Arjun Main Battle Tank (MBT)

[pmaitra]

How many variants does this sight have, It does look similar but not all of it ..

I am thinking something like this:

 

[Dejawolf]

I am thinking something like this:

another blurry image, from indiatoday, showing sight module, connection tube and gunners optics control panel.

this one shows commanders periscopic sight:

 

[ersakthivel]

and just in case you try some other dishonest way of being quarrelsome,
the green lines are around the halfway point of 250. 250/2 = 125.
4000+ 125 = 4125
6250+ 125 = 6375.
6375-4125 = 2250.

in the line drawing above, the ledge in front of the hatch pivot is at 0 meters.
the turret front is at 2260mm. lets start our measures at 0 because then there won't be any way for you to try and confuse people.
you've already accepted the crew needs 600+600mm.
you've already agreed that the sight cutout is 700-750mm.
the length is obviously 2260 from back of TCs seat to front of turret.

and so the formula. 2260-(600+600+750) = 310mm.
this is the truth, and denying it only proves your dishonest argumentation techniques.

now apologize for wasting everyones time.

What you do is fraud by technical drawing,

just wait for a couple days , I will make one conclusive post and close the subject with photo measurement from crew compartment and nail your lies about where the 2260 point is, where the 2250 point is, where the vision block is, where the Tc head rest is,

How far the inside opening for the vision block is from the Tc, seat head rest , from the gunner seat back rest, from the pivot base, and all the wrong points you marked .


Don't worry.

Thumping your chest with shody dimension line won't help you latter, better keep quiet.
So you are the one that is going to apologize in the end , not me

 

[ersakthivel]

This is what I can surmise about the approximate width of the armour behind the sight, given that no one is sure what the real width of the armour is.

So what is the dia meter of the crew entry hole?

it must be around 500 mm minimum.

Also this 0.638 units you marked is the LOS distance in case the channel that brings down the light from the roof top vision block to the gunner's main sight block is perpendicular.

if it is slanted as I estimate it will easily come to around 600 mm plus, which seems to be the case,

 

[Kunal Biswas]

Gunner cannot sit just below it, There is a gap between the sight placement and gunner sitting position under the GAS optics ..

I am thinking something like this:

 

[pmaitra]

So what is the dia meter of the crew entry hole?

it must be around 500 mm minimum.

Also this 0.638 units you marked is the LOS distance in case the channel that brings down the light from the roof top vision block to the gunner's main sight block is perpendicular.

if it is slanted as I estimate it will easily come to around 600 mm plus, which seems to be the case,

I had made a small approximation error:

You are correct. The top armour is sloped at an angle of approx. than 5°.

So, assuming it is 5°, the correct number would be 0.638201 x cos(5°) = 0.638201 x 0.9961947 = 0.6357724537347.

So, if the hatch hole as marked (little less than the diamater) is 500mm, then the armour thickness is around 500mmx(0.6358/0.6977) = 455mm.

 

[ersakthivel]

I had made a small approximation error:


So, if the hatch hole as marked (little less than the diamater) is 500mm, then the armour thickness is around 500mmx(0.6358/0.6977) = 455mm.

See in the image above the Tc seat head rest is right below the pivot base which is 2500 mm behind the front tip of the turret including the gun covering plate.

 

[pmaitra]

See in the image above the Tc seat head rest is right below the pivot base which is 2500 mm behind the front tip of the turret including the gun covering plate.

Please show me your calculations and mark on the image, as to how you arrived that that 600mm value. Otherwise, I am not sure what you are talking about. What is a pivot base? Are you taking about the hatch-lid-hinge?

 

[ersakthivel]

Please show me your calculations and mark on the image, as to how you arrived that that 600mm value. Otherwise, I am not sure what you are talking about. What is a pivot base? Are you taking about the hatch-lid-hinge?

if you drop a vertical line from the pivot base you can see it will touch the Tc seat head rest.

