Dhanush the Indian Bofors

arnabmit

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The range of barell loading guns got increased and accuracy increased due to expanding bullets under heat. same is true about cannons. The sabot will stop this heat transfer to whole of shell body but if we make the shell the way I stated, we will be able to make the shell heat up much faster as more area is available to absorb that energy and also impart more velocity to the shell as the heated shell will transfer its energy to its surrounding air thereby heating it and accelarating it which will remove the need for base bleed.
I am not an expert in guns as such but just using my knowledge of aerodynamics here.
That was for muzzle loaded cannons where the cannonball made of soft metal expanded and created a Hermetic seal for the expanding gasses, thus 1) prevented the cannonball to bounce around as it exits the barrel and 2) allowed the full force of the expanding gas to be utilized to push out the cannonball.

In modern artillery, shells are made of tempered metal and do not expand. Expanding shells are defective and results in burst/bulged barrels.
 

Kunal Biswas

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My point was towards the sabot in your post, It will be made of brass or other metal besides the warhead and fuse in other part of the round, As its a Arty round the sabot will be big and such a piece is expensive compare to a dumb shell ..

Bleed base indeed provide lesser drag but due to the small propellents it gives extra range ..

=======================

What you suggested may not applicable to the Arty rounds design in terms economy, But surely applicable to small arms projectiles and tank rounds like HE and HEAT ..





Cost wise it should be similar to the 'dumb' shells, much lesser than the expensive base bleed rounds.
 

arnabmit

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My point was towards the sabot in your post, It will be made of brass or other metal besides the warhead and fuse in other part of the round, As its a Arty round the sabot will be big and such a piece is expensive compare to a dumb shell ..

Bleed base indeed provide lesser drag but due to the small propellents it gives extra range ..

=======================

What you suggested may not applicable to the Arty rounds design in terms economy, But surely applicable to small arms projectiles and tank rounds like HE and HEAT ..
IMHO the cost of (A spindle shaped dumb shell + a metal sabot) should be far less than a base-bleed shell.

A base bleed shell contains less explosives than a dumb shell as the shell of a base bleed round sacrifices some space to accommodate the gas generator.

The gas generator in the base bleed shell produces negligible propulsion as its only job is to fill up the vacuum created behind the flat base of a normal dumb shell with gas so as to reduce drag created by the vacuum.
 

ladder

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IMHO the cost of (A spindle shaped dumb shell + a metal sabot) should be far less than a base-bleed shell.

A base bleed shell contains less explosives than a dumb shell as the shell of a base bleed round sacrifices some space to accommodate the gas generator.

The gas generator in the base bleed shell produces negligible propulsion as its only job is to fill up the vacuum created behind the flat base of a normal dumb shell with gas so as to reduce drag created by the vacuum.
Arnab da, take look at the below link

Aerodynamics 101
 

arnabmit

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@Kunal Biswas @Decklander @ladder @pmaitra @DivineHeretic @ersakthivel @sayareakd @Twinblade @p2prada

This is a better representation of my idea:



Looks like Bofors also had a similar idea! My solution was a a fixed base with a sabot, Bofors' idea is an expandable base. But ultimately both land up with a 'American football' type of projectile which eliminates the 30% drag produced by the base vacuum.

Method and design for increasing the firing range of artillery shells - Bofors Defence AB

Can anyone explain something to me?

AFAIK, when a shell is fired, a powerful source of drag is the vacuum left behind the shell due to its blunt base, which reduces its range.

Base bleed is one way to reduce this drag, but a small loss of accuracy happens due to the somewhat more turbulent airflow, and a small loss in explosive payload due to some of the shell being taken up by the gas generator.

To overcome this, why can't an aerodynamic spindle shaped shell be used with a discarding sabot?

Green = Shell
Blue = Discarding sabot

If you are talking about tumbling effect, that can be overcome by 2 things:

1) shells are anyway always nose heavy to mantain its ballistic dynamics.

2) Micro Rifling the shell to make it move through the air like the Americal Football.





Cost wise it should be similar to the 'dumb' shells, much lesser than the expensive base bleed rounds.
Hope I am able to explain the fluid dynamics of the expanding gasses better with this diagram.



With the sabot, the barrel and the expanding gasses would act the same way it acts on a normal artillery shell.

However without the sabot, and due to the aerodynamic nature of the base of the shell, there would be extreme pressure built up at the edges where the shell touches the barrel, which might result the barrel to bulge and burst, but at the same time, there would not be enough pressure applied to the center of mass of the shell to propel it far downrange.

This is the basic principle without going into the detailed vector analysis of the expanding gasses.
 
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Kunal Biswas

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Good find, If your idea has to move forward this is the most probable design you must have come with..

And i think, There was probably someone like me opposed the design hence smaller sabot .. :)

====================
@arnabmit, If there is any way you can send your design to OFB or DRDO would be great, In the mean time do not waste time to make a decent article about your idea, This should not go waste, will post this on other forums beside front article on DFI if its ok with other staff

@Yusuf
 
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arnabmit

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:D The smaller sabot came up when I did a more detailed drawing. The first one was just a free hand sketch, hence not very accurate.

