The World’s First Automatic Transmission – The 1904-1907 Sturtevant Automatic Automobile

 

What was the first gasoline-powered automobile with fully automatic transmission? It wasn’t built by GM (which hadn’t even been incorporated yet!), but by the Sturtevant Mill Company in Boston, about 120 years ago. Here’s a brief history of the 1904–1907 Sturtevant Automatic Automobile, and how their pioneering self-shifting transmissions worked.

 

The Sturtevant Mill Company in Harrison Square, Boston, Massachusetts, was originally a manufacturer of fertilizer-processing machinery. It was founded by Thomas L. Sturtevant, a Harvard Law School alumnus who had previously been treasurer of the Bowker Fertilizer Company. As a 1919 item in the journal Farm Chemicals explained:

The difficulties encountered by the Bowker Fertilizer Company in grinding the various fertilizer ingredients with the machinery of those days led Mr. Sturtevant to invent many improvements in both machines and processes of manufacture, and the Sturtevant Mill Company was formed in 1883, to build these devices for the fertilizer industry.

In the 1890s, T.L. Sturtevant was joined by his younger brother, Thomas J. Sturtevant, an MIT alumnus. Together, they accumulated dozens of patents related to industrial machinery and industrial engines.

 

Around 1902, the Sturtevants decided to branch out into the new and trendy field of automobiles. Their first car (above), shown in the late summer of 1904, was a touring car on a 108-inch wheelbase, with a 314.2 cu. in. horizontally opposed four making about 30 hp at 1,500 rpm. The car had a variety of advanced features, including centrifugal spark advance, but the most significant was its self-shifting change-speed transmission.

The Sturtevant Automatic Transmission

The early Sturtevant car used a two-speed layshaft transmission controlled by a pair of “wet” centrifugal multi-plate clutches located in a hollow flywheel drum full of oil. Here’s an illustration of it from the Sturtevants’ initial 1904 patent:

 

How did it work? The two clutches were each controlled by a set of spring-loaded centrifugal weights, as shown in the contemporary illustration shown below. (This is from The Horseless Age, but it’s closely adapted from Fig. 2 of the US766551 patent; I used this version because it’s a little clearer.)

 

As engine speed increased, centrifugal action would shift those weights outward, which would actuate a lever forcing the clutch plates together. The weights had pressure screws that could be adjusted to vary the speed necessary to engage each clutch. Let’s take another look at the cross-section (again using the version from The Horseless Age), this time adding color to better illustrate which pieces were which. I’ve used red to highlight the low clutch, which was set to engage first. When it engaged, it sent power through the reduction gears. As engine speed increased, centrifugal action would engage the direct clutch, which I’ve highlighted in blue, sending power directly through the output shaft.

 

The low clutch remained engaged in high, but a roller-type one-way clutch (highlighted in green) would let the low gears overrun idly. Reverse was engaged with either a pedal or a side lever, which actuated a lever (purple) to move a sliding gear into mesh with the reverse gears. Interestingly, the transmission would still shift automatically in reverse.

If engine speed dropped enough, either due to decreased road speed or increased load, the high clutch would automatically disengage, eventually followed by the low clutch, dropping the transmission out of gear and allowing the engine to idle. The Sturtevants emphasized that this arrangement made it impossible to stall the engine even when climbing hills at very low speeds, although you could end up in neutral when you didn’t necessarily want to be.

By late 1904, the Sturtevants had come up with a new clutch arrangement, allowing multiple clutches to share the same set of centrifugal weights. Each clutch was carried on a separate spider and was engaged or disengaged sequentially. (As before, I’ve used red to indicate the low clutch and blue to indicate the high clutch.)

 

This functioned basically the same way as the original arrangement, but it made it easier to incorporate additional clutches for additional forward speeds. In 1906, the Sturtevants installed a three-speed version of this transmission on a two-cylinder Maxwell touring car and a four-cylinder Franklin. The three-speed looked like this in cross-section:

 

I haven’t gone to the trouble of color-coding the clutches in the above illustration, but as you can see, it incorporated three clutches rather than two and had an additional set of reduction gears. Also, the output was now through the layshaft (the bottom shaft, labeled “Q”) rather than the main shaft, so high gear was indirect rather than direct. This change facilitated a new feature, which The Horseless Age explained like this:

Sliding gear W [highlighted in green above] also has a neutral position in which the jaw clutch is disengaged, but the reverse combination not meshed. When the elements are in this position the direct drive is cut out entirely, as the high clutch acting through spider F revolves idly the free member of the jaw clutch in shaft L”. In traveling very hilly country it might sometimes happen that on account of the high road resistance the car could run only occasionally on the high gear, and then, owing to the great tractive resistance, would not make so good speed as it would were it running on the middle speed with full engine power. By thus disconnecting the high gear, the car becomes practically a two speed vehicle and the full engine speed can be utilized to drive on the intermediate speed.

Otherwise, the Sturtevant transmissions remained completely automatic, with no manual clutching or hand-shifting required. Sturtevant proclaimed, “Self-control tames the driver, and prevents many mischiefs,” and advised, “Ladies, also, please take note, that if you drive the family horse, you can easily manage an Automatic Automobile.”

The Sturtevant Automatic Automobile

Sturtevant Mill Company offered several passenger car models. The original 1904 four-passenger touring car on its 108-inch wheelbase, with the 314.2 cu. in. H-4 engine, was followed in 1905 by a touring car with a 477.1 cu. in. H-6 and about 45 hp, mated to the three-speed automatic. The Automobile noted in August 1905, “Only a few of these machines were built this year, but the Sturtevant Mills [sic] Company is at work on some important designs at its factory in Dorchester.”

