Some thoughts on troubleshooting

I have now debugged all the heddles (cross fingers that they keep working!). I’ve gone from this:

to this:

Along the way, I’ve figured out how to replace stuck valves, malfunctioning pistons, and bent heddles. And, more importantly, how to diagnose and fix each. Tronrud Engineering provided excellent documentation, which really helps!

There are a few things left to troubleshoot. The strain gauge on the top warp beam is delivering strange readings (the strain gauges are used to monitor and control the warp tension). The auto-controlled warp tension doesn’t seem to be working properly, and neither is the auto-advance. I have sent an email to the support team asking for help in troubleshooting those three items. (I suspect that they are all part of the same problem, and that once we figure out how to fix the strain gauge, the others will fall into place.)

One of the side effects of having to fix a couple dozen tricky heddles is that I now feel much more comfortable with the loom. One thing I have noticed, in myself and others, is a tendency to regard equipment, especially complicated equipment, as something magical that only a magically expert person can figure out. And Amazing Grace is pretty darn complicated. So it’s easy (and very tempting!) to throw up your hands and leave it to the experts.

However, a wizard is simply someone who understands how magic works! And once you understand it, it’s not that magical after all. In fact, once you understand the system, it seems pretty obvious (in retrospect) how everything works, what caused the problem, and how to fix it. As long as you have faith that things will make sense eventually, and apply critical thinking, eventually you’ll figure it out.

And, in fact, that’s basically what’s happened with Amazing Grace. I went from a magical system – press the pedal and the shed magically opens! – to an understanding of the real, physical system, which in turn has helped me diagnose and fix the problems. What happens in the physical system is that the computer electrically triggers some coils, which in turn open up valves for the heddles that will be lifted. The vacuum pump sucks air through the open valves, which raises pistons, and since the heddles are attached to the pistons, the heddles rise.

Once I understood that, I could think critically about what might happen to bollux up the system. If the coil isn’t working correctly, the heddle won’t move. If the valve isn’t opening and closing correctly, the heddle will get stuck consistently up or down (depending on which way the valve gets stuck). If the piston gets stuck, the heddle will either get stuck halfway or else consistently rise/stay down when it shouldn’t – depending on where the piston gets stuck. And if the metal heddle is bent, the heddle gets stuck as well.

So diagnosing problems with the magical shed really comes down to figuring out which of four parts is malfunctioning. And that can be fairly simply done. If the heddle looks bent, replace the heddle. If you feel resistance while manually moving the piston up and down, the piston is stuck and you need to replace the piston. Run the coil test in the software to test the coils. And if all else fails, it’s probably the valve.

And presto, the system is no longer magical. (Or perhaps I’ve become a wizard.)

Speaking of magical, our socks have begun mysteriously migrating around the house again. Of course, once you understand the mechanics of the system, it’s easy to understand how and why it happens. Fixing it, on the other hand, may be a bit more difficult. Here’s Fritz the Sock Thief, caught in flagrante delicto: