Motometer (instrument)

Boyce MotoMeter model "Midget", brass version, on the radiator of an American Car-Nation from 1913. This is the manufacturer's smallest device and can be read on both sides. Possibly a reproduction.

The term motometer is a short form of motor thermometer . Originally the company and brand name of the long-standing market leader Motometer , it established itself as a collective term for a device on early automobiles with water cooling . The device is screwed onto the radiator cap (later also clamped) and uses a sensor in the cooling circuit to measure the water or ambient temperature in it, and more rarely its water level. The result is displayed on a scale that is visible from inside the car. There were a number of manufacturers with different technical solutions.

In contrast to hood ornaments , motometers fulfill a functional task and not only (but also) serve the aesthetics of the vehicle.

history

At the beginning of the engine there were no displays of the operating temperature . Excessively high water temperatures often led to irreparable damage. The future market leader Boyce MotoMeter started producing such measuring devices in 1912. At first, versions appeared that had to be read directly from the engine. The motometer was a good interim solution until temperature displays were available on the dashboard, after all the car no longer had to be left to read it.

A measured value display directly on the dashboard was only made possible by the capillary tube remote thermometer brought out by Boyce in 1917. Motometers became obsolete after the appearance of electrical indicators. Today there is a niche market in the field of automotive restoration .

Structure and functionality

Boyce motometer, readable on both sides, with decoration on a US American Pierce-Arrow from 1919. The radiator cap is clamped in place and can be swiveled forward with the wings serving as a handle. From this side only the top area of the temperature display is visible.

At that time, a thermosiphon cooling was generally used for automobiles with internal combustion engines and water cooling . This cooling has a lower boiling point than a system that works under pressure. When calibrated accordingly, motometers work in both systems.

The motometer is an ordinary thermometer which, depending on the manufacturer, is usually designed as a liquid or bimetal thermometer . It usually consists of a housing with a foot, a temperature sensor and a display.

Initially the housings were made of cast brass , later of die-cast zinc . When bare brass parts became outdated from around 1915, lacquered or nickel-plated devices came onto the market. More rarely, such as from Radiametre Maxant have been Bakelite Enclosures used. A sheet metal disk with a printed scale is fitted on the inside of the housing. In front of it a glass capillary tube is inserted vertically so that the scale and the tube with the display liquid form the actual temperature display. The display is calibrated so that the cold point is displayed below and the boiling point above, the latter with a warning of overheating. The normal operating temperature in summer is set above the middle. Mercury or red colored alcohol is usually used as the indicator liquid in the tube .

A cover glass serves as a cover, which is screwed together with the bezel and sealing ring to the case in a watertight manner. The back of the housing (i.e. the part facing the direction of travel) is often decorated with ornaments or has an insert with the logo of the car brand.

The housing is screwed onto the radiator cap in such a way that the temperature sensor protrudes through the cover into the upper reservoir of the cooling system. As a rule, the existing radiator cap has to be drilled through or replaced.

Either the water temperature is measured using the temperature sensor reaching into the cooling water. However, it is better if the ambient temperature is measured immediately above it. If the sensor protrudes into the air space above the cooling water level, a loss of coolant can also be detected on the Motometer display, because the temperature in this air space then rises above the boiling point of the coolant. Market leader Boyce consequently switched to reading the air temperature.

The driver reads the scale through the windshield. To make this easier, the housing is turned slightly towards the driver; d. That is, there are versions for left and right-hand drive vehicles.

Boyce 1926

Boyce Motometer lists four different basic types for 1926:

model	application	Price US $
default	large cars	10.00
Universal	Utility car	7.50
Junior	small utility cars	5.00
Midget	Small car	2.50

Special versions were for trucks and the Ford Model T made.

Individual parts can be exchanged on the better thermometers. The manufacturer made recommendations on this.

However, many motometers were made cheaply. Often the display and cover glass were then soldered in; such devices cannot be repaired.

In general, the purely mechanical technology of these devices is not particularly precise; Deviations of 10 degrees Celsius up or down are possible. Reading at night or in bad weather is hardly possible. After all, the instrument was inexpensive to manufacture and gave at least an indication of the condition of the engine.

variants

Reproduction of a Boyce motometer that can be read on both sides with a twist grip designed as a swing arm for the radiator cap on a Ford Model T from 1914.

Motometer from an unknown, probably British, manufacturer on an American King from approx. 1915 shows the temperature with a pointer on a scale from "Cold" to "Normal" to "Hot".

Engine thermometers that could be read from both the front and the rear were very popular. Instead of a housing, these devices have a metal ring, a bezel on both sides and an additional metal disc that is attached back to back with the first in the ring. At the top both have a round opening through which the "hot" area of the thermometer can be read. So only the critical temperature range can be seen from the front, there is space for a brand logo or an advertising message. For the driver, however, the entire capillary tube is visible. This motometer is being offered again as a reproduction and is often used for classic car restorations.

