of our tour, which will of course happen in the usual manner: Outside first, engine and then in part two we go inside Pleasantries out of the way let’s get going Now we’re going to start off with the first elephant this particular M4 has been parked in between its two close contemporaries: The T34/76 on one side, the Panzer 4 on the other, and immediately you will see that this tank is not the smallest of the three Most of this extra height is in the hull, the turrets are pretty much equivalent Now, you may at first think this is actually a good thing because you’ve got more room, you’ve got more comfortable positions for the crew, you’ve got more storage… you also have a bigger target Now, the reason this was done is located to my left, here The engine in the tank is mounted pretty much the same way as it is on this stand, a slight forward angle to allow the power shaft to go under the turret basket It’s a a tall engine, you need a tall engine bay But the other advantage to the tall engine bay is that you can fit a whole variety of engines into this one tank which is applicable considering the American manufacturing capability of the time Moving to the hull, the cast hull marks this as an m4a1 Welded-hull variants were simple M4s Now, there was a composite or hybrid version which had a cast front and a welded back, the US Army categorized those as plain M4s The armor is about two inches thick, starts at about 37 degrees goes up to about 55 at the top giving them an effective thickness of between two-and-a-half to three-and-a-half inches On a welded hull Sherman that 2-inch plate is an even 57 This, if you count the slope is the better part of three and a half inches and compares quite favorably need to, say the t-34 and better than most of the german tanks There are however to small catches Those are the bulges for the driver and the bow gunner These are weak points, surprise, surprise, so what they ended up doing was welding, you will often see a lot of times, a piece of sheet metal welded in front of these bulges to give a little bit extra protection The other catch with this is what you call a small hatch Sherman The early versions, because they have that steep slope, didn’t have much room on the roof of the hull to allow the hatch, so the hatches on the early versions are very small The earliest m4s actually came with a direct vision port in the bulge itself, but that was soon deleted Moving on to the components,

we’re going to start off with the most important part of the tank No it’s not the gun, at least, not in this case If you think about it, it’s a small quirk of geography Unlike most of the other combatants, the US was separated from the rest of the world, and the fighting, by couple of small bodies of water called the Atlantic and the Pacific This meant that you had to get whatever it was you built in Ohio and in Detroit and Wisconsin, and everywhere else that they were making tanks, from the US to, say, Europe on a ship To get it onto the ship you had to lift it up We didn’t have back then the roll-on/roll-off ships that we’re familiar with today You actually had get a crane, hook onto the lifting eyes, lift it up, put it over and down into the hold Now, your next catch is that most of the cranes of the time had a weight limit and a lot of that weight limit was frequently 40-ton, which basically put upper end limit You could build a heavy tank in the US, but if most of your ship cranes are most of your land cranes couldn’t lift it in and out of the ship, it’s not going to do you heck of a lot of good So that was why the American heavy tank never really found great favor Now, there were other problems with them as well The M6 heavy for example was mechanically unreliable, god-awful huge, and ugly and whatever, but by large the Americans pinned their flag to the medium tank, and of course the lights As we move on a little bit, we have the brush guards covering the service lights and marker lights, another brush guard for the siren, and we have a “G” stamp for General Steel General Steel is basically a subcontractor If memory serves, there are about 4,237 parts in an m4a4 and about 80 subcontractors used This meant that General Steel, who were of course in the US, were shipping these castings to Montreal for final production As we move further on, we go to the three-piece transmission housing Of course, later on you ended up with single piece and then finally the shark nose, but all the Grizzlies were made, as near as we can tell, with the three-piece This is one of the later versions of the three piece, though, because you have this little lip protecting the bolts The idea of the bolts was simple enough If you have to change out the transmission or something like that you simply unbolt this, hook up a crane, pull off the housing, there’s the transmission right in front of you Took about two hours to change a transmission which, by the standards of the time, especially compared to the Panther we did before, is pretty quick The bolts were originally open and exposed and susceptible the enemy fire which meant that when you had to quickly change the transmission, you had to spend half the time just shearing off the bolt, so this lip was added for protection By the end of Sherman’s production run, though, the housing completely encased the bolt, the bolt was within a recess and thus much more protected Now, while I’m here, I’m going to go off on a bit of a tangent I was having a chat once on the ‘phone with Tom Jentz, and who made me feel like I knew absolutely nothing, but he postulated to me that Sherman’s reputation for reliability was overstated, and that in fact it was not any more reliable than any other tank of the time Which of course raises in eyebrow because we all know that Sherman was praised for its reliability And to some extent it was I mean, if you compare with the early Cromwells for example yeah it definitely was, but to compared to other in-service vehicles, I have never actually done a per-mile breakdown rate assessment The way he put it was and I think he might have been onto something, the reliability of Sherman came from the operational readiness rate When the Commander said “tomorrow morning we’re going to attack with my 100 tanks”, how many of them would actually cross the start line? It would will be 99 or 100 tanks The reason they could do that was because of the maintainability of the tank There are a couple of features here First we’ve already mentioned how quickly it is to exchange parts, the second thing is that the Americans brought spare parts and they brought a lot of them, unlike, say, the Germans, where units would be fighting each other at the train depot to get a part Americans had spare parts coming out the wazoo, they basically had entire tanks in individual component form sitting in warehouses So, if we have to repair tank, let’s say the transmission needs replacing, pull off the housing, go get a spare part, bring the spare part back, plug it in, it will fit perfectly because American parts were built to high design tolerances If you saw something like a vice or other fitting materials on the workbench, it was a sign of incompetence because if you did your job right the first time, the part fit So you now have this part which fits, goes right in you, close up the transmission housing you’re done in two hours, you can go on to the next tank

