476 Molesworth’s pocket-book
Boilers. B<mbd of Trade and Lloyd’s Rules—continued.
The factor of safety F — 5 under the following conditions :
(1) Best materials; (2) Rivet-holes drilled in place; (3) All
joints butt, with double straps; (4) All seams double riveted
with an allowance of not more than 75 per cent, over single
shear ; (5) Full inspection during construction.
When these conditions are not observed, F will be increased
as follows:—
Additions to Factor of Safety for After 1 bend- 1 tag. Before bend- ing. Riveting.
Single. Double. Treble.
s /'Drilling out of place •15 •3
Punching ,, Holes not good or fair — •3 •5 ——
•75 —- .»■« 1 ■ —— —
Lap joints — 1-0 ■2 •1
Ö Butt „ single strap —. —- —— 1-0 •3 •15
„ „ double „ Drilling out of place — — — 1-0
— •1 •15 —— —-
<Z> Punching „ Holes not fair or good —- •15 •2
•2 — — —. - —
Lap joints — — —- •2 •1 .
co Butt „ single strap —— 1 •2 •1
p „ „ double „ Strakes not quite under and over.. ., .. - i •1
0 •25 —
Long boilers or flues .. •3 — —
Seams improperly crossed •4 — — — — ——
Doubtful material .. .. •4 —
Not inspected during con- struction 1-65 — — — —* ■
Rules for Rivets in Ship-building.
d = diameter of rivet.
Minimum distance of rivet from edge of plate, &c. = d
Maximum pitch of rivets........................= 4 d
Minimum „ ..........................— 3 d
Minimum overlap single riveting............... 3; d
„ „ double „ ................ 5i d
Pitch of rivets in outer row of treble riveting.. .. = 8 d