Most of the folks I know will not bother to replace the springs. As long as the train is moving forward slowly, the knuckles will open anyway.
Regardless, here is how I replace them:
I use a miniature pair of wire cutters to cut the head off the old rivet, and push it out with a pin punch. The knuckle and any remains of the old spring can now be pulled out. I then start inserting the rivet back into the knuckle, just far enough to put the new spring over the rivet. The straight end goes inside the coupler body, with the bent part in the knuckle opening. I then slide the knuckle in, pushing the spring back into the opening, while holding the rivet against the body of the knuckle so the spring does not pop off. Once the hole in the knuckle is aligned with the rivet, it will drop in, and the rivet can be headed.
I find that the black rivets are easier to head (clinch) than the silver ones.
Once you have removed the old stuff, turn the coupler upside down. put the rivet partway in, so you can place the spring over the rivet. The straight end goes inside the cavity. The bent part should be facing up (towards the bottom, because you are holding it upside-down). As you slip the knuckle into place, the cam will push the spring back into the cavity. Once the hole in the knuckle lines up, continue to push the rivet through the knuckle, and through the bottom half of the coupler.
Is the knuckle you're working with made of metal or plastic? It would be confusing to try to fix a plastic coupler with instructions for a metal one, which is what we're giving you. Here is my take on replacing the spring for a metal knuckle:
Do not try to pry the knuckle pin out with a pair of diagonal cutters or any other way. If you can even get a purchase on the pin, you will probably make a mess of both it and the coupler body. Put the coupler upside down on top of the jaws of a vise which have been opened just enough to clear the head of the pin or wood surface with clearance for the knuckle pin to come out. . Then drive the pin out with an ice pick--the old slender kind, not a fat modern one. The tip of the ice pick goes into the depression at the bottom of the pin and follows the pin into the coupler as the pin is forced out, keeping everything together. It's easier if you have the coupler or even the truck separate from the car, but not worth it if that involves any extra work at all. Remove the ice pick, the knuckle, and the pin. There is no reason to save a broken spring. If the bottom of the pin is spread too much to go back into the coupler, work it back into shape with the smooth back part of the jaws of a pair of pliers. However, a little resistance is better than a completely loose fit, since it helps to keep things together when reassembling.
Put the new spring onto the pin. The straight end goes inside the coupler body. The bent end extends across the opening of the coupler. I put the knuckle hinge against the side of the pin, with the spring slid to the top of the pin. Carefully withdraw the pin, sliding it along the knuckle hinge. When it just clears the top of the hinge, move the knuckle into place, while the last little bit of the pin keeps the spring securely in place. Push the pin back in, through the knuckle hinge and all the way through to the bottom of the coupler body. Finally, spread the riveted end of the pin with a center punch, but not tight, instead, just enough to keep it from falling out. This makes it easier to remove the next time.
If you happen to bend or otherwise damage the pin, use a new one. But I find that I almost always can reuse the old one, which often has a different head appearance than the replacement.
Bob Nelson
I don't use the minature diagonal cutters (designed for electronics work) to pry the old rivet out. I cut the head off. There is usually enough play to get the jaws underneath the head. I don't think you can do this with full sized diagonal cutters. Some original rivets are crimped in a fashion that makes driving them out with a punch (or ice pick) just about impossible without damaging the coupler head. So both techniques are good under difference circumstances, provided you have proper tools.
After I watched a couple of springs fly away on me I devised this method which makes things a little easier.(When you are familiar with the placement of the spring.)I use a small nail about two inches long that is a little smaller than the pin.I use this to set everything in place from the bottom of the knuckle.When everything is in place I slowly slide the rivet in from the top.The point of the nail fits into the depression on the end of the rivet so you can just slide it into place.The pin will push the nail out and everything will be in place.If you have big fingers like I do the nail is easier to handle then that tiny rivet.
Ed
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