Week 9 Lab Data: Bronze Age Saws

Introduction

This data report is jointly written by Claire Saunders and Caleb Valentino, and pertains to the horizontal saw.

Saw Design

The original saw design featured a vertical pendulum beam which would be pulled back and forth via rope. The horizontal arm had the blade on one end, and on the other a wooden brace which fit around the vertical beam such that as the vertical beam moved back and forth, it pushed the horizontal arm back and forth.

After only 5 back-and-forth swings (8 seconds), the wooden brace connecting the horizontal pendulum arm to the vertical part broke, so we adapted by instead tying the rope to the horizontal arm itself, and pulling the arm back and forth with the rope from both sides. This meant we lost the actual gravitational advantage of the pendulum design, so it was less effective and harder to use than it probably otherwise would be.

Process Data

We sawed the stone for 3951 seconds (01:05:51), for a total of 1,785 back-and-forth swings of the pendulum saw. That averages out to about 2.2 back-and-forth swings per second, but that rate varied depending on who was pulling the rope. Emery and water was added periodically (roughly every 40-60 back-and-forth swings, or 90-130 seconds), sometimes by mixing together a paste (about a 3:1 emery to water ratio, sort of a wet-sand texture) and then applying it to the stone, and sometimes by pouring water over the stone and flicking on dry emery.

At first, we tried to cut the stone without chiseling a guide line, but we were struggling to get any sort of cut started, so after 74 swings (140 seconds) we stopped and chiseled a line.

After around 317 swings (611 seconds), we began to see a visible cut mark, as well as a grayish slurry.

We needed to move the saw forward into the cut(s) roughly every 120 back-and-forth swings (260 seconds). The blade got loose and needed to be tightened first after 354 swings, then again after another 460, at which point we replaced the screws with bolts. After which the blade continued to be loose, but we continued sawing anyway.

Final Cut Data

Due to some issues with our saw moving up and down while cutting, we made two cuts in the stone, Cut A (upper) and Cut B (lower). Both measured 1cm in width, and we measured the depth of each cut at 0.5cm increments along the cut.

The cut-side surface of the stone was not flat, so we used a yardstick to measure depth from a flat position and then subtracted the width of the yardstick.

Cut A (upper)

Distance from end (cm)	Cut Depth (mm)
0	-1.02
0.5	-0.72
1	-1.46
1.5	-2.44
2	-2.88
2.5	-3.06
3	-3.6
3.5	-3.84
4	-5.23
4.5	-4.86
5	-5.05
5.5	-5.48
6	-5.36
6.5	-5.96
7	-6.68
7.5	-7.39
8	-6.25
8.5	-6.49
9	-7
9.5	-7.98
10	-8.65
10.5	-8.94
11	-9.14
11.5	-9.35
12	-9.34
12.5	-9.66
13	-9.9
13.5	-10.28
14	-10.27
14.5	-10.38
15	-10.78
15.5	-10.96
16	-10.77
16.5	-10.71
17	-11.45
17.5	-11.62
18	-11.28
18.5	-10.95
19	-11.04
19.5	-10.69
20	-10.62
20.5	-10.6
21	-10.62
21.5	-10.61
22	-10.11
22.5	-9.99
23	-9.73
23.5	-9.67
24	-9.57
24.5	-9.57
25	-8.43
25.5	-8.37
26	-7.97
26.5	-7.86
27	-6.74
27.5	-6.13
28	-6.13
28.5	-5.91
29	-5.31
29.5	-4.74
30	-4.15
30.5	-4.14
31	-3.62
31.5	-2.69
32	-1.78
32.5	-1.34
33	-1.22
33.5	-2.32

Cut B (lower)

Distance from end (cm)	Cut depth (mm)
0	-2.8
0.5	-2.8
1	-2.9
1.5	-3.39
2	-4.05
2.5	-4.47
3	-4.92
3.5	-5.2
4	-5.74
4.5	-5.93
5	-6.55
5.5	-7.02
6	-7.24
6.5	-7.91
7	-8.21
7.5	-8.41
8	-8.77
8.5	-9
9	-9.57
9.5	-10.15
10	-10.23
10.5	-10.23
11	-10.58
11.5	-11
12	-11
12.5	-11.39
13	-11.46
13.5	-11.51
14	-11.61
14.5	-11.61
15	-11.31
15.5	-11.33
16	-11.54
16.5	-11.65
17	-11.31
17.5	-11.67
18	-11.22
18.5	-11.15
19	-10.38
19.5	-9.83
20	-9.53
20.5	-9.23
21	-9.19
21.5	-9.17
22	-9.18
22.5	-10
23	-10.34
23.5	-10.6
24	-9.66
24.5	-9.17
25	-7.68
25.5	-6.22
26	-5.25
26.5	-4.78
27	-4.19
27.5	-3.77
28	-3.34
28.5	-2.99
29	-2.62
29.5	-2.2
30	-2.28
30.5	-2.28

Additional Notes

After sawing, the blade edge had been worn down to have a curve.