A different type of material for receivers

**lysander** · 05-20-24, 09:32

Originally Posted by tangolima

Magnesium alloy can burn quite easily.

-TL

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See below

**lysander** · 05-20-24, 09:32

Originally Posted by Diamondback

There's a reason mot of the B-36 fleet were very prominently marked "NO SMOKING WITHIN 100 FEET" and the Fire checklist went straight to "Put On Chute And JUMP"--didn't take much to make them go up like the Hindenburg, especially with a full train-load of high-octane avgas filling the tanks.

The ignition temperature of magnesium is around 880°F to 1,150°F, depending on the alloy. Aluminum will also burn at around 1,050°F.

The major difference is how fast it absorbs heat, and how fast it can reject it. Magnesium tends to retain heat, a .10 inch thick piece of pure magnesium heated with a localized 2,000°F flame will ignite after about 5 minutes, some of the better alloys can last up to 30 minutes before igniting.

The NO SMOKING rule has more to do with the 30,500 gallons of 120 octane gasoline, than the magnesium. The F-15 has a lot of magnesium in it, and they aren't prone to spontaneous combustion. The actual fire checklist for the B-36A was:

3-1 FIRES.

3-2 ENGINE FIRE ON THE GROUND.

3-3. Pilot shall advise his crew, signal to ground crew equipped with portable equipment, and notify the control tower. Flight engineer shall position his controls as follows:

a. Exciter Control Relay Switch (26, figure 1-4) - "OFF," if engine on fire is equipped with an alternator.
b. Mixture Control Lever - "IDLE CUT-OFF."
c. Throttle Lever - ''CLOSE.''
d. Engine Air Plug Control Switch (103, figure 1-4) -"CLOSE."
e. Fire Extinguisher Discharge Selector Switch ( 46, figure 1-4) - "DISCHARGE # 1."
f. Fire Extinguisher Engine Selector Switch (45, figure 1-4) -When the engine has almost stopped, hold the switch "ON" for at least five seconds.
g. Engine Fuel Valve Switch (88, figure 1-4) - "CLOSE."
h. Engine Oil Shut-off Valve Switch (47, figure 1-4) -"CLOSE." .
i. Ignition Switch (55, figure 1-4) - "OFF."
j. Fire Extinguisher Discharge Selector Switch - "DISCHARGE # 2," and repeat step f if first discharge is not adequate.

3-4. ENGINE FIRE IN FLIGHT.

3-5. In the event of an engine fire the pilot shall warn and advise all members of the crew. The flight engineer shall position controls of the affected engine as follows:

a. Exciter Control Relay Switch- "OFF."
b. Engine Fuel Valve Switch- "CLOSE."
c. Engine-Oil Shut-off Valve Switch - "CLOSE."
d. Propeller Feather Switch (121, figure 1-4) - "FEATHER."
e. Mixture Control Lever - "IDLE CUT-OFF," simultaneously with feather.
f. Engine Air Plug Control Switch - "CLOSE."
g. Fire Extinguisher Discharge Selector Switch" DISCHARGE # 1."

Note
If fire fails to go out after the first discharge, place the discharge selector switch in the "DISCHARGE #2" position and repeat step h:

i. Ignition Switch- "OFF."
j. Cabin Pressure Wing Shut-off Valve Switch (96, figure 1-4) - Shut off pressure from wing which has engine fire and use the pressure from the other wing if it is needed.
k. Cabin Heat and Tail Anti-ice Control Switch (105, figure 1-4) - "OFF," if fire is in engine No. 3 or No. 4.
h. Fire Extinguisher Engine Selector Switch - On correct engine number; hold "ON" for at least five seconds.
l. If fire is in engine Nos. 1, 2, 5, or 6, appropriate Anti-ice Control Switches (104, figure 1-4) - "OFF."
m. Cooling Air Control Switch (95, figure 1-4) - "OFF," if fire is in engine No. 4.

3-6. FUSELAGE FIRES.

3-7. Reduce drafts by shutting off the pressurized or ventilating air. Isolate the fire by use of valves and doors. Know locations and limitations of fire extinguishers.

a. Crew-Close doors or other openings.
b. Locate cause of fire.
c. Crew-If electrical, isolate the circuit.
d. Crew-If caused by fluid leak, stop the flow.

