Repairing a Cracked Cylinder

Today repairing a crack is actually very easy. Go to the hardware store and purchase some JB Weld or similar epoxy paste containing steel. Prepare the crack by drilling two small holes to arrest the crack. The holes should be 4mm (1/4") from either end of the crack and the final two are at the visible extremity of the crack as the crack is likely to extend beyond the visible ends. The holes should be around 4mm (1/4"). Tap the holes and screw in an appropriate sized screw. Cut and file the screw flush both inside and outside the cylinder. Using a drill clean the crack inside and out. Mix the JB Weld and and press it into the crack. Allow it to cure, then file inside and out flush with the surface.

A more traditional method requires some 2mm annealed copper sheet, some soft gasket material, and a number of 4mm (1/4") screws. The sheet should be at larger than the crack by 20mm all around. Follow the previous method until just before you would put in the JB Weld. Cut the copper sheet and gasket material to size. Smear the gasket material all over with red lead (today you'll have to use something like high temperature RTV silicone). Place the gasket and copper sheet onto the cylinder and secure top and bottom by drilling through the copper and gasket into the cylinder but not all the way through. Tap the hole and insert an appropriate screw. Now hammer the copper with a mallet to make it conform to the shape of the cylinder. Now drill and tap holes (not all the way through) all around the outside edge of the copper with about a 4mm (1/4") gap between each screw hole. Insert screws into each of the holes and tighten down. Do not run the engine until the red lead (or in our case RTV silicone) has cured.

It may seem that this method would not work very well, but I've seen an engine which was built in 1902 and patched in 1925 - it is still running today.

In July 2000 Tommy Stojanov posted the following to the Stationary Engine List

From: "Stojanov" Dear List, Hello, Tommy here. While I was sandblasting the rest of my Fuller and Johnson 3hp NB head, over the welds, when I noticed a split occuring between the head and the old welds. This crack occured on the water jacket, probably due to freezing. It must have danced and moved due to different temperatures. I will probably end up grinding the weld off and creating a V surface to work with. I am not sure if I should weld it or braze it? I have no oven to heat it in (except the kitchen oven, or the ones at the restaurant, mom and the health inspector will love a head in the oven. [:)] ) Should I heat the head before welding or brazing it, so it does not warp? I was told it was possible to do with a rosebud torch. What would be the best way to do it? I should probably find an oven. Any reccomendations between welding and brazing? Thanks.

Farmer Robinson (he really is a farmer :) responded suggesting the following:

On such cast items I prefer arc welding with nickle rod but that is just my preference. Where I can I always try to preheat at least some. I have one of those LP torches that attaches to a 20 pound tank like for a BBQ Grill that puts out a huge blue flame. It does a good job of heating a large area more evenly. You can find them at most farm stores as they are often used for flaming fence rows. If you get the whole thing really hot then bury it in dry sand to hold the heat in with just the area to be welded sticking out it will not cool down as quick. I too would grind a "V" first. It can also sometimes help to drill a small hole at each end of the crack. Weld the ends of the crack first then a strip in the middle and then weld the rest in short alternating hitches but long enough at a time to get a good arc established. Otherwise you won't get good enough penetration. Chip the flux constantly and keep tapping all around to relieve stress (the part, not yours). [;-)] An oven would be nice but it takes a strong oven to hold the weight. I read somewhere that Henry Ford heat cured his first engine block in his wife's kitchen stove and ruined the stove. Almost as good as an oven is heating the casting in an enclosed place, a 3 sided shelter made of a few loose laid firebrick works well. That way much more heat stays with the item as it is heating. After welding bury the whole casting in dry sand to hold the heat and keep it from cooling too quickly. After it cools do a little more light tapping. Don't get too carried away grinding the weld flush as you can weaken it too much. I would rather just take off the worst bumps and then use J.B. Weld to level the surface to look original and leave the bulk of the weld there. Good luck farmer Central Indiana USA robinson@svs.net