So you can change 3 Sherman transmissions in, say, the same amount of time it would take you to do one Panther Put that way, I think he very well may have had a point Now, again, I have not done the per-mile reliability assessment rating checks, if anybody out there on the web has done so and can link to them, please put it in the comments, I’ll be curious to see the results Other the features on the front, that little tangent over, the gun crutch, AKA travel lock, gun crutch of course is what the English would call it, and the bow 30 caliber machine gun That’s the front, that didn’t take too long, let’s go around the side As you come around to the side of the tank you see that the running gear was pretty much taken straight off of the M3 medium There are a couple of minor differences; the tracks are not one of them They’re the same 16 and 9/16th of an inch wide, they came in a smorgasbord of variations and I’m not going to go list them all right now I am going to mention the Canadian Dry Pin CDP was a shorter pitch track, more links per side, that meant that you have to have more teeth on the sprocket wheel, so if you’re looking at a sherman and you see that there seems to be a rather inordinate amount of teeth on the sprocket wheel, the chances are you’re dealing with a Commonwealth vehicle Obviously the Canadians liked CDP the most, but I do believe that the British used them as well Now, the problem with the narrow track also carries on from M3 medium The thinking behind it is if you have a small narrow track, there’s less weight of metal that you have got to haul around, your tank will go faster Which is fine on hard surface, not so fantastic if you’re going around in the mud in Russia So some workarounds were developed The first work-around with a simple duck-bill, it’s an extended end connector and is basically a little plate that comes out a couple inches, gives you a little bit more surface area in contact with the ground If this wasn’t enough you could then move to the easy nine suspension and what this was, was there was a spacer that will put in between the bogie and the hull side This would shove the bogie out about six inches, and is another advantage to the modularity of bogie system You then had enough room to mount additional extended end connectors on the inside of the track, and this really did increase the flotation capability of the vehicle One of these E9s is still visible at the National WW2 Museum down in New Orleans, if you happen to be down that way and want to look it up The bogies were originally the light-duty version, or at least what is now known as the light duty, the return roller was up top and center In the middle of 1942 they changed, and moved the roller to the rear, it’s your visual identifier They replace it with a metal skid, and that design kind of tweaked a bit over time, but most important was they increased the diameter of the springs under here from seven inches to 8 inches making them a lot more durable The whole system would span a seven and a half foot trench, it would climb a 24 inch wall You look at the M10 that we did before and that would only scale an 18 inch wall Why the difference, because the running gear is the same? Near as I can tell, it’s a matter of weight The m4 had more weight pushing down on the track and that gave a little more grip The last thing I’ll mention while we’re on the subject of running gear is the gap in between the bogies Now, on most M4s, the spacing between the wheels is pretty much the same as you have here The exception is the m4a4 This had a longer engine, the entire hull needed to be extended which meant that the bogies were spread out a bit further So an m4a4 would have a gap between the bogeys, maybe the size of an additional roadwheel The primary user of the m4a4 was the British There was also the M4A6, but you almost never see any of those As we move up a little bit just forward there is a mount for either a radio antenna, or if there’s no radio because it’s not a command tank a, ventilator, and then we move to the sponson where much of the ammunition was stowed This is actually in common with a lot of other tanks, despite the reputation which M4 had for burning It was indeed the ammunition that was the cause not the petrol, and there were a couple of different solutions proposed Eventually, of course, wet stowage, but the interim solution was appliqué armour You simply put more armor between the guys shooting at you and the ammo Whether or not actually did sufficient amounts of use is another matter, but so they put the applique anyway, and then you put a nice big white helpful aiming mark so the Gunners could still get their detonations anyway As you move further up, you’ll see a lot of Shermans will have similar applique armor on the front of the turret The reason this was done was that in order to make room

