Riveting draft gear

SN 1005's excursion career saw it shipped all over northern California in freight trains. It is not built as strongly as freight cars, so it tended to take the brunt of the damage in rough handling and switching accidents. Needless to say, a lot of this fell on the couplers and draft gear. Previously, both ends' couplers and draft gear had been disassembled. Subassemblies had been repaired, including a complex steel forging in the shape of a "C" which wraps around the draft gear springs. This is riveted to the coupler body with two large 1-1/4" rivets.

These rivets are special. They are flat-head rivets. They must lay flush against the draft gear when they are done. Their holes are countersunk with a bevel, so the rivet is shaped like a flat-head screw. It's that way on both sides.

What makes a rivet a rivet (and not a bolt) is that it is heated to yellow-hot, inserted into the hole, and hammered. This makes the rivet expand fully into the hole, leaving no space. If the hole is irregular, the rivet fills it all, at least near the hammered end. Most rivets start with their familiar button-head already on one end. But this rivet is flat-head. It must expand into a countersunk hole. To get a good start, the rivet is turned with the correct shape of head. Even so, this will be heated, and will deform and expand to fill the hole.

One of the tricks with any riveting job, and this one especially, is to compute the correct amount of metal to be in the rivet to expand into the hole and yet leave the correct amount of metal in the head. With button head rivets there are familiar formulas. Ah, but what volume of metal will fill that beveled countersink? That required the sharp pencil and a fair bit of calculating.

Another way to make the rivet fit is to drill out the hole. This was more complicated because the coupler body is hollow, so each hole through the coupler body is not continuous steel. When the hole picks up on the other side, it doesn't quite align. "Misaligned holes" is a common problem when riveting. (Especially when riveting bridges, hold that thought.) We started with drill bits, stepping up in 1/64" increments, which made the developing hole tend to center itself. The coup de grace was delivered by a bridge reamer. It has a tapered shank, which centers on a slightly misaligned hole, and aligns it by enlarging it. Our finishing size was 1 and 5/32", or 1/32" over nominal rivet size.

Another problem - how do you hold the rivet gun onto a flat-head rivet? On a normal button-head rivet, the rivet itself does the job. The shop crew created a solution: The C-shaped bar was steel, so it could be welded. They found a pipe that would just fit around the rivet gun. They cut about a 2-inch length of that pipe, and tack welded it in the right place to guide the rivet gun over the rivet. Problem solved!

On the first coupler, this preparatory work was done Tuesday. On Wednesday, the rivets were driven. The rivet must easily go into the hole when it is heated. Heating makes it bigger. Which is the idea behind drilling the hole 1/32" oversize. It wasn't enough - on our first try, the hot rivet would not go in the hole. It was let to cool, and 1/32" was turned off it on the lathe. It worked the second time. Lessons learned, the second rivet went in fine. A fair bit of grinding followed, and riveting is now complete on one coupler. You can barely tell there are rivets there.

Are the rivets in shear? No, they aren't. Coupler draft (tension) and buff (compression) both go through a big spring that goes in the empty space you see. More on that later.

Reverser repaired

Over the previous week, the 1005's reverser drum was repaired, tested and reinstalled. The reverser's job is to reverse field connections on each of the traction motors. On a series-wound traction motor, the field is in series with the armature. That means every field must take full traction motor current, and thus, so must the reverser. It must have a circuit for each motor, i.e. four, and at least four contact blades per circuit.

This makes for a very big switch, and it's built as a multi-pole drum switch. Because of its size, it takes a lot of force to throw. The muscle actually comes from air. Electrical signals operate a "magnet valve" which applies air to a piston, which throws the drum switch over. There are two magnet valves, one for each direction. The electrical signal to each magnet valve goes through an interlock on the drum itself, which cuts power to the magnet valve (and thus air to the piston) once the drum reaches the desired position.

You may recall two articles (1) (2, photos) about the third rail changeover switch. This switches even more current, but only one circuit. They were usually reversers with their many contacts ganged together to increase current capacity.

The Westinghouse HL equipment also has switch groups, which is a footlocker-sized cabinet with 6-8 large contactors in it. 1005 in fact has two complete sets of switch groups; that's because the additional complexity of the 600/1500V changeover required more switches than one group contained. Al has been overhauling some of the switch groups. Here you see him working on some interlock fingers. These don't carry full traction current, but signaling current. Their job is to interlock other contactors which should never be closed at the same time, such as series/parallel transitions.

M.U. sockets complete

The connections to the M.U. sockets have been tested and are complete. That says all the M.U. connections are correct, and by extension the control stands are correct. The testing is done with a very old "ringer box" containing two 6 volt batteries and an electromechanical bell connected to some very long wires. The ringer box proved persnickety and of course needed repair of its own.

One twist (literally) in the M.U. wiring is the forward/reverse controls. Forward on one controller is the same as reverse on the other controller. Similarly, the pin in the M.U. wiring for "forward" on one end, must be the pin for "reverse" on the other end. As you can imagine, there's only one way to resolve this: "twist" the forward and reverse pins halfway down the car, so forward goes to reverse and vice versa. But how does it get back to normal for the next car? Heh - there's also a twist in the M.U. jumper cable.

M.U. wiring complete

Another big wiring job completed is the multiple unit wiring. This is the 12-pin jumper plug discussed earlier, and its numerous connections throughout the car.

The multiple-unit control plug carries signals which control forward/reverse, series/parallel and the various resistance points. This wiring must go to a remarkable number of places on the car. On each end, it goes to three places - motorman's control stand and also to two jumper plugs. The seventh connection is to the switch group which actually controls the car's motors.

