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oldtop · ***Power User*** Offline Joined: Mar 17, 2006 Posts: 70

The M46A1 had a bore evact, it was an up grade during the Korean war.

SHAWN · ***Power User*** Offline Joined: Jan 31, 2006 Posts: 484

hey fellas,
thanks for the input. learned a little bit more.

ole top, i hadnt fully realized that about the panther, chaulk up one for for the germans thinking.

shawn

Jinx · Posted: Mon Mar 20, 2006 8:38 pm Post subject: Re: fume extractors-- questions?

- mike_Duplessis

I'm trying to think - who gets credit for first putting a 'modern' bore evacuator can onto a gun barrel? The British 20 pounder? The M47's 90mm gun, or the 100mm gun on the T-54? They all seemed to pop up at exactly the same moment!

Ok, i have been waiting for someone to bring up this topic (so i wouldn't i have to).

Question 1 - "Fume extractor" and "bore evacuator": what is the difference, if any?

Question 2 - How exactly do they work?

I have seen these on many a tank's main gun barrel.....but i have never been able to find out how the accursed things actually work.

Any descriptions and/or diagrams would be greatly appreciated.

Chris_C · Posted: Mon Mar 20, 2006 8:52 pm Post subject: Re: fume extractors-- questions?

- oldtop

The M46A1 had a bore evact, it was an up grade during the Korean war.

Actually, all M46s should have had bore evacuators, since they were all armed with the 90mm gun M3A1. This weapon first appeared on the M26A1 Pershing in 1948.

Jinx, here's a sketch to show how bore evacuators work. It's hosted on steelbeasts.com.

SHAWN · ***Power User*** Offline Joined: Jan 31, 2006 Posts: 484

you will get more elaborate and/or more technical definitions for the extractor but it is basically thisÃ¢â‚¬â€?
and as the above mentioned link will explain to you...

on firing, fumes are forced into the extractor by the high bore pressure after the shell has passed the extractor tubes. gas flow ceases when the pressure in the extractor is equal to the pressure in the bore. as the shell exits from the muzzle, the pressure in the barrel drops rapidly and the high pressure fumes exit from the extractor towards the muzzle. this then causes fumes remaining in the chamber to be drawn forward, and the barrel is finally purged by air also moving forward when the breech is opened immediately on run-out

oldtop · ***Power User*** Offline Joined: Mar 17, 2006 Posts: 70

You got remember that all production M46s were reworked M26s, there were no new vehicles (don't get the M46 covertion version mixed up with the T-40s prototypes).. what happened was the Korean war. and the M46s were so badly needed that the M3A1 guns were fitted to the M46, later any left over went to the M26s. Some say that the records show differant but whats in the records ain't carved in stone, if you look at the left front towing clevis mount and front slope plate there are two differant serail numbers one for the M26 and one for the reworked M46.

Jinx · Posted: Tue Mar 21, 2006 3:16 am Post subject: Re: fume extractors-- questions?

- Chris_C

Jinx, here's a sketch to show how bore evacuators work. It's hosted on steelbeasts.com.

Excellent! That was exactly what i was looking for. I really appreciate it.

Of course, this brings up another question : how often does this have to be cleaned? I am guessing that over time residue from the propellant will clog up the vent tubes.....no?

Dontos · Posted: Tue Mar 21, 2006 12:13 pm Post subject: Re: fume extractors-- questions?

Currently, crews do PM which can include pulling the Bore Evacuator and cleaning the 'jets' out with pipe cleaners and cleaning the carbon buildup off the gun tube, when ever needed. Frequency is based on use. Its not too difficult a task a length of rope (or several rags), green scratch pad, and some 'breakfree'.

L.Delsing · ***Power User*** Offline Joined: Feb 10, 2006 Posts: 960

[quote="Dontos"][quote="Roy_A_Lingle"]

- Dontos

- Joe_D

Shawn,
With all that, aquestion for Dontos. Riddle me this, was it authorized on the M1A1/A2 to fire main gun with the engine off ???? War time doesn't count.
Joe D

Sgt, Scouts Out!

The NBC system which is required to overpressurize the tank, works off of the running engine.

There are a couple of other reasons I can think about but nothing 'official' that I can remember.

Hello,
So, if I understand correctly you have to put the NBC overpressure system on (which needs the engine) to fire the maingun.

The M1 and Leopard have both the same gun with the gun of the M1 licence built with some minor changes. When firing the main gun (Leopard) I never experienced much fumes. Most of the times with only main gun actions the turretventilator was off because of the noise of it.

Of course when firing the coax the ventilator was on.

Is this NBC thing on M1s because of enviromental/health regulations???

Regards,
Lesley

Dontos · Posted: Tue Mar 21, 2006 8:45 pm Post subject: Re: fume extractors-- questions?

- L.Delsing

Hello,
So, if I understand correctly you have to put the NBC overpressure system on (which needs the engine) to fire the maingun.

The M1 and Leopard have both the same gun with the gun of the M1 licence built with some minor changes. When firing the main gun (Leopard) I never experienced much fumes. Most of the times with only main gun actions the turretventilator was off because of the noise of it.

Of course when firing the coax the ventilator was on.

Is this NBC thing on M1s because of enviromental/health regulations???

Regards,
Lesley

Lesley

The NBC system works thru the engine, so if the engine is off, the NBC system is non-operational.

'Officially' a 'non-operational' NBC system, is a safety deadline. so one can use the system to get work done on a higher priority, if you 'threaten' to deadline the tank.

There is no 'official' prohibition to firing, shutdown.

Firing the main gun has no affect on the NBC system and vice-versa. Going 'COAX', the system cuts on as a turret blower, so if the engine is off, the crew sucks up more fumes....

Hope that clears up things a little.

Jinx · Posted: Tue Mar 21, 2006 10:49 pm Post subject: Re: fume extractors-- questions?

- Dontos

Currently, crews do PM which can include pulling the Bore Evacuator and cleaning the 'jets' out with pipe cleaners and cleaning the carbon buildup off the gun tube, when ever needed. Frequency is based on use. Its not too difficult a task a length of rope (or several rags), green scratch pad, and some 'breakfree'.

Thank you for the info, sir!

L.Delsing · ***Power User*** Offline Joined: Feb 10, 2006 Posts: 960

Thanks Don!

Regards,
Lesley

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