Some motometers such as the Arrometer from Bushnell , the Calometer (later Calormeter ) from Wilmot or the Morden Indicator show the temperature with an arrow on a scale. Boyce also offered a similar version, which is still documented for the Ford Model A (1928–1931); the scale consisted of a semicircle with three sectors; the one on the left was labeled "Cool Motor" and the middle one was labeled "Driving Range". The right sector was smaller and labeled "Steam" (steam, boiling point). In addition, there was a window with a green background under the scale, which was covered by a red sheet metal disk as the temperature rises.

The Bemometer the Great Northern Sales Company has a metal housing with a circular sight glass. Behind it, a red, round disc moves upwards with increasing temperature until it is completely visible at the boiling point.

The Moore Motor Semaphore from the Semaphoric Indicator Company in Chicago works in a similar way . It works with one red and one green disk. The float moves two levers that act on one disc each. When cold, only the green disk can be seen. The more of the red is visible, the higher the engine temperature. Both panes are partially visible at operating temperature; If the red disk remains permanently visible, there is not enough water in the circuit.

The Metro Scope - Benson Favorite of the Auto Radiator Meter Company from Seattle has a circular scale which only leaves a circumferential, glass arc . The display is made by two red flags behind the scale. These move upwards in opposite directions so that the circular arc is gradually colored red on both sides. The operating temperature is reached when this is about 2/3. If the two displays above meet, there is a risk of overheating.

The WB Jarvis Co. in Grand Rapids (Michigan) has found an interesting approach : It is not the temperature that is measured, but the water level in the upper cooler reservoir. The hotter the water - i.e. the more steam forms in the system - the lower the water level drops. This is indicated by means of a long pipe that protrudes far into the cooler and a float that is in turn connected to a display. When the tank is full, the float is at the upper limit. This can be seen by means of a pointer on a vertical scale. The more water evaporates, the lower the display sinks. This also reminds the driver to top up the cooling water in good time.

Remote thermometer

As described, Boyce came out on the market as early as 1917 with the first capillary tube remote thermometer . The company described the functioning later as: the capillary tube remote thermometer "consisted only of three parts: the heat sensor (tube), the capillary and the Bourdon tube . However, the invention was spectacular, because it enabled using the fluid pressure linear display Once the tube. was immersed in a warm or cold liquid, the Bourdon spring tended to stretch or contract. The resulting deflection of the pointer indicated the respective temperature on the scale ".

The display itself was round, had indirect lighting and a metal base that was attached to the steering column with a pipe clamp. It was recommended to place the temperature sensor in the water hose on the outlet side of the cooler.

Automotive accessories

Motometer on a De Dion Bouton 12/24 CV from 1924; probably a Bushnell Arrometer

For many manufacturers, the motor thermometer was not part of the standard equipment. It was often offered as a factory accessory, but some original equipment manufacturers also offered their advertisements early on in the brand-independent accessory trade. Motometers were available in numerous versions from inexpensive mass-produced items to artistically designed individual items. Because of its prominent position at the very front of the vehicle, it also became an artfully designed decorative part. Some devices had glass lids on both sides so that the temperature could be read from the front when the vehicle was stationary. Others used the back of the device for decorative figures and other displays. Many motometers have a handle between the lock and display with which the cooler can be opened more easily. A decorative part developed from this, often in the form of wings . More expensive motometers have a more elaborately machined housing and sometimes also a figure, so they also serve as an ornament.

The housing of the motor thermometer was originally made of brass. When nickel became established for the surface treatment of bare metal parts from around 1915, they were also nickel-plated. Simple designs were often painted. Only a few engine thermometers were originally chrome-plated because the instrument was replaced by displays on the dashboard around the time (from around 1930) when chrome was used instead of nickel for bare parts.

Manufacturer (selection)

On vehicles with a "shovel nose" the radiator is either in front of the front axle or, as on this Renault NN from 1927, behind the engine; The engine thermometer is attached accordingly close to the driver. The closure in front of it is the fuel tank cap.

The most important manufacturer of such advertisements was Boyce in the USA. The Boyce MotoMeter was part of the original equipment of numerous automobile manufacturers. The licensee in Germany was Motometer .

Moto-Meter-GmbH , Frankfurt a. M. and Moto Meter Hermann Schlaich GmbH , Stuttgart ( Motometer )
American Motor Safety Corp. , Kalamazoo ( Michigan ); "Unbreakable hydrometer
Great Northern Sales Co. , registered office unknown, "Bemometer"
GH Morden Co. , London , "The Morden Indicator"
Auto Radiator Meter Co. , Seattle, Washington ( Metro Scope - Benson Favorite )
Boyce MotoMeter ( Long Island City , New York )
Bushnell Manufacturing Co. , Berkeley , California ( Arrometer and Junior Arrometer )
WB Jarvis Co. , Grand Rapids, Michigan
Radiametre Maxant , Paris
Wilmot-Breeden, Ltd. (United Kingdom)

Accessories for motometer

Sockets and fasteners

Various manufacturers offered alternative bases and locks which were supposed to offer added value in terms of convenience or security beyond the pure aesthetics. Many radiator caps are just screwed on. Opening it takes strength and can be very uncomfortable when the engine is hot or cause injury. Catches, some of which were also offered in the accessories trade, offered a solution; the effort required has been significantly reduced by means of long, side-mounted handles. These were either already part of the cast iron or were simply screwed on at the side. Because they had a thickening or a screwed-on ball made of metal, plastic or wood at the outer end, they were also popularly called "dog bones".

