My first attempt at building a tower crane from K'NEX.

Specifications:
Height from floor to mast: 200cm/79 inches; if not for ceiling height limitations, it would have been 215cm/83 inches tall
Jib span: 160cm/63 inches
Total span: 240cm/94.5 inches
Base diameter: 46cm/18 inches
Maximum load: approx. 1 lb (yes, it sucks; K'NEX was not designed to handle large loads without an excessive amount of pieces to support its own structure)
Counterweight: 111 red rods, 62 yellow connectors, 36 red connectors
Time used to build: Less than 3 hours

Words of caution:
-Make sure you are in a very large and/or empty room when building this.
-You may exhaust your red rod collection; be sure to have a lot of them.
-This is an ad-hoc model; it may or may not undergo further modification (such as adding string, trolley, motor, etc.).

References:
- knex crane https://www.instructables.com/id/knex-crane/
- The LEGO inspiration: http://www.philohome.com/towercrane/tc.htm
- HowStuffWorks: http://science.howstuffworks.com/tower-crane.htm

Step 1: Base

Very simple lattice of grey and red rods with purple connectors. Red rods have been substituted by their metallic-coloured counterparts.

The crane base is fortified with purple and yellow connectors with green rods.

Step 2: Center and Counterweight

The counterweight will require many many red rods and connectors.

Step 3: Crane Jib

Caution: this part, containing purple connectors for its connections, is very weak and susceptible to collapse if left standing on its own without the counterweight.

The length of the jib is 7 grey rod + 7 sets of purple connectors ( +1 yellow rod for the bottom of the jib)

Step 4: Connect Them All

Now be careful and connect the jib to the crane + counterweight, and then connect that assembly to the top of the tower via that bottom white connector below the large gear.

All that this crane is missing are cables for lifting and a trolley. I may or may not implement these at a later time.