ROLAMITE

Rolamite letter scale

This is an exclusive letter scale. Instead of linkages and sliding pivots in bearings, a rolling construction is applied. Rolling friction results in far less losses compared to sliding friction. In de period 1966-1975 an extensive variety of applications was invented for mechanisms with rolls and thin foil bands. Donald F. Wilkes is the person named most frequently with these "Roller-band devices" later better known under the name Rolamite. He patented it June 1969, with patent number 3,452,175. He was an engineer at Sandia National Laboratory in Albuquerque, New Mexico, USA. The design of the postal scale is made by Carleton W. Sprague. The patent was granted in 1971 in America with the number 3,621,928.  This US-patent number is moulded  into

back of the scale

the box shows a different geometry

click to start animation of scale, the curve wheel is also easy to view

advertising texts on the side of the box

the side of this letter scale. At the bottom is still present the text: "patent applied for", there is also a sticker with the indication: model US70. According to an extensive article of C. Lushbough in Equilibrium, number 3, 2000, pp 2477/2478 and 2499-2504, this scale was already produced by Rolamite Inc. during the years 1969 and 1970. Later this firm merged into another and the rights of the patent went to Data-Link Corp. This firm made the scales from 1972 until 1977. The postal rates at the sticker date from the period March 1974 till the end of December 1975. The really made scale presented here, differs substantially from the patent. According to the referenced article one, two or three prototypes with the counterweight instead of the tension spring exist. Probably to maintain the parts always in their proper positions, the counterweight was replaced by a tension spring. The spring is attached to a chain. To get a suitable characteristic the chain runs onto a curve wheel. The claim that this scale operates friction free, is nonsense with the spring, chain and curve wheel. Based on the rolling contacts between the cylindrical parts, it's fair to state this is a friction poor design. At several zones the thin foil band is laid superfluously double. The range is 16 ounces or 1 Lb. The chart is subdivided into half ounces. Below some more photos of this letter scale.

the figure of the patent shows the design with the counterweight

exploded view of the scale down left the geometry of the foil band

two positions of the transparent cover	apart designed chart	postal rates label
with and without the transparent cover	chain on the curve wheel	no new postal rates label is a dollar saved
the US patent number 3,621,928 of 1971	the adjusting knob to tune the scale	at the text label: 1 dollar to get a new postal rates label