Slide Charts and Specialized Calculators

The majority of slide rules most of us know about were general purpose calculators, some with a few more scales than others, but generally speaking, all interchangeable. Of course slide rules sometimes were designed to handle specific specialty calculations; these are much prized by collectors today.

Special purpose calculators are very often found instead in the form of slide charts, and come in a huge, and colourful variety. Slide charts are almost always designed with ease of use in mind, yet can perform some very complicated math. They are the ephemera of the slide rule family: made inexpensively from materials that often are quite perishable, and filling a computational need that generic slide rules don't easily support.

Depending on the application, specialty computation slide rules could be moderately or very expensive. Largely, they were inexpensively made, usually of cardboard or may plastic. They might be given away by a manufacturer, or sold for a nominal price.

Their low cost and simple construction has made them useful for industrial applications, where the environment might be too harsh for more delicate instruments, such as your costly engineering slide rule or electronic calculators.

Slide charts tend to be designed to simplify computation; the user needs no arcane math skills operate them, and needs only one or two steps to obtain an answer. Some special purpose slide rules are built that way, others might need a separate manual.

Slide charts are generally made for purpose on behalf of manufacturers, and are very much marketing vehicles. They typically support computations that involve whatever products the manufacture sells, and often incorporate information about about the manufacturer's product lines .

Slide charts don't necessarily do computation. Many are designed to present data in an accessible manner. Those seemed to be normally called datacharts.

In this section I have both slide charts and slide rules, to compare and contrast. I have to say, I very much like these devices.

Barber Green made made road paving equipment. As if by coincidence, they supplied a calculator that supports the road paving industry. Instructions on the face make the inputs and outputs very easy to find.

It appears that the front face (top photo) calculates the rate at which the paving equipment must drop its load (in tons/hr), and the other side calculates material volumes required for different layers of the road surface.

Again, it's a calculator made by the company to compute important numbers for the tasks it's product supports.

Despite my use of the term 'ephemera' earlier, this calculator, as many other slide charts, is pretty rugged; it could stand up to a harsh work environments.

The two calculators above are wood closed framed calculators...built in the shape of traditional slide rules.

I haven't been able to find any current information on Catsman Coal Co., though they show up on some historical documents via Google. The longer slide rule for"Master builders" appears to be from a company still in business; Master Builders Solutions BASF ; "Pozzolith", is their registered trademark.

The calculators look like they lost their cursors, but in fact, a cursor is unneeded.

The calculators achieve a single move computation by having an inverted B scale. 'Width' on the inverted scale is placed under 'Depth' on the A scale, then Volume is read off D, by finding it below 'Length' on the C scale.

Atlas Steels was a Canadian steel manufacturer. At the time this slide chart was designed, they were owned by Rio Algom Mines. The slide chart was made by Perrygraf, copyright 1963.

This calculator was designed to calculate the weight of steel given dimensions and configurations. It has scales for shapes presumably were delivered by Atlas: bar stock, angles, circles, rings, etc. The makers of this slide chart were able to fit a small slide rule scale (bottom of top picture) to accommodate multiplication/division.

As is common for slide charts, this tool provided by a manufacturer of a product assist customers in a common calculation needed for the product.

Among other things, the Warner and Swasey company made rather large turret lathes, whose workings I suspect this calculator was designed to aid. The calculator is copyrighted at 1962.

The calculator calculates the time needed to cut different amounts of metal.

The math for that should be applicable to any lathe. However, the calculator was also supplied with 2 data sheets that had information about the speeds and gear settings for Warner and Swasey equipment. Possibly this calculator was included with purchase of equipment, as a quick job aid for the operator.

The back side of one of the slides has a series of drawings of Warner and Swasey lathes, to keep their customers pining for the next model up.

Cleaver-Brooks is still operating today, in the same industry too.

The device will calculate the cost to produce steam given fuel price and efficiency and thermal output. There's a handy pointer showing Cleaver-Brook products would deliver a whopping 80%.

It's interesting to see the costs that pertained back in the day: Oil prices in the range of 2-10 cents per gallon and $3-$10/ton for coal.

This calculator, unlike most the branded calculators on this page, is really a sales tool. You are expected to be enticed to buy a steam generator from this company after you learn just how much you are about to save.

Here is a good example of a slide chart that ISN'T solving a math problem. The Ampex stereo graph would instead be classified as a data chart. It's purpose is to provide guidance on how to set the controls for your particular application.

I have it is set to 'record stereo from external sources' at the top and setting your knobs and switches are displayed, and keyed to the picture on the right so you know which knob is what. The reverse has some supplementary information, largely helping you figure out how much playing time you get for a reel of a certain size.

This handy data chart above offers conversions between imperial and metric units in play at the time. The item above was a data converter, rather than a calculator, so you if needed to convert some value not on the menu, you were on your own. Canada went metric in the mid 70's, and this one looks like it was manufactured towards the end of the metrication program. I expect it probably saw use as a cheat sheet, during and after the program went live.

The converter has the brand "PrecisionCraft", still operating today.

Below is a slide rule version of a metric converter, made by Sterling.

This one looks like it's built on a Sterling Precision frame. The slide rule has 2 log cycles so you won't go off-scale doing a conversion. Conversion factors are grouped on the faces of the slide: volume and weight are on one face (top photo), distance and area on the other (lower photo). The arrows provide gauge marks on both sides of each conversion. Because it is based on logarithmic scales, you can perform both computation and conversions with it. One apparent difference from other items on this page is that it's from a slide rule maker and has no particular manufacturer's branding.

SHURE (and OHMITE) were very well known maker of slide chart calculators for electronics. Hobbyists would probably have a few of them in their work rooms.

They remain much loved by collectors, particularly those with a background in electronics engineering. This slide chart computes resonant frequency of a tuned circuit, given known values of the relevant components, and on the reverse side, calculates reactance of components given frequency, all quantities used in electronics design.

Shure is famous for its iconic microphones, used for recording studios and broadcasting. I believe they also made phono cartridges. The company is still in business.