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Unstabilized Sights And Motion Sickness


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I'm not sure why you think this is a pissing contest. I merely pointed out that alternatives were possible. Not to mention that the Abrams is notably not the machine it was when it had a 105mm.

Never said it was. As was mostly referring to historical aspect, not only current day.

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A bit of a search finds that the currently selected gyro is a G-2000 series from Northrop Grumman. Its design appears to be fairly traditional. It's a rate sensor with low drift rate and spins up in 1.4 to 3 seconds.

Perhaps hidden away from the crew and 1st level maintainers insofar as interface and usability is concerned?

I find it very strange. Why hide the fact that gyroscopes are used? Particularly from people who work with the tank?

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I don't think it was hidden, the army just didn't spend a whole lot of time on details that weren't deemed relevant to crewing the tank. Since there was effectively no warm up time for the M1 stabilizer you just turned on turret power and it worked. If id didn't work you worked through the troubleshooting steps in the manual. If that didn't resolve it you punted to the company turret mechanic. Since fixing things at the company level involved swapping out circuit cards or major assemblies and shipping the bad ones off to higher level maintenance shop there wasn't much call for going into the nuts and bolts of how all those boxes scattered around the turret worked.

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In Kings example he is sitting motionless whilst an unstabilised picture tells his brain he is moving. Surely, in a real moving vehicle the problem would be with stabilised sights telling you you are motionless whilst your inner ears told you you were moving?

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I don't think it was hidden, the army just didn't spend a whole lot of time on details that weren't deemed relevant to crewing the tank. Since there was effectively no warm up time for the M1 stabilizer you just turned on turret power and it worked. If id didn't work you worked through the troubleshooting steps in the manual. If that didn't resolve it you punted to the company turret mechanic. Since fixing things at the company level involved swapping out circuit cards or major assemblies and shipping the bad ones off to higher level maintenance shop there wasn't much call for going into the nuts and bolts of how all those boxes scattered around the turret worked.

More specifcally, I'm 99.9999% certain that the electronics box that contained the gyro was not Field reparable. I expect it was a sealed unit that was clean room only before you cracked the case. [edit, it's a tiny component. Likely it was mentioned about as much as the various caps, resisters and other discretes on the system.

 

 

 

There must be a misunderstanding. Because, all gyros needed a minimum time to reach the necessary minimum speed. That's regularly 90 seconds.

Which is probably something that's embedded in the startup and self check of the system. I presume there was some sort of 'boot process' for the system, not as far as a consumer level computer, but it likely had to energize, align resolvers, devices etc. For soldier proofing I'd suspect it was as simple as a set of indicator lights that would show a powered status and then some level of component ready state and finally a "ready" light.

 

But....looking at NG's site on the product, it's TINY. A bit larger than a penny in cross section. (.37 cubic inches) and light weight (<25 grams)!

 

hero_G--10112.jpg

 

https://www.northropgrumman.com/Capabilities/G2000DTGGyroscope/Pages/default.aspx

Edited by rmgill
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This is an interesting thread drift.

 

 

G-2000 advantages
  • Small size (.37 cubic inches) and light weight (<25 grams)
  • Angle Random Walk of <0.005°/√hr
  • Random drift of 0.02° to 0.6°/hr, 1σ
  • High shock capability of 750 g's (2 μsec, 1/2 sine)
  • High MTBF of 100,000 hours
  • Low power consumption
  • Fully qualified to MIL-spec performance
  • DGCU servo card option for turnkey, enhanced performance.

     

    :D

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This is an interesting thread drift.

Likely due to precession :P

 

 

 

On the Leopards and Marders there are adjustment knobs to correct for the little deviations that make the reticle wander on its own. And yes if you leave it like that after starting up the fire control system the turret starts to turn very slowly on its own. Though once I forgot to do it, because I had sinmply forgotten to check but I still completed the fire drill succesfully. I guess I went so fast from ranging to shooting that the little movement did not really matter in the end. But sometimes the movement is very noticeable which automatically makes you grab the knobs and correct the drift.

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There must be a misunderstanding. Because, all mechanic gyros needed a minimum time to reach the necessary minimum speed. That's regularly 90 seconds.

 

Been checking through what material I can find on the M1 turret and only reference I've found for any kind of wait time after turning on turret power was for the computer self check, there's a note in a checklist that says do not perform until turret power has been on for at least 90 seconds.

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Stephan, I think that the type of gyros you may be referring to are sized to actually perform the stabilization, rather than being rate sensors. In the former, they resist the torque inputs directly so need to be large. In the latter they sense the torque and send commands to drive motors to oppose it. The advantage is that they won't topple like big mechanical gyros, and as noted they spin up rapidly.

 

I expect that internally they make Swiss watches look crude.

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Resolver without gyroscope is meaningless. And gyro without resolver is also meaningless. In order to determine whether a deviation from the setpoint angle has occurred, we need a fixed point for the measurement. The fixed point can only be a gyro. Because the gyro does not move while turret or gun swing.

 

A rate (gyro) sensor is usually a gyro with 2 degrees of freedom + resolver as signal transducer.

 

A322.jpg

as exemple

Edited by Stefan Kotsch
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Resolver without gyroscope is meaningless. And gyro without resolver is also meaningless. In order to determine whether a deviation from the target angle has occurred, we need a fixed point for the measurement. The fixed point can only be a gyro. Because the gyro does not move while turret or gun swing.

 

A rate (gyro) sensor is usually a gyro with 2 degrees of freedom + resolver as signal transducer.

 

A322.jpg

as exemple

 

There are devices that can replace gyroscopes.

 

https://en.wikipedia.org/wiki/Ring_laser_gyroscope

 

https://www.siliconsensing.com/technology/mems-gyroscopes/

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Just found in my archive:

 

""

US Army Mechanical Maintenance
Senior Officer Correspondence Course

 

Introduction to the M1 Abrams Tank: Armament

 

Task 4. Describe the components of the gun/turret drive and stabilizing systems

...

2. Gun/Turret. Drive and Stabilization Systems

...

a. Azimut Channel

...

(1) Gyros. Azimut stabilization signals ar obtained from two gyros: the hull gyro and the azimut axis of the sight gyro. The hull gyro provides the information nessecary to maintain the turret stabilization when the hull moves beneath the turret. The azimut gyro ist located in the LOS head assembly. It reports any azimut motion in the turret and thereby refines the correction in azimuth.

...

b. Elevation Channel

...

(1) Operation. ... The sight gyroscope senses movement of the sight head mirror and sends the sight elevation to the LOS electronic unit. This keeps the head mirror steady while the M1 and the sight move up and dow.

...

""

 

And, yes, each gyro is connected to a resolver to send a signal corresponding angle and angel velocity.

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