These connections happen in three control boxes - one at each end and one in the middle of the car. The end control boxes connect to the motorman's control stand, two jumper plugs and the middle control box. The middle control box connects to the end control boxes and to the switch group. With 12 wires per connection, it gets pretty crowded in those boxes!

3rd rail changeover switch complete.

The wiring for the changeover switch is complete. You can see the parts which have been reused and which had to be made from scratch. It was not possible to obtain a solid piece of maple large enough, so the drum is a glued composite. The latches are a stock item from McMaster-Carr.

Third rail changeover switch

The 1005 is being restored to its 1934 configuration and appearance. In 1934, the Sacramento Northern operated on both overhead wire and third rail.

Electrically, it would be simplest to wire the trolley poles/pantographs to the third rail shoes at all times. However that is illegal and unwise. There must be a changeover switch that connects car power to the active one while isolating the other.

On the 1005, this is fully automatic. This is done with a pair of relays in the baggage compartment of the car. One relay picks up if power is present on the trolley wire. The other picks up if power is present on the third rail. If "trolley" is on and "third rail" is off, it energizes a wire which runs down to the changeover switch and says "switch to trolley". Or vice versa.

Alongside this relay box are four resistors. Two are dropping resistors for the two relays present in the box. The other pair are dropping resistors for the two wires going down to the changeover switch. One pair of resistors was fine (it was made of cartridge resistor elements which removed like a fuse.) The other pair was totally defective and new resistors had to be made. The order came in; it was wrong and had to be remade. They were further modified to replicate the original mounting style. This work was completed last week and the relay box and resistors are remounted in the baggage compartment.

The changeover switch is underneath the car. It processes each signal further. For instance if the "switch to trolley" signal is energized, it will switch to trolley, but only if it's not already in trolley, and only if the car is coasting (not motoring). If all conditions are met, the signal reaches a magnet valve, which applies air to muscle over a big rotary switch similar to a reverser. There is yet another interlock, which assures the switch will only operate when the car is configured for 600 volts DC (not 1500 volts DC).

As to the changeover switch itself, the restoration had a challenge.

Normally on a third rail car, all third rail shoes on the car are connected together electrically. Third rail shoes on one side are touching the third rail; on the other side they stick out, energized and dangerous. Crews in third rail territory are trained on this, and civilians are kept away. That is how SN 1005 was configured in 1934. The Key System bought the car in 1942. The Key used third rail to come over the Bay Bridge and into the San Francisco terminal, but they had low level platform loading. Passengers could easily touch a third rail shoe. So, Key required a more sophisticated changeover switch which isolated third rail shoes on each side of the car. They removed and scrapped the original changeover switch!

The correct changeover switch would have to be remade from scratch.

Changeover switches are very similar to reversers. The air motor, magnet valves and some other parts were scrounged from an old reverser. Outside of that, the changeover switch was built from scratch over the last two years, using the reverser on another car as a model. This was a considerable undertaking. It took about two years, and is complete. It has been installed and the heavy power connections have been made.

What remains is the small signal connections. At this writing, wiring has been pulled through conduit, between the changeover relays, the changeover switch, and the 600/1500 interlock.

What's in a plug? A challenging fabrication

Interurbans such as the SN 1005 frequently ran together in trains. The motorman worked the controls in the first car, and all the cars with motors responded in sync to his actions. This is done through "multiple-unit control", or "M.U." A control cable runs the length of the train, and jumps from car to car via plugs.

Ah, the lowly plug. We use plugs and sockets for so many things in our society, but who ever thinks about them? You need four to charge a cell phone. Nowadays plastic insulates the various pins. But what do you suppose they did in 1910?

There's a surprising answer. Maple.

The Western Railway Museum plans to M.U. the 1005 with other units, such as the 1020. The M.U. plugs on 1005 needed work. The copper pins were shot (fabricating them is another story!) and the maple insulators were in poor shape. How do you make one of these?

It's not as simple as you'd think. All the holes must have a very particular relationship to the index key. If any of them are off, the plug won't mate. And we had several to make. (they are four inches in diameter.)

Two approaches were tried. Rather than try to machine each plug individually, one of our machinists made a steel "cap" which could fit over the insulator. In this cap, he carefully drilled holes in the right places. A tedious job, but done once, it provided a jig that properly located the holes for any piece. A second approach was explored in the digital realm: software that would tell a CNC router how to cut the part out of a block of wood. Software incompatibilities slowed that project, and the traditional machinist won. Jawn Henry would approve.

The insulators were drilled, shouldered and tapped 1/4-20 for the pins, which screw in. Maple is a hardwood which accepts threads well. These pieces are almost 2 inches thick, and tapping them required special nut taps.

Maple is already an excellent insulator, but only when dry. One way to solve that problem is to boil the maple in paraffin, driving water out and wax in. However, in this case, the pieces were painted with Glyptal paint designed for high insulation value. The pieces really "drank up" the Glyptal. Bolts were screwed into the threaded holes to "mask" them from the Glyptal. The bolts came out easily.

Soldering wires onto the pins was the next step. For each plug location, the crew measured the distance to the junction box, and they cut 12 wires of this length. They tinned 12 pins then cleaned the threads of each pin, screwed the pin into the maple block, and soldered a wire to it. It wasn't necessary to mark which wire went to which pin; the wiring crew will ring those out later. No ribbon cable here!

The twelve wires were threaded through a cast iron rear cap, then inserted into the back of the cast iron housing and the rear cap was installed. The result is the picture you see at the top.

Click on any picture to zoom in. This work was completed on June 30.