Note
If the ventilating fans are operating, they must be turned off by placing the Cabin Pressure Wing Shut-off Valve Switch in the "OFF" position.

e. Engineer-Cabin Pressure Wing Shut-off Valve Switch-"OFF," if necessary.
f. Engineer-Aft Cabin Pressure Control Switch (97, figure 1-4)-"OFF," if necessary.
g. Crew-Aft Cabin Manual Pressure Shut-off Valve (figure 3-1)-"OFF," if necessary.
h. Crew-Oxygen masks-As required.
i. Crew-Hand fire extinguishers. (See figure 3-2.)
j. Crew-Open dump valves, doors, or blisters as required, AFTER fire is out.

3-8. WING FIRES.

3-9. A wing fire involving fuel or oil tank leaks, etc., may be difficult to identify because the smoke or flame will probably emerge from the engine-nacelle. A wing fire will therefore probably be reported as an engine fire by scanners in the rear cabin and should be fought as such until all methyl bromide is exhausted. The engineer will turn off the anti-icing and cooling systems and will stop the flow of cabin pressure air from the wing on fire by positioning the cabin pressure wing shut-off valve switch. Use pressure from the other wing. After the fire is out, allow a reasonable length of time for fumes to disappear before investigating the damage via the wing crawlway.

**lysander** · 05-20-24, 09:52

Originally Posted by Diamondback

The rub would be the price tag - magnesium was expensive shit when we were making B-36s out of it, and very flammable. So expensive and valuable that when they chopped those behemoths they melted them into metal ingots on-site at the Boneyard.

Magnesium runs around $7,200 per ton

Aluminum runs around $6,000

Stainless steel - $34,600

Titanium - $76,500

**lysander** · 05-20-24, 10:19

Oh, and by the way, other aircraft parts made from magnesium:

- brake calipers of a B-52
- cabin pressurization valves for the B-52, F-15, and F-16
- AMAD (airframe mounted accessory drive) on the F-16
- leading and trailing edge flaps, multiple aircraft, both commercial and military
- other control surfaces, multiple
- engine gearboxes, multiple
- intake manifolds on many GA engines
- main transmission housing on CH-53 helicopters (about 600 lbs and 4 feet tall and 3 feet in diameter)
- main transmission housing on UH-60 helicopters
- accessory gearbox housing on AH-64 helicopters
- RR RB 211 accessory gearbox housing
- outer casing of the F110 turbofan engine
- outer casing and accessory drive gearbox on the F119 turbofan engine

There is a lot more magnesium in cars than you think, too, 31 pounds of it in an F150 pickup truck, 58 lbs in GM full-size vans, the engine block of some BMWs.

The flammability of magnesium is a bit over rated, corrosion is a bigger issue.

**1168** · 05-20-24, 11:47

Yeah, I have some experience in igniting magnesium (and aluminum, also) and it’s a lot harder than people talk about. Though magnesium is easier than aluminum, IME. It burns freaking incredibly once ignited, of course. I’ll leave that at that. As lysander said, there are lots of products made of magnesium alloy that are used in close proximity to things that would burn the shit out of your hands if touched during normal operation.

I can’t see any scenarios in which a rifle’s magnesium receiver ignites from any event that wouldn’t have already killed its user.

I think V7 still makes receivers from some exotic alloy of aluminum.

Brass was done by some mad-lad using recycled cartridge casings and posted somewhere on the internet, not sure if it was functional or not.

I say we use toenail clippings reinforced epoxy.

**kirkland** · 05-20-24, 12:04

Maybe we could use porcelain like the Glock 7

**Defaultmp3** · 05-20-24, 12:48

Originally Posted by 1168

I think V7 still makes receivers from some exotic alloy of aluminum.

They make 2055 receiver sets.

Umbrella Corporation was suppose to make 7068 billet receivers at one point, I don't know if they ever came to production. Master of Arms had some receivers in 7095.

**tangolima** · 05-20-24, 16:18

Originally Posted by lysander

See below

I still remember the chemistry lesson at middle school. The teacher put a strip of magnesium to a Bunsen burner with a pair of forceps. It started burning brightly almost instantly. It is result of violent oxidation due to magnesium's chemical activeness, the teacher explained.

I used to work for Nokia Mobile Phones. A few of the early phone models used magnesium alloy as shielding cover over the radio circuits. It was surprisingly light. But quickly it was replaced by metalized plastics. Talking to the mechanical engineer, fire hazard was one of the reasons, especially so when we started using lithium ion batteries. Before that the batteries were nickel cadmium and then nickel metal hydride.

-TL

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