A. To crushing strains and to those of unequal contraction and expansion.
20. Q. How are the sheets of a fire-box supported?
A. They are supported by staybolts screwed through the inside and outside sheets with their ends riveted over.
21. Q. In what manner is a crown sheet supported?
A. By crown bars or radial staybolts.
22. Q. What are the bad features about crown bars?
A. They are hard to keep clean and frequently cause crown sheets to become mud burned.
23. Q. What are the advantages of radial stayed crown sheets?
A. They are easier to keep clean and cheaper to repair.
24. Q. How are the inside and outside sheets of a fire-box secured at the bottom?