The head rest of the Tc seat which is right below the pivot base of the standing vertical hatch cover(the 4.0 meter point) is s 2500 mm behind the front tip of the turret which includes the gun covering plate (the 6.5 meter point ).

If you don't include the gun covering plate the head rest of the Tc seat will be 2350 mm behind the front tip of the turret (the green line.)

Take a careful look at the electric bulb in the top left corner of the picture below, judging from the photo above the roof top vision block must be right at the point of the center of the electric bulb.i.e at the base of the gunner's main sight white colored block containing the binocular like eye piece.

The 20 cm marked by Dejawolf must include the Tc nose as per the anthropological head measurement. He has excluded it. So you include it and judge the distance.

You can calculate this distance yourself.

 

[militarysta]

You are correct. The top armour is sloped at an angle of approx. than 5°.

So, assuming it is 5°, the correct number would be 0.638201 x cos(5°) = 0.638201 x 0.9961947 = 0.6357724537347.

It's slopped at exatly 8 so maybe 0.638201 x 0.990 = 0.63181899
So maybe 500mm x 0.63181899 = 315mm

Is this correct pmaitra?

ps. if it's slopped at 6° or 7° then result will be circa 320mm. So exatly as Dejawolf job, and my own mesurment usinf bal holder lenght.

 

[ersakthivel]

Please show me your calculations and mark on the image, as to how you arrived that that 600mm value. Otherwise, I am not sure what you are talking about. What is a pivot base? Are you taking about the hatch-lid-hinge?

http://upload.wikimedia.org/wikipedia/commons/6/61/HeadAnthropometry.JPG

pmaitra,
In the link above human head average measurements are given,

In that table the height of the human head from chin to skull is given as 23.2 mm for 50 percent of males in item no-14.

In the picture posted above 1.7143 is the ratio of this human head height to the Tc seat head rest behind him at a point close to the left side edge of the head rest.

So the height of the head rest is 23.2/ 1.7143= 13. 53 mm,

http://upload.wikimedia.org/wikipedia/commons/6/61/HeadAnthropometry.JPG

In the picture below the ratio of the [horizontal distance between the front surface of the TC head rest ] / [height of the Tc seat head rest is ] = 85

So 85 x 13.53 = 1149 mm. from the front surface of the Tc seat head rest



[So from the 2500 mm pivot base point (if we exclude the gun covering plate this 2500 mm point becomes the 2350 mm point, because we have to give a 150 mm depth for the gun covering plate)the roof top vision block opening is situated 1149 mm away.Dejawolf too agrees with this and has a claim of 1200 mm for the same region. So no dispute here just 50 mm this way or that way.

See in the photo above the vision block over the tc's seat is well behind the pivot base and not even visible

In the picture above , In the same way the ratio of [ distance from front tip of the turret(excluding the gun cover plate) to the pivot base of the hatch cover ] / [ distance from tip of the turret (excluding the gun cover plate) to for hatch cutaway ] is 3.14 .

In the image below distance from front tip of the turret(excluding the gun cover plate) to the pivot base of the hatch cover is 2250

so 2250 / 3.14 = 716 mm is the gap for the hatch cutaway.

.

So 2350 - 1149 - 716= 485 mm.

So 485 mm is the LOS for armor behind main sight till the opening of the roof top vision block into crew compartment.

What is the bone of contention is what happens after that, I am arguing based on the shape of the rectangular cut , that the light from the roof top vision block comes through a rectangular channel and after that channel there is a small block of armor 200 mm more in depth above the orange dial box, which is not accepted by any one here.

 

[militarysta]

They are 3 proofs why Arjun Mk.I LOS after main sight is circa 320-350mm max, and why ersakthivel is wrong in this thema:

1. @pmaitra obseravation whit prooper angle 8°

More or less @pmaitra obseravation whit prooper angle 8° degree (or 7°) give us result:

It's slopped at exatly 8° so maybe 0.638201 x 0.990 = 0.63181899

So maybe 500mm x 0.63181899 = 315mm
Even if hatch is 550mm width we have result 347mm (350mm).


