It has been reported that Howard Carter came up with the idea for the two engine automobile after an incident where he was not able to start his car; later he reasoned that if one engine let you down, you would have the other to fall back on to continue on your journey. Carter then proceeded design, patent and build a car that had two compete, but separate engines, each with its own set of ignition, induction, exhaust, and cooling systems. They could also be operated singly or together.
- Engine and drivetrain photos, “The Motor”, January 1908.
The two 35-40-h.p. engines each drove a shaft (I in the patent drawing below) that was supported by a bearing on the front of the center crossmember (L). Towards the rear end of each shaft can be seen a sprocket (S) that drives a roller-chain to sprockets (Q and R) on the center shaft (M). This center shaft then drives a conventional transmission (O) and in turn the rear differential (P) through drive shaft (N). You can view the entire patent and another drawing for the Carter Two-Engine Car here.
Each engine could be started separately by its hand crank after its clutch was disengaged. The second engine could then be started by engaging its clutch and using the running engine to turn it. In actual use, one engine was adequate for driving in normal conditions; if more power was needed the second engine could be started and it would thereby double the power output by producing some 70-80-h.p.
Howard first considered manufacturing his automobile in Detroit, but ultimately decided on Hyattsville, Maryland. A new plant was built and just about completed in 1907 when he discovered that the public was quite happy with only one engine and his new car would not sell. The factory was then was used to manufacture the Washington automobile which was of conventional construction. More information can be found on the Carter in an article in the January 1908, The Motor.