Manuscripts/Mixed Material Notes by Alexander Graham Bell, February 21, 1902
The wooden strips mentioned in yesterday's notes, pp. 579 to 581 were made originally under instructions to make them ⅛th in. square, but they turned out to be 5mm. square. It is obvious, therefore, that they were not carefully or acurately made. They probably vary slightly in their dimensions and a very slight variation of thickness will make a considerable difference in the stiffness or resistance to bending. I do not therefore consider the table on p. 580, illustrated graphically on p. 581, as reliable in all its details.
I had some wooden strips made at Ballauf's, very carefully, and I think they can be relied upon as being accurately made according to instructions. One set consist of sticks 28cm. long, 5mm. wide, and 2mm. thick In the other set the sticks have the same length and width, but are 3mm. thick. I tested the stiffness of these sticks last night when loaded in the middle.
STRIPS 2MM THICK.
Dimensions of strip in mm. 280 × 5 × 2. Weight supported by strip without touching table in grammes, as follows: — 60 not 70 gms. 70 not 80 “ 80 not 90 “ 90 not 100 “
60 not 70 gms.
70 not 80 “
80 not 90 “
90 not 100 “