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| Mrs. Robinson, Revisited....... |
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| Stilldrillin:
After almost a couple of years delay. I've made a tentative start, on completing my Robinson engine rebuild. Shop time is still very limited. But, I'll post whenever there's some progress. Here's the original saga. Just getting the engine to the condition I hoped it would be in, when it arrived...... http://madmodder.net/index.php/topic,3555.0.html The flywheel casting halves are eccentric to each other, and the bosses have been machined true to the opposing sides! :scratch: Turned away as much of the balance weight as I could....... The engine has been dropped, and one foot is broken. Milled away the ragged edge...... And made a cast iron block to fit in the recess........ I've had little practice at silver soldering. But, never (yet) had a failed joint. What's the best sequence to use, for a sound joint in this situation? Should I flatten the wire, and lay between the parts? Any tips would be much appreciated. David D |
| vtsteam:
Stilldrillin, the main thing to try to do is not crack the casting. Too much localized heat and too rapid cooling can cause cracks. I would have a bucket of wood ashes nearby to plunge the part into and let cool for half a day. But I have a wood stove, don't know whether you do. Parts must be absolutely clean in joint -- no fingerprints. flux parts. Clamp parts or wire them so they can't move. If a joint is close, but not absolutely closed. I'd feed from the outside -- the braze will wick in usually. When heating the part. play the flame over a large area, to heat gradually instead of too localized, Gradually focus down onto your braze area. Both parts need to be equally hot, so spend more time on the more massive piece. When flux boils from the metal heat (not the flame) usually it's time to apply silver braze. Braze should melt from contact with the hot metal rather than just the torch. If the metal is too cool, the braze will ball up in the torch flame instead of flow onto the metal. Hold the flame on the metal just long enough to get good flow but no so long that it flows off the piece or overheats it. You can back the joint with aluminum sheet if you think solder will flow through and drip out. That's about all the tips I can think of. |
| Divided he ad:
Good luck David! :thumbup: Talk about a steep learning curve! All sound advise above from all the things I've heard in the past.... Still makes it no easy task in reality... If you have any spare stuff I'd suggest a practice run. The wiring together works for me too.... Worked well recently on my rocket. I might thin that new part down a bit too... Much less to remove once the shape is all big and awkward to hold/machine. Ralph. |
| Stilldrillin:
VT. No wood ashes here....... Central heating, powered by natural gas condensing boiler. Thanks for the run through. Just the usual common sense set up, and procedure. Allied with careful heating. :thumbup: I just wondered if c/i needed any special treatment. Thanks for the alloy sheet tip! Ralph. Thanks for your sympathy! No spare stuff...... Especially castings! Yes! the block can be reduced a little at one end, as the joint face is tapered. Thanks, both, for the support. Just needed a slight confidence boost, having only done 3 or 4 conventional joints previously........ :scratch: Win, or loose...... Pics will be shown! David D |
| Stilldrillin:
Well..... When I'd dropped the insert on the floor, for the third time, while trying to wire it into place. I realised, it was April 1st.... :bang: Finally got it fixed, with flux more or less where I wanted it, and positioned on a fire brick. After some time of heating, I realised my blowlamp was ok for copper plumbing. But, well underpowered for this job! :palm: The flux was bubbling, but no sign of any red heat! :( Only thing to do was dab and hope......... The solder slowly melted, and puddled. So, I dabbed some more. Hoping it might flow through. Then I went for me lunch, leaving it to cool........ Turned it over, a couple of hours later. Not too bad........ Milled off excess. Expecting it to come unstuck. Why do we always go that one thou too deep? :palm: Still attached. Looking ok......... Rolled it over. Angle grindered and drilled 5mm........ A couple of dabs of filler and some paint, should look ok! :D Thanks for the support Chaps. Much appreciated! :thumbup: David D |
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