What is the name of this particular mechanical linear position switch made of perforated spring strip?

Engineering Asked by Conrado on August 12, 2020

I’m writing a few elementary paragraphs about switches and switch technology, and I cannot for the life of me remember what a particular kind is called, to give it an honorable mention.

Here is a sketch of the switch in question:

roller/strip switch

It is constructed of at least one roller, past which a strip of spring is pulled or pushed. The spring has cut-outs of various shapes, which can be regular or irregular, making the spring strip "prefer" some positions over others, requiring a certain force to overcome them. Various combinations of perforations and rollers could be used to create very complex "preference" patterns. You can see the usefulness: you can put the switch in any one of it’s "stop points" and it just stays there until you move it away; and it gives wonderful oportunity (from a design standpoint) for what is now called "haptic feedback".

I learned about them in grade school, studying simple and complex machines, but now I can’t remember any sort of name for them. I’ve combed the LEXICON encyclopedia, where I seem to remember having seen the thing in the first place, and all the switches I come up with are electrical switches. In Google, ditto, along with a great number of maddening diagrams of gamers mechanical keyboard switches and their various merits.

I’m not a well-formed engineer, so I beg you have patience if this isn’t the right place to ask; or tell me what other information I should give and I will try.

I’m looking generally for example uses, but I’ll be quite happy if someone kindly just gives the name, as I will probably be able to do the rest of footwork myself. Cheers!

EDIT1: 27-JUL-2020:
Kevin gave the right name, and now I see that my recollection went astray: the rollers actually roll on each other with only the band between them, and they have (in many cases, at least) mobile axes, constrained by the rigidity of the band.

2 Answers

The name Rolamite was given to the concept of a flexible metal strip wrapped around rollers, to form a linear bearing. Not pictured in your image, there would be an outer casing which fixes the ends of the strip and prevents the rollers from moving perpendicularly to the length of the strip. And, if one or more of the rollers are to be attached to anything externally, an axle for it with rotating bearing, unless you want your connection to both rotate and translate! (Though apparently several applications where that was desirable or incidental were suggested in this archive of articles on the subject which Conrado found, such as a pendulum's bearing or a curve generator.)

Your description adds the concept of gaps in the strip to make it exert a position-dependent force.

I heard (but do not have a source handy for) that the reason the Rolamite did not find broad applicability is that its lifetime was limited by fatigue of the strip as it is repeatedly flexed in two directions.

Correct answer by Kevin Reid on August 12, 2020

Kevin Reid answered the question, and I've accepted it-thanks, Kevin! This answer is to post a copy of relevant parts of the original article that had become rather blurry in my memory. I'll probably post other related info as I dig it up in order to catch the best selection of search keywords possible in case anyone else ever looks for sliding mechanical switches on Eng.SE. It's from the Lexicon Universal Enciclopedia. The figure is especially pertinent because this is what I was trying to depict in the sketch that I posted in my question, only my memory omitted some important details. Just looking at the strip with a series of round perforations, I can almost feel the smooth "sinusoidally varying resistance"!:


rolamite ... It was developed in 1966 Donald Wilkes as a result of his search for a reliable miniature mechanical switch. The switch that Wilkes designed was one-eighth the size of the previous switch and had about half the number of parts.
In its simplest form the rolamite consists of a rectangular frame, two rollers, and a flexible band. The rollers are suspended within the 5-shaped loops of the metallic band When the band is tightened the rollers are in pure rolling contact with the band and there is no slippage. This configuration allows the rollers to roll within the guide rails with as low as one-tenth the friction of the best ball and roller bearings in a similar application. In this rudimentary form the rolamite functions as an almost frictionless suspension system for the rollers By using bands with varying widths or cutouts, the rollers can be made to seek preferred positions between the guide rails. This effect is caused by the tendency of each band loop to straighten itself out as long as the band width is constant, the straightening forces are equal and the rollers move freely If the bandwidth on the rollers are different, the roller with the wider band will dominate, the band will try to unwind and a driving force proportional to the difference in band widths will be created. By varying the shapes of the cutouts and the diameters of the rollers, rotates, with a wide variety of springlike characteristics can be obtained. ...


  • Bad things happen when the ribbon breaks. It overcomes a problem seldom seen. Bad things happen when the ribbon stretches. Compound bearings are well understood and available. Did I mention bad things happen with that ribbon? Imagine what would happen if somebody put a penny or FOD of any kind on the ribbon, frinstance. Probably why D9 Cats use segmented tracks instead of ribbon.
    -- A thread at

  • It looks like a lot of hype--almost like perpetual motion, with real believers writing stuff like: "virtually zero friction". I've never seen an application where the thing was actually in use, and the only one that is claimed to exist is in a ground-penetrating nuclear bomb, rather conveniently out of my reach, unfortunately.

Answered by Conrado on August 12, 2020

Add your own answers!

Ask a Question

Get help from others!

© 2024 All rights reserved. Sites we Love: PCI Database, UKBizDB, Menu Kuliner, Sharing RPP