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Door Latches for 1947-1951

by Roy "boltare" Marks
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Basic info: How door latches work

      It is easiest to understand how these latches work by looking at three seperate functions.

      * The first function is simply the “catch” function.
      * The second is the safety catch function.
      * The third is the locking function.

      I have included a drawing (below and here's a much larger image) with labels that will help you understand the descriptions below. This is the right side door latch for a 1947 - 1951.

      The image to the left here is known as " the strike plate."

 

The “catch” function

      When the door closes, the rotor rotates around the upper “bump” on the striker plate. The rotor pawl (see diagram below) rises in the eccentric hole in the latch housing under spring tension and slides over the notches on the sector and lodges in one of them. These notches allow a solid latch at any point in the travel providing a firm door closure. The free end of the sector rides on top of the safety catch. To open the door, the safety catch is pulled out from under the sector in one of two ways. Either by the outside door handle rotating the release lever or by the inside door handle rotating the remote control arm which, in turn, rotates the release lever. In either case, the safety catch is pulled out from under the sector allowing it to drop. Tension is removed from the sector, and the rotor can turn freely back around the upper strike plate “bump” allowing the door to open.

      This function can be tested or observed in the following way. First, we need to determine the state of the rotor. To do this just observe where the rotor pawl arm is. If it's anywhere in the notched section of the sector, it is in the “closed” position. If the pawl arm is free of the sector, as in the diagram, it is in the “open” position. To “close” the latch, simply use thumb pressure to rotate the rotor. It takes some effort but when you do, the rotor pawl arm should rise and slide over the sector notches. To “open” the latch, pull the remote control arm against the spring tension and away from the edge of the latch housing. It should move freely for a bit. Keep pulling it CCW and it should pull the safety catch out from under the sector. Now use your other hand to rotate the rotor to its “open” position. If it won't go, the sector is probably stuck. Push down on the free end to get it out of the way and put some lube on it. On most latches, the sector will not drop a great deal but will allow the rotor pawl arm to move.

The safety catch function

      The safety catch is held in the down position by the safety catch spring. When the door is closed, the safety catch rides up and over the lower “bump” on the strike plate. If the door is properly aligned, the only way the door can open is if this catch is raised. As described above, the catch is either raised by turning the outside door handle which rotates the release lever against the arm of the safety catch or by the remote control arm being rotated by the inside handle and doing the same thing.

      To check the function of the safety catch, simply be sure it is free by pushing it with your thumb up into the rotor housing. It should have considerable tension but should move freely. You should also be able to move it using the remote control pawl arm or by using a screwdriver placed in the square hole for the outside door handle and rotating it.

The locking mechanism

      The latch can be locked in two ways. The first way is to push the inside door handle all the way forward (clockwise rotation). If adjusted properly that pushes the remote control arm into the position shown in the diagram. If it won't go into the position shown, the hidden remote control lock is already in the locked position. If you look down from the top of the latch towards the square hole, you will see that there are two “plates” in there. The “plate” against the housing is the actual locking mechanism for the inside door lock. When the remote control arm is in the locked position, this plate is held by the remote control lock arm and will not rotate. Therefore, the outside door handle can not be turned IF the shaft of the handle extends into the plate as it should. Some remanufactured handles have shafts that only go into that first plate. If this is the case, the latch will work fine except the outside door handle will unlock the door even if the inside door handle is in the locked position. If the plate is in the locked position but the remote control arm is not, you need to turn the locking plate with either the door handle or a big screwdriver making sure you engage that plate while turning. Once properly positioned, the remote control arm should be able to move into the locked position.

      The other way to lock the door is with the key. The key lever is shown in the unlocked position in the diagram. When the key is turned (CCW), that lever rotates upward and locks the safety latch in position.

Hints, tips, etc.

      Make sure your door handle shaft is long enough! Use gunk, rust remover, penetrating oil, carb cleaner, etc. to get the entire latch mechanism squeaky clean and rust free. Then lube it up good with a good lock lubricant. Work every part for a while using the procedures above. I found a number of these latches that seemed broken, only needed a little TLC. They are virtually indestructable. The only part that really wears out is the rotor. You can get “clips” from most of the vendors that snap over the rotor and it's nearly good as new. Another good idea is to shim the strike plates. As the truck comes from the factory the rotor only catches a small amount of the upper “bump” and the safety catch only a small amount of the lower “bump”. The best way to do this is to buy a new pair of strike plates then cut the old ones down so that you have a set of four shims with the two recessed holes in each one. These will fit between the new strike plate and the pillar and give the latch more grab and a safer door.

       After struggling for hours to figure these latches out, I thought that others might benefit from the effort. (That's the Stovebolt Spirit ~~ Editor)

Roy Marks
"boltare"
1951 Chevy 3600 3/4-Ton
Bolter # 11197
Norfolk, Virginia


       Here is another tech tip about strikers and latches for a later series Stovebolt which is a bit different.

       Be sure to check out our extensive Forums discussions -- from General Truck talk, Electrical Bay, Big Bolts, Panels and Burbs, Engine and Driveline, Paint and Body, Interiors, Tool Chest -- The Stovebolt Collective can help in your quest and walk you through the mire and magic of working with old iron. ~~ Editor .         

v. June 2006


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