2. Bar holder lenght used as mesurment point:

Again circa 315mm!

3. Compare between known Arjun draw and Leo-2A4 factory draw:

And as Dejawolf said:

in the line drawing above, the ledge in front of the hatch pivot is at 0 meters.
the turret front is at 2260mm. lets start our measures at 0 because then there won't be any way for you to try and confuse people.
you've already accepted the crew needs 600+600mm.
you've already agreed that the sight cutout is 700-750mm.
the length is obviously 2260 from back of TCs seat to front of turret.

and so the formula. 2260-(600+600+750) = 310mm.
this is the truth, and denying it only proves your dishonest argumentation techniques.

more or less 3 diffrent methods give us circa 315mm value.

 

[pmaitra]

Reference image.

Schematic image and calculation.

The final formula is in red. Plug in x to get y.

 

[ersakthivel]

EDIT,-------for the post-5651

In the picture below the ratio of the [horizontal distance between the front surface of the TC head rest to the roof top vision block opening inside the crew compartment] / [height of the Tc seat head rest is ] = 85

So 85 x 13.53 = 1149 mm. from the front surface of the Tc seat head rest,

Sorry I have left the crucial words,----to the roof top vision block opening inside the crew compartment , without which there is no meaning.

 

[pmaitra]

@militarysta, thank you. I think our numbers are more or less same. I have one concern. I think I am not very sure about the width of the crew hatch (x in my figure) in terms of circumference through centre to centre of chord. If I can know that, I think my formula will give a reasonable thickness of the behind-sight armour.

 

[ersakthivel]

They are 3 proofs why Arjun Mk.I LOS after main sight is circa 320-350mm max, and why ersakthivel is wrong in this thema:

1. @pmaitra obseravation whit prooper angle 8°

More or less @pmaitra obseravation whit prooper angle 8° degree (or 7°) give us result:

It's slopped at exatly 8° so maybe 0.638201 x 0.990 = 0.63181899

So maybe 500mm x 0.63181899 = 315mm
Even if hatch is 550mm width we have result 347mm (350mm).


2. Bar holder lenght used as mesurment point:

Again circa 315mm!

3. Compare between known Arjun draw and Leo-2A4 factory draw:

And as Dejawolf said:


more or less 3 diffrent methods give us circa 315mm value.

See the post-5651, You can not counter it any way.

you can use bar holder length only on the outside,

I have explained with detail the LOS behind the main sight by comparing the distances in the crew compartment, which is what counts.

 

[militarysta]

@up
and result is circa 330-340mm LOS -yes?

 

[militarysta]

@militarysta, thank you. I think our numbers are more or less same. I have one concern. I think I am not very sure about the width of the crew hatch (x in my figure) in terms of circumference through centre to centre of chord. If I can know that, I think my formula will give a reasonable thickness of the behind-sight armour.

It's very good acually.
I check this myself for: 6° 7° 8° and 500 and 550mm hath width.
The result is between 315 and circa 350mm LOS behind main sight.
So again - the result are quite possible for Yours, my and Dejawolf job

 

[ersakthivel]

It's very good acually.
I check this myself for: 6° 7° 8° and 500 and 550mm hath width.
The result is between 315 and circa 350mm LOS behind main sight.
So again - the result are quite possible for Yours, my and Dejawolf job

See the post-5651and with an EDIT in 5654, You can not counter it any way.

you can use bar holder length only on the outside,

I have explained with detail the LOS behind the main sight by comparing the distances in the crew compartment, which is what counts.

 

[pmaitra]

I think we have all presented our numbers. So, we can lay this to rest. We can only corroborate if someone (perhaps @Kunal Biswas or @sayareakd?) visits this tank and takes some real measurements.