You might want to look at this document dated Aug 1956:
https://www.sto.nato.int/publication...AGARD-R-80.pdf
US Army testing Tandem-wheeled gears on Piper L-19
Direct quote:
"The Whitaker tandem 4-wheel landing gear was designed for use on the L-19 airplane to facilitate its operation on rough fields and to provide increased flotation when operating on soft surfaces. Two standard L-19 airplane wheels are tandem mounted on a yoke on auxiliary axles - one ahead and one behind the main axle. The yoke is supported by the main axle which is bolted directly to the lower end of the spring landing-gear strut. The yoke and wheels are permitted to oscillate about the main axle to reduce the ground shock transmitted to the air frame. A hydraulic brake is provided for each wheel of the gear assembly.
The tandem-wheeled gear has been procured and tested in limited quantities for use in the Army aviation program and has met with some degree of success. The gear permitted landings and take-offs over 12-inch furrows in a plowed field. It was also determined that, in soft snow, operational abilities of the aircraft were greatly enhanced by use of the gear: take-offs were made in 12 inches of snow, landings were made in 18 inches, and taxiing was accomplished through 24-inch drifts. In addition, the gear permitted more effective operations in mud, soft sand, and rough fields. It was also determined that the use of this gear prevented breakthrough of river ice not capable of supporting an aircraft equipped with the conventional gear. This gear is now stocked by the Army for special-purpose missions."
Plenty of pictures on pages 19 - 23 (27-30 on the pdf), including a very good picture of the tandem landing gear kit on page 21 (29 on pdf).