Repairing Early Sturmey Archer Trigger Shifters

 

The 1940 Schwinn New World project continues, but I took a little time off that project to work on some early Sturmey Archer Trigger shifters. These are the "long arm" handlebar shifters used from the late 1930s to the late 1940s. They have some peculiar features and can be somewhat tricky to repair.

First, remove the external r-spring (if it's not already missing). Then the two binder pins are knocked out, from back to front, using a slender punch. The center pin that holds the lever and ratchet assembly goes first, then the rather/lever assembly slides out. Be careful - there are two small, grub pins holding this assembly together. Do not lose them. Second, the corner pin is knocked out, which will take the pawl with it.   

Dissaembled Shifter with Labels

Second, clean and straighten the inside of the shifter frame. Be careful - the metal is somewhat soft and thin. After cleaning, check to see if the shifter frame is loose on the handlebar clamp.

 

Tops of two rivets holding the shifter frame to the clamp

There are a couple versions of the rivets attaching to two. Early shifters have two, domed rivets that often work loose. Later versions have stronger rivets and don't loosen as easily. If your shifter frame is loose, you can tighten them using two punches or an arbor press. Place an appropriately sized punch in a vise and mount the shifter body so that the punch is against the rivet head. Next, use a second punch to strike the opposite side of the rivet. The rivet should be "sandwiched" between the two punches, tightening the fit. Be careful doing this, not to hit your hand or allow the punches to move.

The two-punch way of tightening rivets

 

Third, clean the ratchet and lever assembly. Make sure the grub pins are properly in place. Also, clean the pawl and make sure the pawl's arms are straight. Gently straighten the pawl if it is bent. Also, gently clean the faceplate. Gently straighten the face plate as needed. Be careful, the faceplate is fragile. I use a little WD40 on a soft cloth to clean the face plate. 

Disassembled Shifter

Now that everything is clean and straightened, you can re-assemble. Lubricate all the moving parts with medium oil or light/thin grease. Put the face plate back in place and insert the pawl into the shifter frame. Take the corner binder pin and slide it into position until it's aligned with the hole in the back of the frame. Tap it through with a hammer so that it protrudes from the back. Set the pin back on an anvil/vise face and flatten it by striking the pin head. The vise/anvil will spread the pin back so it stays in place and binds the pawl and face plate into place.

Partially reassembled - pawl, faceplate, and first binder pin in place

 

Re-insert the ratchet and lever into the shifter frame. Take the remaining binder pin and slide it through the holes until it reaches the hole in the back of the frame. Tap the pin through. Set the pin back on the vise/anvil and strike the head with the hammer (as you did for the other pin). 

 Take your r-spring, insert it and pop it into position on the pawl. 

If you need to make a new r-spring, you can make one from a 1/4-inch hitch pin clip. These are available at some of the big-box and hardware stores (in the USA at least). Gently open the clip a bit with a screwdriver. The legs will need to be shortened and flatted. A dremel tool works well for this cutting and flattening task. If you have a good spring, you can copy the dimensions of that. Or you re-assemble your shifter first and then hand-fit the shortened clip until it works correctly. 

 

 Above is a package for a 1/4" hitch pin clip. The package shows the original shape and the modified clip is on top of the package for comparison. Note the shape of the clip has been changed and the legs shortened. Don't bend too far - it will lose its springiness if you go too far.

 

Side view of the modified clip spring

Another option is to use a 1960s-70s era wire spring, as shown in the photo below. If you wanted to do this, you would attach the spring back in the step when you re-installed the corner binder pin and pawl. The photo shows how it would work. Make sure your wire spring is long enough to reach (some springs may not be long enough). 

Side view of the wire spring repair 

 

 

The final product is a nice, clean, functioning early trigger shifter. A few words of caution are needed. First, it is possible to lose the R-spring because it falls out of the shifter. This often happens when the lever is pulled too far, causing the pawl to twist out of position and the spring to lose tension. Without any tension on the spring, it is free to fall out and get lost. This is how so many of these shifters turn up without springs today. Second, abuse of the shifter will cause the rivets to loosen and the whole shifter to become wobbly on the clamp. Go easy on these old parts.

 

 

But the final product is a nice, old piece of technology from before Sturmey Archer had perfected the trigger concept. The 1949 and later triggers are much better parts, but these older shifters serve a place on three speeds dating to the late 1930s through the late 1940s. They served on many bikes during the same era as the quadrant top tube shifters.