Antique gas engine repair
Plumber's stove for melting babbitt.
The wear and tear an oil field engine experiences as one of our toys is probably pretty mild compared to the abuse it experienced in its working life in the field. We pamper our engines, making sure they are well oiled and in good working order. Unfortunately, these engines don't always come to us in good shape forcing us into antique gas engine repair. I have seen many old engines knocking from worn out bearings, and I've even seen an engine using shims from an old cereal box.
Some engines wouldn't even get new bearings poured when they wore. I have seen several that were put back into service with a piece of leather belt wrapped around the shaft and plenty of oil to remedy the offending bearing. Sometimes the worn shell on the bottom would be swapped with the other half in the bearing cap. As collectors, however, our labor of love forces us to properly repair these problems, which often means pouring babbitt bearings.
Babbitt is a mixture of lead and tin, and for obvious reasons much softer than your crankshaft. It is normally 80-1/4 percent lead, 14-3/4 percent antimony and 5 percent tin. This material will serve as a durable bearing for wear surfaces for years if oiled well and not run hot. Babbitt can be purchased from many places, but you can also salvage what you melt out of your old bearing or from other shells when re-babbitting an engine. When you melt out old Babbitt all the nasty stuff (such as dirt, old oil and grease) burns off or rises to the top of the molten pool. Using an old plumbers soldering iron (or other piece of flat steel) you can rake the contaminants off the top of the molten pool. Small quantities of wax from a toilet bowl ring can be dropped in to assist the separation of the babbitt from any dirt. A good trick when heating babbitt is using a piece of Cedar wood to determine if the babbitt's hot enough to pour. Dip the wood into the molten pool, and if the wood burns with a flame the babbitt's hot enough to pour. If the wood's only scorched it needs more heat. I am told this is around 650 degrees F.
Before I go further on this subject, I must stress the need for absolute care, as hot babbitt can cause severe burns. Common sense and rigid safety practices should be observed when handling molten metals. Always wear protective clothing and gear, and remember that water is a no-no around molten babbitt: It can cause it to explode. Please, practice safety first.
The first thing you'll need is some way to melt the babbitt. I use an old white gas plumber's stove, but a rosebud torch will work. You will need a torch to melt out remnants of the old bearing and to burn off the remainder of the old oil and grease. An acetylene torch and an assortment of ladles and pots for melting the babbitt will be necessary - most importantly you'll need a good long-handled ladle with a notched spout for pouring.
You'll also need a commercial version of damming clay, which is usually available from industrial supply catalogs, and of course all the necessary equipment for lifting and blocking up the flywheels and crankshaft. Keep some flat pieces of wood and pieces of leather for shim spacers handy, and possibly a toilet bowl ring or beeswax and a cedar shingle.
The biggest job in making a new babbitt bearing is the preparation - the actual pour is one of the last steps. If the dam isn't prepared properly or other details are overlooked, you'll find yourself redoing bad pours. This happened to me once when the vent I made to allow air to escape the dam also allowed liquid babbitt to flow out faster than I could add it! My mistake was in failing to extend the vent above the highest spot on the bearing.
The first order of business, once the flywheel and crankshaft are jacked up and blocked out of the way, is to melt out all the old babbitt and clean or burn out the old oil grease and dirt. The crankshaft should then be leveled in relation to the bedplate of the engine, and situated so as to allow for the added thickness of the new bearing. A bubble level is helpful in doing this, as long as both the crank and bedplate are leveled together. Measurements are taken off the crankshaft in relation to the bedplate and its bearing saddle in order to assure the best possible alignment. The crankshaft (but not the saddle area) is then blackened with an acetylene gas torch with the flame turned low in order to produce 'soot.' This keeps the babbitt from sticking to the crankshaft.
Always pour the bottom half first. Cut blocks of wood to fit into the saddles where the cap had been. These serve as a dam along the face of the shaft and at the seam between the top and bottom half of the bearing. Damming clay is then stuffed into the areas around the ends of the bearing saddle. This can be modeling clay or play dough, or one of the commercially available products in industrial supply catalogs such as 'Dammtight' or 'Casting retainer putty.' These latter products perform best as they are made for the job. Casting retainer putty, for example, melts at 978 degrees F, but is a bit expensive. Play dough will work, but be sure to use plenty as it will melt until the babbitt sets, which doesn't take long. Modeling clay seems to resist heat fairly well, but it's not as good as the commercial stuff. I've seen a lot of folks have good luck with a mix of play dough and modeling clay.
It's also a good idea to place a lead wire around the shaft at the point where the bearing is dammed in order to make a good-looking edge on the bearing. If you don't do that, at least make sure your clay is packed neatly at that point. You'll also need to determine how to vent air from the pouring area to prevent air pockets, voids and bubbles. This requires placing a hole or holes in the damming clay to allow air to escape while the bearing is filling.
Keep in mind that a ladle full of babbitt can be deceptively heavy - you're lifting liquid metal. The pour hole for the babbitt should be at the highest point of the lower bearing between the crankshaft and bedplate saddle. The top half of the bearing, which is poured into the bearing cap, is usually poured through the oil hole. The top half is dammed in a similar fashion as the lower half. You always want to make a pour in one step, filling the bearing area completely.
After pulling out all the damming material, flash and other babbitt that may have seeped into areas where it's not needed can be scraped back or cleaned with a wire wheel in a hand drill. Oil holes will need to be re-drilled in the cap and oil grooves (shallow channels for even oil distribution) should be cut into the face of the babbitt with a scraper or rotary burr in a hand drill. These grooves should never extend beyond the edge of the bearing, as that would channel oil out rather than spreading it evenly within the bearing. During final fitting of the crankshaft to the bearings you'll want to cut some leather or wood shim spacers to put under the bearing caps to ensure proper tolerances. These same shims can be removed to make up for bearing wear as time and wear dictate.
I'd like to thank Leroy Goodwin and Ron Trent for their help in preparing this article, and also Don Romine and Dave Artmeier for letting me photograph their bearing projects. I'm sure there's more to write on this subject, and if any of our readers would like to share their experiences pouring babbitt I'd like to hear from them.
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