There are a few problems with the title of this thread. Firstly, the Johnson-Hamilton
Gyroplane was not a "VTOL" design. Jesse C. Johnson never made such a claim. In his patent application, Johnson said that his key goal was to use "a pair of lifting propellers or helicopters ... to create a partial vacuum above the wings ..., and thus increase the lifting effect and aid in the rise of the plane." In other words, Johnson intended to use 'helicopters' (his term for lifting propellers) to create a STOL aircraft.
The second issue is with the name '
Maiden Milwaukee' - assigned to James S. McDonnell's original 1927 H-18 design - (N)C235 - intended to demonstrate Hamilton's steel propeller and all-metal construction (and to participate in Ford's 1927 National Reliability Air Tour). It is accurate to say that this original CTOL aircraft was "designed by Hamilton Metalplane Company". But the 'helicopter' modifications were entirely the design of Jesse C. Johnson.
Mod: Perhaps this thread should be retitled 'Hamilton Metalplane Projects' or some such?
BTW: There is footage of the Johnson-Hamilton
Gyroplane - aka the 'Johnson Helicopter Aeroplane' - on the Moving Image Research Collections at the University of South Carolina's website. This 7 minute video from a Fox Movietone newsreel shows the aircraft taxiing, taking-off, and landing on 09 Nov 1929.
Johnson helicopter monoplane--outtakes
Fox Movietone News Story 4-191
Temporal Coverage
Filmed on November 9, 1929
mirc.sc.edu
Although the Johnson-Hamilton
Gyroplane was a built conversion, there
was an unbuilt project aspect as well. Johnson's patent is mainly about his conceived drive mechanism for the lifting propellers within the structure of the wings. However, he also discussed a future scheme to add propulsion to his design "so that the propellers may be adjusted with respect to the wings and used either as lifting or traction propellers, means being provided whereby the propellers maybe rotatably adjusted about the centers of their driving shafts and thus resist a tendency of the shafts to become disaligned." So, our STOL conversion was built but Johnson also envisioned a future 'convertiplane'.
... And since there appears to be only a single engine, it would likely power either those or the front one. Then, assuming that by some magic that thing would actually leave the ground vertically, the transition should be interesting...
The idea of a single engine seems to have originated with
Aerofiles who said "In the helicoplane mode, power to the tractor propeller was halved and the lateral screws started." [2] Other sources state that a second, 150 hp engine (type unspecified) was installed in the former cabin area of the fuselage. In the newsreel video you can clearly see the oil cooler for that second engine protruding between the spars above the central fuselage.
Patented extension shafts drove those underwing propellers at 500 rpm. As mentioned, Johnson intended a future convertiplane type where, once off the ground, those lift propellers would rotate to the vertical to provide propulsive thrust. It is reasonable to assume that Johnson intended his future convertiplane to be single-engined. He did hold a patent for a "Toy helicopter aeroplane" - US1793368A - which showed a centrally-mounted engine driving the same three-prop layout as the full-sized Johnson-Hamilton
Gyroplane. I presume that the nose propeller would provide the propulsive thrust during take-off while the erstwhile horizontally-positioned underwing props were providing the added lift.
Johnson's convertiplane concept seems related to his earlier aircraft patent - US1485269A of 1924 - which involved multiple, transverse-shaft-driven propellers to maintain airflow over wings. Johnson describes these outward-mounted props as "revoluble traction helicopters". For take-off and landing, changing the angle of these 'helicopters' would maintain airflow over the wings regardless of angle of attack.
Anyway, the built Johnson-Hamilton
Gyroplane conversion was test flown at Milwaukee by Victor Allison who took off "almost vertically after a run of 35 feet at a speed of 30 miles an hour" according to a note in the 16 Nov 1929 Joplin
Globe newspaper. A Mr. A. S. Eliott was also involved (as a mechanic, perhaps? A photo of Eliott with Johnson appeared in the 20 Sept 1929 edition of the Sherbrooke
Daily Record).
Although not considered completely successful, the Johnson-Hamilton
Gyroplane held the USAAC's attention for several years. The Air Corps' Materiel Division expressed some interest in the "Johnson Helicopter Aeroplane" as late at June 1936 - placing it among the "proven inventions of definite military value". [2]
Some sources:
--
https://patents.google.com/patent/US1713874
--
https://patents.google.com/patent/US1793368A/en
--
https://sites.google.com/site/stingrayslistofrotorcraft/hamilton-metalplane-maiden-milwaukee
-- http://members.eaavintage.org%2Fwp-content%2Fuploads%2F2013%2F02%2FVA-Vol-4-No-5-May-1976.pdf
-- The EAA's
The Vintage Airplane, Vol 4, No. 5, May 1976,
The Hamilton Metalplane, George Hardie Jr., pp 3-8
_____________________
[1] Another error in the
Aerofiles listing for the H-18 include an obviously wrong 9 feet for underwing propeller diameter. (
Modern Mechanix of November 1929 listed 18 feet diameter, on page 233 of the February 1930
Popular Mechanics it says 22 feet. The former is generally accepted as accurate.)
[2] This from a letter from FT Martin, Materiel Division, to Materiel Liaison Section, OCAC,12 June 1936, quoted in
Army Air Corps Airplanes and Observation 1935-1941, Howard K. Butler, Historical Office, United States Army Aviation Systems Command, Saint Louis, Missouri, February 1990, pg.147.