NASA-Threads
Work and Mechanics
Lesson 52: Truss Design
Truss Member Materials and Dimensions
Watch truss fabrication movie, review the truss dimensions below, and provide truss
building materials to teams.
compressive members
tensile members
Specimen Dimensions:
 member length = distance between holes
 member width = ½ inch
 cut strips 1 inch longer than “member length”
 punch 7⁄32 inch diameter holes ½ inch from
ends
 glue stiffeners to sides of member; cut
stiffeners about 2 inches shorter than the
“member length”
Paper Mat Board Provided to Each Team:
 mat board strips pre-cut to ½ inch wide
 length provided should be about 6 times the
span
Specimen Dimensions:
 member length = distance between holes
 cut strips 1 inch longer than “member length”
 member width = ½ inch at ends
 member width narrows to ¼ inch at center
 make narrow region at least 1 inch long
 glue 1 inch mat board pieces to each end
 punch 7⁄32 inch diameter holes ½ inch from
ends
File Folder Material Provided to Each Team:
 one file folder uncut OR precut strips ½ inch
wide
 if precut strips are provided, then provide each
team with a length about 5 times the span
Aluminum Screw Posts Provided to Each Team:
 a total of 12 screw posts, with the option of
getting more as needed
 2 screw posts 1/8 inch long
 5 screw posts 3/16 inch long
 5 screw posts ¼ inch long
Tools Supplied by Students:
 scissors
 flat head screw driver
 ruler
Tools Supplied by Instructor:
 hot glue gun (low temp) with glue sticks
 7/32 inch heavy-duty hole punch
 Paper cutter (if folder strips are not pre-cut)
NASA-Threads
Work and Mechanics
Lesson 52: Truss Design
Design Tips
You choose your favorite truss design and think about the number of members that you
would like to use. A truss with more members is harder to build, but it looks really cool!
1. Howe truss with 21
members
2. Howe truss with 13 members and 45 degree angles
3. Howe truss with 13 members and low angles
4. Howe truss with 13 members and high angles
5. Center member removed; truss with 12 members and
high angles
6. Simplest possible truss with 3 members (this is a
Kingpost truss with the vertical center member missing)
Zero Force Members: The center vertical members in trusses 1 through 4 above are zeroforce members. That is, they theoretically carry zero load. They are included to make the
truss more stable. Since you don’t have to worry about stability very much (due to the
transparent side plates on the truss testing apparatus), zero force members may not
increase the strength of your truss very much. Your truss analysis will tell you whether or
not a member is a two force member, but a general rule is provided below.
Spotting Two Force Members: When three members intersect at a joint and two of the members
are co-linear (they are in line with one another), then the third member is a zero-force member if
no external load or reaction is applied at the joint.
Design Work
Spend the rest of class working on your design (you may start on fabrication if you are
ready).