for the gun control equipment on the inside of the tank they had to shave out some of the metal of the wall of the turret This meant that you had thin armor now between the outside world and the gunner and the TC The long-term solution was a new casting of the turret You’ll see some turrets and actually have a bulge cast into it The short-term solution was just from the factory, additional plates of applique armor that be simply welded to the side So now we come to the back of the tank where ordinarily I talk about track tension, and I’m not going to do this time Half of you are going “hooray” and the reason for this it’s exactly the same as you saw on the m3 medium the M10 tank destroyer It’s the big wrench, the big bolt, that’s as far as I’ll go with that Instead I will mention the engine, the Wright Whirlwind R975 When we first encountered this engine in the m3 medium it was rated by the manual at 400 horsepower running a higher octane level of fuel In this installation though, the manual rates it as only 350 horsepower running on 80 octane Now the engine had a couple of quirks and the first one was its tendency to over rev I was talking with a driver of the time and he said that the problem was in times when you really, really needed the power, like somebody’s shooting at you and you want to go somewhere really quickly, you didn’t think too much about the engine You just put your foot down, the engine would rev up, and you had a good chance of blowing the engine The other problem, being a radial engine, is that you have to hand-crank the thing because all the fluids and oils will all settle into the bottom cylinders and you end up with a hydrostatic lock As a result if you have a cold engine you have got to turn it over, hence “turning over the engine” and to do that you use the hand crank, which is simple enough Insert it into this little hole back here The m18 gun motor carriage, the Hellcat, had the same thing Just feed it through it hooks in to a little notch in there and you can then start cranking 60 times before the engine is considered to be suitably rotated and you can start it up To give you have better idea as to what’s going on back here let’s move over to demonstrator model we have around the corner So now we have the demonstrator model you can see the aiming mark that’s on the inside of the tank and you can also see from the bar just how deep inside it is Fit it into the notch, start cranking, you start seeing the cooling fans turning on the front side I’m not going to do it all 60 times So, that done let’s put this right back in Of course you wouldn’t have to do this if the engine was warm but still I have no doubt that crews were really happy to get engines a bit more modern later on in the war that you didn’t have to do this every time, Again, the m18 gun motor carriage you still had to, it had the radial engine While I’m back here, the other two things to see here are the large air filters and the exhaust ports, the cooling air would be blasted through the big gap in between the hull roof and the back wall It would be deflected downwards right into the dust and dirt, just what you didn’t want to have signifying your position to anybody within miles in North Africa’s desert There were also sand shields You’ll see on the side of the hull the holes for the mounting of the sand shields, they did not last very long Once they were broken off nobody ever bothered trying to repair them Getting up, this is not the hardest time to get up on You got good handholds and of course you can use the bogies So now we’re up here we can start talking about the different engine deck variants M4s and M4A1s with the Continental radial, they had an engine deck similar for this with an armored intake up the front and no grill further back The M4A2 is the twin diesel version and used the same power pack we saw on the M10 This had large grills opening up on the rear deck M4A2, of course, was mainly a lend-lease tank, the Soviets used it, the British got some them, and of course the US Marines used them as well simply because they were the only Shermans that they had available at the time, and the Marines said “well we’ll take these now please, thank you very much” The m4a3 was the version that had the Ford V8, the GAA Excellent engine, at 500 horses,

became the de facto American tank after the war, saw plenty of service in Korea This also had large grills on the back, a different filler port configuration, of course because there’s only the one engine, and the grills were a little bit larger than those on the M4A2 The M4A4 was the one with the wonderful chrysler 30 cylinder contraption, the A57 multi-bank This was the longer engine with the longer engine deck and your visual identifier was outside The British really actually liked the M4a4 and we’ll be coming to that one in a future story The M4A6 was another version based off of the m4a4 chassis so it also elongated It had a Caterpillar multi-fuel radial engine However only 75 of those were built and they only ever saw service in the u.s so if you see a tank with spaced roadwheels and it’s actually on operation in Europe it’s a British probably, but it’s certainly an M4A4 There was the m4a5 designation which you will note i have skipped The m4A5 is what the Americans called the ram Quite why they did that I don’t know, because the Ram was really an m3 based vehicle if you look at the builder’s plate of this Grizzly, it actually says “Montreal locomotive works m4a1”, so perhaps that’s why they didn’t come up with a separate designation for the Grizzlies themselves Ok so to get the engine deck up which is a two-man job I have summoned my beautiful assistant here meathead This is your moment of fame now to the inside the hatch audience If you don’t know him he’s popular enough on the na community side of things – So if you give me a hand here please – Absolutely – Thanks very much – That was heavy – Go away – Ok So now we have the engine bay open you can see the Continental as it is installed inside the tank It is mounted on the brackets, there are 4 large bolts that are holding it in place So if you wanted to pull the engine out you’d undo the deck, lift that out of the way, lift out the engine by of course disconnecting the power shaft, fuel lines or what-have-you This particular engine would get the tank up to burst speed of 24 miles an hour and a sustained speed of about 21 Of course this was the weakest of the engine options, later versions of the tank would go a little bit faster, up to 30 You can also see in here the red pipes for the fire extinguisher system This was a two shot system It could be fired from either inside the tank or by use of a handle on the engine deck just left rear of the turret Further forward under its own fuel tank port is the axuliary motor This would be used for running the systems without draining the main fuel tanks, and of course putting wear and tear on the main engine Speaking of fuel, the fuel in this system will be a hundred and sixty eight gallons That will be about enough to get you a hundred and twenty miles Some help he was I told him to go away and he took it literally Well that brings us to the end of part one and of course part 2 will be the interior positions which we’ll get to at a later date I’ll see you then Later vehicles showed up with a new suspension… hello spider Are you having fun? I’m going to skip forward a little bit though very quickly to some time in 1943 Wait one I imagine that music would be played over this You are going to be relocated from the Sherman to the t-34