After the American T26E1 prototype was deemed a successful design, and the M26 Heavy Tank began development, there was thought that even more heavily armed tanks would be needed. So, in early 1944, a new super heavy tank was designed to counter the new German heavy tanks, such as the Tiger II. With a 105 mm high velocity gun, three 7.62 mm machine guns, two coaxial and one mounted in the bow, a roof-mounted 12.7 mm machine gun, very thick armor of 279 mm on turret, 102 mm on hull, a crew of six, and a weight of 69.5 tons, the T29 was a true monster of a vehicle. The prototype had the same forward hull as the T26E3, but extended, with the addition of two more road wheels and a new engine, the 770 hp Ford GAC engine. The top speed was 22 mph, but the range, like the armor thickness, is now unknown. The T29 was not the only tank of this basic design however; it had two other 'siblings', as well as two improved variants, the T29E2 and E3. The specifications of the E2 have been lost to history, but it is known that the E3 model added a stereoscopic rangefinder to the turret, with two projector boxes mounted on the turret sides to assist in long range targeting.