72. Sometimes you need a year to figure things out …


Waaaay back in Post 43 I discussed the door locks and I mentioned that I was having some difficulties getting BPhillips’ lock solution working for me.  I struggled with it for about a week before giving up and moving on.  Try as I might, I just couldn’t ever get the spring to work well enough to make the lock/unlock motion reliable enough that I was comfortable incorporating it into my build.  There was just too much friction in the mechanism – I tried a number of different springs, both length and rate – but at times the mechanism would stay locked when I tried to unlock or would stay unlocked when I tried to lock.

Here’s a pic of Bill’s modification from the wiki:

In Bill’s design a spring is attached between the pivot arm and lock assembly.  When the key is moved from lock/unlock the spring pulls back on the lock mechanism to get it past the “halfway point”.
I couldn’t use a flat piece of aluminum for the pivot arm because it interfered with the locking mechanism.
So I put a jog in the plate at the 2 lines.  This allowed me to get the tip of the hinge up high enough to clear the lock assembly.

The issue I had is the springs I tried using tended to drag across the plate, had too much tension or not enough tension.  After trying for what seemed to be forever, I could never find the right balance between spring tension and assembly friction.  I just couldn’t get it working reliably.

So I gave up.  Yep – I’ve been cruising around with no functional door locks for the last year.

While I had the doors apart for this re-dip I decided I’d take another run at tackling this issue.  I really want lockable door handles!  It was getting to be about 11PM and I had to get up in 7 hours for work when it hit me that the key to my problem (haha, see what I did there?) was in reducing friction in the system and getting a reliable spring pull.  If I could reduce the friction at the spring mount then I could get it to swing back and forth freely, making the “pull” action cleaner (to swing the lock assembly all the way over to lock or unlock).  I had spent so much time trying to replicate Bill’s mechanism that I didn’t step out of the box enough and just re-jigger it – so that’s what I did at 11PM at night because I couldn’t sleep.

I replaced the screw that secures the pivoting hinge with a longer bolt.  I then secured one end of the spring to this longer, cantilevered bolt.  This gets the spring up away from the aluminum plate and centers it with the locking mechanism – so whenever the key is turned to lock or unlock, the spring is always wanting to pull it back down, past the “halfway point”.  This is the critical piece for making the mechanism work reliably (for me).  This version reduces the friction at the spring pivot (because it just turns on the shaft of the bolt) and across the entire length of the spring (because it’s no longer rubbing against the aluminum plate).  With this reduction in friction it was no longer necessary to get the spring tension tuned just right.

So here’s what I came up with!  I’ll call it Rumbles v2.0 since his design was the inspiration for this:

Side view – the jog in the plate lifts it up high enough so it doesn’t interfere with the lock assembly.  The jog is needed because the plate needs to mate with the tensioner spring (otherwise you could just use a stack of washers to raise the plate).  A small jam nut is used to keep the pivoting plate secured against the handle assembly.
The pivoting plate is very similar to Bill’s original.  I didn’t cut up the lock assembly bracket and I kept the plastic bushing to further reduce the friction in the system.  A small hole drilled into the end of the bushing allowed me to run the end of the spring through it.  The other side of the pin gets hooked around the extended bolt.  The lock mechanism is in the LOCKED position.  Pulling on the handle swings the aluminum plate upward where it interferes against the lock mechanism.
Here’s the lock mechanism in the UNLOCKED position.  With the bracket in this lower position the aluminum plate is free to swing upward to unlock the door.
Pull the handle … et voila!
The longer springs from this assorted I purchased at Home Depot works perfectly.

Having functional door locks makes the SLC a much more usable car; I’m still going to be paranoid about leaving it out of sight, but at least I’ll know that random dude who tries doors to see if any are unlocked is going to be disappointed when he comes across mine!

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