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Inside the Chieftain's Hatch, Sentinel Pt 2


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The_Chieftain #1 Posted Apr 12 2016 - 19:22

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Slayer_Jesse #2 Posted Apr 12 2016 - 20:14

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The_Chieftain #3 Posted Apr 12 2016 - 20:24

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I figured that would get a laugh. I forced the camerman to climb out in order to get the shot.

shapeshifter #4 Posted Apr 12 2016 - 20:26

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Ha!

TwixOps #5 Posted Apr 12 2016 - 21:13

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Quite interesting.  the AC 1 was a tank I personally knew very little about, so these videos have been particularly informative for me.  

CapturedJoe #6 Posted Apr 12 2016 - 21:32

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That actually justifies this tank's awful aiming time in-game.

Howie_Eye #7 Posted Apr 12 2016 - 22:43

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Shouldn't the lever be painted "BLUE"? I am a bit long in the tooth

Blackhorse_Six_ #8 Posted Apr 12 2016 - 22:58

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View PostThe_Chieftain, on Apr 12 2016 - 14:24, said:

I figured that would get a laugh. I forced the camerman to climb out in order to get the shot.

 

To be fair, the weight of the receiver-body of the MG must have balanced that uh, nose assembly, nicely ...

Anlushac11 #9 Posted Apr 12 2016 - 23:35

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How much larger was the 6lbr than the 2lbr? 

 

I have read that the AC1 Sentinel originally designed for a 6lbr.



hoom #10 Posted Apr 13 2016 - 03:37

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Isn't this the mystery turret chute?

I'm thinking there could be a hole under the bracket there & its intended for the spent casings from the Maxim? Or something like that?


Edited by hoom, Apr 13 2016 - 06:39.


Nathan454 #11 Posted Apr 13 2016 - 13:28

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Outstanding video, it shows that tanks are more then, and sometimes less then, what the raw armor/gun values appear to be.

1SLUGGO1 #12 Posted Apr 14 2016 - 02:58

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It's too bad the later mods really never came to fruition. There would be a much different episode climbing in the ac4 turret with a turret ring bigger than the t-34-85's.

 

 


Edited by 1SLUGGO1, Apr 14 2016 - 03:00.


AndrewSledge #13 Posted Apr 15 2016 - 03:09

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I just don't understand how the turret can be that cramped...surely with the number of them made, they would have been able to make some changes to how the seats were placed? Like a height adjustment or something?

ErikTheVikingMoose #14 Posted Apr 24 2016 - 19:10

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about that mystery slot in the turret

 

Is it possible it was meant for machine gun ammo belt for a MG to be mounted outside the turret ?

with the ammo belt magazine/box  being inside the turret for what seemed like a good idea at the time ?



Jarms48 #15 Posted May 07 2016 - 09:39

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I saw this comment over on SEA, I'm not sure how credible it is, but it shows some more light on the Australian Cruiser.

 

View PostMaximumSomething, on 07 May 2016 - 06:16 AM, said:

View PostThe_Chieftain, on 28 March 2016 - 10:13 AM, said:

 

 

 

I almost wasn't going to bother but I can't sleep so, "Things Which Are Missed Or Wrong in Part 2":

 

The swivelling commander's seat: There is a remark something along the lines that the commander's seat height adjustment range be increased by turning additional groves in the support, it is possible that the swivel is a by product of the height adjustment, or that it is not locked or tightened down properly. It is possble the gunner has some height adjustment also, it might be in the field trials report but I don't have a copy of that.

 

Commander's position: The curved box to the rear (The Chief's right elbow) is for Bren magazines. A Bren came standard with the tank for protection from aircraft. The two mounting points for it are on the Commander's cupola, you can see where the plugs are retained by short chains at the start of the video.

 

Gunner's position: The manual is not unclear about disconnecting the manual traverse handle. The manual doesn't mention it because disconnecting it is not possible. It is not possible because it is not required and the handle is not going to "come 'round and take your leg off". Working backwards the turret ring has teeth cut in it in the form of a large ring gear. A pinion from the turret drive gearbox (behind Nick's left shoulder) engages this ring. In the gearbox is a differential, arranged in the opposite manner to a car axle but a differential nonetheless. One of the inputs to the differential is a worm wheel driven by a worm powered by the turret traverse motor (bottom left of the screen). The second is a worm wheel driven by a worm turned by the manual traverse handle. It should be clear at this point that the worms function as one-way drives and it is therefore unnecessary to disconnect the manual traverse.

 

40 volt Generator: Yes there is a gain of truth in what Nick says, but the overall impression conveyed is wrong. The voltage does vary, at 1200, 1300, 1600, 2000, 2400, 2500 rpm (2800 and 3000 could not be obtained due to a faulty engine) volts were 46, 49, 42, 38, 40 and 40 respectively. This variation is unimportant as there is a voltage regulator and the output from that is 40, 40, 40, 38, 38, and 38 respectively, so within 5% and later adjusted on the tank under test to give 41 volts under load. So as far as the turret traverse system is concerned there is effectively no variation in voltage as a result of changes in engine rpm.

 

There is only one shunt motor (sort of visible behind the periscope). All the shunt motor does is switch the traverse motor on and off very quickly, the duration of the "on" time being determined by the position of the gunner's controls. It is essentially a pulse width modulation system. There is no reversing motor, there is a set of switches in the traverse controller that do that.

 

Power traverse: What Nick points to as he says power traverse is a secondary control method that seems to have been intended to be used to smoothly track moving targets. The primary control method is back down on the manual traverse crank. Just visible is some of the shots is a line of three gears between the handle and the central axis of the crank, this connects to a second shaft running up through the bevel gears to a sprocket and chain under the cover running over to the shunt motor assembly. By pulling on a trigger/lever on the handle (missing on that tank by the looks of it) a clutch engages and by twisting the handle this motion is transferred by the gears to the sprocket and chain to the traverse controller, which begins sending pulses to the traverse motor which moves the turret under electrical power in a continuous range from 0 to around 20 degrees a second left or right depending on which way the handle was twisted.

 

The guns: The gun mounting is pretty much a standard British 2 pounder tank gun mounting, shoulder controlled elevation and everything. I believe the drawing for it may have been obtained from Canada. Yes there are two handles, same as you'd find on any British tank so armed, Crusaders, Valentines, etc. See for example the Chieftain's Hatch, Matilda part III at about 9 minutes, it has two handles. So right hand on the weapon to be used for the selected target, left hand on the crank moving to the hand wheel if the target is moving such that it needs to be tracked and you can't manage the fine control required through the hand crank.

 

The gunner's periscope or lack thereof: The periscope Nick mentioned is on the Thunderbolt, not the Sentinel. So it is late production ... kind of. The loader has one too on the Mark 3.

 

The Vickers: I do not know what Nick means by "big" and  "huge", a quick look at the numbers suggests it is about the same length and weight as say a Besa, the Vickers has more volume around the barrel but it's water cooled so you'd have to expect that.

 

The ammunition stowage: The hull ammo racks are bolted to the hull side but they sit above the battery boxes. At a guess, in a museum vehicle you'd probably want to at least disconnect the batteries if not remove them altogether to eliminate the possibility of acid leaks or short circuits from old wiring. To do either of those the hull stowage bins need to be moved out of the way.

 

The steering system: The 58 feet quoted is the circle drawn on the ground by the outside track, as the sprocket and tensioning idler sit off the ground so the actual cleared area required to turn is larger at about 63 feet. There is no particular reason why the Sentinel should turn any tighter than the M3 or M4 as the controlled differential gearing is unlikely to have been altered. The Sentinel does have compressed air powered brakes/power assisted brakes but that won't help it turn any tighter. It is likely just different characteristics being measured vs the M4.

 

Top speed: The Sentinel hit a maximum speed of 40mph in tests with a sustained average of 39mph, so the gauge is more realistic than you might think. The 24mph is the maximum training speed, the maximum permissible is 29.5mph.

 

The further developments and the rest: There were something like a half a dozen or more different guns produced in Australia during the war including the likes of the 6 pounder, and 3 and 3.7inch anti aircraft guns, and the 17 pounder. The 6pdr tank gun order was placed but not acted on, by the time this had been realised it would have taken the same time to make 6 pounder tank guns as 25 pounder tank guns so the 6pdr was skipped. The 25 pounder tank gun was first tested in June 1942, which is a couple of months prior to the first production tank leaving the production line and the twin 25 and 17 pounder in November 1942 or 4 months after the first production tank. To fit the 25pdr and its ammo, and the 17pdr for that matter, they had to get rid of one of the machine guns (singular) specifically the hull gun. The coax remained, it is in photographs, the specification, even the stowage lists item (9) Vickers MkXXI (coax) 1 in turret and item (15) Ammunition .303 (10 boxes) 2500 4 boxes in turret - 6 in hull. So while a tank without a machine gun may be bad, all the Australian cruisers have at least one machine gun. Just as a side note the AC3 gunner's seat is described as comfortable. The AC4 is not an AC3 turret with a 17 pounder, it was going to be a new hull with a larger turret and turret ring, and then an even more extensively redesigned turret with a sort of mechanical magazine in the turret bustle none of which was completed when the project was shut down. With regard to production, only one of the 6(?) state railway companies was working on tanks, probably a greater disruption to their regular business were things like the local pattern carrier work and making parts and ammunition for 25 pounders. Australia did cancel projects that were deemed no longer necessary of its own volition, like the 3" mortar carriers and the Heavy Armoured Car, however the cruiser tanks were killed off primarily due to American insistence, absent that Australia would have continued making tanks through 1943 at least. The parts commonality sounds good in theory but in practice the Australian forces needed their own supply chain anyway as the most used Australian tank in the Pacific ended up being the Matilda and not the M4, by comparison the Sentinel does have some parts interchangeable with the M3 and M4.

 

None of the ex-Melbourne Tank museum tanks nor the Puckapunyal tank have the escape doors welded shut, that might have been done to the Bovington tank to prepare it for shipment to the UK.

 






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