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

Thanks Don!

Regards,
Lesley

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!

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.

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 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'.

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?

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.

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

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.

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.

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

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.

mike_Duplessis · ***Power User*** Offline Joined: Jan 24, 2006 Posts: 236

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!

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

When firing the 90mm on the M48 (even with it's "bore evacuator") the breech gases were so bad I wore a M14-17 vehicle crewmen's field protective masks, if you left the @#$@ turret blower on you couldn't hear a thing, with the M48A3 you had a air filtering unit and you could plug your mask into it.
....The main gun round ( 90 and even 105) were some what smaller back then and a lot of loaders (me when acting as a loader) would "lap-load" which was when the loader sat on his knees just behind and to the left of the main with four or five rounds across his lap, the gunner cold fire four rounds in 30 sec this way. The breech gases would get very thick .
....On the selfpropelled guns like the M109 ( first versions 155 mm Howitzers) the bore evacuators worK with rolling ball check valve system and in Nam they quickly wore out and became useless (someone forgot to reorder them and the "O" rings in the supply system...something like repair parts for that @#%$# Ontos M50 "PIG"!!!!.
....Sorry I get a little upset when thinking about the Marine Corps so called "supply system" Grrrrrr. Anyway the fumes would get so bad in the gun cabs you worked in a greenish haze and when you stood down from a fire mission your skin was covered with a coating that you had to wash off with soap and water (if you didn't use soap the coating turned to a greenish slime) you also deveolped what was called "gunner's chough" as the slime came out of your lungs
...Even as the Battery maint chief I stood in as a "number one man" in a gun section (thats the rammer-jammer) . As No. 1 you rammed home the projo with your fist (hyd rammers were only used for "danger close" missions) then loaded the propelent charge, hit the breech cam (this relested the the 100 lbs breech block which was under spring pressure, this was watch your fingers time!!) The no.1 man also had his mouth full of primer cartridges and he would insert one in the percussion mechanism and slap it to firing postion, the command was "stand by....fire" and you pulled the lanyard (not jerk) ..band and the gun recoiled back ,the breech open on return to "battery" and the breech cam plate held it open.
...In May of 1969 Kilo 4/12 went into a fire mission at 08:00 and at 08:00 the next morning they were still in that mission, the guns were so hot that the water they were being sponged with was turning to steam and the Hyd fluid was blowing out of the system acculators.. there were greenish fumes that could be seen drifting out the cabs side hatches. This fire mission was in support of the Army troopers fight for "Hamburger hill".
...The empty powder cans and projo pallets were piled over 8' high behine each gun, during this fight kilo 4/12 was under "counter battery" fire by 130mm guns in the DMZ over 30,000 yards away, Kilo never broke from the support mission , they took the enemy fire and kept on firing. At the time Kilo's postion was at a little hell hole of a fire base called "The Rockpile". The Battery fired over 3,000 rounds during the fire mission. A side note, the rate of fire for an M109 by the book was one round per minute, Kilo was firing 3 to 4 per minute...how those boys did shine!
...By the way the German WW II Panther tanks had an "air injection" system to clear the fumes out the muzzle from the breech and gun tube.

Joe_D · Posted: Mon Mar 20, 2006 1:33 pm Post subject: Re: fume extractors-- questions?

So that's the rest of the story,

It happens.

Joe D

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