I have no way of communicating with OFB or DRDO... Maybe @Decklander can help with his contacts. :(

I am not on any other forum except DFI... So if you could do the honors please... :namaste:

Good find, If your idea has to move forward this is the most probable design you must have come with..

And i think, There was probably someone like me opposed the design hence smaller sabot .. :)

====================
@arnabmit, If there is any way you can send your design to OFB or DRDO would be great, In the mean time do not waste time to make a decent article about your idea, This should not go waste, will post this on other forums beside front article on DFI if its ok with other staff

@Yusuf
 
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ladder

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I have Zero knowledge about artillery cell.

But let me put-out some points which I think I could gather. ( Please correct me if I am wrong)

1. There are two type of stabilization in flight a] Spin stabilized ( as in this case) b] normal stabilization without spin.

With spin we have to have Px( point of maximum pressure) ahead of Cg (center of gravity) and is stabilized by gyroscopic effect but opposite for non-spin stabilized.
So, if the Cg moves ahead of Px then there will be problem in stabilization.
If we reduce weight by trimming the rear end then Cg will shift forward. At a unique case Cg and Px will lie in a same plane ( for American football shape). Due to which we might have a toppling effect.( Alternation between two conical ends in mid flight).

Also, as you rightly pointed out, we need a flat base at the time of firing for proper pressure distribution.
Which can be achieved by two method.
Full sabot ( as you had earlier suggested)
Partial sabot ( later suggestion)

Full sabot, as it encloses the shell so, might not need a explosive charge and would simply fall off after shell leaves barrel.
With partial sabot, you have to attach the sabot with shell and so would need explosive bolts, to detach it from the shell once it clears the barrel.
Otherwise if both sabot and shell are in contact with rifling, due to their difference in mass properties, they both will have difference in rpm.

So, finally, choosing the design as in the patent, with Kevlar expandable base is good idea as the change in cg will be minimum.
But other factors do come in, which includes, cost, difficulty in manufacturing and complexity of the system.

Also, effect of explosive charge and sudden weight reduction ( detachment of partial sabot) needs to be studied in accordance with gyroscopic motion.
With my limited knowledge I think, if not executed along the axis of shell, might kick the nose up or down.

So, as the patent shows, it is possible, but with raiders.

Do we have mechanical/ aeronautics engineer here at DFI? They might give a detailed explanation about gyroscopic effect and it's effect on flight stability.
 
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agentperry

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what i feel is that major issue with the ordinance factory product is quality only. if slight attention is put on how things are made instead of how many then the army will be more willing to absorb indian made defence goods
 

The Fox

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If the Govt and MOD is smart they would privatize all the OFB's across India and let the Indian private firms run the OFB's Only then the IA can get the quality product and on time delivery and also say for Example. if the gun manufacturing sector has two branches in different locations one it should be given to two private firms so that there is competition between them....... care to jump in this discussion...
 

jmj_overlord

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If the Govt and MOD is smart they would privatize all the OFB's across India and let the Indian private firms run the OFB's Only then the IA can get the quality product and on time delivery and also say for Example. if the gun manufacturing sector has two branches in different locations one it should be given to two private firms so that there is competition between them....... care to jump in this discussion...
privatizing all the OFB's, we will have quality and innovative products, but also increases the chances for sabotages and high prices , right ?
 

The Fox

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Not if the Government monitors them........ all the defense private firms generally run on Govt funded projects so the MOD knows the cost involved in it and also sabotage i believe private companies will protect their secrets more intensely than govt firms OFB's actually do......
privatizing all the OFB's, we will have quality and innovative products, but also increases the chances for sabotages and high prices , right ?
 

SilentKiller

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Not if the Government monitors them........ all the defense private firms generally run on Govt funded projects so the MOD knows the cost involved in it and also sabotage i believe private companies will protect their secrets more intensely than govt firms OFB's actually do......
Well OFB's can remain with govt as they r too few to make any change, encourage private players to setup their own companies and this will bring competitiveness.
defence industry entirely in private hands in not a good option for india right now..
its good that india is sticking with few things as made in india and few only by private players.
e.g. Wheeled and tracked guns (even though its quite late now)
Transport plane and offset clause.
 

sayareakd

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In Indian Defence market their is place for all.

Private and small firms can go for non lethal products and services.
 

Apollyon

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The Fox

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Well OFB's can remain with govt as they r too few to make any change, encourage private players to setup their own companies and this will bring competitiveness.
defence industry entirely in private hands in not a good option for india right now..
its good that india is sticking with few things as made in india and few only by private players.
e.g. Wheeled and tracked guns (even though its quite late now)
Transport plane and offset clause.
the problem with this type if arrangement is that still the govt will prefer the PSU over private industry
 

sayareakd

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Army to Induct Bofors based 155 mm 'Dhanush' gun

The Indian Army will soon be adding the 155 mm gun 'Dhanush' to its range of guns which have been proving their prowess and deadly firepower in various battlefields.

