It is a rigid frame made with chromoly tubing... was told that the straight gauge carbon steel version that was made to test was not strong enough to support the design and it did have it's wheel pressed into the fender after it failed.

The builder weighs 275 pounds so is also an excellent bike tester... his personal Cygnet is a number of years old and he rides it on the road with an 8 speed drive.

Makes me wonder how robust the original Cygnet was as materials technology was not as advanced and would suspect the original must have been made of nearly solid tubes.