Accession No

2307

Brief Description

slide rule for calculating dimensions in wooden roof-trusses, by Holtzapffel and Company, English, 1885 (c)

Origin

England; London; 64 Charing Cross

Maker

Holtzapffel and Company

Class

calculating

Earliest Date

1885

Latest Date

1885

Inscription Date

Material

wood (boxwood); metal; ivory

Dimensions

length 241mm; breadth 58mm; thickness 8mm

Special Collection

Provenance

Purchased from L and M Heffer Antiques, King Street, Cambridge, England, 5/5/1977.

Inscription

‘GANGARAMS PATENT SCALES FOR SCANTLINGS OF TIMBER IN
FLAT ROOFS
HOLTZAPFFEL & CO 64 CHARING CROSS’ (obverse of slide)
‘GANGARAMS PATENT SCALES FOR STRAINS ON TRUSSES’ (on obverse of stock)

Description Notes

Boxwood slide rule, ends bound with metal alloy. Obverse stock carries, on upper part, scale of slope divided 6:1 - 1:1 numbered 6:1, 5:1, 4:1, 3:1, 24˚, 2:1, 28˚, 7:4, 30˚, 3:2, 35˚, 4:3, 5:4, 1:1 Also scale of ‘principal rafter span in feet’ divided 14 - 70 numbered 14, 16, 18, 20, 25, 30, 35, 40, 50 , 60, 70; 14- 20 subdivided to 0.25, 20 - 40 subdivided to 0.5, 40 - 70 subdivided to 1. Also table giving correlation between angle of slope and ratio of half-span to rise.

Lower part of stock scale of slope divided 6:1 - 1:4 numbered 6:1, 5:1, 4:1, 3:1, 24˚, 7:4, 30˚, 3:2, 35˚, 4:3, 5:4, 1:1, 4:5, 3:4, 2:3, 1:2, 1:3, 1:4. Also scale of ‘span in feet tie beam’ divided as scale for the principal rafter span.

On slide scale of ‘coefficient of transverse strength’ divided 1200 - 100 numbered 1200, 1000, 800, 700 ... 200, 150, 100; 1200 - 800 subdivided to 50; 800 - 400 subdivided to 20, 400 - 200 subdivided to 10, 200 - 100 subdivided to 5.
Scale of ‘ coefficient of deflectional elasticity’ divided 8000 - 500 numbered 8000, 7000 ... 3000, 2500, 2000, 1500, 1000, 500; 8000 - 4000 subdivided to 200, 4000 - 2000 subdivided to 100, 2000 - 800 subdivided to 50, 800 - 500 subdivided to 20.
2 scale of ‘depth in inches’ divided 2 - 25 numbered 2, 3 ... 10, 12, 14, 16, 18, 20, 25 subdivided to 0.25

Reverse, upper part of stock:
scale of ratios of breadth to depth divided 1:5 - 1:1 numbered 1:5, 2:9, 1:4, 2:7, 1:3, 2:5, 1:2, 5:9, 5:8, 2:3, 1:√2, 3:4, 1:1
scale of ‘span in feet’ divided 2 - 20 numbered 2, 3 ... 10, 12, 15, 20 subdivided to 0.25.
strength formula given as W=(2bd2)/(SxL)P

On lower part of stock scale of different ratios as before and scale of ‘span in feet’ as before. Also stiffness formula given as d=(5WL3)/(8Ebd3)

Secondary ivory slides set into each part of stock with scales marked ‘load in lbs per rgft=wft per sup:ft x spacing’
Upper one divided 1500 - 30 numbered 1500, 1000, 800, 600, 500, 400, 300, 200, 150, 100, 80, 60, 50, 40, 30; 1500 - 800 subdivided to 50, 800 - 400 subdivided to 20, 400 - 200 subdivided to 10, 200 - 80 subdivided to 5, 80 - 40 subdivided to 2, 40 - 30 subdivided to 1.
Lower scale divided 1500 - 20 numbered 1500, 1000, 800, 600, 400, 300, 200, 100, 80, 60, 50, 40, 30, 20; 1500 - 800 subdivided to 50, 800 - 400 subdivided to 20, 400 - 200 subdivided to 10, 200 - 80 subdivided to 5, 80 - 40 subdivided to 2, 40 - 20 subdivided to 1.

Slide has 2 scales of ‘strain in lbs’ divided 1000 - 50000 numbered 1000, 2000 ... 6000, 8000, 10000, 15000 ... 40000, 50000; 1000 - 2000 subdivided to 20, 2000 - 4000 subdivided to 50, 4000 - 10000 subdivided to 100, 10000 - 20000 subdivided to 200, 20000 - 40000 subdivided to 500, 40000 - 50000 subdivided to 1000.
2 scales of ‘load in lbs’, one divided 100 - 5000 numbered 100, 150 ... 400, 500 ... 1000, 1500, 2000 ... 5000, the other divided 200 - 10000 numbered 200, 300 ... 800, 1000 ... 2000, 3000 ... 10000. All these scales for calculating quantities for ‘king-post trusses’.

One edge carries scale of inches divided [0] - 8 numbered by 1 subdivided to 1/8. Other edge carries diagrams showing different possible positions of trusses.

Condition fair; complete

References

Events