Seat belt mechanism design 1

[freerangequark]

Hello,

I am having difficulty understanding part of the seat belt mechanism design shown at 3:21 on the following video:

The piece shown in orange appears to float coaxially to the spool shaft until it is accelerated, where it then is pulled off axis, rotating about the pivot point, so that the teeth engage in a lead-in manner thus acting as a brake.

My question is, what holds the orange piece centered? I'm not seeing anything in the video, and perhaps something was not shown for clarity.

 

[3DDave]

There is a probably a tiny spring, not shown in that video, that is shown in a video of a real seatbelt retractor mechanism with a similar function restraint.

 

[freerangequark]

^ That one seems to be a somewhat different mechanism.

I thought about the spring idea, but the original video states that the orange piece is not affix and is "free to move".

But then I found this video which shows the same mechanism as the OP, but the actual mechanism, not an animation.

 

[3DDave]

See that pin that stick out of the cam? There will be a spring attached to that to push the cam to the center.

I know it was a different mechanism - one that also uses a spring outside of the cam to move the cam back into the center.

I cannot help that the first video said "free to move." The lesson here is that not all videos are complete and not all presenters are precise. But many wrecking yards will sell seatbelt retractors for very small amount of money and you can take one apart yourself to see how it works; just be aware, as in the video I posted, that some have explosive pre-tensioners and to be cautious about handling them.

 

[freerangequark]

I couldn't sell anyone here on putting explosive pins into the design I am working on (not a safety belt). I guess the need for a pretensioner has to be legit and not just for engineers to have fun playing with