An improvement that is often made concerns the replacement of the screw closure with a snap closure with a bracket. This system is also known from bottles with swing top. Various manufacturers such as the Elison Bronze Company in Jamestown (New York) constructed ingenious mechanics in their base. Handles, often designed in the form of wings, lock the motometer. If they are opened, this can be folded away to reveal the filling opening.

Himes offered a patented , two-part base. Its lower part was connected to the cooler so that the adjustment of the motometer, which was connected to the upper part, was made easier.

Hood ornament

Boyce motometer on a Packard Six model 226 from 1926. To open the radiator, the figure and motometer are folded back and the clip lock forwards, whereupon the radiator cap can be unscrewed. The hood ornament "Goddess of Speed" and the Packard logo in the advertisement indicate a factory accessory.

The useful motometer was often used in conjunction with a hood ornament. Instead of a base, this one had a round opening. The base of the motometer was passed through this opening and screwed onto the radiator cap, which also fixed the figure. A radiator cap with a tilt function was a bit more complex. The figure and motometer were attached to the lid, to open the cooler only the lid was opened.

lighting

Probably the most efficient approach to reading the display at night is Boyce's "Glo Light" . It consists of a (nickel-plated) brass housing that is screwed directly onto the side of the motometer facing away from the driver. The lamp it contains backlight the display. The light also falls through three lenses. The largest of these is colored white and shines in the direction of travel, a red and a green lens are attached to the side as a kind of position light.

The very rare accessory is switched on via a switch on the dashboard and should have blinded both oncoming traffic and the driver. An even rarer variant was the lamp from the Never-Out Company in Philadelphia . Here a blue light is used to backlight the scale.

Boyce went a somewhat bizarre way with the Cowl Light , a lighting that is attached to the torpedo plate directly in front of the windshield. It is nickel-plated, has the shape of a can, a removable lid and side openings into which colored glass lenses are fitted. The housing only contains a light bulb which backlight the lenses. A white lens illuminates the motometer, a red and a green lens are arranged on the side and serve as position lights. A nickel-plated acorn was included, which was screwed onto the housing cover. It was purely decorative and can be replaced by any radiator mascot that was commercially available at the time. The Cowl Light was available from accessory stores for US $ 3.50 and is very rare today.

"Protect-O-Cap"

Protect-O-Cap was an aluminum base onto which the motometer was screwed. It contained an opening to the cooler, which was covered and secured by an inclined flap with a brass knurled screw. With the flap open, cooling water could be refilled without having to remove the entire thermometer. It may be that Protect-O-Cap available with various decorative motifs. A version with swing arms is known. The manufacturer was the Up-To-Date Machine Works in Chicago .

"Topper"

With a bracket screwed to the top of the motometer, so-called "toppers" could be attached. Toppers can be coats of arms , logos , figures, letters, flag stands or other symbols with a closure that matches the motometer. Similar to today's stickers, they convey the owner's preferences and hobbies (sports, political parties, organizations, clubs, etc.) or even just an advertising message.

Toppers were offered by the equipment manufacturers but also by other companies, such as the LV Aronson foundry . This company later became the lighter manufacturer Ronson .

Theft protection

Unlike folding motometers, standard versions can be easily unscrewed. The JC McAdams Sales Company in New York City produced an anti-theft device based on a patent from the founder of the Boyce MotoMeter Company, Hermann Schlaich . It is made of chrome steel and nickel-plated brass and consists of a chain, a hinged anchor and a fastening which is carried out by means of a knurled screw directly on the base of the motometer.

Further customizations

The aforementioned Moore Motor Semaphore had a metal badge on the front. A vertical tube was hidden between this and the housing, which was used as a flag stand on special occasions.

Advertising medium

The manufacturer's logo on the motometer was widespread.

In addition to the aforementioned "toppers", it was also possible to convey individual advertising messages behind the sight glass. To do this, the manufacturer printed the desired message on its sheet metal discs in the appropriate number of copies and built this into its devices. Such thermometers were often given by workshops and agencies as promotional gifts or included when buying a car.

Motometer gallery

Reproduction of a motor thermometer on a beech from 1912
Motor thermometer readable on both sides with decorated housing on a Stutz Bearcat , approx. 1913
Boyce motometer with Art Deco decoration on a Pierce-Arrow from 1919. The wings serve as a handle to fold the radiator cap and motometer forward.
Boyce motometer on a Packard Twin Six from 1921
Motometers were also used on racing cars , here on the winning car of the French GP in 1921 and the Indianapolis 500 in 1922, a Duesenberg Type 183.
Motometer on a Delage from the 1920s
Unusual motometer on a Wolseley , ca.1930.