Chapter 10

Two of the women were particularly skilled in basket making, so Doug assigned them the job of making the casings for the bombs. He wanted the baskets to be as strong and as dense as possible, so the women made them as double layered containers. There was no need for them to be spherical; the trebuchet certainly didn't care! The structure they came up with was a nearly cylindrical, truncated cone. There was a flat bottom and a flat top, and the fuse was run out the top. The casing was lined with concrete and filled with a mixture of broken rock and gunpowder; Doug figured that the combination of the concussion and the flying shrapnel would produce the maximum destructive effect against the people that he was expecting.

Doug's biggest problem was in obtaining uniform weight, since the workers wanted to pack into each bomb as much destructive power as possible. Doug finally got the need for uniform weight across by holding a demonstration with the prototype/training trebuchet. He had two rocks of the desired weight and one rock about 25% heavier prepared. When each of the rocks were test fired, the two of the same weight hit at very nearly the same place, but the heavier rock fell short because the trebuchet could not get as much "whip" into its throwing arm. The whole balance of the machine was thrown off by the heavier missile; thus, the aiming was all messed up. This was the convincer needed, and the people were more careful to obtain a consistent weight for the bombs.

Once all three trebuchets were functioning, Doug held training exercises once a week to keep the crews and the machines in peak condition. He had decided to keep the smaller trebuchet in commission to use as a "close in" weapon against smaller groups of attackers who managed to get too close to the cliff. He really didn't expect to get much use from this smaller trebuchet, but it was a great morale builder to have 3 weapons instead of 2.

The last great problem that Doug wanted to solve was getting water from the large stream that ran below the cliff. To do so, they would have to lift the water 30 feet just to get it up to the level of the first houses, and lift it a total of 60 feet to get the pressure that Doug felt was necessary to accommodate all of their needs. He had several alternative ways to lift the water, but he wanted to do it in a way that would not attract attention from potential attackers. His idea was to save the water coming from the pool at the top of the cliff for emergencies, and use the water from the stream for day-to-day routine activities.

The final solution that Doug came up with was to use a series of Archimedes screws driven by wind mills on top of the cliff. With some careful work, they could raise the water they needed about 15 feet with a single screw, so they would need a total of 4 screws and 4 windmills. The first screw would feed a small intermediate tank from the stream, and the other 3 screws would work from tank to tank until the water was finally pumped to the main holding tank 60 feet up from the stream.

He had no metal to work with, so he would have to use masonry and wood as his only building materials. The wind at the top of the cliff was steady, both in velocity and direction, so the windmill fans would not be difficult to construct and install. However, connecting from the windmill shaft to the water-lifting screws would be the real challenge.

This was solved with a rope and geared-pulley design. A very long rope was fashioned with large knots every 6 inches so that the result resembled the beaded drive-chain that all mechanical engineers would be familiar with. The pulleys for this rope to work over were constructed from round pieces of wood with sturdy wooden spokes projecting out from the hub. The rope was threaded among the spokes so that the knots would catch on the spokes and force the hub to turn. This worked very well after a little tinkering to get out the bugs. The result was such a strange looking device that the locals would never have any idea that the ropes they could see could have any practical value.

Doug knew from his research that the Clovis people had been wiped out by a surge in the ice around 10,000 BC. He wanted to protect his people from that fate, so he began his campaign to build up their stockpile of food and other necessities in preparation for the event. There was no question of a return of the ice which lasted long enough to kill off almost all life north of New Mexico. Doug was determined that his people would survive.

One thing he had to do was to come up with a heating system for warming their homes which did not depend on fire or direct sunlight. They were already starting to deplete the local trees, so there was no way that they could depend on fires for warmth, and there would be so much dust in the air that the sun would be blocked for years. Doug searched his memory for some hint of a way around the problem; finally, he had a glimmer of an idea.

If air is compressed, it gets hot, and if compressed air is decompressed, it gets cold. With a little ingenuity and a lot of sweat, Doug might be able to make use of those two facts to solve a lot of his problems. He could heat air for warming their homes and cool air for building refrigerators, maybe even freezers. Now, he was on to something!

The first thing Doug had to do was to make a suitable air compressor. He had a reliable power source in his windmills, so that part of the solution was already on hand. For his compressor, Doug built a cylinder from concrete, about 12 inches inside diameter and 24 inches long. One end was plugged by a concrete disk sealed to it, and a similar disk of casein plastic was made to act as a piston. Several holes were molded into the piston to act as valves with leather flaps for seals. The piston rod was hooked to an eccentric crank coming from a windmill to move the piston back and forth in the cylinder. He built this weird device over a period of nearly 3 months, using handy spectators as help when he needed assistance. His biggest bottleneck had been in getting enough milk for the casein plastic, but the nursing mothers cooperated, and he finally got enough.

Much to Doug's amazement, the compressor worked better than he had expected, and he could generate a respectable quantity of either hot or cold air as desired. He found out that it was not really practical to try to get both hot air and cold air on different strokes of the same cylinder. It was theoretically possible, but a big hassle to do it in real life. However, he did arrange his valves so that he could get either hot or cold air from the prototype cylinder by adjusting a few valves. Once he was satisfied with his machine, he held a public demonstration.

By this time, the whole town knew what he was trying to do, but most people thought that he didn't stand a chance of making it work. His family and a few close friends had sufficient faith in Doug to believe in his efforts, and were very happy when he said that he was ready to justify that faith. The first thing Doug demonstrated was puffs of very hot air coming from his cylinder. So what? Anything that would burn would produce more heat than that. It was an amusing toy, but what good was it?

Doug got a lot more surprise and interest when, with the adjustment of a few valves, cold air shot from the machine. Now, that was impressive! Up until then, they were convinced that only the Spirit of Winter could produce such cold air. It surely was as cold as the wind blowing off the big ice sheet miles to the north. This produced a lot of quiet talk resembling, "See, I always said that Doug was a benign spirit in disguise!" coming even from his worst critics.

The test was so successful that, when Doug talked of heating their homes in winter with the warm air produced by the "heat pump," he had a number of people who wanted him to build them one right away. Doug had to point out that the situation was more complicated than that. There simply was not enough room up on the plateau over their heads to put in individual windmills for each home. What they needed was a way to power several compressors from one windmill. Fortunately, Doug had a plan to cover that, but it would require the labor of the entire community. Anybody who did not work on the project did not get a compressor, it was a simple as that!

Everybody clamored to sign up, so he apparently had sold his idea, but there was a lot of work ahead before the job was completed. Doug and Little Bear had worked out the job assignments beforehand, certain that the project would go through. It was already late in the year, so food requirements had to come first, but the schedule was set up so that the big project could be worked on during the winter. If everything worked out right, every home would have its heat pump ready before spring.