.png)
Tweet
Some might recall that I posted some pics of a diesel engine heat exchanger repair that I did a couple of years ago. The exchanger consists of a cast aluminium tank with two tube stacks, a large one for water/coolant and a smaller one for oil. They rely on a single O-ring on each stack end to keep raw (salt) water, which passes through the tubes, out of the engine coolant and oil and, just as important, away from the bronze/aluminium junction at the ends of the stacks. Inevitably after 45 years service this seal has leaked, more than once in the life of the engine.
This is the worse end of the tank:-
The previous one I had bored out the ends in the mill, and made 316 inserts for the ends out of solid bar (very wasteful). That was for a 6-cylinder engine, the latest job was for an 8-cylinder version of the same engine and so bigger, and too tall to fit under the head of my mill. If I removed all the fittings from the tank it would just have clearance to swing in the (19") lathe, but how to hold it? I'd thought about making a wooden mandrel - the bore for the tube stack is 5.75" - but didn't have anything suitable lying around. Supporting it was easy enough, gripping inside with a 3-jaw on the lathe spindle and with a revolving 3-jaw in the tailstock, but the ends needed to be bored out. In fact I found that I could tighten the little 3-jaw inside the tank bore, fairly tight, and simply screw the chuck further in with the tailstock ram without difficulty. Luckily the tailstock on my big lathe has a good length of extension available, so it would go far enough in to allow boring tools alongside the ram.
One of my concerns doing it this way was that there was nothing holding the big unbalanced lump positively against the chuck jaws on the main spindle, where the engagement of the jaws was fairly limited, but there was never the slightest sign of it trying to come away.
I started gingerly, but then by pushing the tailstock chuck further in was able to use a decent sized boring tool:-
For the previous job, I'd enquired about getting some sort of 316 tube to do the job but was told there was nothing available & so had to bore out solid bar.
This time, the stockholder persuaded me that some 6" schedule 80 pipe would do the job. The dimensions he quoted looked just about OK, so I ordered a piece. In fact, the ID was a bit bigger than he had quoted, might just about have been useable except that it was way out of round and nowhere near concentric with the OD.
There was no time to mess about arguing with the supplier and re-ordering, so I built up the critical area on the inside with some TIG welding (it just has to hold an O-ring under compression) and machined it out. My TIG skills are not very advanced, but good enough to get the job done.
Here is one of the inserts, and then fitted and with the water stack in place:-
There was some corrosion on one end of the seating for the oil stack, it wasn't too bad so I repaired that with some Devcon Aluminium epoxy putty.
Tim
This is the worse end of the tank:-
The previous one I had bored out the ends in the mill, and made 316 inserts for the ends out of solid bar (very wasteful). That was for a 6-cylinder engine, the latest job was for an 8-cylinder version of the same engine and so bigger, and too tall to fit under the head of my mill. If I removed all the fittings from the tank it would just have clearance to swing in the (19") lathe, but how to hold it? I'd thought about making a wooden mandrel - the bore for the tube stack is 5.75" - but didn't have anything suitable lying around. Supporting it was easy enough, gripping inside with a 3-jaw on the lathe spindle and with a revolving 3-jaw in the tailstock, but the ends needed to be bored out. In fact I found that I could tighten the little 3-jaw inside the tank bore, fairly tight, and simply screw the chuck further in with the tailstock ram without difficulty. Luckily the tailstock on my big lathe has a good length of extension available, so it would go far enough in to allow boring tools alongside the ram.
One of my concerns doing it this way was that there was nothing holding the big unbalanced lump positively against the chuck jaws on the main spindle, where the engagement of the jaws was fairly limited, but there was never the slightest sign of it trying to come away.
I started gingerly, but then by pushing the tailstock chuck further in was able to use a decent sized boring tool:-
For the previous job, I'd enquired about getting some sort of 316 tube to do the job but was told there was nothing available & so had to bore out solid bar.
This time, the stockholder persuaded me that some 6" schedule 80 pipe would do the job. The dimensions he quoted looked just about OK, so I ordered a piece. In fact, the ID was a bit bigger than he had quoted, might just about have been useable except that it was way out of round and nowhere near concentric with the OD.
There was no time to mess about arguing with the supplier and re-ordering, so I built up the critical area on the inside with some TIG welding (it just has to hold an O-ring under compression) and machined it out. My TIG skills are not very advanced, but good enough to get the job done.
Here is one of the inserts, and then fitted and with the water stack in place:-
There was some corrosion on one end of the seating for the oil stack, it wasn't too bad so I repaired that with some Devcon Aluminium epoxy putty.
Tim
Comment