Hey Everyone!
This is my first post here on Practical Machinist. I am a senior mechanical engineering student at Embry-Riddle Aeronautical University in Prescott, Arizona. I am working on a rocket engine for my school, and I just encountered a serious problem. I was hoping advice on how to proceed, because everyone on practical machinist seems to be very knowledgeable.
The problem I am having is getting fluidic connections (fittings) to the engine. Shown in the pictures, swaglok fittings were welded to the engine. The welds resulted in ~60 thou of deformation. I knew that there was going to be deformation, but I didn’t think there would be so much deformation that it likely will have to be scrapped. Unfortunately, the person that welded the engine accidentally did two passes on each weld causing further warping.
Currently the plan is to fix this part by putting the part in an oven and slowly heat it to 1200F. Once heated, a press will then attempt to push it back into place, removing the 60thou of deformation. Does anyone recommend any other techniques for reducing residual stresses in welds?
If this doesn’t work, then the part will have to be scrapped. I could attempt to reweld the engine with smaller fillets, but I am still concerned about warping.
What are people’s opinions about furnace brazing? The part is tightly toleranced and has sealing surfaces, so I thought that furnace brazing would reduce potential warping.
I am also considering shrink fitting the fluidic connections onto the engine and then tac welding them into place. They would need to be tac welded, because liquid oxygen which is -300F will be plumbed into the engine. I would be concerned about the fittings coming lose at cryogenic temperatures.
What are people’s opinions about shrink fits? Do you think they can withstand the temperature cycling?
I can’t use boss ports and NPT taps due to weight constraints and packaging problems with the engine.
I realize this is a long post. I have no idea if anyone will read this much, but I figured it would be worth a shot, because I am quite desperate. Attached are pictures.
Thank you for the advice and any information would be appreciated!
This is my first post here on Practical Machinist. I am a senior mechanical engineering student at Embry-Riddle Aeronautical University in Prescott, Arizona. I am working on a rocket engine for my school, and I just encountered a serious problem. I was hoping advice on how to proceed, because everyone on practical machinist seems to be very knowledgeable.
The problem I am having is getting fluidic connections (fittings) to the engine. Shown in the pictures, swaglok fittings were welded to the engine. The welds resulted in ~60 thou of deformation. I knew that there was going to be deformation, but I didn’t think there would be so much deformation that it likely will have to be scrapped. Unfortunately, the person that welded the engine accidentally did two passes on each weld causing further warping.
Currently the plan is to fix this part by putting the part in an oven and slowly heat it to 1200F. Once heated, a press will then attempt to push it back into place, removing the 60thou of deformation. Does anyone recommend any other techniques for reducing residual stresses in welds?
If this doesn’t work, then the part will have to be scrapped. I could attempt to reweld the engine with smaller fillets, but I am still concerned about warping.
What are people’s opinions about furnace brazing? The part is tightly toleranced and has sealing surfaces, so I thought that furnace brazing would reduce potential warping.
I am also considering shrink fitting the fluidic connections onto the engine and then tac welding them into place. They would need to be tac welded, because liquid oxygen which is -300F will be plumbed into the engine. I would be concerned about the fittings coming lose at cryogenic temperatures.
What are people’s opinions about shrink fits? Do you think they can withstand the temperature cycling?
I can’t use boss ports and NPT taps due to weight constraints and packaging problems with the engine.
I realize this is a long post. I have no idea if anyone will read this much, but I figured it would be worth a shot, because I am quite desperate. Attached are pictures.
Thank you for the advice and any information would be appreciated!