The Indian army, which already has the 155 mm Bofors gun, will induct Dhanush, which would add even more might to the regiment of artillery, said army officials at the Exercise Mahasangram, which was conducted in the firing ranges of the School of Artillery at Deolali on Tuesday.

Army officials said that while the Bofors has a rate of fire of three rounds per 14 seconds, the indigenous Dhanush could fire eight rounds per minute. Dhanush, which in the trial stage, would soon be inducted, said the army officers.


Apart from that, Swathi, an upgraded weapon locating radar (WLR) and Kshitiz, equipment for obeservation, would also be inducted in the plethora of the new generation surveillance and target acquisition equipment, the army officers added.

Both Swathi and Kshitiz are indigenously made. While the former is an upgraded version of the US-made WPL ANTPQ-37, the latter will be an upgraded version of the Israel-made long-range reconnaissance and observation system (LORROS).


The gunners of the Indian artillery displayed their skills at Exercise Mahasangram, conducted by the officers undergoing the prestigious long gunnery staff course, through a tactical situation requiring appreciation of the operations and preparation of an artillery fire plan in support of the operation.

The entire range of guns – from the indigenous 120 mm mortars, 105 mm Indian field gun, 105 mm light field gun, 130 mm medium gun to the state of the art 155 mm FH 77B Bofors, 122 mm multi-barrel rocket launcher grad BM 21 and the 300 mm Smerch multi-barrel rocket launcher – demonstrated their destructive power during the exercise.

Asn array of new generation surveillance and target acquisition equipment like the unmanned aerial vehicles, surveillance sensors and weapon locating radars were also put on display.

Officials said that besides being the eyes of the commanders, these devises, when used in conjunction with guns, were capable of augmenting the effect of fire power, thereby acting as force multipliers.

The Cheetah and Chetak helicopters flown by the army aviators demonstrated flying skills of pilots, as they flew just a few feet above the ground, merging with trees and shrubs, concealing their movement, in what is called the nap of Earth, flying to engage enemy tanks and other targets. They also airlifted a 120-mm mortar for delivering firepower resources in inaccessible areas, as part of the exercise.

The event was witnessed by visiting officers of the Defence Services Staff College, Wellington and the Military Institute of Technology, Pune. A foreign defence delegation from Nepal also observed the event. Lt General A K Misra, AVSM, Commandant, School of Artillery, who was present at the event, interacted with various participants and delegations.

A large number of school children and NCC cadets from nearby schools were invited for the event to give them a glimpse of the might of the Indian Army and the artillery.

School of Artillery, Devlali

The School of Artillery, the alma mater of gunners, enjoys the unique status of an outstanding and unparalleled military institution whose alumni have excelled in all actions since the World War II.

It was set up in Kakul (Quetta) in Pakistan in 1918

Was moved to Deolali in 1941 with field and air defence wings

Surveillance and target acqusition (SATA) wing was established in 1958

Trails wing was established to evaluate equipment for induction in 1969

Air Defence wing bifurcated and moved to Gopalpur in 1985

Aviation wing moved to Nashik Road

The first commandant of the School of Artillery was Lt Col G H Johnson

Army to Induct Bofors based 155 mm 'Dhanush' gun along with New weapon locating radar " Swathi" | idrw.org
 

sayareakd

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Re: Army to Induct Bofors based 155 mm 'Dhanush' gun


Army officials said that while the Bofors has a rate of fire of three rounds per 14 seconds, the indigenous Dhanush could fire eight rounds per minute. Dhanush, which in the trial stage, would soon be inducted, said the army officers.


Apart from that, Swathi, an upgraded weapon locating radar (WLR) and Kshitiz, equipment for obeservation, would also be inducted in the plethora of the new generation surveillance and target acquisition equipment, the army officers added.

Both Swathi and Kshitiz are indigenously made. While the former is an upgraded version of the US-made WPL ANTPQ-37, the latter will be an upgraded version of the Israel-made long-range reconnaissance and observation system (LORROS).

wondering what is long-range reconnaissance and observation system (LORROS)

here
[PDF]http://elbitsystems.com/Elbitmain/files/LORROS.pdf[/PDF]
 

Twinblade

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Re: Army to Induct Bofors based 155 mm 'Dhanush' gun


Army officials said that while the Bofors has a rate of fire of three rounds per 14 seconds, the indigenous Dhanush could fire eight rounds per minute. Dhanush, which in the trial stage, would soon be inducted, said the army officers.




Idiots will now say that the Indian gun has a lower rate of fire than the original gun while neglecting the cool off period required in the FH-77 after the 3 round burst.
 

Blackwater

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Re: Army to Induct Bofors based 155 mm 'Dhanush' gun

Idiots will now say that the Indian gun has a lower rate of fire than the original gun while neglecting the cool off period required in the FH-77 after the 3 round burst.

Did we upgrade it or Downgrade??
 

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