 

Those new models arrived for 1906. The six-cylinder engine was dropped in favor of two new inline-4 engines, a 283.7 cu. in. version making 30–35 hp and a bigger 475.2 cu. in. engine making 45–50 hp. The smaller engine was installed in the new Sturtevant Automatic Flying Roadster, a three-passenger rumble seat roadster on a 98-inch wheelbase, which Sturtevant claimed was “a fine combination for nimbleness, speed, and hill climbing.” It started at $3,500, increased to $4,000 for 1907.

 

The bigger engine was installed in a new seven-passenger tourer, the Sturtevant Automatic Touring Car, with a 120-inch wheelbase and a base price of $5,000, raised in 1907 to $6,000. In 1907, there was also a four-seater tonneau touring car with the smaller engine, priced at $5,000.

 

The seven-passenger Touring Car used the three-speed automatic, while the Flying Roadster had the two-speed, but the brochure advised Roadster buyers that “four speeds can be easily arranged (at a slightly increased price) when wanted.” This curious arrangement, which was apparently standard on the four-passenger Touring Car, gave four gear changes, but there were two direct drives. I couldn’t find any pictures of this setup, but I assume it mounted two two-speed transmissions in series. The brochure implied that the same could be done with the three-speed transmission, giving a total of six gear changes, again with two direct drive gears.

 

Curiously, late Sturtevant cars now had a clutch pedal in addition to the centrifugal mechanism, allowing the driver to manually control the engagement of the low-speed clutch. As the brochure explained rather owlishly:

the clutch can also be manipulated by the foot just as in other cars, to allow the motor to run free at any time, or to develop its full power on any set of gears. But automatic pedal control cannot be improved for any purpose; for it always does the right thing at the right time, and never forgets or mistakes — and requires no skill. But manual control is at hand for those accustomed to like it. They will soon see the difference.

Here’s an illustration of the clutch, from The Horseless Age:

 

Here’s a brochure illustration of the complete system — I think this is the two-speed:

 

The final iteration of the three-speed automatic, shown in the illustration below, could now be shifted manually between low and intermediate. The Horseless Age explained, “The direct drive is always under control of its special automatic clutch, but either the intermediate or the low gear may be made operative under the influence of the other clutch” by moving the jaw clutch H (which I’ve highlighted in purple below). It was also still possible to lock out high gear by shifting its jaw clutch J (highlighted in green below) to the neutral position.

 

Sturtevant cars were very easy to drive for gasoline-powered cars of the 1900s, which attracted considerable attention, but not many sales. Modern sources often claim there were reliability problems with the centrifugal clutches, which is plausible, but I think the bigger problem was price. MeasuringWorth estimates that the $4,000 price tag of a 1907 Sturtevant Flying Roadster represents a relative worth of about $318,000 in 2025, while the $6,000 price of a seven-passenger Automatic Touring Car $6,000 had a relative worth of around $477,000. That was Packard money at the time, and since Sturtevant cars were built only to order, with a 50 percent nonrefundable deposit up front, they were a very expensive proposition even in an age when most cars were still rich man’s toys. I haven’t found any production figures, but the total was undoubtedly very small.

 

The Sturtevant brothers had considered spinning off the automotive business as a separate subsidiary company, but it appears that by the end of 1907, they had realized that it wasn’t going to be financially viable. It was a sideline anyway, and they still hoped they could interest outside licensees. As The Horseless Age remarked while describing the latest Sturtevant automatic transmissions in their January 8, 1908 issue:

It is not the intention of the Sturtevant Company to manufacture these clutches, transmissions or the complete cars embodying them, but to devote themselves to developing to a commercial point the principles of automatic control, leaving to subcompanies or licensees the task of producing them and placing them on the market.

As far as I know, the Sturtevants found no takers. (The Franklin and Maxwell cars with Sturtevant transmissions appear to have been test mules rather than factory options.) However, there were various later efforts at automatic and semiautomatic transmissions that also used some combination of centrifugal and overrunning clutches to change gears, including Oscar Banker’s Mono-Drive transmission, developed over 20 years after the Sturtevants’.

Reliability questions aside, the downfall of transmissions like this was that they had limited ability to respond to changes in load — the transmission wouldn’t delay an upshift unless the engine simply couldn’t turn fast enough to engage the next centrifugal clutch, and it couldn’t downshift automatically unless engine speed actually dropped due to increased load. That might have been fine for underpowered early cars, or for heavy trucks or buses, but as automotive engines became more powerful, it meant the transmission was largely limited to always shifting at the same speeds regardless of accelerator position. The great advance of Hydra-Matic was that its hydraulic controls measured both road speed and throttle opening and balanced both in determining upshift and downshift points.

Although the Sturtevants’ automotive venture didn’t pan out, it didn’t do them any great harm either. The Sturtevant Mill Company continued very successfully in its original fields. Thomas L. Sturtevant died in 1925 at the age of 84. Thomas J. Sturtevant took over as president of the company until his death in 1944. The Sturtevant company still exists today, and one of their modern business lines is processing equipment for the lithium carbonate used in electric car batteries.

 

I don’t know if any Sturtevant cars survive intact today, but if they do, they’re significant historical artifacts. Trying to identify the first of anything is always tricky, but the Sturtevant Automatic Automobile was (probably!) the first production car with true self-shifting transmission.

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