M7 Door Mechanism

[hellopig]

Does anyone know why the M7s' doors close the way they do?  Meaning that they beep and slide shut, but they're not fully closed for another 2 seconds or so until they do this last stretch/click and the red door lights go out.  Is this intentional by the designers / is there a practical reason for that?

[Ernie]

Well... picture them sliding completely shut in one smooth motion. Then picture someone who hasn't completely moved thru the door, perhaps reaching back in for a forgotten briefcase. 

The doors thus close tight on the outstretched arm. Flesh separates. Blood spurts. Hilarity ensues.

I believe elevator doors work the same way, they seem to pause at the last closing moment, then slowly shut tight. It's just a safely feature.

[Dump The Air]

I always said the LIRR and TA should put razorblades on the edges of the doors instead of rubber gaskets, you think anyone would hold the doors then?

[diffusedmind]

I always said the LIRR and TA should put razorblades on the edges of the doors instead of rubber gaskets, you think anyone would hold the doors then?

I love it.

[RetiredLirrConductor]

Its called a positive lock system. The doors close just about the whole way, and then lock shut.
The engineer can not get a door light unless the door is shut.
If there is something caught in the door, no positive lock, and no door light.
On an m-3, with the "pushback" feature, and soft rubber frame, someone or something could be caught in the doors, and the engineer could still get the door light.
I once had a guy who stuck his briefcase in the door, and was caught by the wrist, and we still had the door light.
Lucky for him we were not on a curve and I saw it.
If we had been at syosset, he might have been dragged if he did not have the common sense to let go of the briefcase.
This cannot happen on an M-7 with the positive lock system..

[Alchemist]

If you listen carefully, you can hear a low "clunk" when the lock takes effect.

[hellopig]

Its called a positive lock system. The doors close just about the whole way, and then lock shut.
The engineer can not get a door light unless the door is shut.
If there is something caught in the door, no positive lock, and no door light.
On an m-3, with the "pushback" feature, and soft rubber frame, someone or something could be caught in the doors, and the engineer could still get the door light.
I once had a guy who stuck his briefcase in the door, and was caught by the wrist, and we still had the door light.
Lucky for him we were not on a curve and I saw it.
If we had been at syosset, he might have been dragged if he did not have the common sense to let go of the briefcase.
This cannot happen on an M-7 with the positive lock system..

Ahh, that explains everything perfectly, thanks.