Sunday, November 9, 2014
Canopus: Biting The Bullet
The instructions say to use solder to affix the retaining nuts in place. Experience from building the Quarry Hunslet suggests this doesn't work very well. The problem is that you need to fix the nut before snipping off the excess pin and filling the nut thickness down. When soldering the nuts the solder doesn't penetrate all the way through the nut which means when you start filling it down the first thing you do is file off the solder and the nut becomes loose. On the Quarry Hunslet I secured the coupling rod in place with superglue but still found this difficult as you get so little time to check and adjust things.
For Canopus I took a slightly different approach and have used LOCTITE 243 medium strength threadlocker. This gives me (according to the datasheet) 5 minutes fixture time (that's for brass, it's 10 minutes for stainless steel). Also unlike superglue it is designed to be reversible, assuming you can supply 26 Newton-metres of torque. I used a slip of paper to try and stop the stuff getting anywhere it shouldn't as well as ensuring that I didn't over-tighten the nuts. This seems to have worked well although removing the last bits of paper was a bit of a pain.
I haven't yet removed the excess crank pin or filled down the nut (this was as much stress as I wanted today) but having had it on the rolling rod everything seems to be working nicely. You can tell that the threadlocker is working as previously running in one direction would cause the nuts to work loose which is no longer happening. Now I've got past this point hopefully progress will pick up a little.