Twin BMW M73b54 Engines in W24 Hot Rod Madness!

Story by: Dale Pelvit and Gary Kollofski

Edited by: Mike Oswald


Carl Wepplo of Atlas Tractor (Atlas) in Blaine, Minnesota, was called in to design and manufacture the connecting gearbox.
Atlas builds gearboxes for those outrageous multi-engine pulling tractors, so this job was just another day at the office for them.
The resultant gearbox uses a pair of splined stub shafts that bolt to the BMW crankshafts. Then the gearbox slides onto the shafts
and bolts to the connecting plate atthe ear of the engines.

Above: CNC milling the gear box cover.

Above: Orientation of the 5 gears. All of the gears are the same diameter, so there is no gear reduction or multiplication. The gearbox has five gears.
One on each side accepts the splined shaft attached to each crankshaft, and two idler gears in board of them transfer power to the
central gear and output shaft. The idlers are necessary to turn the output shaft in the same rotation as the crankshafts.

The gearbox was kept as compact as possible, and has a limited capacity for gear lube. As a precautionary measure, an electric pump will draw fluid from
the bottom of the gearbox and circulate it through and oil cooler equipped with an electric fan. The fluid is then reintroduced to two
points on top of the gearbox, positioned to return the fluid directly to the top of the gears.

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If you would like to add any comments, remarks and/or corrections to this article, feel free to email Mike Oswald and we'll put it on our site. Share your experiences with us so others may benefit from it.