Dalton Dead Reckoning Computer Model G

Astronomy

Accession Number: 2019.ast.175

Description:

This is a metal instrument shaped like a rectangular box. On the top, it has a flat metal plate that is affixed to the box below by a hinge along one edge. When flapped down, this plate sits horizontally over the top of the box. On the plate, there is a circular metal disk with a non-linear scale around the rim, labelled in “Minutes” and “Km Minutes”. There is a circular scale on the metal plate around the edge of the disk; this is labelled in “True Alt.” “Miles” and “True A.S.”. On the interior of the disk, there are two arc-shaped holes each with short scales drawn on the disk above or below the arc; the ends of these have a small raised section, to allow a better grip for the disk, which can be rotated around a central pin. These scales permit conversion from “Air Temp. Centigrade” to “Ind. Height Thousand Feet” and the reverse.

This plate flaps up to reveal the rectangular box-shaped instrument underneath. It consists of a top metal plate with a circular hole in it. This is covered by a plastic window. Visible through the window there is a red grid pattern printed on a paper or fabric sheet. This can be moved up and down along its x-axis by turning a ridged knob on one side of the box. Around the edge of the window on a silver-coloured circular rim there is a scale graduated in degrees, and with cardinal directions indicated. This rim can be rotated by turning a ridged metal handle on one side of the box.

On one edge of this rotating disk, there is an arc-shaped section with a scale along the bottom edge, graduated in units from 0 in the centre to 40 on each side. One side of this is labelled “Drift Port Var. East” and the other “Var. West Drift Strbd”. In the centre of this arc, pointing towards the rotating circle there is an indicator arrow labelled “True Course”.

Attached lengthways to one side of the box there is a hollow cylindrical tube. On the underside of the flat top, there are two plastic rods for holding something flat.

Lying loose between the top plate and the rotating circle there is a brown card tag, with a reinforced hole punched at one end. The tag is two-sided and has spaces for information about the instrument and, on the other side, its calibration. The information side has been filled out by hand.

On the base, there are four screws.

Primary Materials:

Metal: Iron Alloy, Metal: Aluminum, Card, Textile (Grid).

Markings:

Engraved and enamelled on the lid: “I.C.A.N.
CALIBRATION”

Engraved and enamelled next to the grid window: “DALTON DEAD RECKONING COMPUTER
MODEL G
STANLEY MANUFACTURING CO. LIMITED
TORONTO, CANADA”

Printed/written on the paper label: “RETAIN THIS TAG”
“Section…6-B Ref No….425 Part. No….
Description… Computor Navigation
Type “D”
Serial No…. O’Hauled by…
Unit…I-E D Date…17/10/46 Remarks…
Visual Inspection
Certified Serviceable… Date…”
“R.C.A.F.- W H
300M-10-42(2841)
H.Q.–885 – W 11”

Stamped over this: “R.C.A.F.

581”

“To be used with all instruments, etc.
subject to calibration or checking before issue.
Ensure all information required is entered.”

“TO BE WITH ARTICLE
RETURNED AT OVERHAUL”
“Running Time Since New”
“CALIBRATION”
“Running Time Since O’Haul…
Installed in… Date…
Returned for O’Haul… Reason…
Unit…
Signature and Rank…”

On the base: “X.Y.2822”

Scratched into the base: “↑
R.C.A.F.

Dimensions (cm): Height = 3.5, Width = 16, Length = 16.

Function:

The Dalton Dead Reckoning Computer is a mechanical calculator designed to aid with flight planning, including (according to the Wikipedia page on the similar E6B) “fuel burn, wind correction, time en route, and other items.”

Condition:

Good: The instrument’s surface shows some evidence of use. The black paint is chipped and worn off surfaces of the lower part of the box, particularly on the edges and corners. There are some scratches on the top of the box.

The hinges of the lid are rusty, as are small screws used to hold the instrument together; the instrument lid no longer fully opens. The underside of the lid, particularly around the hinges, is covered with a white powdery residue. The continuous rotating grid inside the instrument is broken and no longer rotates; however, the circular scale still rotates. The plastic window covering it is yellowed. The cardboard label is bent, but in good condition aside for some watery ink smudges.

Manufacturer:

Stanley Manufacturing Co. Limited, Toronto, Canada

Date of Manufacture: c. 1939-1946

Provenance:

This artifact was purchased as surplus following WWII and may have been used for teaching at the Department for the Astronomy & Astrophysics or at the David Dunlap Observatory, possibly as a slide rule. If the former, it was probably moved at some point to the Observatory for storage. The sphere was kept at the David Dunlap Observatory until 2009. Upon the sale of the Observatory, it was moved to the University of Toronto’s Department of Astronomy & Astrophysics at the St George Campus. In 2017 it was moved to a new storage location in McLennan Physical Laboratories.