Tuesday, January 23, 2007

Armored Humvee's causing fatalities in Iraq

I-MEF
One of the top killers of Soldiers in Iraq isn't necessarily combat-related.
Since operations began in March of 2003, many Soldiers have been killed when they can't escape a Humvee - often because it has rolled into one of Iraq"s numerous irrigation canals.

When an armored truck is upside-down or on its side, it can take three Soldiers to push a door open enough to get out, and if the doors are sunken into the mud, it can be nearly impossible[...]
There are pics at the I-MEF link of a field expedient device that has been devised to assist with this issue. That is probably about as good as they'll get in dealing with units in the field.

Now I put on my engineer hat and take a look at this problem from a mechanical design POV. There's a couple of design issues here.

1) The jamming doors
2) The balky "combat locks"

We can see from the pics of the humvee that #1 is probably being exacerbated by the Humvee door frame/door design. There are sharp edges at the front of the door. When you want to avoid jamming of mechanical parts during distortions, you want to avoid sharp edges like that. Rounded corners should be the rule. Rounded corners distribute stress, square corners concentrate it. A good layman's explanation of why rounded is better than square can be found in Carroll Smith's outstanding Engineer to Win book on race car design. Specifically in the chapter on "why things break". Smith writes well, and that book is about a whole lot more than just "race cars". Most of what he talks about is an outstanding guide for the general design of mechanical things you don't want to fail. The principles apply as well to Microwave ovens, bicycles and Humvees as well as they do high performance race cars.

The door hinge design itself is obviously part of the problem. Traditional hinges bind when distorted. We need to accept that and find a way around it. The problem as I see it, is that the door/hinge mechanism is basically bolted together (or may as well be when a door is closed/jammed. This is not a solution that anticipates getting wrecked - its a solution that presumes not getting wrecked. That's fine for the front door on your house or your fridge door, but its not so fine for a combat vehicle. What we need is a sturdy hinge that can be cutaway on a moments notice.

This ties in with the balky combat locks. You got difficult hinges on one side, and a difficult lock on the other - a fixed 2-point retaining system. If either the hinges or lock (preferably both) could be quickly released, the door could be kicked out when a bind-free door/frame design is present.

How to solve the hinge problem? I believe we need to look to the most successful parachute release design on the market today - Bill Booth's 3-ring system. The 3-ring provides massive mechanical leverage advantage in a very compact "bind free" design. Booth's 3-ring release has saved my life 3 times during parachute malfunctions. I will personally attest to its simplicity and tendency to "just work".

I believe a door hinge attachment pivot based on a simple locating cone scheme attached with a variation of the 3-ring will solve both hinge binding and quick release issues. As you can see from the 3-ring pull force chart at the link above, there can be 2,000lb of pressure on a standard 3-ring and it will still release with only 9lb of pressure. With a locating cone scheme on the hinge pivots, the hinge side of the door will WANT to pop out when there's distortion - that's a good thing.

The balky combat lock issue could be solved with the same locating cone and 3-ring scheme so the whole lock mechanism itself could be released from the vehicle frame by a passenger inside. If you can release the hinges, and the combat lock, and the door frame has tapered steps and rounded edges to avoid binding it'll pop right off when you yank the 3-ring releases.

With some added Cypres Cutter type hardware, an external rescue option wouldn't be too hard to add. That would be an externally operated pyrotechnic type cutter head added to the 3-ring release locking loop. Fire the cutter(s) and the 3-ring would release.

1 comment:

Wickedpinto said...

If you turn the Individual servicemember into a tank, they will move slower than a tank, and they will die more easily. FUCKING LIBS!

"we should NOT go to war until our servicemembers are made of titanium" is BULLSHIT, and a 1/8th ass argument.

"our troops were unequiped when they went to Iraq"

Question?

Were they unequiped when they went o Afganistan?

I fucking hate Dems when they talk about WAR, they are cowards to the core. I know, I'm a coward, I smell my own.