Clogged arteries, good heart.
I just finished executing the most deft example of mechanical improvisation in repair work I’ve ever achieved. Thursday and Friday were an encompassing tour de force for me. Let’s go back to May 22, 1979. The day my machine was made.
First, a little background about the foundational principals of mechanical precision. The fundamental building block of mechanical precision is the flat plane. To make a machine tool that gives superlative precision requires flat surfaces that are able to slide past one another in only a single direction (or axis) with no movement in the other directions. The confinement of the axes in which one does NOT want movement typically hinders movement in the desired axial direction. There are several ways (hahaha!) to achieve a compromise, but at the heart of the best solutions to this problem are the issues of stability, maintainability, and comfort. Without a disquisition on mechanics, the simplest way to explain those concepts is:
1. Will [the system] do what you want?
2. Can you accommodate for wear over it’s life?
3. How easy is it to take care of?
The first question has many potential solutions. Answering the second question is where the tradeoffs come in. And the third question is my machine comes in.
My machine is 2000 pounds of precisely made cast iron slabs that mate together and slide past one another in beautiful ways (haha!). And the guys who designed it were kind enough to create a circulatory system made of grooves, channels and pipes that pump oil to all the places where oil needs to go so that the system stays in good condition for as long as it can.
That system was malfunctioning.
Sure, I could just manually squirt oil at the intersection of sliding surfaces, and move things around to disperse it, but I wasn’t comfortable with that decision. Many machines don’t have such an elaborate system for the oiling sliding surfaces, but this machine was designed to be able to make parts with the narrow tolerances required to go into spacecraft, or into someone’s heart, and I wanted to honor that intent.
I actually have two machines like this, a newer one, and the one I’m speaking of. The newer one was abused and in rough shape when I got it, and over the years, I’ve rebuilt just about everything about it, and through all the work I’ve done with it, the pens have gotten better, I’ve learned a lot, and I’ve had fun doing it. But the damn thing had, and still has, a lot of problems. One of them was the little pump that pumps the oil through it’s circulatory system wasn’t pumping, and last year, I decided to figure out why.
After taking it apart, I was able to find out that basically, my system still had a strong heart, but clogged arteries. I removed the pump, put air pressure into the inlet, and let a few atmospheres of air pressure get the clogs out for me. That took time, but it worked. I cycled the system with high pressure thin viscosity oil, and after a few hours of waiting–and hilarious flatus coming from the machine–I got it cleaned out. I refilled it with the correct oil, and now it runs excellently.
The machine I worked on this week has a critical add-on part blocking complete removal of its pump, and I (foolishly) assumed it was the same as the other one, and that I could open it, put air in and reproduce the magic of last year. Well, I broke something–a tiny copper tube that connects the pump to the actual oil inlet–and it hasn’t functioned properly since.
So this week I delicately removed the (expensive, fragile, bulky, asymmetrical) add-on part I was speaking of, and pulled out the oiler assembly. I saw what I had done, thought about it for a while, called a friend who knows these machines inside and out, asked for advice, felt inCREDibly dumb, and then I went to work with a repair, ending on Thursday night at 7 with a plan that I was sure I could bang out in an hour the next day, Friday.
Friday came, hours later, and I had my first attempt at a repair installed, and it failed immediately upon testing.
There were two little holes in question; an output for the pump, where the oil the pump pumps shoots out, and a hole where the oil is supposed to go to get to the rest of the machine. Those two holes were supposed to be connected by the little copper tube I found sitting at the bottom of the tank where the oil goes in. The original copper tube was connected on one end with a tight press fit, and on the other end with…solder. Well, I’m no good at soldering, so my first brilliant idea was to make two press fit connections to those holes with some short bits of aluminum tubing I had around. With those in place, I could then just slip some flexible silicone tubing I have (for Pump Pistons!) over both ends and call it a day!
I tried it, but in testing, oil pressure just pushed the tubing off one end.
So I tied the tubing to both ends with some wire.
Oil pressure ruptured the tubing.
After that it was 1 o’clock. Still enough time for some skullduggery, but my energy wasn’t going to last forever.
I decided I would make a new tube out of all aluminum, and try to press fit it into each hole. The direction of the holes in question are not on intersecting planes, so the tubing would need a loop and a bend to make the trip.
If I didn’t get this back up and running, the machine in question might not get properly lubricated. It was designed to have such a lubrication system, and without it working properly, there was a good chance that the machine could wear itself apart in time, rendering it incapable of delivering the precision and performance for which it was initially designed. Do I need to be able to make pen parts to the fifth decimal place? Not necessarily, but I don’t just make pens.
The holes were a little over 1/8”, and the tubing I have was 1/8”. I decided to measure an appropriate length of aluminum tubing, and stretch the diameter by squeezing it from the inside.
I remembered I had this set of rusty pins made of hardened steel in a bunch of sizes I couldn’t bring myself to throw out several years ago. They’ve lived under my porch, in my shop, and sometimes in my car this whole time while I worked up the nerve to throw them away, and I finally, FINALLY had an opportunity to use them.
I took out one that was just larger than the hole in the tubing, ground a bevel (or chamfer, if you will) on the end, and pressed it into the tubing to the depth I wanted the expanded part to be. It swelled up like a balloon animal balloon. Very satisfying. I repeated the process, stepping up in size, until I got the tubing to be about 0.001 inches larger than the holes the tubing would go into. (For reference, a human hair is about .004” in diameter.)
Why go through this swaging process? Why not just re-use the copper that came with it? Well, copper is harder to swage. And because the bent tubing is supposed to be inserted into other holes, it actually needs to flex somewhat to fit where it goes, and I know that copper tends to work harden. Between me not wanting to learn how to copper solder on this critical job, on top of dealing with annealing (to soften the copper after it work hardens) with a blowtorch in a confined space with meltable, flammable stuff nearby, I thought aluminum might be a safer choice. Aluminum work hardens too, but it’s a third the density of copper, so it might still be easier to work with; at least until it breaks!
Finally, I had my straight piece expanded on both ends. I bent it carefully, slid it almost into position, and then I trotted out my next trick. I needed to push it in, and this tiny, bent tube would need some heavy force to get where it needs to go. I didn’t like the idea of doing this with my bare fingers, and I learned from experience that a press fit strong enough to resist blowout from oil pressure is hard to do by hand under ideal circumstances. And this was considerably less than ideal.
So! I found some square aluminum bar. I drilled a hole in it the same diameter as the tubing, chopped it off and cut it in half lengthwise. I put each half around the tubing near where the joint would be, and squeezed it around the tubing with a pair of locking pliers so I could grab the bar and twist the tubing into place without distorting it.
After checking for clearance, installation and testing, the new part seemed to work. I spent about half an hour pumping the oiler, and it seemed to be performing adequately.
5:00 Friday. I called my buddy back and told him all about it. He told me to go have a beer. I didn't have the nerve to tell him I don't really like beer.
Pierre