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MarkHolloway

www.youtube.com/watch?v=DwtP188z9ZQ

Doug_Kibbey

EXACTLY as I was trained (though they are a little casual and slow about the commands, no doubt for training purposes, as they are using voiceovers). Especially notable and different from any MBT was the action of the TC when firing main gun. In MBT, he was to be looking through binocs to spot for gunner and help apply burst-on-target. In the Sheridan, the drill was for the TC to grasp the spade grips on the locked-down .50 and hold on (for very good reason!). Laughing

JeffStringer · ***Power User*** Offline Joined: Jan 24, 2006 Posts: 637

That's a gem of a video! Mr. Green

- Jeff

Doug_Kibbey

Notice the film is dated 1969 and they are using HEAT to engage bunkers. I suggest that this is why we see it in the other M551 thread, HE-T was not yet available in quantity.

www.com-central.net/in...ic&t=13629

MarkHolloway

I guess you guys didn't notice but if you listen to the sound of the tank in the video you will hear the soundtrack of an M60. Quite different from those old whining 6V53T's. A mistake that only an old Sheridan loader would notice was when they showed the 'safe-to-fire' indicator it was out of range (low gun mount pressure). The other thing I noticed was when the TC gave a coax fire command the first thing the gunner did was turn on the turret power. This should already have been on!!! This would delay your engagement time by about 20 seconds. But I loved the video anyway Smile

Doug_Kibbey

- MarkHolloway

I guess you guys didn't notice but if you listen to the sound of the tank in the video you will hear the soundtrack of an M60. Quite different from those old whining 6V53T's. A mistake that only an old Sheridan loader would notice was when they showed the 'safe-to-fire' indicator it was out of range (low gun mount pressure). The other thing I noticed was when the TC gave a coax fire command the first thing the gunner did was turn on the turret power. This should already have been on!!! This would delay your engagement time by about 20 seconds. But I loved the video anyway

Mark,
A member over at tank-net noted the 20sec. time to full turret power engagement and asked why. As I don't recall myself, I suggested that you would likely know. I'd guess it has to do with the stab system (like spooling up gyros on an M60A2 or something) but am not sure.

How different is this from modern tanks in terms of time? What's the reason?

Thanks,
Doug

C_Sherman · ***Power User*** Offline Joined: Jan 24, 2006 Posts: 590

Hi,

I can't speak for Sheridan's, but I remember that M60's took as much as 10-12 seconds to charge the hydraulics, depending on how much they had bled down. If the accumulator had held pressure, it wouldn't take any time at all from switch-on to ready. But a flat accumulator would recharge with a gawd-awful howl from the pumps, for as long as it took.

I don't remember any other reason that there would be a delay between switch-on and ready to fire, but I might be wrong. It's been a few years...

C

Doug_Kibbey

- C_Sherman

Hi,

I can't speak for Sheridan's, but I remember that M60's took as much as 10-12 seconds to charge the hydraulics, depending on how much they had bled down. If the accumulator had held pressure, it wouldn't take any time at all from switch-on to ready. But a flat accumulator would recharge with a gawd-awful howl from the pumps, for as long as it took.

I don't remember any other reason that there would be a delay between switch-on and ready to fire, but I might be wrong. It's been a few years...

C

There was a delay in the M60A2 series that was definitely the gyros spinning up to something like 40,000 rpm's for the stab system. At shut down, you could hear those puppies winding down for 15-20 minutes.

MarkHolloway

I'll tell you the answer but it will be a let-down for all of those who marveled at how modern the Sheridan was. The 18 to 22 second time delay was to allow the vacuum tubes to warm up! Like the old TV sets. If you are in a Sheridan turret there are two white boxes under the radio. The one on the left (Amplifier Integrator) has latches and can easily be opened. There are tubes mounted inside the cover. Vic Pitts just replaced these on his Sheridan in North Carolina.

Part 2: When the turret power in the Sheridan was turned on then the missile system was automatically placed in stand-by mode. (Gunners may remember the missile 'power supply' light coming on for a second when the turret power was switched on. That's because the missile system is turning on.) Part of the missile system, the rate sensor, had gyros that would start spinning as it went into stand-by. These same gyros were what made the stabilized mode work therefore when the 'STAB' switch was turned on there was no warm-up because the gyros were already operating. This also explains why you could not fire a missile is stabilized mode-the rate sensor could not do both jobs. It either sensed turret movement for missile guidance or it sensed turret movement for stabilized mode but could not do both.

Doug_Kibbey

Thanks, Mark, passed that tidbit on and it was appreciated. By me, too.

Doug_Kibbey

P.S. A viewer writes...

"I didn't notice any "Null" or "Balance" knobs for the stab, were there none, or were they just not visible? "

As I'm too lazy to look through my TM, what is your recollection about Sheridan stab? We never used it once I was out of Sheridan school.

Dontos

We interupt this thread for a couple of COOL PHOTOS.....

A couple of all you OLD light tank guys.....

Regards
Don

Doug_Kibbey

I hope they moved those duffle bags first! Laughing

Nah, I know it's not the same vehicle....

MarkHolloway

Doug,
Theoreticallyonce you had the turret trimmed in the normal power mode you would not need to make any further adjustments when switching to 'STAB'. There was a box behind the TC's seat known as the accessory box. It is full of circuit boards. If the turret starts to drift when switching to STAB mode then this could be adjusted by turning small screws on the A-12 (traverse) or A-13 (elevation) circuit boards in the accessory box. These are the equivalent of 'stab trim knobs'. This work was done by turret mechs or wanna be turret mechs (me).

When I first got on Sheridans in Germany we were told never to turn the STAB on because it could result in a runaway turret. These runaway turrets were simply a result of the turrret electric drive system not being 'balanced'. At some point we were required to fire a STAB engagement on Table 8. That's when we had to start checking them out. It was my experience that the STAB would work fine after a few adjustments in the accessory box.

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