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Pump rod cracked or snapped

Written by Ben
Last updated on 2008-06-16


Problem

The pump rod of your water gun has snapped in some place.

This problem can usually be prevented if a 1/4 inch diameter wooden dowel is put inside the hollow part of the pump rod. Why Larami or other water gun companies don't fill that rod in is unknown. They should, because it prevents a common break.

Solutions

The first and most obvious solution to this is to replace the pump rod of this gun with another one. Some people might have old broken guns that have good pumps, and making a substitution is the easiest way to fix this problem.

For everyone else, you will have to repair the broken pump, which is easier than you might initially believe.

Some other possibilities are epoxying a dowel in the center of the pump and then making a handle for that, or making a homemade pump.

Materials

  • 3/16 inch diameter wooden dowel
  • Epoxy or some other strong bonding glue (hot glue will not work)
  • Brass tube that fits over your pump rod (part number 8859K33 on McMaster-Carr is what I used, but which size tube you need varies from gun to gun)

The tools you will need for this repair include coarse sandpaper, a drill (hand drill or drill press are both fine), a 1/4 inch drill bit, and a hacksaw.

Instructions

The photo above shows the pump rod. The top left image is a closeup on one of the snapped parts. The pump rod snapped right on the hole that the pump handle attaches on. That's the hardest to repair spot, but, I still repaired it with relative ease. Because I had to repair a hole and others might have snapped the pump rod in a different location not requiring a hole, don't drill a new hole if you don't have to. That's pretty much common sense.

The bottom image above shows how I will repair this snap. I will brace the rod from the inside and outside. The inside is braced with a wooden dowel rod. The outside is braced with a brass tube that slides over the pump rod with little clearance. The fit should be as tight as possible. For me, this meant a 1/2 inch OD tube available in most hobby stores under names like telescoping brass tubes. It is also available on McMaster-Carr as part number 8859K33. That tube may or may not be correct for other water guns, so be sure to measure the diameter with a caliper and buy an appropriate tube.

The top image shows the wooden dowel and brass tube. The brass tube should be about an inch and a half long like above to make an adequate overlap. When cutting the brass tube, be sure to put something like the pump rod in there to prevent the tube from bending while you cut. Put the pump rod in there, but don't put it all the way through. Put it thought just enough to provide some support for the cut.

The middle image shows the dowel rod cut to about the length of the other part of the tube. To keep the hole in the center, a hole has to be drilled into the dowel. I pushed the dowel all the way down the pump rod, and then drilled into the dowel using one side of the rod as a guide. I then cut the dowel short. You don't have to put the hole in or cut the dowel short if you are reinforcing a tube snapped at a place without a hole.

The bottom image shows the combination of the brass tube and wooden dowel. The brass tube had a 3/16 inch hole drilled into it.

You then reassemble the pieces as they were originally, with the braces on. Make sure the pump handle can be closed over the pieces. If it can't be, you might have to modify the handle or change the brass piece somehow. Post at our forums if you have that problem.

After you are sure the handle will close over the braces, get your epoxy and coarse sandpaper out. Sand the inside of the brass tube. You might have to roll the sandpaper up to get inside of the tube. Sand the end of the wood and sand the inside and outside of the two pieces of the pump rod. Apply epoxy to all these pieces and assemble the parts. Let the epoxy cure for the amount of time suggested on the bottle.

Your pump rod is repaired! Enjoy the water gun.

Links


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